Hi bemfarmer,

I never heard of that theorem either. You seem to be on the right track though. SteveMacc, I have the radius going through the end points of the airfoil, so that the chord works out. I have never tried fitting an ellipse to the data. The trailing edge works out as is. You can use the NACA points and the ter they define with no issue. The ler and the data are what do not agree. In order to keep the chord, using the radius they define, I curve fit the data points. If you know of another way, please demonstrate. I'd be interested in looking at it.