= I set the pitch at 19° which is equal to 54" pitch. = static rpms yielded the same as my 2-blade Sterba 56x64 prop
+++++++++++++++++ Turning 10" less pitch at the same RPM is a bit like a car in a lower gear, i.e. a ratio that provides less fwd speed for the same rpm. I would expect the static thrust to be higher. In addition, I believe that three blades are better than two in the thrust dept. (not cruise) so that will further contribute to the results you observed. Like any other "wing" at an AoA over 16 degrees - a propeller blade at typical cruise or take-off rpm and zero fwd movement (static) is stalled to some degree, over varying parts of the blade surface. The more pitch, the greater the degree and the more of the blade lifting surface will be stalled, producing higher drag, thus lugging the engine RPM down and producing less (static) thrust. The same propeller will unload as the "apparent" angle of attack reduces due to fwd movement, thus improving in efficiency as the aircraft accelerates - hopefully peaking (in efficiency) closer to the desired operating speed. An under-pitched propeller will show promising static thrust levels because the set-up is more efficient (less inefficient). This propeller will probably reach max efficiency sooner in the take off roll and may be substantially less efficient at the desired speeds of climb and cruise. Just like a car would be in the cruise at anything less than top gear (higher ratio). As we know, the trick fixed with pitch propellers will always be to find the best compromise for the plane / engine combo and even that will change with weight, temps and general requirements on the day - but I somehow doubt that a propellers' efficiency under static conditions could be a reliable indicator of a good compromise - these are not conditions the airplane will ever encounter in normal flight - maybe just as it stalls, but that is hardly normal flight. I would hang back with re-pitching the plank until you have established what the plastic will do in the cruise. The plane looks really good and I am pleased that the spinner saga turned out Ok. Good luck Steve J Zambia
