Magnum .52 FS - Prop size?

Try a 11-5 a 12 inch is too much and the engine is probably knocking when you speed it up

Straight from the instructions...... 11x7,8,9: 12x5,6,7; 13x4 ! I' m running a 12x6 TF Power Prop on mine on my 71" Cub and it works fine - IIRC it spins about 9300 on 10% nitro and it's got about 2 hours time on it.. That Magnum will free up some more as you get more time on it. You did not spec the %nitro, so the rpm may or may not be OK. That 11500 to 12000 is probably with 11x7 or 12x5. Don't worry so much about rpm, just 'does it fly your plane OK' ? I've got a Magnum 61 FS turning an 11x7 3 blade at only 9800 rpm, and it pulls my 6.5lb SPAD Debonair aroung quite nicely.
David

Bob Mine is happiest on a 12/6 . RPMs don't sound out of line.
Ed

Thanks, I'll try that.
Bob

I am running 15% nitro. The plane flys a bit sluggish - On my second and third flight, it had great vertical, now falls off quickly.
Thanks, Bob

Mine depends upon the plane. Probably due to weight. I had a 12x5 on it while flying a Magic 3D. Loads of power. Pulled out of hover with authority. Now motor is on a Magic Extra. I found 11x6 best so far. The 12x5 did not seem to do well. I did pick up a 13x4 wood the other day - will try that. I know of others runnig 11x7 and 12x6 and are happy. One guy has a 12x7 in a Kadet.
BTW - adjust the valves. Mine needed adjusting after less than a gallon.
Mark