where V„ can now be represented by induced velocities. Thus 



-^ f V £- 

 V £ V 



s J s 



C DC = V- V £V- V 3n dx (43) 



By writing 



V L 



v £ V k-1 



k=l 



1 

 C DC " 47Tr J ^ C k ^ X ^(^i xl+C o V 2n 



1 , L 



= 47Tr \2L 2-, c k a i x +c oZ c k x v 2n » y dx 



o V i k=l k-1 



where 



r Yc = tJ - and Y dx = 1 



J 



2irV, 



"o 



Likewise the sectional lift coefficient can be written 



C L = c J (p-K.) dx = |£ J V^ f- dx 



ok k 



4Trr /> c, x y dx = 4-rrr / c^ P fc (44) 



19 



