sproket is right, the awful world of a helicopter blade is a far cry from that of an airplane wing in cruise. The properties of the airfoil are often selected as a compromise beyween the need for low drag in hover, high lift in high speed maneuvering, and low induced drag near stall. It is possible that the kinds of things that work on steady flow on an airplane have little positive effect when the blade goes from near transonic to near low speed stall in 150 milliseconds, and does that alternatively for hours at a time!