Interesting when (at about 10:00) Strojnik and Arnold discuss the wing's airfoil and smoothness. Strojnik ("Mr Laminar") and Mike appear to agree that, for low drag, the smoothness of the finished wing is as/more important than the airfoil chosen. Strojnik: "It is the quality of the wing that counts, not the airfoil."
It is a reference to propeller efficiency so the power curve of the engine does not play into it. (That would be propulsive efficiency, not propeller efficiency.)I'm with Mike, then. I hadn't heard of pitch/diameter ratio as an indicator of efficiency. Seems a lot would depend on the airspeed of interest and the RPM vs power curve of the chosen engine/PSRU.