propeller recomendation to mvvs .90

I would say for speed go fir a square prop and a smaller diameter than normal..I know tuned 36's run on 8x8 whereas a 10x6 or 11x4 is a 'sport' prop for that sort of size..try a 10x10?

That engine will swing a 13" prop so if he's thinking 11" and 12" I think it's going to turn(revs) up just fine. Get a few different ones and try them 12X8 12X9 12X10. I have this engine with a pipe but had to get a Perry carb it get it to run reliably. How is yours? mk

Here is a couple of links that may help you:

and: What I have done is to go one size smaller than I intend to fly with and trim the tuned pipe header until it comes on line. I.E., 11X6 tuned for static peak rpm. Then change to a 12X6 and go test fly. It will not be on the pipe until the engine unloads with speed and may still need some tweaking to get it right. (This for my MVVS .60. on a Simitar designed by Bill Evans) For a smaller and lighter airplane I probably would use a 11X8 or 10X10.

One of the best spots to discuss speedy aircraft is the Extreme Speed Forum on RCU... many very knowledgable folk who, collectively, tried all sorts of combinations of engine sand props. Most of them are simply flying sport aircraft faster than their buddies, versus building and flying dedicated speed aircraft, so there is a good spectrum of experience there.

My starting points would be 10-10 or 11-9, and tweak the pipe to work. Many folks flying fast on .90's use 11 or 12" props clipped down to retain hub cross section, but unless this is one really hot .90 I wouldn't sweat it too much. But I doubt you'll over speed a 10-10 with that motor. And no, it's not too small a prop for a .90 at all, but you'll surely hear some squawking about it.

Mike D.

That's handy to know..

Didn't know there WAS an 11x12 prop..must be some mother of a plane anyway..hope your reflexes are up to it..