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48 Surpass with APC 12x6

Old 08-09-2015, 05:10 PM
  #1  
Jennifer Curtis
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Default 48 Surpass with APC 12x6

I have a brand new OS 48 Surpass which I just mounted
on my Four Star 40. It flies well with a number of props
but the one I like best is the APC 12x6. With this prop
the plane looks, flies and sounds like a 120 size plane.

I am concerned that I am working the engine too hard.
On 5% Omega fuel, It peaks at 9,300 rpm. I set the
needle rich to 8,800 rpm, and at the end of a flight,
when the tank is low, full throttle is at 9,300. During
each flight I run about equally between 1/2 throttle
and full throttle. Not much at idle.

Normally I'd just leave it like that, but since it is a new
engine, and replacement parts are hard to get for it,
I'd rather not burn it out prematurely. Am I likely to
egg out the conrod or do some other avoidable
damage by running this propeller?

Thanks.

Jenny
Old 08-11-2015, 09:24 AM
  #2  
Bax
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Default

That may be too much propeller. Depends upon the blade thickness and profile. You should be turning between 10,000 and 11,000 RPM when leaned to just rich of peak RPM on the ground. Try this list (per OS, but we still think some are a bit large):

10x7.5, 11x6, 12x5, 12x6 (2-blade), 9x7 (3-blade)

The one that flies the airplane the best is the one to use.

Last edited by Bax; 08-11-2015 at 11:27 AM.

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