The frame is braced further by an upwardly arched strip of bamboo, as shown indiagram 11, this strip being 2¹⁄₂″ in height. At the top of this brace are two bronze strips of No. 32 gauge brass, one above the other, one on top of the brace and the other below.
Adjacent the ends of these strips of metal are perforations through which pass bracing wires, one of which wires runs to the front of the frame where a hook is mounted for its reception, and the other two wires extend to the rear of the frame where they are secured to the propeller brace. The propeller brace consists of a strip of streamlined spruce 11³⁄₄″ in length, the propellers being at an angle, thus clearance is allowed ¹⁄₄″ wide at the center, tapering to ³⁄₁₆″ at the ends. The ends of the propeller brace extend out one inch from the side members of the frame, to allow room for the rubber strands to be used as motive power. In order to avoid slotting the ends of the side members of the frame so that the propeller brace can be secured therein, thin strips of bamboo aresecured above and below the end of each side member, by binding with silk thread and gluing, the space between these bamboo strips being utilized for the brace which is securely bound and glued therein. The propeller bearings consist of strips of very thin bronze (No. 32 gauge), about ³⁄₁₆″ in width, bent over ⁵⁄₈″ strips of German silver tubing, the tubing being soldered to the bronze strips and the propeller brace, which fits between the upper and lower portions of the bronze strips, is securely bound and glued thereto.
The propellers are cut from solid blocks of pine, and are 12″ in diameter. The blade, at its widest portion, measures 1³⁄₈″. The blades are cut very thin, and in order to save weight, they are not shellacked or painted.
The propeller shafts are of piano wire (No. 20 size) to fit the tubing used in the bearings, pass through the propellers and are bent over on the outer side to prevent turning. A few small bronze washers are interposed between the propellers and the outer ends of the tubing to minimize friction when the propellers are revolving. Twelve strands of rubber are used for each propeller, the rubber being ¹⁄₈″ flat.