Engineering Wonders of the World
Volume III

THE CONSTRUCTION OF AEROPLANES AND AERIAL PROPELLERS. A PART from the engine, propeller, and Z-X under-carriage, the aeroplane may A -*• appear to the uninitiated to be an apparatus that could easily be constructed by any person “ clever with his hands.” The decks are merely wooden frames covered on one or both sides by fabric, the spars and outriggers nothing but easily-shaped pieces of wood. Such staying with, cross wires as is necessary looks a simple enough job. In short, the building of an ordinary pleasure boat would seem to be a much more difficult business for any one who had never tried his hand on it before. A closer examination of the matter shows, however, that the aeroplane is not so simple a structure as a first view might lead one to think. The designer has constantly to wrestle with an arch enemy, weight, which will sneak its way in if given half a chance ; and in keeping it at bay, he must be careful not to open the door to weakness. Then, too, he has to beware of exposing an undue amount of resisting—as distinguished from lifting— surface to the air, lest he should waste the power of his engine in useless work. To begin with the materials used. Bamboo is commonly considered to be extraordinarily strong for its weight. As a matter of fact, it is in this respect decidedly inferior to many other woods ; while its hollowness, and the impossibility of shaping it to any required section, restrict its usefulness considerably. A table of relative strengths shows that Honduras mahogany is, weight for weight, two and a half times as tough as bamboo ; lancewood, twice ; spruce, one and a half times ; ash, one and a third times. As the chassis of a motor car is built entirely of metal, but different metals are used for different purposes, so in the wooden frame- work of an aeroplane we find different kinds of wood W°°ds used, selected for special duties. Upright stanchions between decks may be of ash ; the main spars of spruce ; the ribs of ash, hickory, or poplar—woods which can easily be bent to the proper curves. For the main spars of a deck, spruce is most commonly used when it can be obtained in sufficient lengths, and is free from knots and “ shakes.” To the spars are attached the ribs, which are steamed and bent to shape on wooden templates. The number of spars varies Recording to the type of machine. Biplane decks usually have two only. A monoplane deck, having to rely on itself for stiffness, as the girder form of con- struction is not available with a single tier of decks, may possess several auxiliary spars, in addition to the two main ones. These last, in the case of the Bleriot short-span mono- plane, have projecting ends which fit into sockets in the body of the machine, to render the wings easily detachable for transport. Poe K e t Flexible BacKEdge Fig. 1.—A SINGLE-SURFACED DECK, SHOWING POCKETS COVERING SPARS. Decks are either single or double-surfaced. The first type (see Fig. 1) has the ribs attached to the top of the front spar 1 Decks« and to the under side of the rear spar. The fabric—cotton cloth or silk impregnated with rubber or faced with cellu-