OS .91 II Surpass- 3-blade prop??
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OS .91 II Surpass- 3-blade prop??
*Hi, Whats a very good 3-Blade prop for a Newer OS 91 II Surpass engine??
*The .91 Surpass and 3-prop will be in a 9-pound Warbird.
*What would be the biggest 3-blade prop I can use on this OS .91 II Surpass??
Thanks.
*The .91 Surpass and 3-prop will be in a 9-pound Warbird.
*What would be the biggest 3-blade prop I can use on this OS .91 II Surpass??
Thanks.
#2
RE: OS .91 II Surpass- 3-blade prop??
I tried a 12X7 from Master Airscrew in a P-47 with the new 91 Surpass II. The RPM was acceptable, but the model was just plain sluggish. Give it a try, if you wish, but I found that the model was much more responsive with a conventional 14X6 two blade.
Bill, AMA 4720
WACO Brotherhood #1
Bill, AMA 4720
WACO Brotherhood #1
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RE: OS .91 II Surpass- 3-blade prop??
We always recommend a 2-blade propeller because they just work out better. There's no direct relationship between the size of a 2-blade prop and a 3-blade prop. Usually, though, people will go one inch smaller in diameter with the same pitch when going from a 2-blade to a 3-blade. The best thing, though, is to use a 2-blade prop for flying. After all, nobody can see what kind of prop you're using, and there are many, many props available to try out to see which flies the model the best. Not so with a 3-blade prop. Use the multi-bladed propeller for static display, and a 2-blade prop for flying.
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RE: OS .91 II Surpass- 3-blade prop??
Thanks Bax.
But what would be a good 2-blade for the .91 Surpass II on a 9-lb. Warbird or what would be the biggest 2-blade I can use on this eng.??
Thanks.
But what would be a good 2-blade for the .91 Surpass II on a 9-lb. Warbird or what would be the biggest 2-blade I can use on this eng.??
Thanks.
#7
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RE: OS .91 II Surpass- 3-blade prop??
For an O.S. .91 Surpass II engine, we'd use an APC 12 x 10 or 13 x 8 to start with. You want to prop the engine to turn in the mid-to-high-9,000's, or even as high as 10,000 RPM when on the ground. Any prop that will turn that RPM when the engine's leaned to just rich of peak RPM and fly your model well is the 'correct' propeller.
You don't go for the "largest" prop, or the "coolest-looking" prop. You want one that gives you the performance you want. In your case, even a 14 x 8 or 7 may do the job, but remember to keep the RPM within the 9,000's and you'll do OK.
You don't go for the "largest" prop, or the "coolest-looking" prop. You want one that gives you the performance you want. In your case, even a 14 x 8 or 7 may do the job, but remember to keep the RPM within the 9,000's and you'll do OK.