174 S. Schuster and H. Schwanecke 
The lift then has only one-half the magnitude it has in great depth; that means in this case 
only the lift of the lower side is effective. 
Now a curved profile may be considered, for instance a circle segment profile with 
camber m and angle of incidence @ eom Of the chord. For this the contour of the chord is 
given by 
HCO) = toe aca (10) 
Then 
Ge) — hee. 2f,x (11) 
where f, and f, may be of small values: 
fy = etn 
f, = -2m. 
For this case Eq. (1) can be written 
i i) Gaerne 
Pay 1 = Ie F(é) eee + cee dé (12a) 
1 (226) =4h fox, 
a (12b) 
f SS 
es F Ee O? + 4h? 
= 4a, EX = \ 
ty 
Equation (12a) gives the lift of a flat plate, 
C,(A*) = nla (h*) + ay 9(h*)| 
and Eq. (12b) gives the additional lift produced by the camber, 
C, (h*) = 2rr|ag ,(h*) ta, (h")| 
The total lift then amounts to 
Cy(h*) = C, (AY) + C (h) 
and is shown in Fig. 25 for a flat plate as well as for a circle segment profile. 
For the profile approaching the surface an apparent camber reduction at the upper side 
occurs whereby the lift of the profile, already reduced by the proximity of the surface, will 
be reduced further. In the actual case of a circle segment profile the lower side is flat; it is 
therefore equal to the lower side of a flat plate and delivers a lift taken as independent of 
the depth h*: 
