HELICOPTERS.
The result aimed at in the helicopter is the ability to rise vertically from the starting point, instead of first running along the ground for from 100 to 300 feet before sufficient speed to rise is attained, as the aeroplanes do. The device employed to accomplish this result is a propeller, or propellers, revolving horizontally above the machine. After the desired altitude is gained it is proposed to travel in any direction by changing the plane in which the propellers revolve to one having a small angle with the horizon.
The force necessary to keep the aeroplane moving in its horizontal path is the same as that required to move the automobile of equal weight up the same gradient—much less than its total weight.
The great difficulty encountered with this type of machine is that the propellers must lift the entire weight. In the case of the aeroplane, the power of the engine is used to slide the plane up an incline of air, and for this much less power is required. For instance, the weight of a Curtiss biplane with the pilot on board is about 700 pounds, and this weight is easily slid up an inclined plane of air with a propeller thrust of about 240 pounds.
Another difficulty is that the helicopter screws, in running at the start before they can attain speed sufficient to lift their load, have established downward currents of air with great velocity, in which the screws must run with much less efficiency. With the aeroplanes, on the contrary, their running gear enables them to run forward on the ground almost with the first revolution of the propeller, and as they increase their speed the currents—technically called the “slip”—become less and less as the engine speed increases.
In the Cornu helicopter, which perhaps has come nearer to successful flight than any other, these downward currents are checked by interposing planes below, set at an angle determined by the operator. The glancing of the currents of air from the planes is expected to drive the helicopter horizontally through the air. At the same time these planes offer a large degree of resistance, and the engine power must be still further increased to overcome this, while preserving the lift of the entire weight. With an 8-cylinder Antoinette motor, said to be but 24 horse-power, turning two 20-foot propellers, the machine is reported as lifting itself and two persons—a total weight of 723 pounds—to a height of 5 feet, and sustaining itself for 1 minute. Upon the interposing of the planes to produce the horizontal motion the machine came immediately to the ground.
Diagram showing principle of the Cornu helicopter. P, P, propelling planes. The arrow shows direction of travel with planes at angle shown.
This performance must necessarily be compared with that of the aeroplanes, as, for instance, the Wright machine, which, with a 25 to 30 horse-power motor operating two 8-foot propellers, raises a weight of 1,050 pounds and propels it at a speed of 40 miles an hour for upward of 2 hours.
Another form of helicopter is the Leger machine, so named after its French inventor. It has two propellers which revolve on the same vertical axis, the shaft of one being tubular, encasing that of the other. By suitable gearing this vertical shaft may be inclined after the machine is in the air in the direction in which it is desired to travel.
The Vitton-Huber helicopter at the Paris aeronautical salon in 1909. It has the double concentric axis of the Leger helicopter and the propelling planes of the Cornu machine.
The gyropter differs from the Cornu type of helicopter in degree rather than in kind. In the Scotch machine, known as the Davidson gyropter, the propellers have the form of immense umbrellas made up of curving slats. The frame of the structure has the shape of a T, one of the gyropters being attached to each of the arms of the T. The axes upon which the gyropters revolve may be inclined so that their power may be exerted to draw the apparatus along in a horizontal direction after it has been raised to the desired altitude.
The gyropters of the Davidson machine are 28 feet in diameter, the entire structure being 67 feet long, and weighing 3 tons. It has been calculated that with the proposed pair of 50 horse-power engines the gyropters will lift 5 tons. Upon a trial with a 10 horse-power motor connected to one of the gyropters, that end of the apparatus was lifted from the ground at 55 revolutions per minute—the boiler pressure being 800 lbs. to the square inch, at which pressure it burst, wrecking the machine.
An example of the gyroplane is the French Breguet apparatus, a blend of the aeroplane and the helicopter. It combines the fixed wing-planes of the one with the revolving vanes of the other. The revolving surfaces have an area of 82 square feet, and the fixed surfaces 376 square feet. The total weight of machine and operator is about 1,350 lbs. Fitted with a 40 horse-power motor, it rose freely into the air.
The ornithopter, or flapping-wing type of flying machine, though the object of experiment and research for years, must still be regarded as unsuccessful. The apparatus of M. de la Hault may be taken as typical of the best effort in that line, and it is yet in the experimental stage. The throbbing beat of the mechanism, in imitation of the bird’s wings, has always proved disastrous to the structure before sufficient power was developed to lift the apparatus.
The most prominent exponent of the tetrahedral type—that made up of numbers of small cells set one upon another—is the Cygnet of Dr. Alexander Graham Bell, which perhaps is more a kite than a true flying machine. The first Cygnet had 3,000 cells, and lifted its pilot to a height of 176 feet. The Cygnet II. has 5,000 tetrahedral cells, and is propelled by a 50 horse-power motor. It has yet to make its record.
One of the most recently devised machines is that known as the Fritz Russ flyer. It has two wings, each in the form of half a cylinder, the convex curve upward. It is driven by two immense helical screws, or spirals, set within the semi-cylinders. No details of its performances are obtainable.
Chapter VIII.
FLYING MACHINES: HOW TO OPERATE.
Instinctive balance—When the motor skips—Progressive experience—Plum Island School methods—Lilienthal’s conclusions—The Curtiss mechanism and controls—Speed records—Cross-country flying—Landing—Essential qualifications—Ground practice—Future relief.
Any one who has learned to ride a bicycle will recall the great difficulty at first experienced to preserve equilibrium. But once the knack was gained, how simple the matter seemed! Balancing became a second nature, which came into play instinctively, without conscious thought or effort. On smooth roads it was not even necessary to grasp the handle-bars. The swaying of the body was sufficient to guide the machine in the desired direction.
Much of this experience is paralleled by that of the would-be aviator. First, he must acquire the art of balancing himself and his machine in the air without conscious effort. Unfortunately, this is even harder than in the case of the bicycle. The cases would be more nearly alike if the road beneath and ahead of the bicyclist were heaving and falling as in an earthquake, with no light to guide him; for the air currents on which the aviator must ride are in constant and irregular motion, and are as wholly invisible to him as would be the road at night to the rider of the wheel.
And there are other things to distract the attention of the pilot of an aeroplane—notably the roar of the propeller, and the rush of wind in his face, comparable only to the ceaseless and breath-taking force of the hurricane.
The well-known aviator, Charles K. Hamilton, says:—“So far as the air currents are concerned, I rely entirely on instinctive action; but my ear is always on the alert. The danger signal of the aviator is when he hears his motor miss an explosion. Then he knows that trouble is in store. Sometimes he can speed up his engine, just as an automobile driver does, and get it to renew its normal action. But if he fails in this, and the motor stops, he must dip his deflecting planes, and try to negotiate a landing in open country. Sometimes there is no preliminary warning from the motor that it is going to cease working. That is the time when the aviator must be prepared to act quickly. Unless the deflecting planes are manipulated instantly, aviator and aeroplane will rapidly land a tangled mass on the ground.”
Result of a failure to deflect the planes quickly enough when the engine stopped. The operator fortunately escaped with but a few bruises.
At the same time, Mr. Hamilton says: “Driving an aeroplane at a speed of 120 miles an hour is not nearly so difficult a task as driving an automobile 60 miles an hour. In running an automobile at high speed the driver must be on the job every second. Nothing but untiring vigilance can protect him from danger. There are turns in the road, bad stretches of pavement, and other like difficulties, and he can never tell at what moment he is to encounter some vehicle, perhaps travelling in the opposite direction. But with an aeroplane it is a different proposition. Once a man becomes accustomed to aeroplaning, it is a matter of unconscious attention.... He has no obstacles to encounter except cross-currents of air. Air and wind are much quicker than a man can think and put his thought into action. Unless experience has taught the aviator to maintain his equilibrium instinctively, he is sure to come to grief.”
The Wright brothers spent years in learning the art of balancing in the air before they appeared in public as aviators. And their method of teaching pupils is evidence that they believe the only road to successful aviation is through progressive experience, leading up from the use of gliders for short flights to the actual machines with motors only after one has become an instinctive equilibrist.
At the Plum Island school of the Herring-Burgess Company the learner is compelled to begin at the beginning and work the thing out for himself. He is placed in a glider which rests on the ground. The glider is locked down by a catch which may be released by pulling a string. To the front end of the glider is attached a long elastic which may be stretched more or less, according to the pull desired. The beginner starts with the elastic stretched but a little. When all is ready he pulls the catch free, and is thrown forward for a few feet. As practice gains for him better control, he makes a longer flight; and when he can show a perfect mastery of his craft for a flight of 300 feet, and not till then, he is permitted to begin practice with a motor-driven machine.
A French apparatus for instructing pupils in aviation.
The lamented Otto Lilienthal, whose experience in more than 2,000 flights gives his instructions unquestionable weight, urges that the “gradual development of flight should begin with the simplest apparatus and movements, and without the complication of dynamic means. With simple wing surfaces ... man can carry out limited flights ... by gliding through the air from elevated points in paths more or less descending. The peculiarities of wind effects can best be learned by such exercises.... The maintenance of equilibrium in forward flight is a matter of practice, and can be learned only by repeated personal experiment.... Actual practice in individual flight presents the best prospects for developing our capacity until it leads to perfected free flight.”
The essential importance of thorough preparation in the school of experience could scarcely be made plainer or stronger. If it seems that undue emphasis has been laid upon this point, the explanation must be found in the deplorable death record among aviators from accidents in the air. With few exceptions, the cause of accident has been reported as, “The aviator seemed to lose control of his machine.” If this is the case with professional flyers, the need for thorough preliminary training cannot be too strongly insisted upon.
Having attained the art of balancing, the aviator has to learn the mechanism by which he may control his machine. While all of the principal machines are but different embodiments of the same principles, there is a diversity of design in the arrangement of the means of control. We shall describe that of the Curtiss biplane, as largely typical of them all.
In general, the biplane consists of two large sustaining planes, one above the other. Between the planes is the motor which operates a propeller located in the rear of the planes. Projecting behind the planes, and held by a framework of bamboo rods, is a small horizontal plane, called the tail. The rudder which guides the aeroplane to the right or the left is partially bisected by the tail. This rudder is worked by wires which run to a steering wheel located in front of the pilot’s seat. This wheel is similar in size and appearance to the steering wheel of an automobile, and is used in the same way for guiding the aeroplane to the right or left. (See [illustration of the Curtiss machine in Chapter V].)
In front of the planes, supported on a shorter projecting framework, is the altitude rudder, a pair of planes hinged horizontally, so that their front edges may tip up or down. When they tilt up, the air through which the machine is passing catches on the under sides and lifts them up, thus elevating the front of the whole aeroplane and causing it to glide upward. The opposite action takes place when these altitude planes are tilted downward. This altitude rudder is controlled by a long rod which runs to the steering wheel. By pushing on the wheel the rod is shoved forward and turns the altitude planes upward. Pulling the wheel turns the rudder planes downward. This rod has a backward and forward thrust of over two feet, but the usual movement in ordinary wind currents is rarely more than an inch. In climbing to high levels or swooping down rapidly the extreme play of the rod is about four or five inches.
Thus the steering wheel controls both the horizontal and vertical movements of the aeroplane. More than this, it is a feeler to the aviator, warning him of the condition of the air currents, and for this reason must not be grasped too firmly. It is to be held steady, yet loosely enough to transmit any wavering force in the air to the sensitive touch of the pilot, enabling him instinctively to rise or dip as the current compels.
Courtesy N. Y. Times.
View of the centre of the new Wright machine, showing method of operating. Archibald Hoxsey in the pilot’s seat. In his right hand he holds a lever with two handles, one operating the warping of the wing tips, and the other the rudder. Both handles may be grasped at once, operating both rudder and wing tips at the same moment. In his left hand Hoxsey grasps the lever operating the elevating plane—at the rear in this type. The passenger’s seat is shown at the pilot’s right.
The preserving of an even keel is accomplished in the Curtiss machine by small planes hinged between the main planes at the outer ends. They serve to prevent the machine from tipping over sideways. They are operated by arms, projecting from the back of the aviator’s seat, which embrace his shoulders on each side, and are moved by the swaying of his body. In a measure, they are automatic in action, for when the aeroplane sags downward on one side, the pilot naturally leans the other way to preserve his balance, and that motion swings the ailerons (as these small stabilizing planes are called) in such a way that the pressure of the wind restores the aeroplane to an even keel. The wires which connect them with the back of the seat are so arranged that when one aileron is being pulled down at its rear edge the rear of the other one is being raised, thus doubling the effect. As the machine is righted the aviator comes back to an upright position, and the ailerons become level once more.
Starting a Wright machine. When the word is given both assistants pull vigorously downward on the propeller blades.
There are other controls which the pilot must operate consciously. In the Curtiss machine these are levers moved by the feet. With a pressure of the right foot he short-circuits the magneto, thus cutting off the spark in the engine cylinders and stopping the motor. This lever also puts a brake on the forward landing wheels, and checks the speed of the machine as it touches the ground. The right foot also controls the pump which forces the lubricating oil faster or slower to the points where it is needed.
The left foot operates the lever which controls the throttle by which the aviator can regulate the flow of gas to the engine cylinders. The average speed of the 7-foot propeller is 1,100 revolutions per minute. With the throttle it may be cut down to 100 revolutions per minute, which is not fast enough to keep afloat, but will help along when gliding.
Obviously, travelling with the wind enables the aviator to make his best speed records, for the speed of the wind is added to that of his machine through the air. Again, since the wind is always slower near the ground, the aviator making a speed record will climb up to a level where the surface currents no longer affect his machine. But over hilly and wooded country the air is often flowing or rushing in conflicting channels, and the aviator does not know what he may be called upon to face from one moment to the next. If the aeroplane starts to drop, it is only necessary to push the steering wheel forward a little—perhaps half an inch—to bring it up again. Usually, the machine will drop on an even keel. Then, in addition to the motion just described, the aviator will lean toward the higher side, thus moving the ailerons by the seat-back, and at the same time he will turn the steering wheel toward the lower side. This movement of the seat-back is rarely more than 2 inches.
Diagram showing action of wind on flight of aeroplane. The force and direction of the wind being represented by the line A B, and the propelling force and steered direction being A C, the actual path travelled will be A D.
In flying across country a sharp lookout is kept on the land below. If it be of a character unfit for landing, as woods, or thickly settled towns, the aviator must keep high up in the air, lest his engine stop and he be compelled to glide to the earth. A machine will glide forward 3 feet for each foot that it drops, if skilfully handled. If he is up 200 feet, he will have to find a landing ground within 600 feet. If he is up 500 feet, he may choose his alighting ground anywhere within 1,500 feet. Over a city like New York, a less altitude than 1,500 feet would hardly be safe, if a glide became necessary.
Mr. Clifford B. Harmon, who was an aeronaut of distinction before he became an aviator, under the instruction of Paulhan, has this to say: “It is like riding a bicycle, or running an automobile. You have to try it alone to really learn how. When one first handles a flying machine it is advisable to keep on the ground, just rolling along. This is a harder mental trial than you will imagine. As soon as one is seated in a flying machine he wishes to fly. It is almost impossible to submit to staying near the earth. But until the manipulation of the levers and the steering gear has become second nature, this must be done. It is best to go very slow in the beginning. Skipping along the ground will teach a driver much. When one first gets up in the air it is necessary to keep far from all obstacles, like buildings, trees, or crowds. There is the same tendency to run into them that an amateur bicycle rider has in regard to stones and ruts on the ground. When he keeps his eye on them and tries with all his might to steer clear of them, he runs right into them.”
Practicing with a monoplane, 20 feet above the ground.
When asked what he regarded the fundamental requirements in an aviator, Mr. Harmon said: “First, he must be muscularly strong; so that he will not tire. Second, he should have a thorough understanding of the mechanism of the machine he drives. Third, mental poise—the ability to think quick and to act instantly upon your thought. Fourth, a feeling of confidence in the air, so that he will not feel strange or out of place. This familiarity with the air can be best obtained by first being a passenger in a balloon, then by controlling one alone, and lastly going up in a flying machine.”
Grahame-White on his Bleriot No. XII. The lever in front of him operates all the controls through the movement of the drum at its base.
Mr. Claude Grahame-White, the noted English aviator, has this to say of his first experience with his big “No. XII.” Bleriot monoplane—which differs in many important features from the “No. XI.” machine in which M. Bleriot crossed the English Channel: “After several disappointments, I eventually obtained the delivery of my machine in working order.... As I had gathered a good deal of information from watching the antics and profiting by the errors made by other beginners on Bleriot monoplanes, I had a good idea of what not to do when the engine was started up and we were ready for our first trial.... It was a cold morning, but the engine started up at the first quarter turn. After many warnings from M. Bleriot’s foreman not on any account to accelerate my engine too much, I mounted the machine along with my friend as passenger, and immediately gave the word to let go, and we were soon speeding along the ground at a good sixty kilometers (about 37 miles) per hour.... Being very anxious to see whether the machine would lift off the ground, I gave a slight jerk to the elevating plane, and soon felt the machine rise into the air; but remembering the warnings of the foreman, and being anxious not to risk breaking the machine, I closed the throttle and contented myself with running around on the ground to familiarize myself with the handling of the machine.... The next day we got down to Issy about five o’clock in the morning, some two hours before the Bleriot mechanics turned up. However, we got the machine out, and tied it to some railings, and then I had my first experience of starting an engine, which to a novice at first sight appears a most hazardous undertaking; for unless the machine is either firmly held by several men, or is strongly tied up, it has a tendency to immediately leap forward. We successfully started the engine, and then rigged up a leash, and when we had mounted the machine, we let go; and before eight o’clock we had accomplished several very successful flights, both with and against the wind. These experiences we continued throughout the day, and by nightfall I felt quite capable of an extended flight, if only the ground had been large enough.... The following day M. Bleriot returned, and he sent for me and strongly urged me not to use the aeroplane any more at Issy, as he said the ground was far too small for such a powerful machine.”
Diagram of Bleriot monoplane, showing controlling lever L and bell-shaped drum C, to which all controlling wires are attached. When the bell is rocked back and forward the elevator tips on the rear plane are moved; rocking from side to side moves the stabilizing tips of the main plane. Turning the bell around moves the rudder.
| The Marmonier gyroscopic pendulum, devised to secure automatic stability of aeroplanes. The wheels are driven by the aeroplane motor at high speed. The pendulum rod is extended upward above the axis and carries a vane which is engaged by any gust of wind from either side of the aeroplane, tending to tilt the pendulum, and bringing its gyroscopic resistance into play to warp the wings, or operate ailerons. |
The caution shown by these experienced aviators cannot be too closely followed by a novice. These men do not say that their assiduous practice on the ground was the fruit of timidity. On the contrary, although they are long past the preliminary stages, their advice to beginners is uniformly in the line of caution and thorough practice.
