ORIGINAL: jefflangton
I have a 1/4 DR1 Fokker that Im going to put a xoar ww1 prop on. It has a dle 30 and now weighs 16lbs. Options are a 20x6 or a 20x8. The larger is the reccommended max for this engine so I dont want to over do it especially in a slower flying ww1 plane.
20 X 6. The lower pitch will not overload the engine, and will give better pulling power at the lower speed.
This for all of the same reasons that full size constant speed props have a lower pitch for takeoff and climb (at the lower speeds in those situations) then go to a high pitch for high speed cruise. Considering the drag of the DR1, I'd recommend staying with the lower pitch. Of course, you'll probably try the 20 X 8 anyway.
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Dash