The best covering for the wings still remains largely an open question. Although your model will make successful flights with almost any kind of covering, you will find that its stability will be increased and the flight lengthened by a little attention to this detail. According to the Wright Brothers, the most successful covering is the one which offers the greatest resistance to the air. The pressure of the air upward under the planes tends to force its way through the meshes of even the finest cloth. The addition of a coat of varnish will prevent this leakage. A light parchment will also be found effective. It will be well to experiment with a variety of coverings.
A very light, serviceable frame may be made for your motor-base by using hollow shafts or sticks. Procure a very thin, light wood, such as is used for veneering, and after cutting it carefully into strips, glue them together to form a hollow shaft about an inch square. Although the shell may be only one sixteenth of an inch thick, the frame will be found strong enough for all practical purposes. A hollow frame of this kind will save several ounces of weight.
The builder of aëroplane models will find a good friend in aluminium. It is strong enough for all purposes of the model air-ship and, even when used freely, adds almost nothing to the weight. The metal costs ninety cents a pound, but it is so light that, at this rate, it will be found a very cheap material. Comparatively thick pieces may be used for braces or for angles, thus making the frame absolutely rigid, while adding but a fraction of an ounce to the weight. The metal, being comparatively soft, is easily worked, and simple castings may be made at little expense.
Many builders of aëroplanes waste time and ingenuity quite unnecessarily in constructing sets of wheels for carrying their models. The time would be better employed in looking to your planes. The amount of friction saved by attaching wheels, even good ones, to your model, is after all very trifling. Should the wheels jam or stick, which is likely to be the case with such small models, they are worse than skids, and besides, add appreciably to the weight. A light skid is better than a clumsy wheel. If your model fails to rise from the ground, the fault is not at all likely to be in the skids, but in the thrust or lifting-surface.
An excellent plan for guiding the flights is to add square frames of soft lead wire to the front or cutting-edge of your front planes. Bend a piece of wire to form three sides of a square, each two or three inches long, and fasten the loose ends to the plane. By bending these up or down, the center of gravity may be altered at a touch. If your model goes askew, you may bend one of these up and the other down, until you get the desired balance.
In actual practice, the soaring- or floating-planes seem to add greater stability to the model and effect to a marked degree the length of the flight. It is difficult to tell exactly why. The planes in passing may create an eddy in the air, a following wave, as it were, which tends to retard the flight, while the floating-plane smoothes this out. In any event, here is an experiment well worth trying.
CHAPTER VI
SIMPLE MONOPLANE MODELS
OF the variety of aëroplanes, there seems to be no end. Nature offers a bewildering variety of models in the innumerable birds and insects, which may be accepted as successful monoplanes. These, in turn, may be copied and modified indefinitely. The science of aviation is still so young that there is ample opportunity for invention and discovery for all, and every new trial adds something to our information, and carries the science a step nearer perfection.
It will be found an excellent plan to build, once and for all, a strong well proportioned motor base, and mount a powerful motor and well modeled propeller. A variety of planes may then be tested out by attaching them to this. The motor base will answer for practically all monoplane forms and many biplane models as well. Such a frame should be about three feet in length and carry one or better two motors, placed side by side.