When the aeroplane is steered to the left, the pendulum swings to the right and depresses the right side of the plane, as in (c). The reaction of the air raises the right side of the plane until both surfaces are perpendicular to the inclined pendulum, as in (d).
Diagrams showing action of Marmonier gyroscopic pendulum.
Even after one has become an expert, the battle is not won, by any means. While flying in calm weather is extremely pleasurable, a protracted flight is very fatiguing; and when it is necessary to wrestle with gusts of high wind and fickle air currents, the strain upon the strongest nerve is a serious source of danger in that the aviator is liable to be suddenly overcome by weariness when he most needs to be on the alert.
In that inclined position the aeroplane makes the turn, and when the course again becomes straight, both the gyroscopic and centrifugal forces cease, and the pendulum under the influence of gravity becomes vertical. In this position it is inclined to the left with respect to the planes, on which its effect is to depress the left wing and so right the aeroplane, as in (e).
Diagram showing action of Marmonier gyroscopic pendulum.
Engine troubles are much fewer than they used to be, and a more dependable form of motor relieves the mind of the aviator from such mental disturbance. Some device in the line of a wind-shield would be a real boon, for even in the best weather there is the ceaseless rush of air into one’s face at 45 to 50 miles an hour. The endurance of this for hours is of itself a tax upon the most vigorous physique.
With the passing of the present spectacular stage of the art of flying there will doubtless come a more reliable form of machine, with corresponding relief to the operator. Automatic mechanism will supplant the intense and continual mental attention now demanded; and as this demand decreases, the joys of flying will be considerably enhanced.
If, when pursuing a straight course, the aeroplane is tilted by a sideways wind (b), the action of the pendulum as described above restores it to an even keel, as in (a).
Diagrams showing action of Marmonier gyroscopic pendulum.
Chapter IX.
FLYING MACHINES: HOW TO BUILD.
Santos-Dumont’s gift—La Demoiselle—Mechanical skill required—Preparatory practice—General dimensions—The frame—The motor—The main planes—The rudder-tail—The propeller—Shaping the blades—Maxim’s experience—The running gear—The controls—Scrupulous workmanship.
When Santos-Dumont in 1909 gave to the world the unrestricted privilege of building monoplanes after the plans of his famous No. 20—afterward named La Demoiselle—he gave not only the best he knew, but as much as any one knows about the building of flying machines. Santos-Dumont has chosen the monoplane for himself because his long experience commends it above others, and La Demoiselle was the crowning achievement of years spent in the construction and operation of airships of all types. In view of Santos-Dumont’s notable successes in his chosen field of activity, no one will go astray in following his advice.
Of course, the possession of plans and specifications for an aeroplane does not make any man a skilled mechanic. It is well to understand at the start that a certain degree of mechanical ability is required in building a machine which will be entirely safe. Nor does the possession of a successful machine make one an aeronaut. As in the case of bicycling, there is no substitute for actual experience, while in the airship the art of balancing is of even greater importance than on the bicycle.
The would-be aviator is therefore advised to put himself through a course of training of mind and body.
Intelligent experimenting with some one of the models described in Chapter XI. will teach much of the action of aeroplanes in calms and when winds are blowing; and practice with an easily constructed glider (see [Chapter XII].) will give experience in balancing which will be of the greatest value when one launches into the air for the first time with a power-driven machine. An expert acquaintance with gasoline motors and magnetos is a prime necessity. In short, every bit of information on the subject of flying machines and their operation cannot fail to be useful in some degree.
The dimensions of the various parts of the Santos-Dumont monoplane are given on the original plans according to the metric system. In reducing these to “long measure” inches, all measurements have been given to the nearest eighth of an inch.
In general, we may note some of the peculiarities of La Demoiselle. The spread of the plane is 18 feet from tip to tip, and it is 20 feet over all from bow to stern. In height, it is about 4 feet 2 inches when the propeller blades are in a horizontal position. The total weight of the machine is 265 lbs., of which the engine weighs about 66 lbs. The area of the plane is 115 square feet, so that the total weight supported by each square foot with Santos-Dumont (weighing 110 lbs.) on board is a trifle over 3 lbs.
The frame of the body of the monoplane is largely of bamboo, the three main poles being 2 inches in diameter at the front, and tapering to about 1 inch at the rear. They are jointed with brass sockets just back of the plane, for convenience of taking apart for transportation. Two of these poles extend from the axle of the wheels backward and slightly upward to the rudder-post. The third extends from the middle of the plane between the wings, backward and downward to the rudder-post. In cross-section the three form a triangle with the apex at the top. These bamboo poles are braced about every 2 feet with struts of steel tubing of oval section, and the panels so formed are tied by diagonals of piano wire fitted with turn-buckles to draw them taut.
Side view of the Santos-Dumont monoplane. MP, main plane with radiator, R, hung underneath; RP, rudder plane worked by wires HC, attached to lever L; VC, vertical control wires; WT, tube through which run the warping wires worked by lever K, in a pocket of the pilot’s coat; B, B, bamboo poles of frame; S, S, brass, or aluminum sockets; D, D, struts of bicycle tubing; G, gasoline; RG, reserve gasoline; M, motor; P, propeller; Q, Q, outer rib of plane, showing camber; N, skid.
In the Santos-Dumont machine a 2-cylinder, opposed Darracq motor of 30 horse-power was used. It is of the water-cooled type, the cooling radiator being a gridiron of very thin ⅛-inch copper tubing, and hung up on the under side of the plane on either side of the engine. The cylinders have a bore of about 4⅛ inches, and a stroke of about 4¾ inches. The propeller is 2-bladed, 6½ feet across, and is run at 1,400 revolutions per minute, at which speed it exerts a pull of 242 lbs.
Each wing of the main plane is built upon 2 transverse spars extending outward from the upper bamboo pole, starting at a slight angle upward and bending downward nearly to the horizontal as they approach the outer extremities. These spars are of ash, 2 inches wide, and tapering in thickness from 1⅛ inches at the central bamboo to about ⅞ inch at the tips of the wings. They are bent into shape by immersion in hot water, and straining them around blocks nailed to the floor of the workshop, in the form shown at QQ, p. 177.
Front view of the Santos-Dumont monoplane, showing position of tubular struts supporting the engine and the wings; also the guys, and warping wires entering the tubes inside the wheels. MP, the main plane; TP, tail plane in the rear; R, radiators; M, motor; P, propeller, the arrow showing direction of revolution.
The front spar is set about 9 inches back from the front edge of the plane, and the rear one about 12 inches forward of the back edge of the plane. Across these spars, and beneath them, running fore and aft, are bamboo rods about ¾ of an inch in diameter at the forward end, and tapering toward the rear. They are set 8½ inches apart (centre to centre), except at the tips of the wings. The two outer panels are 10¼ inches from centre to centre of the rods, to give greater elasticity in warping. These fore-and-aft rods are 6 feet 5 inches long, except directly back of the propeller, where they are 5 feet 8 inches long; they are bound to the spars with brass wire No. 25, at the intersections. They also are bent to a curved form, as shown in the plans, by the aid of the hot-water bath. Diagonal guys of piano wire are used to truss the frame in two panels in each wing.
Around the outer free ends of the rods runs a piano wire No. 20, which is let into the tips of the rods in a slot ⅜ inch deep. To prevent the splitting of the bamboo, a turn or two of the brass wire may be made around the rod just back of the slot; but it is much better to provide thin brass caps for the ends of the rods, and to cut the slots in the metal as well as in the rods. Instead of caps, ferrules will do. When the slots are cut, let the tongue formed in the cutting be bent down across the bamboo to form the floor to the slot, upon which the piano wire may rest. The difference in weight and cost is very little, and the damage that may result from a split rod may be serious.
Plan and details of construction of La Demoiselle.
After the frame of the plane is completed it is to be covered with cloth on both sides, so as entirely to enclose the frame, except only the tips of the rods, as shown in the plans. In the Santos-Dumont monoplane the cloth used is of closely woven silk, but a strong, unbleached muslin will do—the kind made especially for aeroplanes is best.
Both upper and lower surfaces must be stretched taut, the edges front and back being turned over the piano wire, and the wire hemmed in. The upper and lower surfaces are then sewed together—“through and through,” as a seamstress would say—along both sides of each rod, so that the rods are practically in “pockets.” Nothing must be slighted, if safety in flying is to be assured.
Sectional diagram of 2-cylinder Darracq opposed motor.
Diagram of 4-cylinder Darracq opposed motor.
Diagram of 3-cylinder Anzani motor.
Motors suitable for La Demoiselle monoplane.
The tail of the monoplane is a rigid combination of two planes intersecting each other at right angles along a central bamboo pole which extends back 3 feet 5½ inches from the rudder-post, to which it is attached by a double joint, permitting it to move upon either the vertical or the horizontal axis.
Although this tail, or rudder, may seem at first glance somewhat complicated in the plans, it will not be found so if the frame of the upright or vertical plane be first constructed, and that of the level or horizontal plane afterward built fast to it at right angles.
As with the main plane, the tail is to be covered on both sides with cloth, the vertical part first; the horizontal halves on either side so covered that the cloth of the latter may be sewed above and below the central pole. All of the ribs in the tail are to be stitched in with “pockets,” as directed for the rods of the main plane.
The construction of the motor is possible to an expert machinist only, and the aeroplane builder will save time and money by buying his engine from a reliable maker. It is not necessary to send to France for a Darracq motor. Any good gasoline engine of equal power, and about the same weight, will serve the purpose.
The making of the propeller is practicable for a careful workman. The illustrations will give a better idea than words of how it should be done. It should be remembered, however, that the safety of the aviator depends as much upon the propeller as upon any other part of the machine. The splitting of the blades when in motion has been the cause of serious accidents. The utmost care, therefore, should be exercised in the selection of the wood, and in the glueing of the several sections into one solid mass, allowing the work to dry thoroughly under heavy pressure.
Diagram showing how the layers of wood are placed for glueing: A, at the hub; B, half way to the tip of the blade; C, at the tip. The dotted lines show the form of the blade at these points.
The forming of the blades requires a good deal of skill, and some careful preliminary study. It is apparent that the speed of a point at the tip of a revolving blade is much greater than that of a point near the hub, for it traverses a larger circle in the same period of time. But if the propeller is to do effective work without unequal strain, the twist in the blade must be such that each point in the length of the blade is exerting an equal pull on the air. It is necessary, therefore, that the slower-moving part of the blade, near the hub, or axis, shall cut “deeper” into the air than the more swiftly moving tip of the blade. Consequently the blade becomes continually “flatter” (approaching the plane in which it revolves) as we work from the hub outward toward the tip. This “flattening” is well shown in the nearly finished blade clamped to the bench at the right of the illustration—which shows a four-bladed propeller, instead of the two-bladed type needed for the monoplane.
The propeller used for propulsion in air differs from the propeller-wheel used for ships in water, in that the blades are curved laterally; the forward face of the blade being convex, and the rearward face concave. The object of this shaping is the same as for curving the surface of the plane—to secure smoother entry into the air forward, and a compression in the rear which adds to the holding power on the substance of the air. It is extremely difficult to describe this complex shape, and the amateur builder of a propeller will do well to inspect one made by a professional, or to buy it ready made with his engine.
Forming a 4-blade propeller out of 8 layers of wood glued firmly together.
The following quotation from Sir Hiram Maxim’s account of his most effective propeller may aid the ambitious aeroplane builder: “My large screws were made with a great degree of accuracy; they were perfectly smooth and even on both sides, the blades being thin and held in position by a strip of rigid wood on the back of the blade.... Like the small screws, they were made of the very best kind of seasoned American white pine, and when finished were varnished on both sides with hot glue. When this was thoroughly dry, they were sand-papered again, and made perfectly smooth and even. The blades were then covered with strong Irish linen fabric of the smoothest and best make. Glue was used for attaching the fabric, and when dry another coat of glue was applied, the surface rubbed down again, and then painted with zinc white in the ordinary way and varnished. These screws worked exceedingly well.”
The covering of the blades with linen glued fast commends itself to the careful workman as affording precaution against the splintering of the blades when in rapid motion. Some propellers have their wooden blades encased with thin sheet aluminum to accomplish the same purpose, but for the amateur builder linen is far easier to apply.
| This method of mounting the wheels of the chassis has been found the most satisfactory. The spring takes up the shock of a sudden landing and the pivot working in the hollow post allows the entire mounting to swing like a caster, and adapt itself to any direction at which the machine may strike the ground. |
This method of mounting the wheels of the chassis has been found the most satisfactory. The spring takes up the shock of a sudden landing and the pivot working in the hollow post allows the entire mounting to swing like a caster, and adapt itself to any direction at which the machine may strike the ground.
The wheels are of the bicycle type, with wire spokes, but with hubs six inches long. The axle is bent to incline upward at the ends, so that the wheels incline outward at the ground, the better to take the shock of a sideways thrust when landing. The usual metal or wood rims may be used, but special tires of exceptionally light construction, made for aeroplanes, should be purchased.
The controlling wires or cords for moving the rudder (or tail) and for warping the tips of the wings are of flexible wire cable, such as is made for use as steering rope on small boats. The cable controlling the horizontal plane of the rudder-tail is fastened to a lever at the right hand of the operator. The cable governing the vertical plane of the rudder-tail is attached to a wheel at the left hand of the operator. The cables which warp the tips of the wings are fastened to a lever which projects upward just back of the operator’s seat, and which is slipped into a long pocket sewed to the back of his coat, so that the swaying of his body in response to the fling of the tipping machine tends to restore it to an even keel. Springs are attached to all of these controlling wires, strong enough to bring them back to a normal position when the operator removes his hands from the steering apparatus.
The brass sockets used in connecting the tubular struts to the main bamboos and the rudder-post, and in fastening the axle of the wheels to the lower bamboos and elsewhere, should be thoroughly made and brazed by a good mechanic, for no one should risk the chance of a faulty joint at a critical spot, when an accident may mean the loss of life.
Diagram of Bleriot monoplane showing sizes of parts, in metres. Reduced to feet and inches these measurements are:
| 0.60 metres | 1 ft. | 11½ in. |
| 1.50 metres | 4 ft. | 11 in. |
| 2.10 metres | 6 ft. | 10½ in. |
| 3.50 metres | 11 ft. | 6 in. |
| 8.00 metres | 26 ft. | 3 in. |
| 8.60 metres | 28 ft. | 2½ in. |
The diagram being drawn to scale other dimensions may be found. In both the plan (upper figure) and elevation (lower figure), A, A, is the main plane; B, tail plane; C, body; D, elevator wing-tips; E, rudder; a, a, rigid spar; b, b, flexible spar; r, r, points of attachment for warping-wires; h, h, guys; H, propeller; M, motor; R, radiator; S, pilot’s seat; P, chassis.
For the rest, it has seemed better to put the details of construction on the plans themselves, where they will be available to the aeroplane builder without the trouble of continually consulting the text.
Some of the work on an aeroplane will be found simple and easy; some of it, difficult and requiring much patience; and some impracticable to any one but a trained mechanic. But in all of it, the worker’s motto should be, “Fidelity in every detail.”
Chapter X.
FLYING MACHINES: MOTORS.
Early use of steam—Reliability necessary—The gasoline motor—Carburetion—Compression—Ignition—Air-cooling—Water-cooling—Lubrication—The magneto—Weight—Types of motors—The propeller—Form, size, and pitch—Slip—Materials—Construction.
The possibility of the existence of the flying machine as we have it to-day has been ascribed to the invention of the gasoline motor. While this is not to be denied, it is also true that the gasoline motors designed and built for automobiles and motor-boats have had to be wellnigh revolutionized to make them suitable for use in the various forms of aircraft. And it is to be remembered, doubtless to their greater credit, that Henson, Hargrave, Langley, and Maxim had all succeeded in adapting steam to the problem of the flight of models, the two latter using gasoline to produce the steam.
Perhaps the one predominant qualification demanded of the aeroplane motor is reliability. A motor-car or motor-boat can be stopped, and engine troubles attended to with comparatively little inconvenience. The aeroplane simply cannot stop without peril. It is possible for a skilful pilot to reach the earth when his engine stops, if he is fortunately high enough to have space for the downward glide which will gain for him the necessary headway for steering. At a lesser height he is sure to crash to the earth.
An understanding of the principles on which the gasoline motor works is essential to a fair estimate of the comparative advantages of the different types used to propel aeroplanes. In the first place, the radical difference between the gasoline motor and other engines is the method of using the fuel. It is not burned in ordinary fashion, but the gasoline is first vaporized and mixed with a certain proportion of air, in a contrivance called a carburetor. This gaseous mixture is pumped into the cylinder of the motor by the action of the motor itself, compressed into about one-tenth of its normal volume, and then exploded by a strong electric spark at just the right moment to have its force act most advantageously to drive the machinery onward.
The “Fiat” 8-cylinder air-cooled motor, of the “V” type, made in France.
It is apparent that there are several chances for failure in this series. The carburetor may not do its part accurately. The mixture of air and vapor may not be in such proportions that it will explode; in that case, the power from that stroke will be missing, and the engine will falter and slow down. Or a leakage in the cylinder may prevent the proper compression of the mixture, the force from the explosion will be greatly reduced, with a corresponding loss of power and speed. Or the electric spark may not be “fat” enough—that is, of sufficient volume and heat to fire the mixture; or it may not “spark” at just the right moment; if too soon, it will exert its force against the onward motion: if too late, it will not deliver the full power of the explosion at the time when its force is most useful. The necessity for absolute perfection in these operations is obvious.
A near view of the Holmes engine from the driving side.
The Holmes rotative engine, 7-cylinder 35 horse-power, weighing 160 pounds.
An American engine built in Chicago, Ill.
Other peculiarities of the gasoline motor affect considerably its use for aeroplanes. The continual and oft-repeated explosions of the gaseous mixture inside of the cylinder generate great heat, and this not only interferes with its regularity of movement, but within a very brief time checks it altogether. To keep the cylinder cool enough to be serviceable, two methods are in use: the air-cooling system and the water-cooling system. In the first, flanges of very thin metal are cast on the outside of the cylinder wall. These flanges take up the intense heat, and being spread out over a large surface in this way, the rushing of the air through them as the machine flies (or sometimes blown through them with a rotary fan) cools them to some degree. With the water-cooling system, the cylinder has an external jacket, the space between being filled with water which is made to circulate constantly by a small pump. In its course the water which has just taken up the heat from the cylinder travels through a radiator in which it is spread out very thin, and this radiator is so placed in the machine that it receives the full draught from the air rushing through the machine as it flies. The amount of water required for cooling a motor is about 1⅕ lbs. per horse-power. With an 8-cylinder 50 horse-power motor, this water would add the very considerable item of 60 lbs. to the weight the machine has to carry. As noted in a previous chapter, the McCurdy biplane has its radiator formed into a sustaining plane, and supports its own weight when travelling in the air.
