CHAPTER I MODEL AEROPLANES OF 1911
For the average boy there is no more stirring music than the brisk, whirring note of his model aeroplane. Let the propellers spin steadily for ten glorious seconds, and the journey spans a couple hundred feet or more. Double the time and the flight becomes a triumph. Out of the ingenuity of thousands of boy aviators, the world over, has come a surprising development of the model aeroplane. The experimental stage is passed. Any bright boy may now build a model aeroplane which is certain to give results. The distance qualities of your model may even rival your endurance as a runner in keeping pace with it.
Working along different lines, the builders of model aeroplanes, widely scattered, seem to be gradually developing much the same type of air craft. The tendency is toward the construction of much lighter and more logical models than last year. In place of the complicated models supported by several broad planes, we find the most successful amateur aviators expending all their ingenuity upon simple monoplane forms. The biplane forms are being abandoned by model builders, as well as the biplane form of elevating planes. In place of the models made from fifty or more members, we now find excellent models, capable of much longer flights, formed of but a dozen pieces. The builders of model aeroplanes are keeping pace with the development of the man-carrying machines, if they are not passing them, in developing the flying machine of the future.
Improvement in the distance qualities of the model aeroplanes, in the past few months, has been remarkable. At one of the first model aeroplane tournaments, held in New York, less than two years since, the longest flight was under sixty feet. In less than one year, flights of more than 200 feet had become common. To-day the improved racing model aeroplanes have flown more than 2,500 feet. As a result of the labors of the boy aviators, it is much easier to build a successful model flying machine to-day than it was a year ago.
What may be called the 1911 type of model aeroplane looks every inch a racer. Every unnecessary stick and string has been cut away. When skids are used they are of the lightest possible material and the simplest construction. The miniature rubber-tired wheels, with ball bearings, which made many of last year's models so attractive, are rarely used. The plane surface has been reduced fully one half. One great secret of success is in the cutting down of weight. When your propeller has but half the work to do, the length of the flight is, of course, greatly increased.
Our amateur aviators are attacking one great problem of aviation which the pilots of man-carrying crafts are perhaps neglecting. Model aeroplanes are built to maintain their equilibrium in the air automatically. They must not only rise from the ground, prepared for a long flight, but must be contrived to resist all manner of baffling air currents aloft. Watch the successful model as it gains its altitude, settles down to a horizontal flight, is perhaps knocked off its course by a cross current, and steadies itself with a graceful curve and proceeds on its way.
All these problems must be anticipated. The young aviator must ingeniously arrange his planes and ballast in advance. The regular sky pilot, on the other hand, meets the problems of the air as he encounters them, by flexing his wings against disturbing currents or by banking to maintain an even keel at a turn. If the man-carrying airship had to be prepared to meet all these problems before it left the ground, the problem would be, of course, much more complicated.
In other words, if the motor of a large machine were started and the aeroplane launched without a pilot, would its chances of flight be as good, in proportion to its size, as those of our best model aeroplanes? A model aeroplane which flies 300 feet performs as remarkable a feat as would a large machine flying, unguided, a mile or more. The progress in the construction of model aeroplanes, in brief, already deserves serious scientific consideration.
The last twelve months have brought out a surprising number of new aeroplanes, while notable progress has been made in the standard types. To realize the immense strides or flights forward in the construction of heavier-than-air machines, one need only set the 1911 models beside the aeroplanes of a year or two years since. Even to the eye of the layman in such matters, the older machines are beginning to appear obsolete. In a previous volume, it was suggested that within a few years the aeroplane of to-day would appear like cumbersome stage coaches to one familiar with racing automobiles, and certainly the prophecy is being quickly realized.
The general tendency is in the direction of greater simplicity in design in passenger-carrying craft, as in model aeroplanes. Both the monoplane and biplane types are being developed side by side, and each continues to have its enthusiastic advocates. The increase in the passenger-carrying qualities is realizing the most sanguine hopes. Aeroplanes have carried fifteen passengers for several miles. The speed qualities of machines have developed correspondingly.
If the development of model aeroplanes leads the way in perfecting heavier-than-air machines, as many believe, the monoplane form seems destined to replace all multiplane types. During the past year practically all of the biplane forms have been abandoned by model builders. As a result of wide experiments, it has been found that the monoplane exerts more sustension per unit of surface than any two or three-plane machines. In theory, it is, of course, possible to increase the sustained force by setting one plane above another, but in practice it has been found that the planes must be set so far apart that the arrangement is impracticable. When planes are separated, they must, of course, be stayed and trussed to keep them rigid, and all this adds to the weight and complexity of the machine.
