The Aerodynamics of Sails 



I 



Fig. 3 - Comparative rigs for the New York "3Z" 



for the New York "32", the mean lift coefficient is 1.26 and the mean induced 

 drag coefficient is 0.225. The following section will show that the skin friction 

 drag coefficient is on the order of 0.03, and when the effect of parasitic drag of 

 masts and stays is included in the sail skin friction drag, the friction drag co- 

 efficient is on the order of 0.05. Hence, the induced drag is typically about four 

 times as large as the remaining air drag. 



BOUNDARY LAYER EFFECTS ON THIN, 

 HIGHLY LOADED LIFTING SURFACES 



The major effect of viscosity on most airfoils having lift coefficients less 

 than 0.5 is the production of skin friction drag. The boundary layer on such 

 airfoils is quite thin, and a very accurate prediction of the pressure distribu- 

 tion is obtained by solving for the potential flow about the airfoil. When the air- 

 foil is relatively thin, the lift can be easily obtained by the thin airfoil theory 



1411 



