162 S. Schuster and H. Schwanecke 
03 
° @p- 5° 3 
© p 10° | a-20 
Ofp= 5° Laer 
or} = 5° i e 
@p-1" \s 2 
01 02 ~ 03 
Fig. 16. Influence of the dihedral and rolling angles 
on the rolling moment 
15 
O Ham? Apa nb t5 
© v-w * -: 
@ v-w - . 
A 
Fig. 17. Lateral stability of dihedral foils 
3. By rolling, the flow, being symmetrical before, becomes nonsymmetrical. When the 
span is kept equal the aspect ratio and the angle of inclination between foil and water sur- 
face increase for one part as much as they decrease for the other. Indeed rolling has the 
same effect as superposing the influences of aspect ratio and dihedral angle. At small roll 
angles C, and C, are only slightly changed. At greater angles lift and ascent of lift drop 
more and more and the resistance increases. 
