What about the 8H12 airfoil, nobody seems to use it and yet this is the best airfoil for 1:1 autogyro's. Even the [link=http://www.magnigyro.com]Magni Gyro[/link] uses this airfoil.

Reynolds number... An aerofoil working well for full sized autogyros / other aircraft does not usually work well for RC-models. I haven't tried this aerofoil but I believe it doesn't work as well on model autogyros Try searching more information about this reynolds number.

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

On a practical note concerning those of us who build their models from scratch is that a reflexed airfoil section is more difficult to make. My blades are simple balsa, with a spruce LE, and are made with a small razor plane and a strip of balsa which has sandpaper glued to it. Easy!
Colin

Hi ya'll,
Don't know a darn thing about this airfoil but have a good answer for
the reflex comment.
On www.modelairplanenews.com site call up "Quick and Dirty Wings and
Blades"
Note that ANY SHAPE airfoil is easy to duplicate using this method and
results will be excellent plus less effort to produce.
Good luck!

Hal deBolt