160 S. Schuster and H. Schwanecke 
SoscesesreeeeREERE CE 
i ee Spel Ae 
SINE fiers Cane 
mises Sree eae : i 
ees ee peng node ee a 
one ee 
: i oF, : a0 
Fig. 13. Local lift coefficients of the upper and lower sides of 
the flat foil for different h/c ratios 
be changed between 15 degrees and 50 degrees. Variations of span from 200 to 600 mm, of 
roll angle from 0 to 10 degrees, and of angle of attack from —5 to +7 degrees were made. All 
the values of C,, Cp, and Cy, were measured for a constant speed of 4 m/sec. For exam- 
ple such a could be drawn as can be seen in Figs. 14 and 15 for lift and drag, or in 
Figs. 16 and 17 for the roll moment. The results for the mean span of 400 mm were C, 
0.36, dC; /da = 2.72 to 3.14 related to the effective angle of attack, 4(C, = 0) =—4.5 me... 
Cp min = 0-015, and €,,;, = 0.07. 
A comparison of the results for the different variations showed with regard to lift, drag, 
drag-lift ratio, and lateral stability: 
1. The aspect ratio A = 52/ F possibly should be chosen not less than 4. Raising it 
beyond 5 will give but little additional profit. 
2. As long as the proximity of the surface does not influence the complete foil, i.e., as 
long as h,,,, > 1, the dC,, ,/@0 value will increase for decreasing dihedral angles, for 
hax < 1 the ratio diminishes rapidly. For the aspect ratio 4.15 the maximum relative depth 
is 1 for a dihedral angle of 27 degrees. The optimal dihedral angle for this aspect ratio is 
around 30 degrees. 
