Prop Choice?
 

I have a ST61 i just received that is a older engine. In general what is the best prop for this engine for speed and for power?

Thanks

RE: Prop Choice?
 

I think an 11/7 or 11/8 would be a good starting point

RE: Prop Choice?
 

Well from the size you listed it's no wonder it does not spin over about 11.5k with a 12x6 apc prop.

RE: Prop Choice?
 

11500 with a 12x6 APC is probably about right, depending upon a bunch of variables....fuel, weather, etc. An 11x7 would be a good "standard" prop for your engine assuming the plane is reasonably sized and clean, or if it is to power something more on the line of a Cub then the 12x6 would be better.

Clair

RE: Prop Choice?
 

Its sitting in a World Models Supersports 40;) . It will go unlimited vertical but i thought it would be faster in level flight. Ohwell maybe a 75ish will get it moving.

RE: Prop Choice?
 

Ezee,

According to the MAN May, 2003 .60 engines shootout, most muffler equipped .60 engines produce their maximum power output at around 13,000 RPM. Your ST is no different (unless it is equipped with a high RPM tuned pipe, or is in open-exhaust guise...).

So it should use a prop, that it could spin at 11,500 RPM, more or less.
An 11x8, 11.5x7, 12x6, 12.5x5, or a 13x4, should do the job.

In a sport plane at speed, the prop unloads about 1,500 RPM, so the engine will make its maximum horsepower when it is flying your plane.

Using an 11x7, your engine will be close to maximum power on the ground and will be beyond it efficient RPM range, gasping for air, in high speed flight.

It will fly the plane more slowly too.

RE: Prop Choice?
 

Ahhh well thanks for that info. Guess i have about the best prop on it then. It spins about 11.5k static with an apc 12x6. Sounds like it speedsup to around 15k. The plane is actually moving along at a pretty good clip fastest one i have anyway.

RE: Prop Choice?
 

Ezee,

It probably speeds up to about 13,000 (which is very audible).
If it went to over 14,000, you would see all the heads in you flying field turn to see it...

If you still want more forward speed (and your plane isn't a "drag queen"), you could try an 11x8; approximately the same load as the 12x6.