182 S. Schuster and H. Schwanecke 
The quantity 0K 4/0A may be taken from Fig. 29. Furthermore 
Ne ae “a oe y 
dL 2 A hy ho 
dh Ay;byho i A SLOMt A b sin @ 
1 
A 1, hy the 
and 
dc OK * h 7 h 
"lh ™! h 
L A 2 2 
— = C, K_K, cos 8 = ; K 
- Loa P aA A a 
dh ae f sin } 4. \B sing 
K- - K= 
h h 
+ — (24b) 
h ho 
with C, ., = 27 sin (@ + 2m). 
In the case of a submerged dihedral foil or a flat parallel submerged foil the change of 
lift due to changes of submergence will be remarkably less than for the surface-piercing 
dihedral foil, because the first two terms of Eq. (24b) disappear. For a flat foil running at 
depth hg the depth-gradient becomes 
oK> 
= no = pug bee, KK, “= if (K, = 1) (25a) 
A;byhy A ho 
and 
dc, OK; 
ain tallies Cra KpK, aia (25b) 
A,byho A hy 
It can be seen here that for the range of a small depth of submergence (A, < 1) a vertical 
stabilization of a flat foil is quite possible as confirmed by experiments made in the Berlin 
Towing Tank with such a foil in a seaway. The submerged dihedral foil proved to be much 
more unfavorable since only those parts running near the surface are strongly influenced 
by the surface effect. In this case with the lowest point of the foil at depth h, and the 
highest point at depth 4,, 
