Hi
This is the airfoil we used with good success blades 20 ft long by 24 inch cord.
Station
%cord :- upper lower
0.000:- 0.000 - 0.000
0.250:- 1.090 - 1.090
0.500:- 1.527 - 1.527
0.750:- 1.856 - 1.856
1.250:- 2.367 - 2.367
2.500:- 3.268 - 3.268
5.000:- 4.443 - 4.443
7.500:- 5.250 - 5.250
10.00:- 5.853 - 5.853
15.00:- 6.681 - 6.681
20.00:- 7.172 - 7.172
25.00:- 7.427 - 7.427
30.00:- 7.502 - 7.502 Main Spar at this point.
35.00:- 7.440 - 7.440
40.00:- 7.265 - 7.265
45.00:- 7.000 - 7.000
50.00:- 6.655 - 6.655
55.00:- 6.240 - 6.240
60.00:- 5.775 - 5.775
65.00:- 5.190 - 5.190
70.00:- 4.540 - 4.540
75.00:- 3.817 - 3.817 Rear spar at this point
80.00:- 3.053 - 3.053
85.00:- 2.290 - 2.290
90.00:- 1.537 - 1.537
95.00:- 0.760 - 0.760
100.0:- 0.000 - 0.000
The blade wasn't self starting it used a small SV rotor on the top to get it moving the blades where set at 8 degrees helix angle to make it run quieter and the second improvement was fitting vortex generators at 5% cord station spaced every 3 inches along the blade, this gave about 20 percent extra torque.
We used 6 blades on a 10 foot diameter mill, it ran best at 120 to 135 rpm.
All the best
Bob