Balancing a 3 blade prop

[Larry Renger]

Is there a systematic way to balance a 3 blade prop?

Come on, you pro guys, you use them all the time, don’t tell me you just bolt them on and fly, or if you can, the guys who make them know how to get them in balance. Surely it matters to you.

Somebody knows how it is done in an efficient manner. Gimme a break! 

[Larry Renger]

Then you are going back and forth trying to get the balance even. Isn’t there a better procedure?

[FLOYD CARTER]

Put the 3 blade prop into the balancer with one blade "down",  Sand the two "top: blades until they balance.  Turn 120 deg. and repeat.

With one blade "down", gravity does not come into play on that blade.  Leaves just remaining two to balance.

Sanding any blade affects the other 2.  So it is necessary to keep doing this until all 3 blades are the same.

[John McFayden]

I found this Y Tube video useful.




John McFayden

[Howard Rush]

Mike Haverly taught me to balance the hollow Igor props by putting lead on the hub opposite a heavy blade.  This doesn't look like it would work, but it does. I put the lead on with epoxy or Slo Zap, then fine tune by carving little slivers off with an X-acto knife. 

[Massimo Rimoldi]

Hi, I proceed like this:
1) I label the blades (A, B, C) with a felt-tip pen.
2) I place the propeller on the balancer, the blades A and C downwards and the vertical blade B up, in this way I find the lightest blade between A and C (by way of example, let's assume C + light).
3) I place the propeller on the balancer, the blades B and C downwards and the blade A vertical upwards, in this way I find the lightest blade between B and C (by way of example we suppose B + light, which at this point is the lightest of the three blades).
4) I start sanding blade A to balance it with the light reference B and then repeat the operation for blade C.
5) I check the balance of the three blades again in sequence and it is hardly necessary to further adjust them except to compensate for really small deviations.
I hope this helps

Massimo

[Jim Hoffman]

I use this simple aluminum fitting to find the heavy blades on anything with three or more blades.  The bored hole is blind and has a conical bottom.  Center the prop snuggly on the fitting and use a needle as the fulcrum.  Turn the ceiling fans off too.

I don’t recall where I got it decades ago.  Probably not a difficult job for a skilled machinist w/ a lathe.

[Steve Helmick]

I've come to the conclusion that 3 blades are easier to balance than two. Because....you don't have to monkey around with balancing the hub, like you should on a 2 blade propeller. Brett or Paul will be along shortly, to 'splain why I'm wrong.    Steve