Hydrofoils Running Near a Free Surface 
187 
For a submerged dihedral foil the lowest point of which is running at the depth hi, with 
the upper ends at the depth 4, the gradient of the rolling moment in the upright position be- 
comes 
dC 1 
M ~2 dK; 
aa Bg) toe KK. cos fb ca | Wolo ley 
Seed 3 A 4 dh |% 
and the gradient of the lateral force becomes 
dC 1 
Py : 4 = =2 — 
—ag| .. _ = CrokoXpcos @ singb4 x, | qvi- 7? —*| a7 
Ag Bi Rip itis Aycaly = 
with 
H < hy) < hh, . 
For a parallel submerged foil running at the depth Tes 
dC 1 
x a Of Sg 
Raph), 3) = -C,.Kpb ae =. | 7m? V1- 7° dy 
1514/9 0 
= dk-~ 
Bie wi ello 
le ats tals 
and 
aC p 
a = 
= 0 (dA = @gljo= 0) 
dp A,byho 
(36) 
(37) 
(38) 
(39) 
The lateral stabilization due to sideslipping will not be developed here since this can be 
done in a manner corresponding to the treatment of the vertical and of the rolling stability. 
NOMENCLATURE 
b semispan of the hydrofoil 
br0j = 5 cos 8 
c chord length 
