I've read in a few posts here and there about guys cutting down their props for various reasons. I have a few 12x6 APC props with some dings on them that I'd like to make into 10x6 or 10.5x6 props for other planes I have. I'm wondering if this is a bad idea? I worry about the integrity of the prop, and the over all design as well. The tip would no longer be as flat as it was when the prop was a 12x6. What do you guys think?

- Paul

In general this is really a bad idea. When you start cutting down props you run the risk of actually damaging the integrity of the prop itself. Plus, APC props are designed and shaped from the hub to the tip of the prop, and when you start cutting or removing material you change the shape of the prop. This will more than likely make the prop less effective. APC props aren't that expensive and IMHO it's just easier to buy a new prop than spending hours messing with an existing prop that may not even work correctly, or worse yet come apart in use.

Ken

Ummm, not to be rude to you Paul, but that has to be the dumbest thing I heard.
doing so is just asking for trouble. Like Ken said, "it's just easier to buy a new prop than spending hours messing with an existing prop that may not even work correctly, or worse yet come apart in use."

definately not worth the hassle.

While it might not be worth while, if you make sure the prop is balanced both statically and airodynamically (identical tip shape) there should really be no problem in cutting them down. They may not be as efficient as a commercial prop of the same size but; if there are no mechanical defects and balanced, they should be as safe to use as any other prop.

Paul,

I may be in the minority here, but IMHO as long as you work on the tip only, balance when you're done, and don't let the rpms get out of hand, you should be OK.

RCKen is right about the APC props being designed carefully from hub to tip. If you trim the tips, you lose some of the benefit of that careful design. However, if you cut an APC 12 x 6 down to 10 inches and run it on a .40 (which would normally use a 10 x 6) it should work at least as well as a wooden, wide-bladed 10 x 6 that you purchased new. Those have squared-off tips, and other than being a bit less efficient than an APC 10 x 6, they work fine. Just don't alter the hub. If you have a spinner and the hub contacts the edges of the cutouts in the spinner cone, enlarge the cutouts. Modifying the propeller hub is a safety issue.

Duane Gall
RCPRO

p.s. Oops, looks like Rodney got in ahead of me there. What he said!

I'd just go buy a new prop, but I'm lazy

Thanks for the feed back guys. I'm not too poor that I can't buy more props. I've just seen posts where people mention the fact that they cut down their props, and I wanted to get your opinion on it. I think I'll just go buy some more props.

- Paul

I hit the tips a lot and i will shape the tips and reballance on my apc's only,to the point that aprox. 1/2 inch are gone and then start over, only takes a few min. not hours and i keep a couple with me, don't really notice any real diff, of course i am only a sport flyer and not a hot dogger

Two or three props are cheaper than a vist to the emergency clinic...... I never clean up anything over 1/4 inch on each tip, then rebalance. Heavy nicks in the leading edge gets the prop tossed.

Just to confirm what has been said here already. I fly at the same field as the owner of APC props and can tell you from the horse's mouth. APC's are carefully designed and most of the thrust comes from the tips. As I recall in the neighborhood of 80% of the thrust from the APC prop is generated at the tip. Not to mention APC's are also designed to run quiet and you are also losing that effect as well, so keep that in mind when the DB police are around. I will dress the tips from minor dings on my sport planes but nothing more than a ¼” or so.

It can be done but you can't see if the blade is delamanated.
Cheaper just to buy new props and use the old ones for mixing sticks and the like.

Cheers

for just a few dollars why bother just buy a new one and be safe

Aw hell, cut away!

I have cut down many props for a variety of reasons. Different brands too - wood, composite (Although I wouldn't cut a carbon fiber prop, but standard run of the mill props, sure)

And just for the record... No, I DON'T balance them before OR after. Of course, I am very careful to remove the same length off of each end.

But I will also add that I would NOT do this for a prop that will be used for extreme-speeds (Like over 12,000 RPM)