A good specimen of plane building.
"Finish one end of the blade before cutting away the opposite end."
Model aeroplane. Designed by Cecil Peoli.
The builder of model aeroplanes has a great advantage over the designer of man-carrying crafts. The spread of the wings of his model is comparatively small, and the problem of staying and trussing is greatly simplified. The monoplane, especially in a model, requires practically no staying at all. Then again the skin friction is greatly reduced in the monoplane form. Simple as it is, there are great possibilities in the arrangement of these surfaces. The effect of outline upon resistance again may be more closely observed in the monoplane than in the multiplane forms. In other words, if your model goes wrong, it is far easier to locate the fault and rectify it than in the more complicated arrangement of planes.
The flights of the English models this year are longer than those made in America, but, on the other hand, we are solving many practical problems of aviation, in our model building, which the English have not attempted. Even in the case of our single-stick frames built in America, the tendency is toward more stable construction than abroad. The best English models would not qualify for an American model tournament, since they could not rise from the ground.
The best American models, on the other hand, would be outdistanced in an English meet, but their flights would show them to have far greater automatic stability than their English rivals. It is extremely interesting to speculate whether the American or English types of model aeroplanes will survive, and which is contributing more to the solving of the great mysteries of aviation, but, after all, it is a question which only time can answer.
Compare typical flights of the American and English models, and the contrast becomes obvious. The English model is usually held and thrown forward. The starter thus gives it its altitude and direction. Being extremely light, they gain a great deal from the wind. Their flights are usually in straight lines, or in slightly undulating curves. Under favorable conditions, their distance qualities are remarkable. Flights of six or eight hundred feet are common, while the present record is over 2,500 feet or nearly half a mile.
In an American model tournament, the models are set upon the ground and left to themselves. As a rule, it is not even permitted to give them a slight push. The motor must be powerful enough to carry them onward and upward unassisted. In many cases they must be clear of the ground within twenty feet or the flight is disqualified. It is, of course, obvious that the motors must be far stronger than in the case of the English models, and that their frames must therefore be correspondingly heavier to support the weight. The plane surface, in turn, must be increased to support this weight. The average English models, even with American skids, would not leave the ground at all.
Once in the air, the behavior of the American model, again, is entirely different from its English rival. Our aeroplanes are off with a rush. The first part of the flight is at a more or less sharply drawn angle of elevation. It usually rises to an altitude of from ten to twenty feet in a straight line. To secure a good rise requires a much more scientific adjustment of the planes and weighting than in the case of the English models. As it reaches its altitude, it adjusts itself, and here the problem of stability comes in. The marvelous little craft balances itself with the least possible loss of time and power, comes to a horizontal position, and is off on its flight. If its adjustment is not all it should be, it will, of course, fail to right itself and fall backward, or, as the phrase goes "sit on its tail." It is estimated that one-third of the power of the motors is used up in leaving the ground and rising to its maximum altitude.
Our American model builders believe that their flights are far more scientific than in the case of a hand-launched model, and that they are doing more for the actual development of the art of aviation than their English cousins. Whether one prefers to watch an American or English tournament is, of course, largely a matter of taste; certainly both are fascinating.
Much has been learned about motors. It has been found that the rubber motor is capable of great development. Since a flight of one-half a mile may be made by twisted bands of rubber, the average model builder may be content to let clock work and miniature gasoline engines take care of themselves. By building and flying thousands of models, we have found what form of rubber strand is best, just how heavy the strands should be, and the most efficient point of winding. Instead of short heavy bands, we now use much longer and more slender motors. The efficiency of rubber motors has been greatly increased by arranging them in series and connecting them up by gear wheels. It is even possible to buy miniature gasoline motors suitable for model aeroplanes. Flights of more than one mile have been made in this way.
All the best models this year are equipped with twin propellers. It is very little more trouble to build two motors than one, and the model thus equipped will not only travel much further, but will insure much more stable flights. A common trouble in model building has been the lack of stability. Your model has been likely to capsize, even under favorable conditions, spoiling the flight, while a chance gust of wind would knock it out of its course in spite of everything you could do. To overcome this tendency, the surface of the planes might be increased, but this added to the weight of the model, thus cutting down the length of the flights. The twin propellers cut at the root of the problem. They balance the thrust, thus making the flight even and stable. The planes may also be made much smaller with a gain in weight which, in turn, lengthens the flight.
A variation on a familiar form.
An excellent model designed and built by H. Wakkins.