THE CONQUEST OF THE AIR 99 



Shape a 9-inch propeller out of the tin of a coffee can 

 similar to the one cut for the flier (p. 90). If the longitudinal 

 axis of the propeller is made, to coincide with the length of the 

 can, the curve of the tin will give about the right curve to the 

 propeller after it is bent according to the instructions. Or a 

 propeller may be fashioned out of white pine, white wood, or 

 cedar that is straight-grained and free from knots. Cut the 

 block of f-inch stuff 9 inches long and 2 inches wide. Bore a 

 hole at the middle of one broad face just large enough to take the 

 stiff wire that must be used as the axle for the propeller. Draw 

 a square i inch on each side, its center coincident with the hole, 

 its sides parallel to the sides and ends of the block. Draw lines 

 from its corners to points on the adjacent sides 2 inches from each 

 corner of the block. Cut 

 away the sides of the block 

 along these lines. Mark the 

 ends of the block according 

 to the diagram (Fig. 42), 

 and saw away the wood from 

 both sides of the diagonal FIG. 42. Diagram of the end of the 



Strip down to the central block from which a propeller is cut. 



square. By sandpaper held over the thumb to give a curved 

 surface or with bits of broken glass having rounding edges work 

 away the wood of the blades to make them thin and curved 

 according to the heavy line of the diagram. The blades may 

 be shaped so that their outer ends are rounded similar to these of 

 the flier. Cut away the corners of the central block so that it 

 joins the blades in flowing surfaces. 



Pass one end of a 6-inch length of stiff wire through the hole 

 in the center of the propeller so that it protrudes inch. Bend 

 this protruding end down to the wood center and tack it securely. 

 If the tin propeller is to be used, stick the wire through one hole 

 i J inches and b'end it so that the end can be thrust back through 

 the other hole and twisted on the long wire so as to hold the 

 propeller securely. A short block of wood set on the back of the 



