The Boys' Book of Model Aeroplanes / How to Build and Fly Them: With the Story of the Evolution of the Flying Machine

by Francis A. Collins

The question of rudders or guiding planes is very important. It is too much to expect of even the best model that it will fly in an unswerving line. Any simple vertical plane which may be turned from side to side and held in position will act as a rudder. There is great difference of opinion as to the proper size and position of these guiding surfaces. It is argued by some aviators that the rudder should be placed above the plane, where the air is undisturbed, while others believe that the partial vacuum created above the wings in flight makes the propeller ineffective. Still others argue that a rudder placed back of the planes affords a leverage, and is therefore more effective. Try a rudder in each position. It is impossible to lay down a law for all models.

The larger models should be equipped with twin propellers. In building these the greatest care should be taken to have them exactly the same size, weight, and pitch. Twin propellers should, as a rule, be placed at the front of the machine, that is, they should pull and not push the planes. If by any accident the motor of one should fail, the second propeller will continue to keep the aëroplane afloat and break its fall on descending. With the propellers at the stern of the little airship, the failure of one would cause the plane to pitch downward, and the remaining propeller would drive it down to possible disaster.

In winding up the two motors, care should be taken to give both the same number of turns. The aëroplane may be launched by holding a propeller in either hand and releasing simultaneously. The double motor insures a steadier as well as a longer flight. Always turn the propellers in opposite directions. In flying they must spin around either toward each other or away from each other. If they turn the same way they will give the model a torque which no rudder could possibly overcome.

The efficiency of your motor depends more upon its length than its diameter. In constructing the motor-base, especially for the larger models, arrange to have the strands of rubber bands extend the entire length of your aëroplane, and if necessary, project well forward of the front plane. Such a motor in unwinding will exert a more sustained force. The shorter strands of greater diameter will unwind much more quickly and give very short flights.

With a little experience you will soon learn to gauge your motor to the needs of your air-ship. It is, of course, absolutely necessary that the force exerted by the motor should be sufficient to keep your aëroplane in rapid motion, but it is easy to make it too powerful. If it were possible to attach a “governor” to your motor, this would not matter so much. But since this is practically out of the question, the motor itself must be very nicely proportioned to the demand made upon it. You will soon be able to judge between the steady whir of a good motor, and the buzz of a propeller which races. There is a distinct note for each.

The motor is, at present, the great problem of the model aëroplane. The rubber bands are, at best, only a make-shift. It is practically out of the question to get a flight of more than fifteen seconds in this way, so that the distance is limited to a little more than two hundred feet. It is doubtless only a question of time before a much more efficient form of motor will be invented. Very probably, some amateur aviator will be the first to apply a new means of propulsion, which would be an important achievement indeed.

The simplest form of motor after the rubber bands would seem to be some form of metal spring which could be wound up. Long before the days of automobiles, as we now know them, wagons were built with motors of springs, and some surprising runs were obtained. The spring lends itself to many forms of construction, and is not expensive. It will be necessary to control its action in some way, however, to prevent it from racing and running down in almost no time, like the too heavy rubber motors. It might be found interesting to experiment with the spring to be found in the ordinary roller-shade. The weight of these springs is not too great to be carried by a good aëroplane model, which, of course, is a great factor in their favor.

Detail of Rudder and Propeller of Model Built from Drawing ([Plate C]).

A number of experiments have been made in France to equip aëroplane models with compressed-air motors. The compressed air is carried in a hollow tube in much the same position as the rubber bands. Many believe that the motor problem, for the toy aëroplane will be solved in this way. A number of interesting models have also been equipped with clock-work motors. A small movement, such as may be borrowed from some mechanical toys, will run for a minute or more. What glorious flights would be possible if our models could be kept aloft—say five times as long as at present. When you feel that you thoroughly understand your model, borrow the clock work from some old toy and make the experiment. It is possible to buy motors for model aëroplanes. The smallest of these develops one half horsepower, weighs seven pounds and will run for fifteen minutes.