What size prop would you recommend on an OS 25FX for best performance. I am currently running a MA 9x6 and could use some more speed. Would a 9x4 be the way to go, or is there a better selection, I am a bit ignorant on what size prop gives you what kind of performance???

Thanks, :stupid:

In theory, a higher pitch gives you more speed at the same RPM.

However, you should try a MAS 9x4. The 9x4 will turn up to a higher RPM and might be just as fast, or faster than the 9x6.

Most guys use a MAS 9x4 on their combat planes for several reasons. MAS props are most common because they are the most durable.

9x4 is the most common size on .25 engines because you get high RPM and good straight line speed, and more importantly, you don't dump speed in the turns. Most combat pilots will gladly trade a few mph on a straight line for more pull in turns and vertically, since most of us don't fly a lot of straight lines in combat, and you have to turn sooner or later. So a 9x4 might or might not be as fast in the straights, but will certainly pull you through loops and turns much much better, and that's more important for most guys.

I will give the 9X4 a try the next flite.

Wouldn't a 8x6 give a better result though? Shorter Diameter but still the higher pitch, might get more RPMS than the 9X6 while maintaining the pitch? Just a thought.......

An 8x6 would almost certainly give you better straight line speed. BUT, when you pull that high-G turn, you'll bleed almost all your speed away. You won't be able to hold the elevator and loop until you don't feel like looping anymore either, and you won't have the climb rate. I can put my P-47 in to a nearly vertical bank, pull full up elevator, and stay there, turning very very tightly. With an 8x6, you'd bleed speed and fall out of the turn eventually.

So, if I was flying against, you, you might go roaring past at warp speed, but you have to turn sooner or later. So I'll wait for you at the end of the box, and jump you there. If, somehow, you got behind me, I'd either climb vertically, or just start looping or do a tight climbing spiral, knowing that eventually you'll fall off, and I can reverse and drop on you for an easy kill. You'd be forced to dive away from me, and hope you accelerate before I get a line on you.

It's combat, not pylon

Ahhhh, very good point!

I will take your advise and go with the 9x4.....

Hey, props aren't exactly expensive. But one or two of various sizes and try them out, no harm done. Who knows, maybe you have a style of flying that you like that works well with a faster than average plane.