The 180 horse-power engine of Sir Hiram Maxim; of the “opposed” type, compound, and driven by steam.
The Anzani motor and propeller which carried M. Bleriot across the English Channel. The curved edge of the propeller blades is the entering edge, the propeller turning from the right of the picture over to the left. The Anzani is of the “radiant” type and is of French build.
It is an unsettled point with manufacturers whether the greater efficiency (generally acknowledged) of the water-cooled engine more than compensates for the extra weight of the water.
Another feature peculiar to the gasoline motor is the necessity for such continual oiling that it is styled “lubrication,” and various devices have been invented to do the work automatically, without attention from the pilot further than the watching of his oil-gauge to see that a full flow of oil is being pumped through the oiling system.
The electric current which produces the spark inside of the cylinder is supplied by a magneto, a machine formed of permanent magnets of horseshoe form, between the poles of which a magnetized armature is made to revolve rapidly by the machinery which turns the propeller. This magneto is often connected with a small storage battery, or accumulator, which stores up a certain amount of current for use when starting, or in case the magneto gives out.
Sectional drawings showing details of construction of the Anzani motor. The flanges of the air-cooling system are distinctly shown. The section at the left is from the side; that at the right, from the front. All measurements are in millimètres. A millimètre is 0.039 inch.
The great rivalry of the builders of motors has been in cutting down the weight per horse-power to the lowest possible figure. It goes without saying that useless weight is a disadvantage in an aeroplane, but it has not been proven that the very lightest engines have made a better showing than those of sturdier build.
The “Gobron” engine of the “double opposed,” or cross-shaped type. A water-cooled engine, with 8 cylinders.
One of the items in the weight of an engine has been the fly-wheel found necessary on all motors of 4 cylinders or less to give steadiness to the running. With a larger number of cylinders, and a consequently larger number of impulses in the circuit of the propeller, the vibration is so reduced that the fly-wheel has been dispensed with.
The Emerson 6-cylinder aviation engine, of the “tandem” type, water-cooled; 60 horse-power; made at Alexandria, Va.
There are several distinct types of aircraft engines, based on the arrangement of the cylinders. The “tandem” type has the cylinders standing upright in a row, one behind another. There may be as many as eight in a row. The Curtiss and Wright engines are examples. Another type is the “opposed” arrangement, the cylinders being placed in a horizontal position and in two sets, one working opposite the other. An example of this type is seen in the Darracq motor used on the Santos-Dumont monoplane. Another type is the “V” arrangement, the cylinders set alternately leaning to right and to left, as seen in the “Fiat” engine. Still another type is the “radiant,” in which the cylinders are all above the horizontal, and disposed like rays from the rising sun. The 3-cylinder Anzani engine and the 5- and 7-cylinder R-E-P engines are examples. The “star” type is exemplified in the 5 and 7-cylinder engines in which the cylinders radiate at equal angles all around the circle. The “double opposed” or cross-shaped type is shown in the “Gobron” engine. In all of these types the cylinders are stationary, and turn the propeller shaft either by cranks or by gearing.
The Elbridge engine, of the “tandem” type and water-cooled. It is an American engine, built at Rochester, N. Y.
An entirely distinct type of engine, and one which has been devised solely for the aeroplane, is the rotative—often miscalled the rotary, which is totally different. The rotative type may be illustrated by the Gnome motor. In this engine the seven cylinders turn around the shaft, which is stationary. The propeller is fastened to the cylinders, and revolves with them. This ingenious effect is produced by an offset of the crank-shaft of half the stroke of the pistons, whose rods are all connected with the crank-shaft. The entire system revolves around the main shaft as a centre, the crank-shaft being also stationary.
The famous Gnome motor; 50 horse-power, 7-cylinder, air-cooled; of the rotative type; made in France. This illustration shows the Gnome steel propeller.
Sectional diagram of the 5-cylinder R-E-P motor; of the “radiant” type.
Sectional diagram of the 5-cylinder Bayard-Clement motor; of the “star” type.
Strictly speaking, the propeller is not a part of the motor of the flying machine, but it is so intimately connected with it in the utilization of the power created by the motor, that it will be treated of briefly in this chapter.
The form of the air-propeller has passed through a long and varied development, starting with that of the marine propeller, which was found to be very inefficient in so loose a medium as air. On account of this lack of density in the air, it was found necessary to act on large masses of it at practically the same time to gain the thrust needed to propel the aeroplane swiftly, and this led to increasing the diameter of the propeller to secure action on a proportionally larger area of air. The principle involved is simply the geometric rule that the areas of circles are to each other as the squares of their radii. Thus the surface of air acted on by two propellers, one of 6 feet diameter and the other of 8 feet diameter, would be in the proportion of 9 to 16; and as the central part of a propeller has practically no thrust effect, the efficiency of the 8-foot propeller is nearly twice that of the 6-foot propeller—other factors being equal. But these other factors may be made to vary widely. For instance, the number of revolutions may be increased for the smaller propeller, thus engaging more air than the larger one at a lower speed; and, in practice, it is possible to run a small propeller at a speed that would not be safe for a large one. Another factor is the pitch of the propeller, which may be described as the distance the hub of the propeller would advance in one complete revolution if the blades moved in an unyielding medium, as a section of the thread of an ordinary bolt moves in its nut. In the yielding mass of the air the propeller advances only a part of its pitch, in some cases not more than half. The difference between the theoretical advance and the actual advance is called the “slip.”
The Call Aviation Engine, of the opposed type; water-cooled. The cylinders are large and few in number. The 100 horse-power engine has but 4 cylinders, and weighs only 250 pounds. (The Gnome 100 horse-power engine has 14 cylinders.) This is an American engine, built at Girard, Kansas.
In practical work the number of blades which have been found to be most effective is two. More blades than two seem to so disturb the air that there is no hold for the propeller. In the case of slowly revolving propellers, as in most airship mechanisms, four-bladed propellers are used with good effect. But where the diameter of the propeller is about 8 feet, and the number of revolutions about 1,200 per minute, the two-bladed type is used almost exclusively.
The many differing forms of the blades of the propeller is evidence that the manufacturers have not decided upon any definite shape as being the best. Some have straight edges nearly or quite parallel; others have the entering edge straight and the rear edge curved; in others the entering edge is curved, and the rear edge straight; or both edges may be curved. The majority of the wooden propellers are of the third-mentioned type, and the curve is fashioned so that at each section of its length the blade presents the same area of surface in the same time. Hence the outer tip, travelling the fastest, is narrower than the middle of the blade, and it is also much thinner to lessen the centrifugal force acting upon it at great speeds. Near the hub, however, where the travel is slowest, the constructional problem demands that the blade contract in width and be made stout. In fact, it becomes almost round in section.
Many propellers are made of metal, with tubular shanks and blades of sheet metal, the latter either solid sheets or formed with a double surface and hollow inside. Still others have a frame of metal with blades of fabric put on loosely, so that it may adapt itself to the pressure of the air in revolving. That great strength is requisite becomes plain when it is considered that the speed of the tip of a propeller blade often reaches seven miles a minute! And at this velocity the centrifugal force excited—tending to tear the blades to splinters—is prodigious.
Just as the curved surface of the planes of an aeroplane is more effective than a flat surface in compressing the air beneath them, and thus securing a firmer medium on which to glide, so the propeller blades are curved laterally (across their width) to compress the air behind them and thus secure a better hold. The advancing side of the blade is formed with a still greater curve, to gain the advantage due to the unexplained lift of the paradox aeroplane.
Where the propeller is built of wood it is made of several layers, usually of different kinds of wood, with the grain running in slightly different directions, and all carefully glued together into a solid block. Ash, spruce, and mahogany, in alternating layers, are a favorite combination. In some instances the wooden propeller is sheathed in sheet aluminum; in others, it is well coated with glue which is sandpapered down very smooth, then varnished, and then polished to the highest lustre—to reduce the effect of the viscosity of the air to the minimum.
Two propellers, the one on the left of left-hand pitch; the other of right-hand pitch. Both are thrusting propellers, and are viewed from the rear. These fine models are of the laminated type, and are of American make; the one to the left a Paragon propeller made in Washington, D. C.; the other a Brauner propeller made in New York.
In order to get the best results, the propeller and the motor must be suited to each other. Some motors which “race” with a propeller which is slightly too small, work admirably with one a little heavier, or with a longer diameter.
The question as to whether one propeller, or two, is the better practice, has not been decided. The majority of aeroplanes have but one. The Wright and the Cody machines have two. The certainty of serious consequences to a machine having two, should one of them be disabled, or even broken so as to reduce the area, seems to favor the use of but one.
Chapter XI.
MODEL FLYING MACHINES.
Awakened popular interest—The workshop’s share—Needed devices—Super-sensitive inventions—Unsolved problems—Tools and materials—A model biplane—The propeller—The body—The steering plane—The main planes—Assembling the parts—The motive power—Flying the model—A monoplane model—Carving a propeller—Many ideas illustrated—Clubs and competitions—Some remarkable records.
It is related of Benjamin Franklin that when he went out with his famous kite with the wire string, trying to collect electricity from the thundercloud, he took a boy along to forestall the ridicule that he knew would be meted out to him if he openly flew the kite himself.
Other scientific experimenters, notably those working upon the problem of human flight in our own time, have encountered a similar condition of the public mind, and have chosen to conduct their trials in secret rather than to contend with the derision, criticism, and loss of reputation which a sceptical world would have been quick to heap upon them.
But such a complete revolution of thought has been experienced in these latter days that groups of notable scientific men gravely flying kites, or experimenting with carefully made models of flying machines, arouse only the deepest interest, and their smallest discoveries are eagerly seized upon by the daily press as news of the first importance.
So much remains to be learned in the field of aeronautics that no builder and flyer of the little model aeroplanes can fail to gain valuable information, if that is his intention. On the other hand, if it be the sport of racing these model aeroplanes which appeals to him, the instruction given in the pages following will be equally useful.
The earnest student of aviation is reminded that the progressive work in this new art of flying is not being done altogether, nor even in large part, by the daring operators who, with superb courage, are performing such remarkable feats with the flying machines of the present moment. Not one of them would claim that his machine is all that could be desired. On the contrary, these intrepid men more than any others are fully aware of the many and serious defects of the apparatus they use for lack of better. The scientific student in his workshop, patiently experimenting with his models, and working to prove or disprove untested theories, is doubtless doing an invaluable part in bringing about the sort of flying which will be more truly profitable to humanity in general, though less spectacular.
A model flying machine built and flown by Louis Paulhan, the noted aviator, at a prize contest for models in France. The design is after Langley’s model, with tandem monoplane surfaces placed at a dihedral angle.
One of the greatest needs of the present machines is an automatic balancer which shall supersede the concentrated attention which the operator is now compelled to exercise in order to keep his machine right side up. The discovery of the principle upon which such a balancer must be built is undoubtedly within the reach of the builder and flyer of models. It has been asserted by an eminent scientific experimenter in things aeronautic that “we cannot hope to make a sensitive apparatus quick enough to take advantage of the rising currents of the air,” etc. With due respect to the publicly expressed opinion of this investigator, it is well to reassure ourselves against so pessimistic an outlook by remembering that the construction of just such supersensitive apparatus is a task to which man has frequently applied his intellectual powers with signal success. Witness the photomicroscope, which records faithfully an enlarged view of objects too minute to be even visible to the human eye; the aneroid barometer, so sensitive that it will indicate the difference in level between the table and the floor; the thermostat, which regulates the temperature of the water flowing in the domestic heating system with a delicacy impossible to the most highly constituted human organism; the seismograph, detecting, recording, and almost locating earth tremors originating thousands of miles away; the automatic fire sprinkler; the safety-valve; the recording thermometer and other meteorological instruments; and last, if not of least importance, the common alarm-clock. And these are but a few of the contrivances with which man does by blind mechanism that which is impossible to his sentient determination.
Even if the nervous system could be schooled into endurance of the wear and tear of consciously balancing an aeroplane for many hours, it is still imperative that the task be not left to the exertion of human wits, but controlled by self-acting devices responding instantly to unforeseen conditions as they occur.
Diagram showing turbulent air currents produced when a flat plane is forced through the air at a large angle of incidence in the direction A-B.
Diagram showing smoothly flowing air currents caused by correctly shaped plane at proper angle of incidence.
Some of the problems of which the model-builder may find the solution are: whether large screws revolving slowly, or small screws revolving rapidly, are the more effective; how many blades a propeller should have, and their most effective shape; what is the “perfect” material for the planes (Maxim found that with a smooth wooden plane he could lift 2½ times the weight that could be lifted with the best made fabric-covered plane); whether the centre of gravity of the aeroplane should be above or below the centre of lift, or should coincide with it; new formulas for the correct expression of the lift in terms of the velocity, and angle of inclination—the former formulas having been proved erroneous by actual experience; how to take the best advantage of the “tangential force” announced by Lilienthal, and reasserted by Hargrave; and many others. And there is always the “paradox aeroplane” to be explained—and when explained it will be no longer a paradox, but will doubtless open the way to the most surprising advance in the art of flying.
It is not assumed that every reader of this chapter will become a studious experimenter, but it is unquestionably true that every model-builder, in his effort to produce winning machines, will be more than likely to discover some fact of value in the progress making toward the ultimate establishment of the commercial navigation of the air.
The tools and materials requisite for the building of model aeroplanes are few and inexpensive. For the tools—a small hammer; a small iron “block” plane; a fine-cut half-round file; a pair of round-nose pliers; three twist drills (as used for drilling metals), the largest 1/16 inch diameter, and two smaller sizes, with an adjustable brad-awl handle to hold them; a sharp pocket knife; and, if practicable, a small hand vise. The vise may be dispensed with, and common brad-awls may take the place of the drills, if necessary.
For the first-described model—the simplest—the following materials are needed: some thin whitewood, 1/16 inch thick (as prepared for fret-sawing); some spruce sticks, ¼ inch square (sky-rocket sticks are good); a sheet of heavy glazed paper; a bottle of liquid glue; some of the smallest (in diameter) brass screws, ¼ to ½ inch long; some brass wire, 1/20 inch in diameter; 100 inches of square rubber (elastic) “cord,” such as is used on return-balls, but 1/16 inch square; and a few strips of draughtsman’s tracing cloth.
A, B, blank from which propeller is shaped; P, P, pencil lines at centre of bend; C, D, sections of blade at points opposite; E, G, propeller after twisting; H, view of propeller endwise, showing outward twist of tips; also shaft.
As the propeller is the most difficult part to make, it is best to begin with it. The flat blank is cut out of the whitewood, and subjected to the action of steam issuing from the spout of an actively boiling tea-kettle. The steam must be hot; mere vapor will not do the work. When the strip has become pliable, the shaping is done by slowly bending and twisting at the same time—perhaps “coaxing” would be the better word, for it must be done gently and with patience—and the steam must be playing on the wood all the time, first on one side of the strip, then on the other, at the point where the fibres are being bent. The utmost care should be taken to have the two blades bent exactly alike—although, of course, with a contrary twist, the one to the right and the other to the left, on each side of the centre. A lead-pencil line across each blade at exactly the same distance from the centre will serve to fix accurately the centre of the bend. If two blocks are made with slots cut at the angle of 1 inch rise to 2¼ inches base, and nailed to the top of the work bench just far enough apart to allow the tips of the screw to be slid into the slots, the drying in perfect shape will be facilitated. The centre may be held to a true upright by two other blocks, one on each side of the centre. Some strips of whitewood may be so rigid that the steam will not make them sufficiently supple. In this case it may be necessary to dip them bodily into the boiling water, or even to leave them immersed for a few minutes; afterward bending them in the hot steam. But a wetted stick requires longer to dry and set in the screw shape. When the propeller is thoroughly dry and set in proper form, it should be worked into the finished shape with the half-round file, according to the several sections shown beside the elevation for each part of the blade. The two strengthening piece’s are then to be glued on at the centre of the screw, and when thoroughly dry, worked down smoothly to shape. When all is dry and hard it should be smoothed with the finest emery cloth and given a coat of shellac varnish, which, in turn, may be rubbed to a polish with rotten stone and oil.
It may be remarked, in passing, that this is a crude method of making a propeller, and the result cannot be very good. It is given here because it is the easiest way, and the propeller will work. A much better way is described further on—and the better the propeller, the better any model will fly. But for a novice, no time will be lost in making this one, for the experience gained will enable the model-builder to do better work with the second one than he could do without it.
For the aeroplane body we get out a straight spar of spruce, ¼ inch square and 15½ inches long. At the front end of this—on the upper side—is to be glued a small triangular piece of wood to serve as a support for the forward or steering plane, tilting it up at the front edge at the angle represented by a rise of 1 in 8. This block should be shaped on its upper side to fit the curve of the under side of the steering-plane, which will be screwed to it.
The steering-plane is cut according to plan, out of 1/16 inch whitewood, planed down gradually to be at the ends about half that thickness. This plane is to be steamed and bent to a curve (fore and aft) as shown in the sectional view. The steam should play on the convex side of the bend while it is being shaped. To hold it in proper form until it is set, blocks with curved slots may be used, or it may be bound with thread to a moulding block of equal length formed to the proper curve. When thoroughly dry it is to be smoothed with the emery cloth, and a strip of tracing cloth—glossy face out—is to be glued across each end, to prevent breaking in case of a fall. It is then to be varnished with shellac, and polished, as directed for the propeller. Indeed, it should be said once for all that every part of the model should be as glossy as it is possible to make it without adding to the weight, and that all “entering edges” (those which push into and divide the air when in flight) should be as sharp as is practicable with the material used.
The steering-plane is to be fastened in place by a single screw long enough to pierce the plane and the supporting block, and enter the spar. The hole for this screw (as for all screws used) should be drilled carefully, to avoid the least splitting of the wood, and just large enough to have the screw “bite” without forcing its way in. This screw which holds the plane is to be screwed “home” but not too tight, so that in case the flying model should strike upon it in falling, the slender plane will swivel, and not break. It will be noticed that while this screw passes through the centre of the plane sideways, it is nearer to the forward edge than to the rear edge.
If the work has been accurate, the plane will balance if the spar is supported—upon the finger, perhaps, as that is sensitive to any tendency to tipping. If either wing is too heavy, restore the balance by filing a little from the tip of that wing.
