Do i have to do this with every prop i'm planning to install on my plane?

What is the best thing to have to do this? What is the hole purpose of this?

thanks !!

Marc-André

It's not a bad idea to do this with EVERY prop.

Some props come somewhat balanced from the factory, others need some work.

The more balanced the prop ( and don't forget to balance the SPINNER TOO! ) the less vibration the plan may be subjected to in flight and on the ground.

The engine also gains a bit of efficiency too.

okay but you know how to do this?

You put the prop on the balancer.

Make sure the prop is centered on the balancer ( twisting the inner support on the hub helps to do this... ).

The blade that goes down, is the heaviest.

Sand, or shave off a bit of material until you have the blades as level as possible.

I don't go as far as making them level with the ground, but if there is no tendancy to have one more than 10-15% out of level I consider that OK.

Keep in mind that props should (in theory) be balanced in two directions, both tip-to-tip but also across the hub.

A perfectly blanaced prop, when put on a quality balancer, will stay exactly where you put it, no matter where you put it.

The easiest way to balance the prop is to first put it on the balancer. If it doesn't move from various locations, it's already done. If it always moves to a certain spot, chances are that one blade is "down". Now, add weight to the light blade or remove weight from the heavy one until the prop rests level.

Now, if the prop will rest level with one blade on the right, but moves when that blade ison the left, then the hub is a little out. You can remove a bit from the heavy side of the hub until the prop always stays put.

Adding weight to a blade is often done with a little paint or nail polish remover. Removing weight is often done by sanding the flat-back surface of the blade. Don't change the airfoil shape though.

Now, is all that necessary? For small props in the 11" and smaller range? probably not. I usually don't bother.

But the larger the prop, the more it matters. And if you are having vibration problems, like screws coming loose all the time, even with locktite, then the prop is a good place to start.

And finally, some engines are just naturally shakers. All single cylinder engines will vibrate some at certain RPM, but some just vibrate more than others. You can sometimes reduce the vibration by mounting an out of balance prop with the heavy blade directly opposite the piston. The easiest way to do this is to point the heavy blade down when the piston is at the top of it's stroke.

Yup...

Balancing of the blade cross section is a bit "beyond" the beginner arena though...

And even most beginners don't really deal with blade balancing, so the OP is a bit ahead of the game.

Oh, sure, I agree. Unless you're using a giant scale plane as a trainer. (uncommon, but not unheard of).

Frankly, beginners often break props, some beginners break a number of them. If the props aren't lasting long, or are getting nicked up (which changes the balance), then there are other things to worry about. I suspect most people never bother to balance anything.

However, if you're getting a lot of vibration, or if you change props (maybe after breaking one), and the plane seems to vibrate more than it did, it's worth looking in to.

And yes, the info on balancing in both directions is more than a beginner might "need to know", but I always think that it's better to know and not worry about than to not know because no one bothered to mention it. (besides, sometimes I just like typing. Just kidding).

Oh, also, not often, but once in a while you'll get a defective prop with the hole drilled slightly off center. Doing a quick balance check, even if you don't do anything to alter the balance, can be useful to avoid such things. But defective props are rare.

A nice writeup on the articles section would be good for the beginners... and informative for us grey haired types.


Especially if it included things like keeping the spinner balanced, how to enlargen spinner holes with balancing in mind, correctly enlargening prop holes, how to do chordwise balancing, etc.

as for balancing I check my props to see if there way out,if there close,then I don't stress it for a smaller engine.
lets say for a 11/5 prop on a OS 46
for my warbirds then I am more diligent and make sure there as close as possible
Mfg. like Master air screw,APC are pretty close to balance.
its a good thing to check just in case there is always a few rotten apples near the tree so a trip to the balancer is always a good idea.