Hi Bill

Will be using a new OS 91 FS Surpass (pumped) for a 80 "ws, 8lb Stik.

What is the best prop size ? A 12 X 8 or 13 X 8 ?

Thanks

For general-purpose flying, we use an APC 12 x 10 propeller. Turn the engine in the mid-to-high-9,000's when leaned to just rich of peak RPM and you'll be fine. Any prop that turns that RPM and flies the model the way you want is OK.

Thanks Bill. I presume you are referring to an APC 12 X 10 Pattern prop ? Cannot find an APC 12 X 10 Sports prop.

We didn't know there was any difference. The prop we use is listed as a "pattern" prop, but we really don't care about whether it's "pattern" or "sports". We just pick the size. I think they just call higher-pitch props "pattern", and lower-pitch props "sport". Same design, though.

Thanks, Bill !