\ The Aerodynamics of Sails 



loading which would produce minimum induced drag in a uniform wind. This is 

 of little practical importance, since the loading must usually be relatively higher 

 in the lower parts of the sails than that loading which would result in minimum 

 induced drag because of limitations on pitching and heeling moment. 



The effect of the unusually high lift coefficients of sails results in large 

 alterations of the suction side pressure due to boundary layer effects. In some 

 cases these effects are restricted to a thickening of the boundary layer, and in 

 others they result in flow separation. Recently, some analytical methods have 

 been devised to handle partially separated flows. A presentation of this subject 

 is currently being prepared by the author. 



ACKNOW LEDGMENTS 



The author wishes to thank the sponsors of this research for their help in 

 making the work possible. Some of the work was carried out under ONR con- 

 tract N00014-67-A-0204-0022. The remainder of the work was supported by 

 the kind contributions of Mr. Benjamin Gilbert and Mr. Ernest Fay. 



SYMBOLS =''''^ 



A Multiplicative constant or coefficient 



b, B, BB Sail span 



jB Span of a jib 



C Chord length 



Cj3 Drag coefficient 



q^ Lift coefficient 



d. Induced drag per unit span 



D. Total induced drag 



h Gap from bottom or mainsail to image plane 



H Boundary layer shape factor, the ratio of displacement thickness 

 to momentum thickness 



HI Vertical distance from foot of jib to foot of mainsail 



e Lift per unit span 



L Total lift 



Mj^ Heeling moment about the foot of a sail 



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