THE SAILBOAT 



183 



Wind 



Course of 

 ward." 



FIG. 185. 

 boat "beating to 



rind- 



TJse of Keel. A wind blowing against a boat causes it to move in 



the direction of the wind; that is, to " drift." To prevent drifting 



we provide a boat with a "keel" 



or a " centerboard." A keel is a strip 



projecting from bow to stern on the 



bottom of a boat. A centerboard is a 



movable keel. The centerboard can 



be lowered into the water when the 



boat is in deep water, and drawn up 



within the boat when the boat is in 



shallow water. We can illustrate the 



action of the keel by pushing a vertical 

 board side- 

 wise under 

 water. The 

 water re- 

 sists being pushed out of the way, just as air 

 does (cf. 27). 



Use of Wind by the Sail. The sail (Fig. 

 186) is attached so that it can be let out at 

 right angles to the keel, or " hauled in " until 

 it is almost parallel with the keel. Let Fig. 

 187 represent a boat moving in the direc- 

 tion of the keel; that is, forward. The wind 

 is coming from the side, at right angles with 

 the keel. Such a wind is called a " beam 

 wind." It is plain that if the sail were let 

 out completely, no part 

 of the wind would be 



caught, and there could be no forward motion of 



the keel. If the sail were drawn in completely, 



the whole pressure of the wind would be against 



the keel, and there would be only a sidewise 



motion, provided the boat was not capsized. But 



if the sail is set obliquely with the keel, as in Fig. 



187, part of the force of the wind is used in push- 

 ing the boat sidewise (a motion resisted by the 



FIG. 186. 



A Sloop under Full 

 Courtesy of 

 Millspaugh. 



Dr. 



Way. 

 C. F. 



Direction 



FIG. 187. 

 Diagram of a Sailboat. 