The main planes are next to be made. The lower deck of the biplane is of the 1/16 inch whitewood, and the upper one is of the glazed paper upon a skeleton framework of wood. The upright walls are of paper. The wooden deck is to be bent into the proper curve with the aid of steam, and when dry and set in form is to be finished and polished. The frame for the upper deck is made of the thin whitewood, and is held to its position by two diagonal struts of whitewood bent at the ends with steam, and two straight upright struts or posts. It is better to bend all cross-pieces into the curve of the plane with steam, but they may be worked into the curve on the top side with plane and file, and left flat on the lower side. The drawings show full details of the construction, drawn accurately to scale.
It is best to glue all joints, and in addition to insert tiny screws, where shown in the plans, at the time of gluing.
When all the wooden parts are in place the entire outline of the upper plane and the upright walls is to be formed of silk thread carried from point to point, and tied upon very small pins (such as are used in rolls of ribbon at the stores) inserted in the wood. The glazed paper is put on double, glossy side out. Cut the pieces twice as large (and a trifle more) than is needed, and fold so that the smooth crease comes to the front and the cut edges come together at the rear. The two inner walls should be put in place first, so as to enclose the thread front and back, and the post, between the two leaves of the folded paper. Cutting the paper half an inch too long will give one fourth of an inch to turn flat top and bottom to fasten to the upper and lower decks respectively. The two outer walls and the upper deck may be cut all in one piece, the under leaf being slit to pass on either side of the inner walls. A bit of glue here and there will steady the parts to their places. The cut edges at the rear of the deck and walls should be caught together with a thin film of glue, so as to enclose the rear threads.
A, B, plan, and C, section, of steering plane; H, section of lower main plane; L, wood skeleton of upper plane; T, T, silk thread; O, O, posts; J, J, braces; E, rubber strands; D, forward hook; G, shaft; F, thrust-block; K, upper plane of paper; M, elevation of main planes, from the rear.
When the biplane is completed it is to be fastened securely to the spar in such a position that it is accurately balanced—from side to side. The spar may be laid on a table, and the biplane placed across it in its approximate position. Then move the plane to one side until it tips down, and mark the spot on the rear edge of the plane. Repeat this operation toward the other side, and the centre between the two marks should be accurately fastened over the centre line of the spar. Even with the greatest care there may still be failure to balance exactly, but a little work with a file on the heavy side, or a bit of chewing gum stuck on the lighter side, will remedy the matter.
The body of the aeroplane being now built, it is in order to fit it with propelling mechanism. The motive power to whirl the propeller we have already prepared is to be the torsion, or twisting strain—in this case the force of untwisting—of india rubber. When several strands of pure rubber cord are twisted up tight, their elasticity tends to untwist them with considerable force. The attachment for the rubber strands at the front end of the spar is a sort of bracket made of the brass wire. The ends of the wire are turned up just a little, and they are set into little holes in the under side of the spar. Where the wire turns downward to form the hook it is bound tightly to the spar with silk thread. The hook-shaped tip is formed of the loop of the wire doubled upon itself. The rear attachment of the rubber strands is a loop upon the propeller shaft itself. As shown in the drawings, this shaft is but a piece of the brass wire. On one end (the rear) an open loop is formed, and into this is slipped the centre of the propeller. The short end of the loop is then twisted around the longer shank—very carefully, lest the wire cut into and destroy the propeller. Two turns of the wire is enough, and then the tip of the twisted end should be worked down flat with the file, to serve as a bearing for the propeller against the thrust-block. This latter is made of a piece of sheet brass (a bit of printers’ brass “rule” is just the thing) about 1/40 of an inch thick. It should be ¼ of an inch wide except at the forward end, where it is to be filed to a long point and bent up a trifle to enter the wood of the spar. The rear end is bent down (not too sharply, lest it break) to form the bearing for the propeller, a hole being drilled through it for the propeller shaft, just large enough for the shaft to turn freely in it. Another smaller hole is to be drilled for a little screw to enter the rear end of the spar. Next pass the straight end of the propeller shaft through the hole drilled for it, and with the pliers form a round hook for the rear attachment of the rubber strands. Screw the brass bearing into place, and for additional strength, wind a binding of silk thread around it and the spar.
Tie the ends of the rubber cord together, divide it into ten even strands, and pass the loops over the two hooks—and the machine is ready for flight.
To wind up the rubber it will be necessary to turn the propeller in the opposite direction to which it will move when the model is flying. About 100 turns will be required. After it is wound, hold the machine by the rear end of the spar, letting the propeller press against the hand so it cannot unwind. Raise it slightly above the head, holding the spar level, or inclined upward a little (as experience may dictate), and launch the model by a gentle throw forward. If the work has been well done it may fly from 150 to 200 feet.
Many experiments may be made with this machine. If it flies too high, weight the front end of the spar; if too low, gliding downward from the start, weight the rear end. A bit of chewing gum may be enough to cause it to ride level and make a longer and prettier flight.
A very graceful model is that of the monoplane type illustrated in the accompanying reproductions from photographs. The front view shows the little machine just ready to take flight from a table. The view from the rear is a snap-shot taken while it was actually flying. This successful model was made by Harold S. Lynn, of Stamford, Conn. Before discussing the details of construction, let us notice some peculiar features shown by the photographs. The forward plane is arched; that is, the tips of the plane bend slightly downward from the centre. On the contrary, the two wings of the rear plane bend slightly upward from the centre, making a dihedral angle, as it is called; that is, an angle between two surfaces, as distinguished from an angle between two lines. The toy wheels, Mr. Lynn says, are put on principally for “looks” but they are also useful in permitting a start to be made from a table or even from the floor, instead of the usual way of holding the model in the hands and giving it a slight throw to get it started. However, the wheels add to the weight, and the model will not fly quite so far with them as without.
Front view of the Lynn model of the monoplane type, about to take flight.
The wood from which this model was made was taken from a bamboo fish-pole, such as may be bought anywhere for a dime. The pole was split up, and the suitable pieces whittled and planed down to the proper sizes, as given in the plans. In putting the framework of the planes together, it is well to notch very slightly each rib and spar where they cross. Touch the joint with a bit of liquid glue, and wind quickly with a few turns of sewing silk and tie tightly. This must be done with delicacy, or the frames will be out of true. If the work is done rapidly the glue will not set until all the ties on the plane are finished. Another way is to touch the joinings with a drop of glue, place the ribs in position on the spars, and lay a board carefully on the work, leaving it there until all is dry, when the tying can be done. It either case the joinings should be touched again with the liquid glue and allowed to dry hard.
The Lynn model monoplane in flight, from below and from the rear.
The best material for covering these frames is the thinnest of China silk. If this is too expensive, use the thinnest cambric. But the model will not fly so far with the cambric covering. The material is cut one-fourth of an inch too large on every side, and folded over, and the fold glued down. Care should be taken that the frame is square and true before the covering is glued on.
The motive power is produced by twisting up rubber tubing. Five and three-quarter feet of pure rubber tubing are required. It is tied together with silk so as to form a continuous ring. This is looped over two screw-hooks of brass, one in the rear block and the other constituting the shaft. This looped tubing is twisted by turning the propeller backward about two hundred turns. As it untwists it turns the propeller, which, in this model, is a “traction” screw, and pulls the machine after it as it advances through the air.
Details and plans of the Harold Lynn model monoplane. W, tail block; Y, thrust-block; S, mounting of propeller showing glass bead next the thrust-block, and one leather washer outside the screw; B, glass bead; C, tin washer; M, M, tin lugs holding axle of wheels.
The propeller in this instance is formed from a piece of very thin tin, such as is used for the tops of cans containing condensed milk. Reference to the many illustrations throughout this book showing propellers of flying machines will give one a very good idea of the proper way to bend the blades. The mounting with the glass bead and the two leather washers is shown in detail in the plans.
Method of forming propeller of the laminated, or layer, type. The layers of wood are glued,in the position shown and the blades carved out according to the sections. Only one blade is shown from the axle to the tip. This will make a right hand propeller.
The wheels are taken from a toy wagon, and a pair of tin ears will serve as bearings for the axle.
The sport of flying model aeroplanes has led to the formation of many clubs in this country as well as in Europe. Some of the mechanisms that have been devised, and some of the contrivances to make the models fly better and further, are illustrated in the drawings.
At A is shown a method of mounting the propeller with a glass or china bead to reduce friction, and a brass corner to aid in strengthening. B shows a transmission of power by two spur wheels and chain. C is a device for using two rubber twists acting on the two spur wheels S, S, which in turn are connected with the propeller with a chain drive. D shows a launching apparatus for starting. W, the model; V, the carriage; F, the trigger guard; T, trigger; E, elastic cord for throwing the carriage forward to the stop K.
Records have been made which seem marvellous when it is considered that 200 feet is a very good flight for a model propelled by rubber. For instance, at the contest of the Birmingham Aero Club (England) in September, one of the contestants won the prize with a flight of 447 feet, lasting 48 seconds. The next best records for duration of flight were 39 seconds and 38 seconds. A model aeroplane which is “guaranteed to fly 1,000 feet,” according to the advertisement in an English magazine, is offered for sale at $15.
The American record for length of flight is held by Mr. Frank Schober, of New York, with a distance of 215 feet 6 inches. His model was of the Langley type of tandem monoplane, and very highly finished. The problem is largely one of adequate power without serious increase of weight.
Chapter XII.
THE GLIDER.
Aerial balancing—Practice necessary—Simplicity of the glider Materials—Construction—Gliding—Feats with the Montgomery glider—Noted experimenters—Glider clubs.
It is a matter of record that the Wright brothers spent the better part of three years among the sand dunes of the North Carolina sea-coast practising with gliders. In this way they acquired that confidence while in the air which comes from intimate acquaintance with its peculiarities, and which cannot be gained in any other way. It is true that the Wrights were then developing not only themselves, but also their gliders; but the latter work was done once for all. To develop aviators, however, means the repeating of the same process for each individual—just as each for himself must be taught to read. And the glider is the “First Reader” in aeronautics.
The long trail of wrecks of costly aeroplanes marking the progress in the art of flying marks also the lack of preparatory training, which their owners either thought unnecessary, or hoped to escape by some royal road less wearisome than persistent personal practice. But they all paid dearly to discover that there is no royal road. Practice, more practice, and still more practice—that is the secret of successful aeroplane flight.
For this purpose the glider is much superior to the power-driven aeroplane. There are no controls to learn, no mechanism to manipulate. One simply launches into the air, and concentrates his efforts upon balancing himself and the apparatus; not as two distinct bodies, however, but as a united whole. When practice has made perfect the ability to balance the glider instinctively, nine-tenths of the art of flying an aeroplane has been achieved. Not only this, but a new sport has been laid under contribution; one beside which coasting upon a snow-clad hillside is a crude form of enjoyment.
Fortunately for the multitude, a glider is easily made, and its cost is even less than that of a bicycle. A modest degree of skill with a few carpenter’s tools, and a little “gumption” about odd jobs in general, is all that is required of the glider builder.
A gliding slope with starting platform, erected for club use.
The frame of the glider is of wood, and spruce is recommended, as it is stronger and tougher for its weight than other woods. It should be of straight grain and free from knots; and as there is considerable difference in the weight of spruce from different trees, it is well to go over the pile in the lumber yard and pick out the lightest boards. Have them planed down smooth on both sides, and to the required thickness, at the mill—it will save much toilsome hand work. The separate parts may also be sawed out at the mill, if one desires to avoid this labor.
The lumber needed is as follows:
| 4 | spars | 20 ft. long, | 1¼ in. wide, | ¾ in. thick. |
| 12 | struts | 3 ft. long, | 1¼ in. wide, | ¾ in. thick. |
| 2 | rudder bars | 8 ft. long, | ¾ in. wide, | ½ in. thick. |
| 12 | posts | 4 ft. long, | 1½ in. wide, | ½ in. thick. |
| 41 | ribs | 4 ft. long, | ½ in. wide, | ½ in. thick. |
| 2 | arm rests | 4 ft. long, | 2 in. wide, | 1 in. thick. |
| For rudder frame. | 24 running ft., | 1 in. wide, | 1 in. thick. | |
If it be impossible to find clear spruce lumber 20 feet in length, the spars may be built up by splicing two 10-foot sticks together. For this purpose, the splicing stick should be as heavy as the single spar—1¼ inches wide, and ¾ inches thick—and at least 4 feet long, and be bolted fast to the spar with six ⅛ inch round-head carriage bolts with washers of large bearing surface (that is, a small hole to fit the bolt, and a large outer diameter) at both ends of the bolt, to prevent crushing the wood. A layer of liquid glue brushed between will help to make the joint firmer.
Otto Lilienthal in his single-plane glider. The swinging forward of his feet tends to turn the glider toward the ground, and increase its speed.
Wherever a bolt is put in, a hole should be bored for it with a bit of such size that the bolt will fit snug in the hole without straining the grain of the wood.
The corners of the finished spar are to be rounded off on a large curvature.
The ends of the struts are to be cut down on a slight slant of about 1/16 inch in the 1¼ inches that it laps under the spar—with the idea of tipping the top of the spar forward so that the ribs will spring naturally from it into the proper curve.
The ribs should be bent by steaming, and allowed to dry and set in a form, or between blocks nailed upon the floor to the line of the correct curve. They are then nailed to the frames, the front end first: 21 to the frame of the upper plane, and 20 to that of the lower plane, omitting one at the centre, where the arm pieces will be placed.
Some builders tack the ribs lightly into place with small brads, and screw clamps formed from sheet brass or aluminum over them. Others use copper nails and clinch them over washers on the under side. Both methods are shown in the plans, but the clamps are recommended as giving greater stiffness, an essential feature.
At the front edge of the frames the ribs are fastened flush, and being 4 feet long and the frame but 3 feet wide, they project over the rear about 1 foot.
The arm pieces are bolted to the spars of the lower frame 6½ inches on each side of the centre, so as to allow a free space of 13 inches between them. This opening may be made wider to accommodate a stouter person.
Plan and details of Glider. The upper plane has a rib at the centre instead of the two arm pieces.
The posts are then put into place and bolted to the struts and the spars, as shown, with ⅛inch bolts.
The entire structure is then to be braced diagonally with No. 16 piano wire. The greatest care must be taken to have these diagonals pull just taut, so that they shall not warp the lines of the frames out of true. A crooked frame will not fly straight, and is a source of danger when making a landing.
The frames are now to be covered. There is a special balloon cloth made which is best for the purpose, but if that cannot be procured, strong cambric muslin will answer. Thirty yards of goods 1 yard wide will be required for the planes and the rudder. From the piece cut off 7 lengths for each plane, 4 feet 6 inches long. These are to be sewed together, selvage to selvage, so as to make a sheet about 19 feet 6 inches long and 4 feet 6 inches wide. As this is to be tacked to the frame, the edges must be double-hemmed to make them strong enough to resist tearing out at the tacks. Half an inch is first folded down all around; the fold is then turned back on the goods 2½ inches and sewed. This hem is then folded back 1 inch upon itself, and again stitched. Strips 3 inches wide and a little over 4 feet long are folded “three-double” into a width of 1 inch, and sewed along both edges to the large sheet exactly over where the ribs come. These are to strengthen the fabric where the ribs press against it. Sixteen-ounce tacks are used, being driven through a felt washer the size of a gun wad at intervals of four inches. If felt is not readily obtainable, common felt gun wads will do. The tacking is best begun at the middle of the frame, having folded the cloth there to get the centre. Then stretch smoothly out to the four corners and tack at each. It may then be necessary to loosen the two centre tacks and place them over again, to get rid of wrinkles. The next tacks to drive are at the ends of the struts; then half-way between; and so on until all are in, and the sheet is taut and smooth. For a finer finish, brass round-head upholsterer’s nails may be used.
The rudder, so-called, is rather a tail, for it is not movable and does not steer the glider. It does steady the machine, however, and is very important in preserving the equilibrium when in flight. It is formed of two small planes intersecting each other at right angles and covered on both sides with the cloth, the sections covering the vertical part being cut along the centre and hemmed on to the upper and lower faces of the horizontal part. The frame for the vertical part is fastened to the two rudder bars which stretch out toward the rear, one from the upper plane, and the other from the lower. The whole construction is steadied by guys of the piano wire.
Lilienthal in his double-deck glider. It proved unmanageable and fell, causing his death. The hill is an artificial one built for his own use in experimenting.
All wooden parts should be smoothed off with sandpaper, and given a coat of shellac varnish.
To make a glide, the machine is taken to an elevated point on a slope, not far up to begin with. Lift the glider, get in between the arm rests, and raise the apparatus until the rests are snug under the arms. Run swiftly for a few yards and leap into the air, holding the front of the planes slightly elevated. If the weight of the body is in the right position, and the speed sufficient, the glider will take the air and sail with you down the slope. It may be necessary at first to have the help of two assistants, one at each end, to run with the glider for a good start.
Diagram showing differing lines of flight as controlled by changing the position of the body. The wind must be blowing against the direction of flight; in the illustration this would be from left to right.
The position of the body on the arm rests can best be learned by a few experiments. No two gliders are quite alike in this respect, and no rule can be given. As to the requisite speed, it must be between 15 and 20 miles an hour; and as this speed is impossible to a man running, it is gained by gliding against the wind, and thus adding the speed of the wind to the speed of the runner. The Wrights selected the sand dunes of the North Carolina coast for their glider experiments because of the steady winds that blow in from the ocean, across the land. These winds gave them the necessary speed of air upon which to sail their gliders.
The first flights attempted should be short, and as experience is gained longer ones may be essayed.
Balancing the glider from side to side is accomplished by swaying the lower part of the body like a pendulum, the weight to go toward the side which has risen. Swinging the body forward on the arm rests will cause the machine to dip the planes and glide more swiftly down the incline. Holding the weight of the body back in the arm rests will cause the machine to fly on a higher path and at a slower speed. This is objectionable because the glider is more manageable at a higher speed, and therefore safer. The tendency at first is to place the weight too far back, with a consequent loss of velocity, and with that a proportionate loss of control. The proper position of the body is slightly forward of the mechanical centre of the machine.
The landing is accomplished by shoving the body backward, thus tilting up the front of the plane. This checks the speed, and when the feet touch the ground a little run, while holding back, will bring the glide to an end. Landing should be practised often with brief glides until skill is gained, for it is the most difficult operation in gliding.
After one becomes expert, longer flights may be secured by going to higher points for the start. From an elevation of 300 feet a glide of 1,200 feet is possible.
Gliding with a Chanute three-decker. A start with two assistants.
While it is necessary to make glides against the wind, it is not wise to attempt flights when the wind blows harder than 10 miles an hour. While the flight may be successful, the landing may be disastrous.
The accomplished glider operator is in line for the aeroplane, and it is safe to say that he will not be long without one. The skilful and practised operator of a glider makes the very best aeroplane pilot.
