Inserting the struts in their sockets between the upper and lower sections of the same side will now form either of the two sides of the machine complete. Care should be taken to get the rear struts the proper length with respect to the front ones to bring the upper and lower planes parallel. The distance from the top of the lower front beam to the top of the upper front beam should be the same as the distance between the rows of bracing holes in the upper and lower main ribs just above and below the rear struts—about 4 feet 6 inches. It should hardly be necessary to mention that the thick edges of the struts come to the front—they are fish-shaped and a fish is thicker at the head than at the tail.
The truss wires may now be strung on in each square of the struts, beams, and main ribs, using turnbuckles as previously described. The wires should be taut enough to sing a low note when plucked between the thumb and forefinger. If the construction is carried out properly, the framework will stand square and true with an even tension on all the wires. It is permissible for the struts to slant backward a little as seen from the side, but all should be perfectly in line.
For adjusting the turnbuckles, the builder should make for himself a handy little tool usually termed a nipple wrench. It is simply a strip of steel 1 1/2 by 1/2 by 3/32 inches, with a notch cut in the middle of the long sides to fit the flattened ends of the turnbuckle nipples. This is much handier than the pliers and does not burr up the nipples.
It has been assumed in this description of the assembling that the builder is working in a limited space; if, on the contrary, he has room enough to set up the whole frame at once, the work will be much simpler. In this case, the construction bed should be 30 feet long. First build up the upper plane complete, standing it against the wall when finished; then build the lower plane, put the struts in their sockets, and lay on the upper plane complete.
Returning to the plan of assembly by sections, after the side sections or wings of the machine have been completed, the struts may be taken out and the sections laid aside. The middle section, to which the running gear and outriggers will be attached, is now to be built up in the same way. If the builder is following the plan in which there is one main rib between each section, it will be necessary to take off the four inner main ribs from the sections already completed, to be used at the ends of the central section. The plan drawing of the complete machine shows that the ribs of the central section are cut off just back of the rear beam to make room for the propeller. This is necessary in order to set the motor far enough forward to balance the machine properly. The small ribs in this section have the same curve but are cut off 10 inches shorter at their rear ends, and the stumps are smoothed down for ferrules like those for the other small ribs. In the plan which has one main rib between each section, the main rib on each side of the central section must be left full length. In the quick-detachable plan with two main ribs on each side of the central section, the inner ones, which really belong to this section, are cut off short like the small ribs.
In the drawing of the complete machine, the distance between the struts which carry the engine bed is shown as 2 feet. This is only approximate, as the distance must be varied to suit the motor employed. By this time, the builder will have decided what engine he is going to use—or can get—and should drill the holes for the sockets of these struts with due respect to the width of the engine's supporting feet or lugs, remembering that the engine bed beams go on the inside of the struts. In the drawing of the running gear. Fig. 17, the distance between the engine-bed struts has been designated A. The distances, B, on each side are, of course, approximately (6'— 2*A*), whatever A may be.
VIEW OF THE FRENCH AVIATION GROUNDS SHOWING THE HANGARS RANGED ALONG THE EDGES OF THE FIELD
This Photograph Protected By International Copyright
EXAMINATION PAPER
BUILDING AND FLYING AN