I arrived back from Oshkosh and got lots of new ideas. I had a privilege to talk to many aerodynamics people and also aircraft designers. I met professors, homebuilders etc. It was awesome. I was listening to John Roncz's presentation about how high L/D he achieved in this and that airfoil and attempted the same. I did not get yet 75% laminar flow, but quite close - 70% with thickness 15.72%. I think there could be opportunity for even higher L/D by reducing the thickness but I wanted it to be as thick as I could make it as possible for structural reasons. Thick airfoil also has more volume for storing e.g. fuel.
I created this new airfoil which has 70% laminar flow according to the simulation (please note, this is not tested in wind tunnel). It has a little larger pitching moment than the other airfoils I have done, but the L/D at low angle of attack (zero degrees angle of attack is Cl 0.35) reaches L/D over 100 at Re 5000000. The minimum drag count is 30 (Cd = 0.0030) at Re 7000000. At 5000000 the drag count increases to 31.
The airfoil can be downloaded here: KS-70PLAMINAR.dat.
Simulation results at Re 500 000, 1 000 000, 5 000 000, 7 000 000, 10 000 000 (Cl-Cd polar):
Simulation results at 500 000, 1 000 000, 5 000 000, 7 000 000, 10 000 000 (L/D polar):
Pitching moment polar. NACA 2412 and NACA 4412 included for comparison. The pitching moment is between NACA 2412 and 4412 airfoils. Not as good as NACA 23-series airfoils. This airfoil requires aircraft configuration with two surfaces and is not suitable for flying wing.
I will build RC scale model of this airfoil and test it with RC plane. At RC scale it will be a bit worse than best thin turbulent airfoils, but according to simulations, the polars are smooth to low Re which is desirable of course and this airfoil reaches at least the same Cd at the low Re than NACA 2415 unlike some other laminar airfoils.