The lightest of all available materials is bamboo. It is difficult to procure, however, and requires more working up than the others. The best plan is to buy a stick of bamboo, a dry piece, and split it into strips of the desired length and thickness. The grain is so straight that there is practically no waste material as in ordinary wood. The strips may be readily planed or sandpapered. The wood is extremely light and strong enough for all practical purposes of the model aëroplane builder. An old bamboo fishing-pole may answer your purpose.
The first gliders constructed should be of the monoplane form, that is, with a single surface. The biplane or multiplane models will come later. Meanwhile, one is not losing time in working only on these simple models, for the experience is valuable and nothing is lost, since when the frame is properly constructed the motor and propeller may be added. The work throughout is extremely simple, and there are no problems of which the average ingenious American boy need be afraid.
DIAGRAM FOR PLAN OF THE AËROPLANE ON PAGE 58.
DIAGRAM—SHOWN IN PERSPECTIVE.
Plate A.
To construct the model shown in Plate A first make two frames of dowel-sticks, bamboo, or reed, or, if these be lacking, of light lath, the smaller frame 8½ by 19½ and the larger one 10½ by 36½ inches. Care must be taken to have the sides of the rectangle exactly the same length and the joints closely and neatly finished. Some boys prefer to lay one stick over another, then wrap the joint tightly with thin but strong linen thread, and over this brush a coat of thin glue, without using any brads or nails.
In kite-building, to be sure, it would be enough to lay the strips over one another and fasten roughly with a tack. Nor did the lengths of the stick, when covered with paper, make much if any difference. The aëroplane, it must be remembered, travels edgewise, and, having no guiding string, is at the mercy of every gust of wind. If the frames are carelessly proportioned it will not travel true, but is likely to be deflected. Imagine a boat whose sides are not exactly uniform trying to travel in a straight line. It would be lopsided, and would roll and pitch under the most favorable conditions. Now an aëroplane, since it travels in so thin a medium as air, is far more sensitive than a boat, and it becomes lopsided if its proportions be in the least inaccurate. Only the greatest care in construction will produce an air craft which will fly true and straight.
It makes little or no difference in a kite if the ends project a little and the joints be carelessly made. Not only must your aëroplane be perfectly proportioned, but it must be finished like a piece of fine furniture. The question of friction is a very important one in the heavier-than-air machine. You cannot be too careful to round off every corner and smooth every exposed surface. If you have opportunity to see a regular aëroplane, a Wright or Curtiss model, you will find that every part of the machine has been sandpapered and varnished with the greatest care. This is not done for the sake of appearances, but because it has been found that the wind striking against the rough piece of wood meets an appreciable amount of resistance, whereas it slips past a polished surface with little or no friction. Your aëroplane should be finished like a violin.
A Coil of Cane or Reed.
In building these planes be careful to compare the lengths of the corresponding sides throughout. If you prefer to use brads for fastening the joints do so. The dowel-stick and bamboo will take the brads with little danger of splitting. When thoroughly dry, cut away the glue which has squeezed out, round off the ends, and sandpaper with fine sand or emery-paper. If you use brads it will not be necessary to place the joints in a vise while drying. Should your strips split, bore the holes with a fine awl. Some boys after drilling the holes merely tie and glue the sticks together, using no nails whatever.