Originally posted by bruguima
I had an recent experience
Im flying and Extra 300 120. size (goldberg) and I tried first an 13x6 prop at my 71 (2 strokes) engine, the plane flew very well, but when I changed to 12x8, the plane flew much better, much faster, more powerfull on vertical climbs.
very interesting this subject...
May have as much to do with the engine characteristics than the prop. Some engines "breath" much better at higher rpm, and one inch less in pitch might be enough, to have your engine unloading a bit in flight, giving you better overall results. For me, the magic word about props pitch and diameter is EXPERIMENT !!! you don't have to do what everybody else do...
Bernard