The struts, so-called, to continue the analogy with the main planes, are turned sticks of spruce 3/8 inch in diameter. They are fitted at each end with ferrules of thin 3/8-inch brass, or steel tubing, driven on tight. Instead of using sockets, the struts are held at each end, simply by a long wood screw driven through the tin and wood of the plane frame and into the strut. These screws also hold the turnbuckles for the truss wires. For trussing purposes, the elevator is regarded as consisting of two sections only, the intermediate struts being disregarded.
The turnbuckles and wire used here and in the other control members may well be of lighter stock than those used in the main planes. Piano wire, No. 18, or 1/16-inch cable is amply strong. The sheet steel may be about 22 gauge, instead of 16, and the bicycle spokes smaller in proportion. No turnbuckle plates are necessary. The screws running into the struts may be passed directly through the eyes of the turnbuckles, where they would have been attached to the turnbuckle plate. In order to secure a square and neat structure, those struts which have turnbuckles at their ends should be made a trifle shorter than the others.
At each end, the elevator has an X-shaped frame of 1/4-inch steel tubing; at the intersection of the X's are pivots on which the elevator is supported. Each X is made of two tubes, bent into a y and flattened and brazed together at the points. The ends of the X's are flattened and bent over so that the screws which hold the struts in place may pass through them.
Fig. 19. Curtiss Biplane Ready for Flight
To the front middle strut is attached an extension which acts as a lever for operating the elevator. This is a stick of spruce 3/4 inch in diameter and 3 feet 3 inches long. At its upper end it has a ferrule of steel tubing, flattened at the end. The lower part of the stick may be fastened to the strut by wrapping the tube with friction tape, or by improvising a couple of sheet steel clamps. The upper end of the stick is braced by a 1/4-inch steel tube, extending to the top of the rear middle strut, and held by the same screw as the strut. This extension lever is connected to the steering column by a bamboo rod, 1 inch in diameter and about 10 feet long, provided with flattened ferrules of steel tubing at each end. Each ferrule should be held on by a 1/8-inch stove bolt passing through it.
Front and Rear Outrigger Frames. Both the front elevator and the tail and rudder at the rear, are carried, as mentioned above, each on a pair of A-shaped frames, similar to one another, except that those in the rear are longer than those in the front. Both are made of spruce of about the same section as used for the struts of the main frame. These pieces may either be full length, or they may be jointed at the intersection of the crosspieces, the ends being clamped in a sheet-steel sleeve, just like that used on the beams of the main frame. In this case, it is advisable to run a 1/8-inch stove bolt through each of the ends.
Fig. 20. Details of Outriggers and Front Elevating Planes as Seen from Driver's Seat
The crosspieces of the A-frames are spruce of the same section, or a little smaller. At their ends may be used strut sockets like those of the main frame; or, if it is desired to save this expense, they may be fastened by strips of 1/16-inch steel stock with through bolts.