Popular Science Monthly 



'A 



Assuming that the hull resist- 

 ance is not affected by different 

 angles of keel, the course at 

 190^ with the wind is the one 

 in which the boat will make 

 the fastest headway. In the 

 wind tunnel of the laboratory 

 the construction is such that 

 uniformly moving currents of 

 air without swirls in them 

 blow against the object tested. 

 The mast with its sail is set up 

 within the tunnel, and the ef- 

 fect of the wind in the sail is 

 measured. The sail is set at 

 different angles to the direction 

 of the current of air 



For courses from 45° to 160° 

 the angle between the boom 

 and center line of ship should 

 be one-half the angle between 

 the fly and center line of ship. 

 In the wind tunnel measure- 

 ments are made at each angle 

 of the direction of the current 

 of air. The thrust and twist 

 are measured, the experiments 

 being repeated many times 

 with different wind velocities. 

 It is the apparent direction of 

 the wind that concerns the 

 sailing man 



^^!:^:^^ 



J 



Pbotos by Lcvick 



