RE: What prop size for .15 Sport UC plnes?
I have found an 8 x 4 to suit me best on ST G20-15 diesels flown on Old Time Stunt airplanes. A 9 x 4 works OK, but I think the engine is happier with an 8 x 4. I am presently running a Taipan 9 x 4 on an AM 25 and happy with it. I have run 9 x 5 on CS Oliver and the # 13 Taipan. Ed Racer ran best on 8 x 6. I ended up running a 9 x 8 on one of Ian Russel's Cheetah engines. I plan to try an 8 x 8.