Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

size of this prop ok to use

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Old 08-02-2007, 09:52 AM
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suzonka
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Default size of this prop ok to use

on my os 91 BB engine, the nearest prop I have is an 11x7.5 with a wide blades ,the recomend a 12x6, but being that the prop has such wide blades and is almost x8 in pitch will this be OK on this engine until I get a 12x6
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Old 08-02-2007, 10:17 AM
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Mike Connor
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Default RE: size of this prop ok to use


according to ThrustHP the 12x6 has about 10% more load then the 11x7.5 before considering the wide blade. I doubt it would hurt anything. People experiment with all types of props without problems if you stay in the recommended manufactures rpm range.
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Old 08-02-2007, 01:01 PM
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Default RE: size of this prop ok to use


ORIGINAL: Mike Connor


according to ThrustHP the 12x6 has about 10% more load then the 11x7.5 before considering the wide blade. I doubt it would hurt anything. People experiment with all types of props without problems if you stay in the recommended manufactures rpm range.
Thanks mike
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Old 08-02-2007, 02:42 PM
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daven
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Default RE: size of this prop ok to use

Its a little light for a .91 and will probably turn up some pretty good R's, but I wouldn't hesitate to run it. Just keep it a little rich and it should be fine.
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Old 08-02-2007, 02:42 PM
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Default RE: size of this prop ok to use

This is a two stroke, right?
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Old 08-02-2007, 06:22 PM
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Default RE: size of this prop ok to use


ORIGINAL: daven

This is a two stroke, right?
yes bb fx os 61
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Old 08-03-2007, 01:37 AM
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Default RE: size of this prop ok to use

also what do you guys think about an 11x8 on a 91size engine?
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Old 08-03-2007, 07:05 AM
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Default RE: size of this prop ok to use


ORIGINAL: i live for 3D

also what do you guys think about an 11x8 on a 91size engine?
looks like Mike conner knows the right answer, by the RPM's Thats the bottom line, it it sounds like its winding out and screeming in the air its not enough prop
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Old 08-03-2007, 10:06 AM
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Default RE: size of this prop ok to use

prop size depends a bit on the aircraft it will be used on, as well as the engine....

What airplane ?

Stock muffler or something other ?

Typically a stock OS 91 likes to run around 12,000 rpm....
So in general, if you select a prop that hits that peak ground rpm, you are in the right ball park.
An 11x8 is ok, a 12x6 will run about the same.
No, you will not hurt the engine with the smaller prop. It is not going to turn up 'that' high in rpm.

Bob
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