The STOL section is a custom 13% thickness airfoil designed originally as a high lift section by Dean Wilson to fit around the 2.5” spar diameter particularly at the leading edge.

The Speedwing section is based on the STOL having more or less similar pressure gradient and mean line but the camber is reduced by approximately 30%.

Both airfoils are therefore specific to the Avid aircraft.

The closest match to the Speedwing section is a NACA 2212 though there are differences.

NACA 44xx series would provide too much pitching moment for the airframe's length and its limited tail volume and should be avoided.

Graham Laucht