Originally Posted by sraden
So Drela, KFm, and Clark Y would be better than a NACA?
For a 40" span sailplane.. The Drela would give genuinely good performance. The Clark Y isnt really very good for anything that small and slow flying and the KFm just isnt any good for sailplanes unless ease of building is your main driver.
Dont write of all NACA airfoils because there are thousands of variations on the NACA theme. Of the 4 digit type NACA a 3306 would be pretty good for a small sailplane, maybe not as good as the Drela but much better than the Clark-Y and in a different league performance wise from the KFm