I have a beef with the prop manufacturers.
It seems like I have to carve away a very large amount of material to balance my props.

The manufacturers should be able to computer balance them at the factory and drill the hole perfectly every time, right?

I have this problem with MAS and ACP,

Does anyone know of any pre-balaced props?

Ken

When I balance a prop, I do it by removing material from the front face of the heavy blade out near the tip. I remove material from behind the high point of the airfoil. I use sand paper of whatever grit seems needed. APC's are generally balanced or pretty close, and little material needs to be removed. I did get a couple of 11 x 5's some years ago which were way off. One blade was obviously thicker than the other. I had to reshape the heavy blade to get them to balance. It has been posted on another forum that there have been APC's with the shaft hole off center, but I have not seen one. I run mostly APC's.

There are other ways of going about it which are fine. For example, if you paint your prop tips, just put more paint on the light tip.

Jim

Don't remove the material from the hub area, shown in the photo -- the blade can separate.

See Jim Thomerson's post for the "how to".

There is a theory that balancing props is a waste of time on single cylinder engines, because of the inherent internal balancing problems of the engine. I don't particularly agree with it, but it is an interesting theory.

When wood props were pretty much all we had, I used to remove material to balance the props. Now, with the composite props, it is much more difficult to do.

One of our club members is one of the better pylon racers in the country. His engines turn over 20,000 rpm. When I asked him about balancing props, he showed me the APC's he uses. He uses nail polish to add weight to the light tip. If the prop is out of balance in the other direction, he mounts it so the heavy side away from the pistion. I have been using this method for several years with no bad results.

If you get too much nail polish on, it removes easily with acetone. Then, just try again. The nail polish is also fuel proof. Sure takes less time than removing material.

In answer to your real question, I am not aware of any pre-balanced props.

I balance all props since I had one so unbalanced that it shook 3 bolts out of the engine mount. This was a 3 bladed Evo prop. It usually takes only a couple of minutes per prop. Recently, I bought 2 Master Airscrew props. The 11x7 was off a lot, and the 12x6 with painted tips was balanced.

DO NOT use that prop!!!

Prop balancing is WAY over emphasized in this hobby. Some people may say otherwise, but I rarely ever even bother to check a props balance let alone do anything about it.

In either case, you are FAR better off flying an unbalanced prop than to use that prop that has been butchered.

It is DANGEROUS, and an accident waiting to happen!

DO NOT USE THAT PROPELLER

get a can of clear paint and just spray a little at the tip. It will balance your propeller.

Ken,

I second Mike B's advice. You should never remove material from the prop hub to balance. These are where the higest loads are and you could be facing a dangerous situation. There have been a few good tips here on what to do.

If you take off material from closer to the tip, you will find you have to remove only 5 or 10% of the material you would from the hub as the longer moment arm makes the removed material more effective.

Duke

I never balance my props and primarily use APC props. Why bother balancing the prop when the plastic spinner attached to it isn't?

I have just seen this thread and am amazed it took till post #6 for someone to say "DON'T USE THAT PROP" !!!!!! Get some better advice on how to balance a prop than what you have ATM. That prop and any others that you have balanced in that manner are a danger to you and anyone else at the field you fly at. I generaly don't get fazed when bad advice is given because there will always be some one else to post their opinion, but when safety is paramount then I got to say my piece. No attitude intended.

looked like it was handled in post #3 to me.

Another reason to use Mike's (and others) suggested approach is plain physics. According to some well known laws of physics - the balance point is proportional to the mass AND distance from it. Because of this you WILL require to add/remove MUCH MORE weight at the hub (closer to the balance point), rather than at the tip. In simple terms - you will need half of the weight if you move it at the twice the distance (from the balance point).

All that advice is well and good. I won't use the prop.
I can see that I have compromised the structural integrity, and the safety of the thing.

The reason I posted in the first place is because I did not want to have to do this.
As you can see from my photo, the prop was not heavy on one blade or another, it was heavy 60 degrees from one of the blades.
I don't think there is any good way to balance this prop after it has been drilled.

In the future I will try opposing the piston ... but I think all good engines have a counterweight that does that already.

Ken

You can still balance props without worrying about engine balance.

blwblw - What?
I was talking about engine balance in reference to J_R's post (#4) suggesting I could cancel the prop unbalance with the piston unbalance.
Because it is the only post that takes into account my problem - what do you do when the unbalance is NOT ON one of the blades.

I think I will write to ACP and see what they say.

I could have added weight to the other side, but that much weight would be a danger as well. This thing was really out of balance.

Ken,

Agree with you. I have many props, both large and small that are out of ballance at the hub, not the blades. I get it so that each blades are balanced and then do some slight balancing of the hub so that there won't be a heavy side. Also, when a prop is as out of balance as the one in the picture, the hole was probably not drilled on center.

mark

You're right. I missed that post.

You worry to much about that prop balancing..

If you can look at the prop and see that the hole is off center, don't use it. Return it or pitch it... or use it for stirring paint. A couple of years ago, I got a batch of APC's that were off center and sent the props to them. APC replaced them and threw in a couple extra for my trouble.

Normally, props are going to be, very slightly, out of balance at the hub. The forces generated will be very small and can be pretty much ignored, even on an engine turning 20,000+ rpm.

A couple of things about balancing. First, be smart as most of the posters are encouraging. Here is a post on another site that uses an interesting method that seems to work well -> [link=http://www.flyingcirkus.com/forum/forum_posts.asp?TID=400&KW=balance]balance[/link] Haven't tried it on smaller props, but is fine for the larger ones.
I also paint the light blade with clear or whatever to bring it into balance the best I can. It also does no harm whatsoever to cut the longer blade a little, a little, to bring it into balance. Some of the old timers will remember the 1/2A speed engines with one blade props. Sort of the same principle. On larger single cylinder engines this may get dicey, but again, I am running larger twins.
Have a nice day_bob

Excelent link Bob, That looks like a great way to add weight to the hub.

By the way, my butchered APC prop is in the trash.

Thanks everyone