OS40FS prop size?

I'm still looking for this information. rcfaq.com seems to be down, and I can't find any other source of rpm & prop sizes at the moment. The OS Engines site lists props up to 12x7 for this engine but give no indication of RPM.

So if anyone has this information - OS40FS RPM figures with a 12.25x3.75 prop I'd be grateful for your help.

Thanks,

For a Fun Fly-type plane, you need pull, not speed. The .40 can easily handle an 11-4 or even a 12-4. Don't worry about the "recommended" RPMs, just concentrate on how the plane flies. Dr.1 Driver "There's a Hun in the sun!"

OK, I think I'll give up on this. I was looking for maybe 10500 RPM, and now I don't think I'm going to get it from this engine. I'll stick to 2-stroke for this one.

Sure! - but knowing the RPM I can calculate the thrust, and I figured RPM would be the most likely figure to get. I've flown it on a .37 with an 11x4 and need a little more grunt out of the hover. Standard muffler limits me to 12000, a pipe gave me 13400 all with an 11x4 APC. Pipe is much heavier of course and doesn't help with the balance I'm seeking! There's no room to move anything around so adding weight to compensate is the only option - not a good idea in this plane!

I'd just wondered whether I might do better with a 4-stroke as torque/speed curves for 2 & 4-strokes are quite different, and sometimes the lower absolute power from a 4-stroker can still win the day with the right prop choice. In this case I would have a net weight loss on losing the pipe, and might just have gained the rest in a more efficient prop at slower speed.

Good idea. 2-strokes have better power-to-weight ratios than 4-strokes. You want to keep a fun-fly type plane as light as possible.

Morris