THE CONQUEST OF THE AIR 101 



Observe which way the propeller, which is at the front of the 

 machine, should turn in order to carry the machine in the air, 

 then turn it about 150 times in the opposite direction. Head 

 the aeroplane into the wind, set it down on a smooth surface, 

 like a cement sidewalk, release the propeller and the machine 

 should rise and fly. If at first it is not successful try shifting 

 the planes slightly forward or back or changing their inclination. 

 Possibly you can reduce the weight of the machine. It is 

 imperative to keep in mind while building the aeroplane that it 



FIG. 43. The aeroplane complete 



must be exceedingly light in order to fly and that the parts must 

 not be made any heavier than is absolutely necessary. 



A still larger aeroplane with two propellers is made by making 

 a triangular frame of f-inch square strips 42 inches long with a 

 io^-inch strip of the same stuff for the base of the triangle. The 

 apex of the triangle is in this case to be the front end of the plane 

 and is provided with a pair of hooks to take the rubber bands, 

 one set of which runs along under each long side of the propeller 

 bearing at its hind end. The forward plane is small, about 

 12 by 4 inches, and is fastened in the plane of the triangle about 

 6 inches back of its tip, its longitudinal axis perpendicular to the 

 altitude of the triangle. The rear plane is 36 by 5 inches and 



