shown in Fig. 42. Its vertical edge is bent around a piece of heavy wire, as shown in the plan detail of Fig. 42, and the lower end of the wire is fastened upright between the bow ends of sticks A.
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
Fig. 44.—How to Prepare a 9-inch Propeller.
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.