This chapter would not be complete without an adequate reference to the gliders devised by Professor Montgomery of Santa Clara, California. These machines were sent up with ordinary hot-air balloons to various heights, reaching 4,000 feet in some instances, when they were cut loose and allowed to descend in a long glide, guided by their pilots. The time of the descent from the highest altitude was twenty minutes, during which the glider travelled about eight miles. The landing was made accurately upon a designated spot, and so gently that there was no perceptible jar. Two of the pilots turned completely over sideways, the machine righting itself after the somersault and continuing its regular course. Professor Montgomery has made the assertion that he can fasten a bag of sand weighing 150 lbs. in the driver’s seat of his glider, and send it up tied upside down under a balloon, and that after being cut loose, the machine will right itself and come safely to the ground without any steering.
Lilienthal in Germany, Pilcher in England, and Chanute in the United States are names eminent in connection with the experiments with gliders which have been productive of discoveries of the greatest importance to the progress of aviation. The illustration of the Chanute glider shows its peculiarities plainly enough to enable any one to comprehend them.
The establishment of glider clubs in several parts of the country has created a demand for ready-made machines, so that an enthusiast who does not wish to build his own machine may purchase it ready made.
Chapter XIII.
BALLOONS.
First air vehicle—Principle of Archimedes—Why balloons rise—Inflating gases—Early history—The Montgolfiers—The hot-air balloon—Charles’s hydrogen balloon—Pilatre de Rozier—The first aeronaut—The first balloon voyage—Blanchard and Jeffries—Crossing the English Channel—First English ascensions—Notable voyages—Recent long-distance journeys and high ascensions—Prize balloon races—A fascinating sport—Some impressions, adventures, and hardships—Accident record—Increasing interest in ballooning.
The balloon, though the earliest and crudest means of getting up in the air, has not become obsolete. It has been in existence practically in its present general form for upwards of 500 years. Appliances have been added from time to time, but the big gas envelope enclosing a volume of some gas lighter than an equal volume of air, and the basket, or car, suspended below it, remain as the typical form of aerial vehicle which has not changed since it was first devised in times so remote as to lie outside the boundaries of recorded history.
The common shape of the gas bag of a balloon is that of the sphere, or sometimes of an inverted pear. It is allowed to rise and float away in the air as the prevailing wind may carry it. Attempts have been made to steer it in a desired direction, but they did not accomplish much until the gas bag was made long horizontally, in proportion to its height and width. With a drag-rope trailing behind on the ground from the rear end of the gas bag, and sails on the forward end, it was possible to guide the elongated balloon to some extent in a determined direction.
In explaining why a balloon rises in the air, it is customary to quote the “principle of Archimedes,” discovered and formulated by that famous philosopher centuries before the Christian era. Briefly stated, it is this: Every body immersed in a fluid is acted upon by a force pressing upward, which is equal to the weight of the amount of the fluid displaced by the immersed body.
It remained for Sir Isaac Newton to explain the principle of Archimedes (by the discovery of the law of gravitation), and to show that the reason why the immersed body is apparently pushed upward, is that the displaced fluid is attracted downward. In the case of a submerged bag of a gas lighter than air, the amount of force acting on the surrounding air is greater than that acting on the gas, and the latter is simply crowded out of the way by the descending air, and forced up to a higher level where its lighter bulk is balanced by the gravity acting upon it.
The fluid in which the balloon is immersed is the air. The force with which the air crowds down around and under the balloon is its weight—weight being the measure of the attraction which gravity exerts upon any substance.
The weight of air at a temperature of 32° Fahr., at the normal barometer pressure at the sea-level (29.92 inches of mercury), is 0.0807 lbs. per cubic foot. The gas used to fill a balloon must therefore weigh less than this, bulk for bulk, in order to be crowded upward by the heavier air—and thus exert its “lifting power,” as it is commonly called.
In practice, two gases have been used for inflating balloons—hydrogen, and illuminating gas, made ordinarily from coal, and called “coal gas.” Hydrogen is the lightest substance known; that is, it is attracted less by gravity than any other known substance, in proportion to its bulk.
One of the earliest attempts to steer a spherical balloon by retarding its speed with the drag-rope, and adjusting the sail to the passing wind.
A cubic foot of hydrogen weighs but 0.0056 lbs., and it will therefore be pushed upward in air by the difference in weight, or 0.0751 lbs. per cubic foot. A cubic foot of coal gas weighs about 0.0400 lbs., and is crowded upward in air with a force of 0.0407 lbs.
Apparatus to illustrate the principle of Archimedes. At the left, the small solid glass ball and large hollow glass sphere are balanced in the free air. When the balance is moved under the bell-glass of the air pump (at the right), and the air exhausted, the large sphere drops, showing that its previous balance was due to the upward pressure of the air, greater because of its larger bulk.
It is readily seen that a very large bulk of hydrogen must be used if any considerable weight is to be lifted. For to the weight of the gas must be added the weight of the containing bag, the car, and the network supporting it, the ballast, instruments, and passengers, and there must still be enough more to afford elevating power sufficient to raise the entire load to the desired level.
Let us assume that we have a balloon with a volume of 20,000 cubic feet, which weighs with its appurtenances 500 pounds. The hydrogen it would contain would weigh about 112 pounds, and the weight of the air it would displace would be about 1,620 pounds. The total available lifting power would be about 1,000 pounds. If a long-distance journey is to be undertaken at a comparatively low level, this will be sufficient to carry the necessary ballast, and a few passengers. If, however, it is intended to rise to a great height, the problem is different. The weight of the air, and consequently its lifting pressure, decreases as we go upwards. If the balloon has not been entirely filled, the gas will expand as the pressure is reduced in the higher altitude. This has the effect of carrying the balloon higher. Heating of the contained gas by the sun will also cause a rise. On the other hand, the diffusion of the gas through the envelope into the air, and the penetration of air into the gas bag will produce a mixture heavier than hydrogen, and will cause the balloon to descend. The extreme cold of the upper air has the same effect, as it tends to condense to a smaller bulk the gas in the balloon. To check a descent the load carried by the gas must be lightened by throwing out some of the ballast, which is carried simply for this purpose. Finally a level is reached where equilibrium is established, and above which it is impossible to rise.
The earliest recorded ascent of a balloon is credited to the Chinese, on the occasion of the coronation of the Emperor Fo-Kien at Pekin in the year 1306. If this may be called historical, it gives evidence also that it speedily became a lost art. The next really historic record belongs in the latter part of the seventeenth century, when Cyrano de Bergerac attempted to fly with the aid of bags of air attached to his person, expecting them to be so expanded by the heat of the sun as to rise with sufficient force to lift him. He did not succeed, but his idea is plainly the forerunner of the hot-air balloon.
In the same century Francisco de Lana, who was clearly a man of much intelligence and keen reasoning ability, having determined by experiment that the atmosphere had weight, decided that he would be able to rise into the air in a ship lifted by four metal spheres 20 feet in diameter from which the air had been exhausted. After several failures he abandoned his efforts upon the religious grounds that the Almighty doubtless did not approve such an overturning in the affairs of mankind as would follow the attainment of the art of flying.
In 1757, Galen, a French monk, published a book, “The Art of Navigating in the Air,” in which he advocated filling the body of the airship with air secured at a great height above the sea-level, where it was “a thousand times lighter than water.” He showed by mathematical computations that the upward impulse of this air would be sufficient to lift a heavy load. He planned in detail a great airship to carry 4,000,000 persons and several million packages of goods. Though it may have accomplished nothing more, this book is believed to have been the chief source of inspiration to the Montgolfiers.
The discovery of hydrogen by Cavendish in 1776 gave Dr. Black the opportunity of suggesting that it be used to inflate a large bag and so lift a heavy load into the air. Although he made no attempt to construct such an apparatus, he afterward claimed that through this suggestion he was entitled to be called the real inventor of the balloon.
This is the meagre historical record preceding the achievements of the brothers Stephen and Joseph Montgolfier, which marked distinctly the beginning of practical aeronautics. Both of these men were highly educated, and they were experienced workers in their father’s paper factory. Joseph had made some parachute drops from the roof of his house as early as 1771.
After many experiments with steam, smoke, and hydrogen gas, with which they tried ineffectually to inflate large paper bags, they finally succeeded with heated air, and on June 5, 1783, they sent up a great paper hot-air balloon, 35 feet in diameter. It rose to a height of 1,000 feet, but soon came to earth again upon cooling. It appears that the Montgolfiers were wholly ignorant of the fact that it was the rarefying of the air by heating that caused their balloon to rise, and they made no attempt to keep it hot while the balloon was in the air.
An early Montgolfier balloon.
About the same time the French scientist, M. Charles, decided that hydrogen gas would be better than hot air to inflate balloons. Finding that this gas passed readily through paper, he used silk coated with a varnish made by dissolving rubber. His balloon was 13 feet in diameter, and weighed about 20 pounds. It was sent up from the Champ de Mars on August 29, 1783, amidst the booming of cannon, in the presence of 300,000 spectators who assembled despite a heavy rain. It rose swiftly, disappearing among the clouds, and soon burst from the expansion of the gas in the higher and rarer atmosphere—no allowance having been made for this unforeseen result. It fell in a rural region near Paris, where it was totally destroyed by the inhabitants, who believed it to be some hideous form of the devil.
The Montgolfiers had already come to Paris, and had constructed a balloon of linen and paper. Before they had opportunity of sending it up it was ruined by a rainstorm with a high wind. They immediately built another of waterproof linen which made a successful ascension on September 19, 1783, taking as passengers a sheep, a cock, and a duck. The balloon came safely to earth after being up eight minutes—falling in consequence of a leak in the air-bag near the top. The passengers were examined with great interest. The sheep and the duck seemed in the same excellent condition as when they went up, but the cock was evidently ailing. A consultation of scientists was held and it was the consensus of opinion that the fowl could not endure breathing the rarer air of the high altitude. At this juncture some one discovered that the cock had been trodden upon by the sheep, and the consultation closed abruptly.
The Montgolfier brothers were loaded with honors, Stephen receiving the larger portion; and the people of Paris entered enthusiastically into the sport of making and flying small balloons of the Montgolfier type.
Stephen began work at once upon a larger balloon intended to carry human passengers. It was fifty feet in diameter, and 85 feet high, with a capacity of 100,000 cubic feet. The car for the passengers was swung below from cords in the fashion that has since become so familiar.
In the meantime Pilatre de Rozier had constructed a balloon on the hot-air principle, but with an arrangement to keep the air heated by a continuous fire in a pan under the mouth of the balloon. He made the first balloon ascent on record on October 15, 1783, rising to a height of eighty feet, in the captive balloon. On November 21, in the same year, de Rozier undertook an expedition in a free balloon with the Marquis d’Arlandes as a companion. The experiment was to have been made with two condemned criminals, but de Rozier and d’Arlandes succeeded in obtaining the King’s permission to make the attempt, and in consequence their names remain as those of the first aeronauts. They came safely to the ground after a voyage lasting twenty-five minutes. After this, ascensions speedily became a recognized sport, even for ladies.
The greatest altitude reached by these hot-air balloons was about 9,000 feet.
Pilatre de Rozier’s balloon.
The great danger from fire, however, led to the closer consideration of the hydrogen balloon of Professor Charles, who was building one of 30 feet diameter for the study of atmospheric phenomena. His mastery of the subject is shown by the fact that his balloon was equipped with almost every device afterward in use by the most experienced aeronauts. He invented the valve at the top of the bag for allowing the escape of gas in landing, the open neck to permit expansion, the network of cords to support the car, the grapnel for anchoring, and the use of a small pilot balloon to test the air-currents before the ascension. He also devised a barometer by which he was able to measure the altitude reached by the pressure of the atmosphere.
To provide the hydrogen gas required he used the chemical method of pouring dilute sulphuric acid on iron filings. The process was so slow that it took continuous action for three days and three nights to secure the 14,000 cubic feet needed, but his balloon was finally ready on December 1, 1783. One of the brothers Robert accompanied Charles, and they travelled about 40 miles in a little less than 4 hours, alighting at Nesles. Here Robert landed and Charles continued the voyage alone. Neglecting to take on board ballast to replace the weight of M. Robert, Charles was carried to a great height, and suffered severely from cold and the difficulty of breathing in the highly rarefied air. He was obliged to open his gas valve and descend after half an hour’s flight alone.
Blanchard, another French inventor, about this time constructed a balloon with the intention of being the first to cross the English Channel in the air. He took his balloon to Dover and with Dr. Jeffries, an American, started on January 7, 1785. His balloon was leaky and he had loaded it down with a lot of useless things in the way of oars, provisions, and other things. All of this material and the ballast had to be thrown overboard at the outset, and books and parts of the balloon followed. Even their clothing had to be thrown over to keep the balloon out of the sea, and at last, when Dr. Jeffries had determined to jump out to enable his friend to reach the shore, an upward current of wind caught them and with great difficulty they landed near Calais. The feat was highly lauded and a monument in marble was erected on the spot to perpetuate the record of the achievement.
De Rozier lost his life soon after in the effort to duplicate this trip across the Channel with his combination hydrogen and hot-air balloon. His idea seems to have been that he could preserve the buoyancy of his double balloon by heating up the air balloon at intervals. Unfortunately, the exuding of the hydrogen as the balloons rose formed an explosive mixture with the air he was rising through, and it was drawn to his furnace, and an explosion took place which blew the entire apparatus into fragments at an altitude of over 1,000 feet.
Car and hoop of the Blanchard balloon, the first to cross the English Channel.
Count Zambeccari, an Italian, attempted to improve the de Rozier method of firing a balloon by substituting a large alcohol lamp for the wood fire. In the first two trial trips he fell into the sea, but was rescued. On the third trip his balloon was swept into a tree, and the overturned lamp set it on fire. To escape being burned, he threw himself from the balloon and was killed by the fall.
The year before these feats on the Continent two notable balloon ascensions had taken place in England. On August 27, 1784, an aeronaut by the name of Tytler made the first balloon voyage within the boundaries of Great Britain. His balloon was of linen and varnished, and the record of his ascension indicates that he used hydrogen gas to inflate it. He soared to a great height, and descended safely.
A few weeks later, the Italian aeronaut Lunardi made his first ascent from London. The spectacle drew the King and his councillors from their deliberations, and the balloon was watched until it disappeared. He landed in Standon, near Ware, where a stone was set to record the event. On October 12, he made his famous voyage from Edinburgh over the Firth of Forth to Ceres; a distance of 46 miles in 35 minutes, or at the rate of nearly 79 miles per hour; a speed rarely equalled by the swiftest railroad trains.
From this time on balloons multiplied rapidly and the ascents were too numerous for recording in these pages. The few which have been selected for mention are notable either for the great distances traversed, or for the speed with which the journeys were made. It should be borne in mind that the fastest method of land travel in the early part of the period covered was by stage coach; and the sailing ship was the only means of crossing the water. It is no wonder that often the people among whom the aeronauts landed on a balloon voyage refused to believe the statements made as to the distance they had come, and the marvellously short time it had taken. And even as compared with the most rapid transit of the present day, the speeds attained in many cases have never been equalled.
A remarkable English voyage was made in June, 1802, by the French aeronaut Garnerin and Captain Snowdon. They ascended from Chelsea Gardens and landed in Colchester, 60 miles distant, in 45 minutes: an average speed of 80 miles an hour.
On December 16, 1804, Garnerin ascended from the square in front of Notre Dame, Paris; passing over France and into Italy, sailing above St. Peter’s at Rome, and the Vatican, and descending into Lake Bracciano—a distance of 800 miles in 20 hours. This voyage was made as a part of the coronation ceremonies of Napoleon I. The balloon was afterwards hung up in a corridor of the Vatican.
On October 7, 1811, Sadler and Burcham voyaged from Birmingham to Boston (England), 112 miles in 1 hour 40 minutes, a speed of 67 miles per hour.
On November 17, 1836, Charles Green and Monck Mason started on a voyage in the great balloon of the Vauxhall Gardens. It was pear-shaped, 60 feet high and 50 feet in diameter, and held 85,000 cubic feet of gas. It was cut loose at half-past one in the afternoon, and in 3 hours had reached the English Channel, and in 1 hour more had crossed it, and was nearly over Calais. During the night it floated on over France in pitchy darkness and such intense cold that the oil was frozen. In the morning the aeronauts descended a few miles from Weilburg, in the Duchy of Nassau, having travelled about 500 miles in 18 hours. At that date, by the fastest coaches the trip would have consumed three days. The balloon was rechristened “The Great Balloon of Nassau” by the enthusiastic citizens of Weilburg.
Prof. T. S. C. Lowe’s mammoth balloon “City of New York,” a feature of the year 1860, in which it made many short voyages in the vicinity of New York and Philadelphia.
In 1849, M. Arban crossed the Alps in a balloon, starting at Marseilles and landing at Turin—a distance of 400 miles in 8 hours. This remarkable record for so long a distance at a high speed has rarely been equalled. It was exceeded as to distance at the same speed by the American aeronaut, John Wise, in 1859.
One of the most famous balloons of recent times was the “Geant,” built by M. Nadar, in Paris, in 1853. The immense gas-bag was made of silk of the finest quality costing at that time about $1.30 a yard, and being made double, it required 22,000 yards. It had a capacity of 215,000 cubic feet of gas, and lifted 4½ tons. The car was 13 feet square, and had an upper deck which was open. On its first ascent it carried 15 passengers, including M. Nadar as captain, and the brothers Godard as lieutenants. A few weeks later this balloon was set free for a long-distance journey, and 17 hours after it left Paris it landed at Nieuburg in Hanover, having traversed 750 miles, a part of the time at the speed of fully 90 miles per hour.
In July, 1859, John Wise, an American aeronaut, journeyed from St. Louis, Mo., to Henderson, N. Y., a distance of 950 miles in 19 hours. His average speed was 50 miles per hour. This record for duration at so high a rate of speed has never been exceeded.
During the siege of Paris in 1870, seventy-three balloons were sent out from that city carrying mail and dispatches. These were under Government direction, and receive notice in a subsequent chapter devoted to Military Aeronautics. One of these balloons is entitled to mention among those famous for rapid journeys, having travelled to the Zuyder Zee, a distance of 285 miles, in 3 hours—an average speed of 95 miles per hour. Another of these postal balloons belongs in the extreme long-distance class, having come down in Norway nearly 1,000 miles from Paris.
In July, 1897, the Arctic explorer Andrée started on his voyage to the Pole. As some of his instruments have been recently recovered from a wandering band of Esquimaux, it is believed that a record of his voyage may yet be secured.
In the same year a balloon under the command of Godard ascended at Leipsic, and after a wandering journey in an irregular course, descended at Wilna. The distance travelled was estimated at 1,032 miles, but as balloon records are always based on the airline distance between the places of ascent and descent, this record has not been accepted as authoritative. The time consumed was 24¼ hours.
