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Prop pitch advice...

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Old 09-28-2006, 11:27 PM
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Plummet
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Default Prop pitch advice...

I have had a difficult time slowing my Sig 4 Star 40 down for landing (O.S. 46AX w/ 10x6 prop). Someone mentioned to me at the field that the 4 star is notorious for this and that I should move to an 11x4 or even 12x4 where the reduced pitch will have a "breaking affect" at idle.

1st question: does this make any sense?

2nd question: neither 11x4 or 12x4 is listed as a recommended prop size for the O.S. 46 AX. Maybe this is a stupid question, but is that a big concern?
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Old 09-29-2006, 12:04 AM
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carrellh
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Default RE: Prop pitch advice...

A big, low pitch, prop does help the plane slow down.

Lets pretend your engine’s idle speed is 2500 rpm. In a perfect world, various pitches would move the model as follows:
nn x 3.75 = 8.88 mph
nn x 4 = 9.47 mph
nn x 6 = 14.21 mph


A lot of people love 12x4 props for .46 engines.

The APC 12.25x3.75 wide blade prop is also very popular for this engine size. Here’s a link to it
http://www2.towerhobbies.com/cgi-bin...?&I=LX1577&P=7

The engine makers toss out suggestions for prop sizes but they cannot cover every possible combination. They list 12x6 and 12x7 as possibilities but I think those sizes are too much load for a .46 two stroke. My brother had a .46 that performed very well with 11x5 props and pretty well with the 12.25x3.75. Others in our club are extremely pleased with the 12.25x3.75 so that just proves we all like different things.

It really boils down to what you like on your specific engine/airframe combination.
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Old 09-29-2006, 12:49 AM
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Default RE: Prop pitch advice...

Thanks Carrell, my lhs has a pretty good supply of APC props. Assuming I have clearance for a 12" prop... I'll give it a shot this weekend. Thanks again.
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