To cutBlade 2,Blade 1should be held in the left hand andBlade 2cut until the line shown inFig. 3is reached, after which the sandpapering process is carried out in the same manner as in the case ofBlade 1. During all of the foregoing operations it must be clearly borne in mind that theTopof the blank propeller must always face upward, and the cutting should always be done on theStraightlines. Should the straight edge be cut on one edge of the blank propeller and the curved edge on the other, it would result in the blades of the finished propeller having a tendency to push in opposite directions and in consequence no propulsion of the model would be possible.
Attention should next be turned to the back of the propeller blank on which the manner of cutting is exactly like that suggested for the top side, with the exception that instead of cutting along theStraightlines, the cutting is donealong theCurvedlines. In this part of the work great care is to be exercised for by the time the necessary cutting has been done on the back of the propeller the entire structure is very fragile and one excessive stroke of the knife may result in destroying the entire propeller blade. By constantly holding the wood to the light it is possible to determine with a reasonable degree of accuracy the evenness of thickness. To complete theBottomside of the propeller the blade should be sandpapered as was the top.
The method of cutting the second propeller is exactly that used in cutting the first propeller, only that the diagram shown inFig. 4should be used. This will result in two propellers being made that will revolve in opposite directions in order to produce even and balanced propulsion. If both propellers revolved in the same direction the effect would be to overturn the model.