In 1899, Captain von Sigsfield, Captain Hildebrandt, and a companion started from Berlin in a wind so strong that it prevented the taking on of an adequate load of ballast. They rose into a gale, and in two hours were over Breslau, having made the distance at a speed of 92 miles per hour. In the grasp of the storm they continued their swift journey, landing finally high up in the snows of the Carpathian Alps in Austria. They were arrested by the local authorities as Russian spies, but succeeded in gaining their liberty by telegraphing to an official more closely in touch with the aeronautics of the day.
In 1900 there were several balloon voyages notable for their length. Jacques Balsan travelled from Vincennes to Dantzig, 757 miles; Count de la Vaulx journeyed from Vincennes to Poland, 706 miles; Jacques Faure from Vincennes to Mamlity, 753 miles. In a subsequent voyage Jacques Balsan travelled from Vincennes to Rodom, in Russia, 843 miles, in 27½ hours.
The balloon in which Coxwell and Glaisher made their famous ascent of 29,000 feet.
One of the longest balloon voyages on record in point of time consumed is that of Dr. Wegener of the Observatory at Lindenberg, in 1905. He remained in the air for 52¾ hours.
The longest voyage, as to distance, up to 1910, was that of Count de La Vaulx and Count Castillon de Saint Victor in 1906, in the balloon “Centaur.” This was a comparatively small balloon, having a capacity of only 55,000 cubic feet of gas. The start was made from Vincennes on October 9th, and the landing at Korostischeff, in Russia, on October 11th. The air-line distance travelled was 1,193 miles, in 35¾ hours. The balloon “Centaur” was afterward purchased by the Aero Club of America, and has made many voyages in this country.
The Federation Aeronautique Internationale, an association of the aeronauts of all nations, was founded in 1905. One of its functions is an annual balloon race for the International Challenge Cup, presented to the association by James Gordon Bennett, to be an object for competition until won three times by some one competing national club.
The first contest took place in September, 1906, and was won by the American competitor, Lieut. Frank P. Lahm, with a voyage of 402 miles.
The second contest was from St. Louis, Mo., in 1907. There were three German, two French, one English, and three American competitors. The race was won by Oscar Erbslöh, one of the German competitors, with an air-line voyage of 872¼ miles, landing at Bradley Beach, N. J. Alfred Leblanc, now a prominent aviator, was second with a voyage of 867 miles, made in 44 hours. He also landed in New Jersey.
The third race started at Berlin in October, 1908, and was won by the Swiss balloon “Helvetia,” piloted by Colonel Schaeck, which landed in Norway after having been 74 hours in the air, and covering a journey of 750 miles. This broke the previous duration record made by Dr. Wegener in 1905.
The fourth contest began on October 3, 1909, from Zurich, Switzerland. There were seventeen competing balloons, and the race was won by E. W. Mix, representing the Aero Club of America, with a voyage of 589 miles.
The fifth contest began at St. Louis, October 17, 1910. It was won by Alan P. Hawley and Augustus Post, with the “America II.” They travelled 1,355 miles in 46 hours, making a new world’s record for distance.
Among other notable voyages may be mentioned that of the “Fielding” in a race on July 4, 1908, from Chicago. The landing was made at West Shefford, Quebec, the distance travelled being 895 miles.
In November of the same year A. E. Gaudron, Captain Maitland, and C. C. Turner, made the longest voyage on record from England. They landed at Mateki Derevni, in Russia, having travelled 1,117 miles in 31½ hours. They were driven down to the ground by a severe snowstorm.
On December 31, 1908, M. Usuelli, in the balloon “Ruwenzori” left the Italian lakes and passed over the Alps at a height of 14,750 feet, landing in France. This feat was followed a few weeks later—February 9, 1909—by Oscar Erbslöh, who left St. Moritz with three passengers, crossing the Alps at an altitude of 19,000 feet, and landed at Budapest after a voyage of 33 hours. Many voyages over and among the Alps have been made by Captain Spelterini, the Swiss aeronaut, and he has secured some of the most remarkable photographs of the mountain scenery in passing. In these voyages at such great altitudes it is necessary to carry cylinders of oxygen to provide a suitable air mixture for breathing. In one of his recent voyages Captain Spelterini had the good fortune to be carried almost over the summit of Mont Blanc. He ascended with three passengers at Chamounix, and landed at Lake Maggiore seven hours later, having reached the altitude of 18,700 feet, and travelled 93 miles.
Photograph of the Alps from a balloon by Captain Spelterini.
In the United States there were several balloon races during the year 1909, the most important being the St. Louis Centennial race, beginning on October 4th. Ten balloons started. The race was won by S. von Phul, who covered the distance of 550 miles in 40 hours 40 minutes. Clifford B. Harmon and Augustus Post in the balloon “New York” made a new duration record for America of 48 hours 26 minutes. They also reached the highest altitude attained by an American balloon—24,200 feet.
On October 12th, in a race for the Lahm cup, A. Holland Forbes and Col. Max Fleischman won. They left St. Louis, Mo., and landed 19 hours and 15 minutes later at Beach, Va., near Richmond, having travelled 697 miles.
In 1910, in the United States, a remarkable race, with thirteen competitors, started at Indianapolis. This was the elimination race for the International race on October 17th. It was won by Alan P. Hawley and Augustus Post in the balloon “America II.” They crossed the Alleghany Mountains at an elevation of about 20,000 feet, and landed at Warrenton, Va., after being 44 hours 30 minutes in the air; and descended only to escape being carried out over Chesapeake Bay.
In recent years the greatest height reached by a balloon was attained by the Italian aeronauts Piacenza and Mina in the “Albatross,” on August 9, 1909. They went up from Turin to the altitude of 30,350 feet. The world’s height record rests with Professors Berson and Suring of Berlin, who on July 31, 1901, reached 35,500 feet. The record of 37,000 feet claimed by Glaisher and Coxwell in their ascension on September 5, 1862, has been rejected as not authentic for several discrepancies in their observations, and on the ground that their instruments were not of the highest reliability. As they carried no oxygen, and reported that for a time they were both unconscious, it is estimated that the highest point they could have reached under the conditions was less than 31,000 feet.
The greatest speed ever recorded for any balloon voyage was that of Captain von Sigsfield and Dr. Linke in their fatal journey from Berlin to Antwerp, during which the velocity of 125 miles per hour was recorded.
Ballooning as a sport has a fascination all its own. There is much of the spice of adventure in the fact that one’s destiny is quite unknown. Floating with the wind, there is no consciousness of motion. Though the wind may be travelling at great speed, the balloon seems to be in a complete calm. A lady passenger, writing of a recent trip, has thus described her experience:—“The world continues slowly to unroll itself in ever-varying but ever-beautiful panorama—patchwork fields, shimmering silver streaks, toy box churches and houses, and white roads like the joints of a jig-saw puzzle. And presently cotton-wool billows come creeping up, with purple shadows and fleecy outlines and prismatic rainbow effects. Sometimes they invade the car, and shroud it for a while in clinging warm white wreaths, and anon they fall below and shut out the world with a glorious curtain, and we are all alone in perfect silence, in perfect peace, and in a realm made for us alone.
“And so the happy, restful hours go smoothly by, until the earth has had enough of it, and rising up more or less rapidly to invade our solitude, hits the bottom of our basket, and we step out, or maybe roll out, into every-day existence a hundred miles away.”
The perfect smoothness of motion, the absolute quiet, and the absence of distracting apparatus combine to render balloon voyaging the most delightful mode of transit from place to place. Some of the most fascinating bits of descriptive writing are those of aeronauts. The following quotation from the report of Capt. A. Hildebrandt, of the balloon corps of the Prussian army, will show that although his expeditions were wholly scientific, he was far from indifferent to the sublimer influences of nature by which he was often surrounded.
In his account of the journey from Berlin to Markaryd, in Sweden, with Professor Berson as a companion aeronaut, he says: “The view over Rügen and the chalk cliffs of Stubbenkammer and Arkona was splendid: the atmosphere was perfectly clear. On the horizon we could see the coasts of Sweden and Denmark, looking almost like a thin mist; east and west there was nothing but the open sea.
“About 3:15 the balloon was in the middle of the Baltic; right in the distance we could just see Rügen and Sweden. The setting of the sun at 4 P.M. was a truly magnificent spectacle. At a height of 5,250 feet, in a perfectly clear atmosphere, the effect was superb. The blaze of color was dimly reflected in the east by streaks of a bluish-green. I have seen sunsets over France at heights of 10,000 feet, with the Alps, the Juras, and the Vosges Mountains in the distance; but this was quite as fine.
“The sunsets seen by the mountaineer or the sailor are doubtless, magnificent; but I hardly think the spectacle can be finer than that spread out before the gaze of the balloonist. The impression is increased by the absolute stillness which prevails; no sound of any kind is heard.
Landscape as seen from a balloon at an altitude of 3,000 feet.
“As soon as the sun went down, it was necessary to throw out some ballast, owing to the decrease of temperature.... We reached the Swedish coast about 5 o’clock, and passed over Trelleborg at a height of 2,000 feet. The question then arose whether to land, or to continue through the night. Although it was well past sunset, there was sufficient light in consequence of the snow to see our way to the ground, and to land quite easily.... However, we wanted to do more meteorological work, and it was thought that there was still sufficient ballast to take us up to a much greater height. We therefore proposed to continue for another sixteen hours during the night, in spite of the cold.... Malmö was therefore passed on the left, and the university town of Lund on the right. After this the map was of no further use, as it was quite dark and we had no lamp. The whole outlook was like a transformation scene. Floods of light rose up from Trelleborg, Malmö, Copenhagen, Landskrona, Lund, Elsinore, and Helsingborg, while the little towns beneath our feet sparkled with many lights. We were now at a height of more than 10,000 feet, and consequently all these places were within sight. The glistening effect of the snow was heightened by the blaze which poured from the lighthouses along the coasts of Sweden and Denmark. The sight was as wonderful as that of the sunset, though of a totally different nature.”
Captain Hildebrandt’s account of the end of this voyage illustrates the spice of adventure which is likely to be encountered when the balloon comes down in a strange country. It has its hint also of the hardships for which the venturesome aeronaut has to be prepared. He says:—
“Sooner or later the balloon would have been at the mercy of the waves. The valve was opened, and the balloon descended through the thick clouds. We could see nothing, but the little jerks showed us that the guide-rope was touching the ground. In a few seconds we saw the ground, and learned that we were descending into a forest which enclosed a number of small lakes. At once more ballast was thrown out, and we skimmed along over the tops of the trees. Soon we crossed a big lake, and saw a place that seemed suitable for a descent. The valve was then opened, both of us gave a tug at the ripping cord, and after a few bumps we found ourselves on the ground. We had come down in deep snow on the side of a wood, about 14 miles from the railway station at Markaryd.
Making a landing with the aid of bystanders to pull down upon the trail-rope and a holding rope.
“We packed up our instruments, and began to look out for a cottage; but this is not always an easy task in the dead of night in a foreign country. However, in a quarter of an hour we found a farm, and succeeded in rousing the inmates. A much more difficult job was to influence them to open their front door to two men who talked some sort of double Dutch, and who suddenly appeared at a farmyard miles off the highway in the middle of the night and demanded admittance. Berson can talk in six languages, but unfortunately Swedish is not one of them. He begged in the most humble way for shelter ... and at the end of three-quarters of an hour the farmer opened the door. We showed him some pictures of a balloon we had with us, and then they began to understand the situation. We were then received with truly Swedish hospitality, and provided with supper. They even proposed to let us have their beds; but this we naturally declined with many thanks.... The yard contained hens, pigs, cows, and sheep; but an empty corner was found, which was well packed with straw, and served as a couch for our tired limbs. We covered ourselves with our great-coats, and tried to sleep. But the temperature was 10° Fahr., and as the place was only an outhouse of boards roughly nailed together, and the wind whistling through the cracks and crevices, we were not sorry when the daylight came.”
Lest the possibility of accident to travellers by balloon be judged greater than it really is, it may be well to state that records collected in Germany in 1906 showed that in 2,061 ascents in which 7,570 persons participated, only 36 were injured—or but 1 out of 210. Since that time, while the balloon itself has remained practically unchanged, better knowledge of atmospheric conditions has aided in creating an even more favorable record for recent years.
That the day of ordinary ballooning has not been dimmed by the advent of the airship and the aeroplane is evidenced by the recently made estimate that not less than 800 spherical balloons are in constant use almost daily in one part or another of Christendom. And it seems entirely reasonable to predict that with a better comprehension of the movements of air-currents—to which special knowledge the scientific world is now applying its investigations as never before—they will come a great increase of interest in simple ballooning as a recreation.
Chapter XIV.
BALLOONS: THE DIRIGIBLE.
Elongation of gas-bag—Brisson—Meusnier—Air-ballonnets—Scott—Giffard—Haenlein—Tissandier—Renard and Krebs—Schwartz—Santos-Dumont—Von Zeppelin—Roze—Severo—Bradsky-Leboun—The Lebaudy dirigible—Zeppelin II—Parseval I—Unequal wind pressures—Zeppelin III—Nulli Secundus—La Patrie—Ville-de-Paris—Zeppelin IV—Gross I—Parseval II—Clement-Bayard I—Ricardoni’s airship—Gross II—The new Zeppelin II—La Republique—The German fleet of dirigibles—Parseval V—The Deutschland—The Erbslöh—Gross III—Zeppelin VI—The America—Clement-Bayard III—The Capazza lenticular dirigible.
The dirigible balloon, or airship, is built on the same general principles as the ordinary balloon—that is, with the envelope to contain the lifting gas, the car to carry the load, and the suspending cordage—but to this is added some form of propelling power to enable it to make headway against the wind, and a rudder for steering it.
Almost from the very beginning of ballooning, some method of directing the balloon to a pre-determined goal had been sought by inventors. Drifting at the fickle pleasure of the prevailing wind did not accord with man’s desire for authority and control.
The first step in this direction was the change from the spherical form of the gas-bag to an elongated shape, the round form having an inclination to turn round and round in the air while floating, and having no bow-and-stern structure upon which steering devices could operate. The first known proposal in this direction was made by Brisson, a French scientist, who suggested building the gas-bag in the shape of a horizontal cylinder with conical ends, its length to be five or six times its diameter. His idea for its propulsion was the employment of large-bladed oars, but he rightly doubted whether human strength would prove sufficient to work these rapidly enough to give independent motion to the airship.
About the same time another French inventor had actually built a balloon with a gas-bag shaped like an egg and placed horizontally with the blunt end foremost. The reduction in the resistance of the air to this form was so marked that the elongated gas-bag quickly displaced the former spherical shape. This balloon was held back from travelling at the full speed of the wind by the clever device of a rope dragging on the ground; and by a sail rigged so as to act on the wind which blew past the retarded balloon, the navigator was able to steer it within certain limits. It was the first dirigible balloon.
In the same year the brothers Robert, of Paris, built an airship for the Duke of Chartres, under the direction of General Meusnier, a French officer of engineers. It was cylindrical, with hemispherical ends, 52 feet long and 32 feet in diameter, and contained 30,000 cubic feet of gas. The gas-bag was made double to prevent the escape of the hydrogen, which had proved very troublesome in previous balloons, and it was provided with a spherical air balloon inside of the gas-bag, which device was expected to preserve the form of the balloon unchanged by expanding or contracting, according to the rising or falling of the airship. When the ascension was made on July 6, 1784, the air-balloon stuck fast in the neck of the gas-bag, and so prevented the escape of gas as the hydrogen expanded in the increasing altitude. The gas-bag would have burst had not the Duke drawn his sword and slashed a vent for the imprisoned gas. The airship came safely to earth.
It was General Meusnier who first suggested the interior ballonnet of air to preserve the tense outline of the form of the airship, and the elliptical form for the gas-bag was another of his inventions. In the building of the airship of the Duke de Chartres he made the further suggestion that the space between the two envelopes be filled with air, and so connected with the air-pumps that it could be inflated or deflated at will. For the motive power he designed three screw propellers of one blade each, to be turned unceasingly by a crew of eighty men.
Meusnier was killed in battle in 1793, and aeronautics lost its most able developer at that era.
The Scott airship, showing the forward “pocket” partially drawn in.
In 1789, Baron Scott, an officer in the French army, devised a fish-shaped airship with two outside balloon-shaped “pockets” which could be forcibly drawn into the body of the airship to increase its density, and thus cause its descent.
It began to be realized that no adequate power existed by which balloons could be propelled against even light winds to such a degree that they were really controllable, and balloon ascensions came to be merely an adjunct of the exhibit of the travelling showman. For this reason the early part of the nineteenth century seems barren of aeronautical incident as compared with the latter part of the preceding century.
In 1848, Hugh Bell, an Englishman, built a cylindrical airship with convex pointed ends. It was 55 feet long and 21 feet in diameter. It had a keel-shaped framework of tubes to which the long narrow car was attached, and there was a screw propeller on each side, to be worked by hand, and a rudder to steer with. It failed to work.
In 1852, however, a new era opened for the airship. Henry Giffard, of Paris, the inventor of the world-famed injector for steam boilers, built an elliptical gas-bag with cigar-shaped ends, 144 feet long, and 40 feet in diameter, having a cubic content of 88,000 cubic feet. The car was suspended from a rod 66 feet long which hung from the net covering the gas-bag. It was equipped with a 3-horse-power steam engine which turned a two-bladed screw propeller 11 feet in diameter, at the rate of 110 revolutions per minute. Coke was used for fuel. The steering was done with a triangular rudder-sail. Upon trial on September 24, 1852, the airship proved a success, travelling at the rate of nearly 6 miles an hour.
The first Giffard dirigible.
Giffard built a second airship in 1855, of a much more elongated shape—235 feet long and 33 feet in diameter. He used the same engine which propelled his first ship. After a successful trial trip, when about to land, the gas-bag unaccountably turned up on end, allowing the net and car to slide off, and, rising slightly in the air, burst. Giffard and his companion escaped unhurt.
Giffard afterward built the large captive balloon for the London Exhibition in 1868, and the still larger one for the Paris Exposition in 1878. He designed a large airship to be fitted with two boilers and a powerful steam-engine, but became blind, and died in 1882.
The Haenlein airship inflated with coal gas and driven by a gas-engine.
In 1865, Paul Haenlein devised a cigar-shaped airship to be inflated with coal gas. It was to be propelled by a screw at the front to be driven by a gas-engine drawing its fuel from the gas in the body of the ship. An interior air-bag was to be expanded as the gas was consumed, to keep the shape intact. A second propeller revolving horizontally was intended to raise or lower the ship in the air.
