OS 91fs prop
05-08-2004, 12:08 AM
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OS 91fs prop
Bill, I have an OS 91fs Surpass II in a Sportsman Aviation Waco .60 Biplane. I wanted a large diameter prop because of the 7 inch dia. cowl. I tried a 14x6 Master Airscrew but was not impressed. I had an APC 15x7 lying around so I thought I'd try that. I really like the 15x7's great pulling power of the engine and prop combo. The engine turns the 15x7 APC at about 8,000 rpms. Most of the time I fly at half throttle until I want more power. I'm really happy with this setup but will I damage the engine turning this size prop. If this is a problem I'm open to suggestions. Thanks, Tom
05-10-2004, 11:58 AM
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RE: OS 91fs prop
You didn't say what RPM you're turning. The .91 FSR liked to turn near 12K RPM. If it's loaded down to much, it will tend to overheat.
Please remember that with model props, only the outer 1/3 actually does any work. Some models with radial engines have flow successfully with only 1" of prop sticking beyond the cowl. Trying for a scale prop can sometimes be a lesson in futility.
Please remember that with model props, only the outer 1/3 actually does any work. Some models with radial engines have flow successfully with only 1" of prop sticking beyond the cowl. Trying for a scale prop can sometimes be a lesson in futility.
05-10-2004, 01:26 PM
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RE: OS 91fs prop
Billl, please reread my original post. I'm running an OS 91fs Surpass II (not a 91fsr) with a 15x7 APC turning 8,000 rpm with no signs of over heating. Thanks, Tom
PS It's a Monday, I know how that is!!!
PS It's a Monday, I know how that is!!!
05-10-2004, 04:38 PM
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RE: OS 91fs prop
I also have the WACO.......as long as the engine does'nt get too hot this will be ok, your useing
castor oil in your fuel ?? arnt you.
castor oil in your fuel ?? arnt you.
05-11-2004, 09:47 AM
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RE: OS 91fs prop
OOPS! Brain fade! Saw the "91fs", but missed the Surpass part! As long as the engine's turning below 10K RPM, and flying your model well, you'll have no problems. If the engine's staying cool, use any prop you wish. Turning much below the high 8,000's will start to lug the engine, and you'll likely get overheats.
If you can't get enough power out of the FS-91 Surpass when you've got it turning in the high 9's, then you don't have enough engine for the performance you're looking for.
If you can't get enough power out of the FS-91 Surpass when you've got it turning in the high 9's, then you don't have enough engine for the performance you're looking for.
