Engine basics > Engine set up tips

Cutting Down Props

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the original Steve Smith:
I have heard that some flyers buy larger props and cut them down to a smaller diameter.  Why?

Does the center of the prop pull more than the tips?  Is there some advantage to the cut down prop?

Thanks in advance.

Steve Helmick:
A prop with 1" or more extra diameter will have wider, thicker blades, that can be reworked in pitch, airfoil and diameter, until it suits your engine/airplane combination for the current wind, altitude, temp, etc. 

Propellers are one of those things that you can't accurately predict what will work. Experiment, cut & try, borrow, etc., and keep trying any prop that is close to the right size for your engine. There is a huge difference between the wrong prop and the right prop, and you just never know. I'm right pleased with APC and Graupner GRP props, but I'm willing to test anything that seems likely to work and some that don't. The Graupner props actually look like they'd be good stunt props, tho the APC's don't. They do work, however.  8) Steve

RandySmith:
another reason  is that  the larger props cut down  allow  the pilot  to  "load" the motor better.
And many  times  a  11.5 inch prop  is  better  than a  11 or  12, so  the only way you can get that diameter  is  to cut a  12.
My planes I have here have these props
12.2 diameter
11 3/4 diameter
12.6 diameter
and  11.4 diameter

So as you can see  the  optimum size is  not  always  an even inch  size

Regards
Randy

Randy Powell:
When I have a new plane, I will often come to the flying field with two dozen props that I think might work. I will go through them until I find something that is close then modify my approach depending on what I get. I will usually find a prop that works well for whatever conditions I am flying in and a few that I think will work under other conditions. When those conditions come up, I try them and repeat the process.

Usually, after 4 or 5 flying sessions I have a pretty good idea of what props will work where. Usually.

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