It was not until 1872 that he finally secured the building of an airship, at Vienna, after his plans. It was 164 feet long, and 30 feet in diameter. The form of the gas-bag was that described by the keel of a ship rotated around the centre line of its deck as an axis. The engine was of the Lenoir type, with four horizontal cylinders, developing about 6 horse-power, and turned a propeller about 15 feet in diameter at the rate of 40 revolutions per minute. The low lifting power of the coal gas with which it was inflated caused it to float quite near the ground. With a consumption of 250 cubic feet of gas per hour, it travelled at a speed of ten miles an hour. The lack of funds seems to have prevented further experiments with an invention which was at least very promising.
Sketch of the De Lome airship.
In the same year a dirigible balloon built by Dupuy de Lome for use by the French Government during the siege of Paris, was given a trial. It was driven by a screw propeller turned by eight men, and although it was 118 feet long, and 49 feet in diameter, it made as good a speed record as Giffard’s steam-driven airship—six miles an hour.
Car of the Tissandier dirigible; driven by electricity.
In 1881, the brothers Albert and Gaston Tissandier exhibited at the Electrical Exhibition in Paris a model of an electrically driven airship, originally designed to establish communication with Paris during the siege of the Franco-Prussian War. In 1883, the airship built after this model was tried. It was 92 feet long, and 30 feet at its largest diameter. The motive power was a Siemens motor run by 24 bichromate cells of 17 lbs. each. At full speed the motor made 180 revolutions per minute, developing 1½ horse-power. The pull was 26 lbs. The propeller was 9 feet in diameter, and a speed of a little more than 6 miles an hour was attained.
Sketch of the Renard and Krebs airship La France, driven by a storage battery.
In 1884, two French army engineers, Renard and Krebs, built an airship, the now historic La France, with the shape of a submarine torpedo. It was 165 feet long and about 27 feet in diameter at the largest part. It had a gas content of 66,000 cubic feet. A 9 horse-power Gramme electric motor was installed, driven by a storage battery. This operated the screw propeller 20 feet in diameter, which was placed at the forward end of the long car. The trial was made on the 9th of August, and was a complete success. The ship was sailed with the wind for about 2½ miles, and then turned about and made its way back against the wind till it stood directly over its starting point, and was drawn down to the ground by its anchor ropes. The trip of about 5 miles was made in 23 minutes. In seven voyages undertaken the airship was steered back safely to its starting point five times.
This first airship which really deserved the name marked an era in the development of this type of aircraft. In view of its complete success it is astonishing that nothing further was done in this line in France for fifteen years, when Santos-Dumont began his series of record-making flights. Within this period, however, the gasoline motor had been adapted to the needs of the automobile, and thus a new and light-weight engine, suitable in every respect, had been placed within the reach of aeronauts.
In the meantime, a new idea had been brought to the stage of actual trial. In 1893, in St. Petersburg, David Schwartz built a rigid airship, the gas receptacle of which was sheet aluminum. It was braced by aluminum tubes, but while being inflated the interior work was so badly broken that it was abandoned.
Schwartz made a second attempt in Berlin in 1897. The airship was safely inflated, and managed to hold its position against a wind blowing 17 miles an hour, but could not make headway against it. After the gas had been withdrawn, and before it could be put under shelter, a severe windstorm damaged it, and the mob of spectators speedily demolished it in the craze for souvenirs of the occasion.
Wreck of the Schwartz aluminum airship, at Berlin, in 1897.
The type of the earlier Santos-Dumont dirigibles. This shape showed a tendency to “buckle,” or double up in the middle like a jackknife. To avoid this the later Santos-Dumonts were of much larger proportional diameter amidships.
In 1898, the young Brazilian, Santos-Dumont, came to Paris imbued with aeronautic zeal, and determined to build a dirigible balloon that would surpass the former achievements of Giffard and Renard, which he felt confident were but hints of what might be accomplished by that type of airship. He began the construction of the series of dirigible balloons which eventually numbered 12, each successive one being an improvement on the preceding. He made use of the air-bag suggested by Meusnier for the balloon of the Duke of Chartres in 1784, although in an original way, at first using a pneumatic pump to inflate it, and later a rotatory fan. Neither prevented the gas-bag from “buckling” and coming down with consequences more or less serious to the airship—but Santos-Dumont himself always escaped injury. His own record of his voyages in his book, My Air-Ships, gives a more detailed account of his contrivances and inventions than can be permitted here. If Santos-Dumont did not greatly surpass his predecessors, he is at least to be credited with an enthusiasm which aroused the interest of the whole world in the problems of aeronautics; and his later achievements in the building and flying of aeroplanes give him a unique place in the history of man’s conquest of the air.
Type of the later Santos-Dumont’s dirigibles.
In 1900, Count von Zeppelin’s great airship, which had been building for nearly two years, was ready for trial. It had the form of a prism of 24 sides, with the ends arching to a blunt point. It was 420 feet long, and 38 feet in diameter. The structure was rigid, of aluminum lattice work, divided into 17 compartments, each of which had a separate gas-bag shaped to fit its compartment. Over all was an outer envelope of linen and silk treated with pegamoid. A triangular keel of aluminum lattice strengthened the whole, and there were two cars of aluminum attached to the keel. Each car held a 16 horse-power Daimler gasoline motor, operating two four-bladed screw propellers which were rigidly connected with the frame of the ship a little below the level of its axis. A sliding weight was run to either end of the keel as might be required to depress the head or tail, in order to rise or fall in the air. The cars were in the shape of boats, and the ship was built in a floating shed on the Lake of Constance near Friedrichshafen. At the trial the airship was floated out on the lake, the car-boats resting on the water. Several accidents happened, so that though the ship got up into the air it could not be managed, and was brought down to the water again without injury. In a second attempt a speed of 20 miles an hour was attained. The construction was found to be not strong enough for the great length of the body, the envelope of the balloon was not sufficiently gas tight, and the engines were not powerful enough. But few trips were made in it, and they were short. The Count set himself to work to raise money to build another ship, which he did five years later.
View of the Zeppelin I, with portion of the aluminum shell and external fabric removed to show the internal framing and separate balloons. In the distance is shown the great balloon shed.
In 1901, an inventor named Roze built an airship in Colombo, having two gas envelopes with the engines and car placed between them. He expected to do away with the rolling and pitching of single airships by the double form, but the ship did not work satisfactorily, ascending to barely 50 feet.
In 1902, Augusto Severo, a Brazilian, arranged an airship with the propelling screws at the axis of the gas-bag, one at each end of the ship. Instead of a rudder, he provided two small propellers to work in a vertical plane and swing the ship sideways. Soon after ascending it was noticed that the propellers were not working properly, and a few minutes later the car was seen to be in flames and the balloon exploded. Severo and his companion Sache were killed, falling 1,300 feet.
Sketch of the Severo airship, showing arrangement of the driving propellers on the axis of the gas-bag, and the steering propellers.
End view of Severo’s airship, showing the longitudinal division of the gas-bag to allow the driving shaft of the propellers to be placed at the axis of the balloon.
In the same year Baron Bradsky-Leboun built an airship with partitions in the gas-bag which was just large enough to counterbalance the weight of the ship and its operators. It was lifted or lowered by a propeller working horizontally. Another propeller drove the ship forward. Through some lack of stability the car turned over, throwing out the two aeronauts, who fell 300 feet and were instantly killed.
The first Lebaudy airship.
In 1902, a dirigible balloon was built for the brothers Lebaudy by the engineer Juillot and the aeronaut Surcouf. The gas envelope was made cigar-shaped and fastened rigidly to a rigid elliptical keel-shaped floor 70 feet long and 19 feet wide, made of steel tubes—the object being to prevent rolling and pitching. It was provided with both horizontal and vertical rudders. A 35 horse-power Daimler-Mercedes motor was used to turn two twin-bladed screws, each of 9 feet in diameter. Between the 25th of October, 1902, and the 21st of November, 1903, 33 experimental voyages were made, the longest being 61 miles in 2 hours and 46 minutes; 38.7 miles in 1 hour and 41 minutes; 23 miles in 1 hour and 36 minutes.
Framing of the floor and keel of the Lebaudy airship.
In 1904 this ship was rebuilt. It was lengthened to 190 feet and the rear end rounded off. Its capacity was increased to 94,000 cubic feet, and a new covering of the yellow calico which had worked so well on the first model was used on the new one. It was coated with rubber both on the outside and inside. The interior air-bag was increased in size to 17,650 cubic feet, and partitioned into three compartments. During 1904 and 1905 30 voyages were made, carrying in all 195 passengers.
The car and propellers of the Lebaudy airship.
The success of this airship led to a series of trials under the direction of the French army, and in all of these trials it proved satisfactory. After the 76th successful voyage it was retired for the winter of 1905-6.
In November, 1905, the rebuilt Zeppelin airship was put upon trial. While superior to the first one, it met with serious accident, and was completely wrecked by a windstorm in January, 1906.
In May, 1906, Major von Parseval’s non-rigid airship passed through its first trials successfully. This airship may be packed into small compass for transportation, and is especially adapted for military use. In plan it is slightly different from previous types, having two air-bags, one in each end of the envelope, and the front end is hemispherical instead of pointed.
As the airship is designed to force its way through the air, instead of floating placidly in it, it is evident that it must have a certain tenseness of outline in order to retain its shape, and resist being doubled up by the resistance it encounters. It is estimated that the average velocity of the wind at the elevation at which the airship sails is 18 miles per hour. If the speed of the ship is to be 20 miles per hour, as related to stations on the ground, and if it is obliged to sail against the wind, it is plain that the wind pressure which it is compelled to meet is 38 miles per hour—a gale of no mean proportions. When the large expanse of the great gas-bags is taken into consideration, it is evident that ordinary balloon construction is not sufficient.
Attempts have been made to meet the outside pressure from the wind and air-resistance by producing mechanically a counter-pressure from the inside. Air-bags are placed inside the cavity of the gas-bag, usually one near each end of the airship, and these are inflated by pumping air into them under pressure. In this way an outward pressure of as much as 7 lbs. to the square foot may be produced, equivalent to the resistance of air at a speed (either of the wind, or of the airship, or of both combined) of 48 miles per hour. It is evident, however, that the pressure upon the front end of an airship making headway against a strong wind will be much greater than the pressure at the rear end, or even than that amidships. It was this uneven pressure upon the outside of the gas-bag that doubled up the first two airships of Santos-Dumont, and led him to increase the proportional girth at the amidship section in his later dirigibles. The great difficulty of adjusting these varying pressures warrants the adherence of Count von Zeppelin to his design with the rigid structure and metallic sheathing.
The loss of the second Zeppelin airship so discouraged its designer that he decided to withdraw from further aeronautical work. But the German Government prevailed on him to continue, and by October, 1906, he had the Zeppelin III in the air. This airship was larger than Zeppelin II in both length and diameter, and held 135,000 cubic feet more of gas. The motive power was supplied by two gasoline motors, each of 85 horse-power. The gas envelope had 16 sides, instead of 24, as in the earlier ship. At its trial the Zeppelin III proved highly successful. It made a trip of 69 miles, with 11 passengers, in 2¼ hours—a speed of about 30 miles an hour.
The Zeppelin III backing out of the floating shed at Friedrichshafen. The illustration shows the added fin at the top, the rudders, dipping planes, and balancing planes.
The German Government now made an offer of $500,000 for an airship which would remain continuously in the air for 24 hours, and be able to land safely. Count von Zeppelin immediately began work upon his No. IV, in the effort to meet these requirements, in the meantime continuing trips with No. III. The most remarkable of these trips was made in September, 1907, a journey of 211 miles in 8 hours.
In October, 1907, the English airship “Nulli Secundus” was given its first trial. The gas envelope had been made of goldbeater’s skins, which are considered impermeable to the contained gas, but are very expensive. This airship was of the non-rigid type. It made the trip from Aldershot to London, a distance of 50 miles, in 3½ hours—an apparent speed of 14 miles per hour, lacking information as to the aid or hindrance of the prevailing wind. Several other trials were made, but with small success.
The offer of the German Government had stimulated other German builders besides Count von Zeppelin, and on October 28, 1907, the Parseval I, which had been improved, and the new Gross dirigible, competed for the government prize, at Berlin. The Parseval kept afloat for 6½ hours, and the Gross for 8¼ hours.
Meanwhile, in France, the Lebaudys had been building a new airship which was named “La Patrie.” It was 197 feet long and 34 feet in diameter. In a trial for altitude it was driven to an elevation of 4,300 feet. On November 23, 1907, the “Patrie” set out from Paris for Verdun, a distance of 146 miles. The journey was made in 6¾ hours, at an average speed of 25 miles per hour, and the fuel carried was sufficient to have continued the journey 50 miles further. Soon after reaching Verdun a severe gale tore the airship away from the regiment of soldiers detailed to assist the anchors in holding it down, and it disappeared into the clouds. It is known to have passed over England, for parts of its machinery were picked up at several points, and some days later the gas-bag was seen floating in the North Sea.
The “Ville-de-Paris” of M. de la Meurthe.
Following close upon the ill-fated “Patrie” came the “Ville-de-Paris,” a dirigible which had been built by Surcouf for M. Henri Deutsch de la Meurthe, an eminent patron of aeronautic experiments. In size this airship was almost identical with the lost “Patrie,” but it was quite different in appearance. It did not have the flat framework at the bottom of the gas envelope, but was entirely round in section, and the long car was suspended below. At the rear the gas-bag was contracted to a cylindrical form, and four groups of two ballonnets each were attached to act as stabilizers. It was offered by M. de la Meurthe to the French Government to take the place of the “Patrie” in the army manœuvres at Verdun, and on January 15, 1908, made the trip thither from Paris in about 7 hours. It was found that the ballonnets exerted considerable drag upon the ship.
In June, 1908, the great “Zeppelin IV” was completed and given its preliminary trials, and on July 1 it started on its first long journey. Leaving Friedrichshafen, its route was along the northerly shore of Lake Constance nearly to Schaffhausen, then southward to and around Lake Lucerne, thence northward to Zurich, thence eastward to Lake Constance, and to its shed at Friedrichshafen. The distance traversed was 236 miles, and the time consumed 12 hours. This voyage without a single mishap aroused the greatest enthusiasm among the German people. After several short flights, during which the King of Württemberg, the Queen, and some of the royal princes were passengers, the Zeppelin IV set out on August 4 to win the Government reward by making the 24-hour flight. Sailing eastward from Friedrichshafen it passed over Basle, then turning northward it followed the valley of the Rhine, passing over Strasburg and Mannheim, and had nearly reached Mayence when a slight accident necessitated a landing. Repairs were made, and the journey resumed after nightfall. Mayence was reached at 11 P. M., and the return trip begun. When passing over Stuttgart, at 6 A. M., a leak was discovered, and a landing was made at Echterdingen, a few miles farther on. Here, while repairs were being made, a squall struck the airship and bumped it heavily on the ground. Some gasoline was spilled, in some unknown way, which caught fire, and in a few moments the great balloon was totally destroyed. It had been in continuous flight 11 hours up to the time of the first landing, and altogether 20¾ hours, and had travelled 258 miles.
The German people immediately started a public subscription to provide Count von Zeppelin with the funds needed to build another airship, and in a few days the sum of $1,500,000 was raised and turned over to the unfortunate inventor. The “Zeppelin III” was taken in hand, and lengthened, and more powerful engines installed.
The “Gross II” was ready to make its attempt for the Government prize on September 11, 1908. It sailed from Tegel to Magdeburg and back to Tegel, a distance of 176 miles, in 13 hours, without landing.
The Clement-Bayard dirigible entering its shed.
Four days later the “Parseval II” made a trip between the same points in 11½ hours, but cut the distance travelled down to 157 miles. In October, the “Parseval II” was sent up for an altitude test, and rose to a height of 5,000 feet above Tegel, hovering over the city for upward of an hour.
During 1908, an airship designed by M. Clement, the noted motor-car builder, was being constructed in France. It made its first voyage on October 29, carrying seven passengers from Sartrouville to Paris and back, at a speed of from 25 to 30 miles per hour. The illustration gives a very good idea of the peculiar ballonnets attached to the rear end of the gas envelope. These ballonnets open into the large gas-bag, and are practically a part of it.
In Italy a remarkable dirigible has been built by Captain Ricaldoni, for military purposes. It has the form of a fish, blunt forward, and tapering straight away to the rear. It has a large finlike surface on the under side of the gas-bag toward the rear. Its performances show that its efficiency as compared with its motive power is larger than any other dirigible in commission.
Engine of the Clement-Bayard dirigible; 7-cylinder; 55 horse-power; weighing only 155 pounds.
In May, 1909, the rebuilt “Zeppelin III,” now rechristened “Zeppelin II,” after many successful short flights was prepared for the Government trial. On May 29, 1909, with a crew of six men, Count von Zeppelin started from Friedrichshafen for Berlin, 360 miles away. The great ship passed over Ulm, Nuremburg, Bayreuth, and Leipzig; and here it encountered so strong a head wind from the north, that it was decided to turn about at Bitterfeld and return to Friedrichshafen. The distance travelled had been nearly 300 miles in 21 hours. The course followed was quite irregular, and took the ship over Wurtzburg, and by a wide detour to Heilbron and Stuttgart. The supply of gasoline running low, it was decided to land at Goeppingen, where more could be obtained. It was raining heavily, and through some mistake in steering, or some sudden veering of the wind, the prow of the great dirigible came into collision with a tree upon the hillside. The envelope was badly torn, and a part of the aluminum inner structure wrecked. However, the mechanics on board were able to make such repairs that the ship was able to resume the voyage the next day, and made port without further mishap. The vessel having been 38 hours in the air at the time of the accident, so much of the Government’s stipulations had been complied with. But it had not succeeded in landing safely. Nevertheless it was accepted by the Government. The entire journey has been variously estimated at from 680 to 900 miles, either figure being a record for dirigibles.
Accident to the new “Zeppelin II” at Goeppingen. The damage was repaired and the airship continued its voyage the next day.
On August 4, the dirigible “Gross II” made a voyage from Berlin to Apolda, and returned; a distance of 290 miles in 16 hours. This airship also was accepted by the German Government and added to its fleet.
In August, the Zeppelin II was successfully sailed to Berlin, where Count von Zeppelin was welcomed by an immense and enthusiastic multitude of his countrymen, including the Emperor and the royal family.
On September 26, the new French dirigible, “La Republique,” built on the model of the successful Lebaudy airships, met with an accident while in the air. A blade of one of the propellers broke and slashed into the envelope. The ship fell from a height of 6,000 feet, and its crew of four men lost their lives.
View of the damaged Zeppelin from the front, showing the tree against which it collided.
