This frame should be 40 ft. The illustration, Fig. 1, shows the proper form and method of construction. The frame should be in the form of a triangle measuring about 3 ft. on a side. The length of the spruce sticks would be approximately 16 ft. These sections can then be butted and spliced together by short pieces, lapped on underneath, and fastened by bolting and lashing.
Lashing is one of the best ways of making the joint of two or more pieces on an airship.
The frame is hung underneath the balloon by attaching it to the netting on either side by light-weight linen cords, as shown in the sketch. The longitudinal sticks of the frame should be triangular in form, while the cross sticks should be square. The propeller, Fig. 2, would be 10 ft. in diameter, with an equal pitch. The pitch can be secured by fitting the braces which hold the arms of the propeller to the shaft at an angle of 20 degrees from each other. The blade at its widest place should be 2 ft.