Propeller balance ?

I checked my propellers on the 2 airplanes that are giving me engine trouble and I found both props are slightly out of balance. I sanded about 1/32" off the tip of one prop and it almost balances perfect. How close is close enough? I spin the prop a little and it will spin for almost a minute slowing down and finally coming to a stop. It will go back and forth for 30 seconds before coming to a full stop. It is so close to balance the heavy tip never stops in the sames place but its still on the heavy side. Some times the tip will stop at 6 on the clock and some times it will stop at 7 on the clock, sometimes it will stop at 8. It never wants to stop at 5 or 4 on the clock.

The other prop stops with the prop parallel to the work bench. It acts like the hole is not exactly in the center. I can tell from spinning the prop it is not out of balance very much it takes about a minute for it to stop spinning from only a tiny little spin. It goes back and forth several times for 30 seconds before it comes to a stop. I hand sanded the leading edge on the prop full length and trailing edge on the opposite end for 20 minutes and its still stops parallel to the work bench.

Gary, you probably went far beyond what is needed for the normal set-up. However, it is better to balance too well than have one considerably out of balance. But once you are that close, well, close enough.

If the prop hole is off center, however, that can be bad. If so, how far off center is it? On a prop slightly off center, it is possible to enlarge the hole to the exact center and then use a brass bushing to bring the size back down to fit the prop. Or, if it is simply weight--and that is possible, too, that one side vertically is heavier than the other--then you may need to balance in that direction, also.

I have noticed, when buying props, if you are careful to make sure the grain on both blades looks the same, that they will generally be better balanced. If there is much difference in the grain of the blades, the prop will be out of balance, and will more difficult to balance.

Gary,

Both tips should be symmetrical and the same distance from the center of the hole in the prop. Balance by taking material from the entire length of the offending blade usually by sanding material off the back. If the hole is off center take or send the prop back where you got it and have it replaced. We are users, not manufacturers. We pay for good props; the manufacturers don't pay us for using them. See below link:

http://www.uoguelph.ca/~antoon/hobby/props.htm

Some food for thought. Most of our engines are 1 cylinder and are unbalanced to begin with. If your prop is just slightly out of balance, try positioning the end that is slightly heavy in the down position 180 degrees away from the piston when it is at top dead center. Put a small mark on them to indicate the heavy side.

... Some food for thought. Most of our engines are 1 cylinder and are unbalanced to begin with. If your prop is just slightly out of balance, try positioning the end that is slightly heavy in the down position 180 degrees away from the piston when it is at top dead center. Put a small mark on them to indicate the heavy side.
>>Tom

That used to be a common trick back in the 1950's. It works. Prop balancers were not so common back then.