It looked like an airfoil with a flattop hair cut. But it worked, quite well.
That was our first successful type airfoil.
We had tried a triangle facet (flat bottomed with one fold on top at the spar). This airfoil flew fine at higher speeds...but the slower it got, the worse it got...and trying to land the plane looked like the six million dollar man rocking back and forth and crashing!
Then a Cessna engineer flying buddy tried explaining burbles and boundry layers and air seperation...we really didn't have a clue what he was saying...but... we went home and did exactly what you said...gave it a flat top...with a 1" flat section it made for a triple facet (flat bottomed with 3 flat surfaces making up the top wing). This wing flew GREAT, and was the airfoil we stuck with for almost 2 years...and many are still being built and flown. Our Cessna buddy said very much the same thing you did about the sharp leading edge...he said the air flow was close enough to the wing but didn't seperate from it...in effect the air was fooled and "thought" the wing was a true smooth airfoil, as you say the air may "think" the sharp LE is actually round due to the vortex? This is cool...I might actually be able to simi explain it next time it comes up at the field
