Fig. 43.—The Wells Model Propeller.
The Propellers are the most difficult part of the model aeroplane to make. They must be very accurately cut, and must be of identical size and pitch. The pitch of a propeller is, theoretically, the distance forward that it advances in one complete revolution.
[Figure 43] shows one of the propellers of Harry Wells' machine, which is 9 inches in length and has a 27-inch pitch. [Figure 44] shows
How to Prepare the Propellers. The pair must be opposites, that is, one must be of right-hand pitch and the other of left-hand pitch, or, in other words, the upper end of the right-hand pitch propeller turns to the right, and that of the left-hand pitch propeller turns to the left, when viewing them from the rear.
Fig. 44.—How to Prepare a 9-inch Propeller.
Step A consists in properly planing up a straight-grained block of white pine 1½ inches thick, 2 inches wide, and 9 inches long, with its sides and ends straight and true, for