Report KD 733 can be copied for free from my website:
www.kdwindturbines.nl at the menu KD reports. The title of this report is: "Calculations executed for the 2-bladed VIRYA-3.9 and the 3-bladed VIRYA-3.9B3 (both lambda design = 6, stainless steel tapered blades) driving the VIRYA-4.2 generator for 26 V delta and 26 V star".
I think that these are the largest rotors with blades made from cambered stainless steel sheet. Already in 1978 it has been measured in the wind tunnel that rotors with cambered, tapered blades have very high maximum Cp and that they are very silent if they run a bit faster than the design tip speed ratio. These rotors are only meant for well equipped workshops as a strong cutter is needed to cut 3 mm stainless steel sheet and a special tool is required to camber the blades and to separate two blades from one rectangular sheet. A picture of the 3-bladed rotor is added as attachment.
