Hello MOB...

Les Garber and I included the NASA 8H12 airfoil in our wind tunnel tests of rotors with blades of various airfoils. It performed less well (lift vs air speed) in comparision to the Clark Y at air velocities up to 28 mph. At this last point the lifts of the two airfoils were equivalent. The Selig-Giguere 6042 was superior to all those we tested by about a factor of 2 at all but the lowest air velocities.

We published an article in RC Modeler, August 2001, pp 70-76 in which all of the data we collected is summarized.

As to why the 8H12 is used in 'full sized' autogyros probably is based on its reflexed trailing edge. This would tend to counter-act the negative twist caused by the pitching moment of a lifting airfoil on a long, thin blade and hence would keep the blade in a positive or neutral angle of incidence. Others may have comments on this 'explanation'.

Bill