Mart,
As just mentioned on another thread, I believe that that a top-down approach should also be taken toward the development of an optimal blade.[list=1][*]The lift/drag ratio of an airplane wing is far better than that of a helicopter rotor.[*]The primary reason, by far, is that the segments of an airplane's lift surfaces are operating at close to the optimum angle of attack.[*]What, when, where, why, who can be done to significantly improve the helicopter rotor's angle of attack at all blade segments, and velocities?[/list=1] IMHO, Active Blade Twist is, BY FAR, the best way.
Now for the considerations at the next lower level in this top-down approach.
Dave