The Aerodynamics of Sails 



2.4 

 2 3 

 2,2 

 2 I 

 2.0 

 19 



I 

 I 



.7 ' 

 6 H 



0.1 0.2 3 4 0.5 6 7 0.8 0.9 1.0 



FRACTION OF THE CHORD , .^. ■.■ 



Fig. 6 - Shape factor and momentum thickness for 

 a high-lift section with a lift coefficient of 1.9 



10 9 8 7 6 5 4 0.3 2 1 



TRAILING 

 EDGE 



FRACTION OF THE CHORD 

 1,9 IDEAL ANGLE OF ATTACKED. 5° 



LEADING 

 EDGE 



Fig. 7 - Shape of a high-lift section 



The Effect of a Mast 



The flow over a section with an unfaired leading edge spar is shown sche- 

 matically in Fig. 8. The mast acts as a turbulence stimulator. The region on 

 the suction side of the section just aft of the mast has a negative (favorable) 

 pressure gradient which accelerates the boundary layer. Measurements on 

 boxmdary layers in negative pressure gradients aft of the turbulence stimulators 

 were made by Launder (1963). He found that for the range of Reynolds numbers 

 and pressure gradients of interest here, the semi-empirical boundary layer of 

 Spence (1956) gave good agreement with his experiments which showed a very 

 strong thinning of the boundary layer in the favorable pressure gradient. When 



1419 