On April 22, 1910, a fleet of German dirigibles, comprising the “Zeppelin II,” the “Gross II,” and the “Parseval I,” sailed from Cologne to Hamburg, where they were reviewed by Emperor William. A strong wind having arisen, the “Gross II,” which is of the semi-rigid type, was deflated, and shipped back to Cologne by rail. The non-rigid “Parseval” made the return flight in safety. The rigid “Zeppelin II” started on the return voyage, but was compelled to descend at Limburg, where it was moored. The wind increasing, it was forced away, and finally was driven to the ground at Weilburg and demolished.
In May, 1910, the “Parseval V,” the smallest dirigible so far constructed, being but 90 feet in length, was put upon its trial trip. It made a circular voyage of 80 miles in 4 hours.
For several months a great Zeppelin passenger dirigible had been building by a stock company financed by German capital, under the direction of the dauntless Count von Zeppelin. It was 490 feet long, with a capacity of 666,900 cubic feet. A passenger cabin was built with ¼-inch mahogany veneer upon a framework of aluminum, the inside being decorated with panels of rosewood inlaid with mother-of-pearl. The seats were wicker chairs, and the window openings had no glass. It was christened the “Deutschland.”
After many days waiting for propitious weather the first “air-liner” set sail on June 22, 1910, from Friedrichshafen for Düsseldorf, carrying 20 passengers who had paid $50 each for their passage. In addition there were 13 other persons on board.
The start was made at three o’clock in the morning, and the course laid was up the valley of the Rhine, as far as Cologne. Düsseldorf was reached at three o’clock in the afternoon, the airline distance of 300 miles having been covered in 9 hours of actual sailing. From Mannheim to Düsseldorf, favored by the wind, the great ship reached the speed of 50 miles per hour, for this part of the trip, outstripping the fastest express trains which consume 6 hours in the winding track up the valley.
The next morning the “Deutschland” left Düsseldorf on an excursion trip, carrying several ladies among its passengers. The voyage was in every way a great success, and public enthusiasm was widespread.
On June 29, a test trip was decided upon. No passengers were taken, but 19 newspaper correspondents were invited guests. The Count had been warned of weather disturbances in the neighborhood, but he either disregarded them or felt confidence in his craft. It was intended that the voyage should last four hours, but the airship soon encountered a storm, and after 6 hours of futile striving against it, the fuel gave out. Caught in an upward draft, the “Deutschland” rose to an altitude of over 5,000 feet, losing considerable gas, and then, entering a rainstorm, was heavily laden with moisture. Suddenly, without definite reason, it began to fall vertically, and in a few moments had crashed into the tops of the trees of the Teutoberg forest. No one on board received more than slight injury, and all alighted safely by means of ladders. The “Deutschland” was a wreck, and was taken apart and shipped back to Friedrichshafen.
On July 13, another giant passenger airship, designed by Oscar Erbslöh, who won the international balloon race in 1907 by a voyage from St. Louis to Asbury Park, met with fatal disaster. It was sailing near Cologne at an altitude of about 2,500 feet when it burst, and Erbslöh and his four companions were killed in the fall.
On July 28, the “Gross III” left Berlin with the object of beating the long distance record for dirigibles. Soon after passing Gotha the airship returned to that place, and abandoned the attempt. In 13 hours a distance of 260 miles had been traversed.
Undismayed by the catastrophes which had destroyed his airships almost as fast as he built them, Count von Zeppelin had his number VI ready to sail on September 3. With a crew of seven and twelve passengers he sailed from Baden to Heidelberg—53 miles in 65 minutes. It was put into commission as an excursion craft, and made several successful voyages. On September 14, as it was being placed in its shed at the close of a journey, it took fire unaccountably, and was destroyed together with the shed, a part of the framework only remaining.
On October 15, 1910, the Wellman dirigible “America” which had been in preparation for many weeks, left Asbury Park in an attempt to cross the Atlantic. Its balloon was 228 feet long, with a diameter of 52 feet, containing 345,000 cubic feet of gas. The car was 156 feet in length, and was arranged as a tank in which 1,250 gallons of gasoline were carried. A lifeboat was attached underneath the car. There were two engines, each of 80 horse-power, and an auxiliary motor of 10 horse-power. Sleeping quarters were provided for the crew of six, and the balloon was fitted with a wireless telegraph system. All went well until off the island of Nantucket, where strong north winds were encountered, and the dirigible was swept southward toward Bermuda. As an aid in keeping the airship at an elevation of about 200 feet above the sea, an enlarged trail-rope, called the equilibrator, had been constructed of cans which were filled with gasoline. This appendage weighed 1½ tons, and the lower part of it was expected to float upon the sea. In practice it was found that the jarring of this equilibrator, when the sea became rough, disarranged the machinery, so that the propellers would not work, and the balloon was compelled to drift with the wind. Toward evening of the second day a ship was sighted, and the America’s crew were rescued. The airship floated away in the gale, and was soon out of sight.
On October 16, a new Clement-Bayard dirigible, with seven men on board, left Paris at 7.15 o’clock in the morning, and sailed for London. At 1 P. M. it circled St. Paul’s Cathedral, and landed at the hangar at Wormwood Scrubbs a half hour later. The distance of 259 miles (airline) was traversed at the rate of 41 miles per hour, and the journey surpassed in speed any previous journey by any other form of conveyance.
Copyright by Pictorial News Company.
Wellman dirigible “America” starting for Europe, October 15, 1910.
On November 5, 1910, the young Welsh aeronaut, Ernest T. Willows, who sailed his small dirigible from Cardiff to London in August, made a trip from London across the English Channel to Douai, France. This is the third time within a month that the Channel had been crossed by airships.
Diagram of the Capazza dirigible from the side. A A, stabilizing fins; B, air-ballonnet; R, rudder; M M, motors; FS, forward propeller; SS, stern propeller.
Toward the close of 1910, 52 dirigibles were in commission or in process of construction. In the United States there were 7; in Belgium, 2; in England, 6; in France, 12; in Germany, 14; in Italy, 5; in Russia, 1; in Spain, 1.
The new Capazza dirigible is a decided departure from all preceding constructions, and may mark a new era in the navigation of the air. Its gas envelope is shaped like a lens, or a lentil, and is arranged to sail flatwise with the horizon, thus partaking of the aeroplane as well as the balloon type. No definite facts concerning its achievements have been published.
Capazza dirigible from the front. From above it is an exact circle in outline.
Chapter XV.
BALLOONS: HOW TO OPERATE.
Preliminary inspection—Instruments—Accessories—Ballast—Inflating—Attaching the car—The ascension—Controls—Landing—Some things to be considered—After landing—Precautions.
The actual operation of a balloon is always entrusted to an experienced pilot, or “captain” as he is often called, because he is in command, and his authority must be recognized instantly whenever an order is given. Nevertheless, it is often of great importance that every passenger shall understand the details of managing the balloon in case of need; and a well-informed passenger is greatly to be preferred to an ignorant one.
It is ordinarily one of the duties of the captain to inspect the balloon thoroughly; to see that there are no holes in the gas-bag, that the valve is in perfect working order, and particularly that the valve rope and the ripping cord are not tangled. He should also gather the instruments and equipment to be carried.
The instruments are usually an aneroid barometer, and perhaps a mercury barometer, a barograph (recording barometer), a psychrometer (recording thermometer), a clock, a compass, and an outfit of maps of the country over which it is possible that the balloon may float. Telegraph blanks, railroad time tables, etc., may be found of great service. A camera with a supply of plates will be indispensable almost, and the camera should be provided with a yellow screen for photographing clouds or distant objects.
The ballast should be inspected, to be sure that it is of dry sand, free from stones; or if water is used for ballast, it should have the proper admixture of glycerine to prevent freezing.
It is essential that the inflating be properly done, and the captain should be competent to direct this process in detail, if necessary. What is called the “circular method” is the simplest, and is entirely satisfactory unless the balloon is being filled with pure hydrogen for a very high ascent, in which case it will doubtless be in the hands of experts.
When inflating with coal-gas, the supply is usually taken from a large pipe adapted for the purpose. At a convenient distance from the gas-main the ground is made smooth, and the ground cloths are spread out and pegged down to keep them in place.
The folded balloon is laid out on the cloths with the neck opening toward the gas-pipe. The balloon is then unfolded, and so disposed that the valve will be uppermost, and in the centre of a circle embracing the upper half of the sphere of the balloon, the opening of the neck projecting a few inches beyond the rim of the circle. The hose from the gas-main may then be connected with the socket in the neck.
Balloon laid out in the circular method, ready for inflation. The valve is seen at the centre. The neck is at the right.
Having made sure that the ripping cord and the valve rope are free from each other, and properly connected with their active parts, and that the valve is fastened in place, the net is laid over the whole, and spread out symmetrically. A few bags of ballast are hooked into the net around the circumference of the balloon as it lies, and the assistants distributed around it. It should be the duty of one man to hold the neck of the balloon, and not to leave it for any purpose whatever. The gas may then be turned on, and, as the balloon fills, more bags of ballast are hung symmetrically around the net; and all are continually moved downward as the balloon rises.
Constant watching is necessary during the inflation, so that the material of the balloon opens fully without creases, and the net preserves its correct position. When the inflation is finished the hoop and car are to be hooked in place. The car should be fitted up and hung with an abundance of ballast. Disconnect the gas hose and tie the neck of the balloon in such fashion that it may be opened with a pull of the cord when the ascent begins.
The ballast is then transferred to the hoop, or ring, and the balloon allowed to rise until this is clear of the ground. The car is then moved underneath, and the ballast moved down from the ring into it. The trail-rope should be made fast to the car directly under the ripping panel, the object being to retard that side of the balloon in landing, so that the gas may escape freely when the panel is torn open, and not underneath the balloon, as would happen if the balloon came to earth with the ripping panel underneath.
The balloon is now ready to start, and the captain and passengers take their places in the car. The neck of the balloon is opened, and a glance upward will determine if the valve rope hangs freely through it. The lower end of this should be tied to one of the car ropes. The cord to the ripping panel should be tied in a different place, and in such fashion that no mistake can be made between them. The assistants stand around the edge of the basket, holding it so that it shall not rise until the word is given. The captain then adjusts the load of ballast, throwing off sufficient to allow the balloon to pull upward lightly against the men who are holding it. A little more ballast is then thrown off, and the word given to let go. The trail-rope should be in charge of some one who will see that it lifts freely from the ground.
The balloon rises into the air to an altitude where a bulk of the higher and therefore lighter air equal to the bulk of the balloon has exactly the same weight. This is ordinarily about 2,000 feet. If the sun should be shining the gas in the balloon will be expanded by the heat, and some of it will be forced out through the neck. This explains the importance of the open neck. In some of the early ascensions no such provision for the expansion of the gas was made, and the balloons burst with disastrous consequences.
Inflating a military balloon. The net is being adjusted smoothly as the balloon rises. The bags of ballast surround the balloon ready to be attached as soon as the buoyancy of the gas lifts it from the earth.
When some of the gas has been driven out by the heat, there is less weight of gas in the balloon, though it occupies the same space. It therefore has a tendency to rise still higher. On the other hand, if it passes into a cloud, or the sun is otherwise obscured, the volume of the gas will contract; it will become denser, and the balloon will descend. To check the descent the load carried by the balloon must be lightened, and this is accomplished by throwing out some ballast; generally, a few handfuls is enough.
There is always more or less leakage of gas through the envelope as well as from the neck, and this also lessens the lifting power. To restore the balance, more ballast must be thrown out, and in this way an approximate level is kept during the journey.
When the ballast is nearly exhausted it will be necessary to come down, for a comfortable landing cannot be made without the use of ballast. A good landing place having been selected, the valve is opened, and the balloon brought down within a few yards of the ground. The ripping cord is then pulled and ballast thrown out so that the basket will touch as lightly as possible. Some aeronauts use a small anchor or grapnel to assist in making a landing, but on a windy day, when the car is liable to do some bumping before coming to rest, the grapnel often makes matters much worse for the passengers by a series of holdings and slippings, and sometimes causes a destructive strain upon the balloon.
In making an ascent with a balloon full of gas there is certain to be a waste of gas as it expands. This expansion is due not only to the heat of the sun, but also to the lighter pressure of the air in the upper altitudes. It is therefore the custom with some aeronauts to ascend with a partially filled balloon, allowing the expansion to completely fill it. This process is particularly advised if a very high altitude is sought. When it is desired to make a long voyage it is wise to make the start at twilight, and so avoid the heat of the sun. The balloon will then float along on an almost unchanging level without expenditure of ballast. Rain and even the moisture from clouds will sometimes wet the balloon so that it will cause a much greater loss of ballast than would have been required to be thrown out to rise above the cloud or storm. Such details in the handling of a balloon during a voyage will demand the skilled judgment of the captain.
A balloon ready for ascent. Notice that the neck is still tied.
The trail-rope is a valuable adjunct when the balloon is travelling near the ground. The longer the part of the trail-rope that is dragging on the ground the less weight the balloon is carrying. And at night, when it is impossible to tell the direction in which one is travelling in any other way, the line of the trailing rope will show the direction from which the wind is blowing, and hence the drift of the balloon.
The care of the balloon and its instruments upon landing falls upon the captain, for he is not likely to find assistants at hand competent to relieve him of any part of the necessary work. The car and the ring are first detached. The ropes are laid out free and clear, and the valve is unscrewed and taken off. The material of the balloon is folded smoothly, gore by gore. The ballast bags are emptied. After all is bundled up it should be packed in the car, the covering cloth bound on with ropes, and definite instructions affixed for transportation to the starting-point.
It is apparent that the whole of the gas is lost at the end of the journey. The cost of this is the largest expense of ballooning. For a small balloon of about 50,000 cubic feet, the coal-gas for inflating will cost about $35 to $40. If hydrogen is used, it will cost probably ten times as much.
In important voyages it is customary to send up pilot balloons, to discover the direction of the wind currents at the different levels, so that the level which promises the best may be selected before the balloon leaves the ground. A study of the weather conditions throughout the surrounding country is a wise precaution, and no start should be made if a storm is imminent. The extent of control possible in ballooning being so limited, all risks should be scrupulously avoided, both before and during the voyage, and nothing left to haphazard.
Chapter XVI.
BALLOONS: HOW TO MAKE.
The fabrics used—Preliminary varnishing—Varnishes—Rubberized fabrics—Pegamoid—Weight of varnish—Latitudes of the balloon—Calculating gores—Laying out patterns and cutting—Sewing—Varnishing—Drying—Oiling—The neck—The valve—The net—The basket.
The making of a balloon is almost always placed in the hands of a professional balloon-maker. But as the use of balloons increases, and their owners multiply, it is becoming a matter of importance that the most improved methods of making them should be known to the intending purchaser, as well as to the amateur who wishes to construct his own balloon.
The fabric of which the gas envelope is made may be either silk, cotton (percale), or linen. It should be of a tight, diagonal weave, of uniform and strong threads in both warp and woof, unbleached, and without dressing, or finish. If it is colored, care should be exercised that the dye is one that will not affect injuriously the strength or texture of the fabric. Lightness in weight, and great strength (as tested by tearing), are the essentials.
The finest German percale weighs about 2½ ounces per square yard; Russian percale, 3⅓ ounces, and French percale, 3¾ounces, per square yard. The white silk used in Russian military balloons weighs about the same as German percale, but is very much stronger. Pongee silk is a trifle heavier. The silk used for sounding balloons is much lighter, weighing only a little over one ounce to the square yard.
Goldbeater’s skin and rubber have been used to some extent, but the great cost of the former places it in reach only of governmental departments, and the latter is of use only in small balloons for scientific work—up to about 175 cubic feet capacity.
The fabric is first to be varnished, to fill up the pores and render it gas-tight. For this purpose a thin linseed-oil varnish has been commonly used. To 100 parts of pure linseed-oil are added 4 parts of litharge and 1 part of umber, and the mixture is heated to about 350° Fahr., for six or seven hours, and stirred constantly. After standing a few days the clear part is drawn off for use. For the thicker varnish used on later coats, the heat should be raised to 450° and kept at about that temperature until it becomes thick. This operation is attended with much danger of the oil taking fire, and should be done only by an experienced varnish-maker.
The only advantages of the linseed-oil varnish are its ease of application, and its cheapness. Its drawbacks are stickiness—requiring continual examination of the balloon envelope, especially when the deflated bag is stored away—its liability to spontaneous combustion, particularly when the varnish is new, and its very slow drying qualities, requiring a long wait between the coats.
Another varnish made by dissolving rubber in benzine, has been largely used. It requires vulcanizing after application. It is never sticky, and is always soft and pliable. However, the rubber is liable to decomposition from the action of the violet ray of light, and a balloon so varnished requires the protection of an outer yellow covering—either of paint, or an additional yellow fabric. Unfortunately, a single sheet of rubberized material is not gas-tight, and it is necessary to make the envelope of two, or even three, layers of the fabric, thus adding much to the weight.
The great gas-bags of the Zeppelin airships are varnished with “Pegamoid,” a patent preparation the constituents of which are not known. Its use by Count Zeppelin is the highest recommendation possible.
The weight of the varnish adds largely to the weight of the envelope. French pongee silk after receiving its five coats of linseed-oil varnish, weighs 8 ounces per square yard. A double bag of percale with a layer of vulcanized rubber between, and a coating of rubber on the inside, and painted yellow on the outside, will weigh 11 ounces per square yard. Pegamoid material, which comes ready prepared, weighs but about 4 ounces per square yard, but is much more costly.
In cutting out the gores of the envelope it is possible to waste fully ⅓ of the material unless the work is skilfully planned. Taking the width of the chosen material as a basis, we must first deduct from ¾ of an inch to 1½ inches, in proportion to the size of the proposed balloon, for a broad seam and the overlapping necessary. Dividing the circumference at the largest diameter—the “equator” of the balloon—by the remaining width of the fabric gives the number of gores required. To obtain the breadth of each gore at the different “latitudes” (supposing the globe of the balloon to be divided by parallels similar to those of the earth) the following table is to be used; 0° representing the equator, and 90° the apex of the balloon. The breadth of the gore in inches at any latitude is the product of the decimal opposite that latitude in the table by the original width of the fabric in inches, thus allowing for seams.
Finsterwalder’s method of cutting material for a spherical balloon, by which over one-fourth of the material, usually wasted in the common method, may be saved. It has the further advantage of saving more than half of the usual sewing. The balloon is considered as a spherical hexahedron (a six-surfaced figure similar to a cube, but with curved sides and edges). The circumference of the sphere divided by the width of the material gives the unit of measurement. The dimensions of the imagined hexahedron may then be determined from the calculated surface and the cutting proceed according to the illustration above, which shows five breadths to each of the six curved sides. The illustration shows the seams of the balloon made after the Finsterwalder method, when looking down upon it from above.