prop balance

[edward7048]

Has anyone had a dynamic prop balance on a ESLA RV-12 if so where
did you place the weights if needed?

[DHeal]

I placed the two small washer weights required to balance my propeller on the spinner's aft-edge mounting screws inside of the rear spinner bulkhead. The combination of a slightly longer #8 screw plus two washers plus a small fiber-locknut was sufficient to give me 0.02 IPS balance. The only downside of this arrangement is that I will have to remove the top cowling (easy to do) anytime I need to remove the spinner (i.e., I can't access the weight / spinner nut with the top cowling in place). I could probably rig up a more elegant method of securing the screw, but this is easy and works for me.

[Walt]

I've balanced quite a few RV12 and other Rotax powered aircraft, I always drill 2 holes in the spinner bulkhead for the required weights (3/16 bolts/nuts/washers as req'd).

[Chrysopelea]

How exactly is an airplane prop balanced?

Is it removed from the plane?

I've balanced a thousand model plane props, but wondered how the big ones were done.

I've also read about dynamic balancing, going to read up about that too.

[philrisl]

Most props are dynamically balanced using a commercial balancer. These use an accelerometer attached to the engine and a photocell that senses a piece of reflective tape on the spinner or prop blade.
I have both a Dynavibe and an ACES. Both work well.

[ClutchCargo]

I made it through my phase I testing recently, but was very unhappy with the vibration levels especially at 3000-4000RPM.

I flew to a local shop for a balance and found that the prop was so far out of balance that the repair man refused to balance it until I reversed the blades.

That helped only a very minor amount. It still took about 45 grams at the spinner back plate near one blade to bring it into 0.01p limit. The repair guy stated that such an amount was very heavy for a composite prop in his experience.

Although this new balance made the airplane much more fun to fly, I hate to think what forces that weight will place on the spinner bulkhead and whether it will lead to failure at some future time.

My question is whether this is actually a typical weight that other folks have needed. And I wonder why the blades were not better matched by Sensenich before shipping?

Any similar experience?

[RFSchaller]

Mine required just a#4 machine screw.

[rvbuilder2002]

Originally Posted by ClutchCargo

My question is whether this is actually a typical weight that other folks have needed. And I wonder why the blades were not better matched by Sensenich before shipping?

Any similar experience?

It is not at all typical. The most weight I have had to use is less than half that amount.

An additional influence of prop balance is both blades being at the exact same pitch angle.
I will except no more than .1 degree difference, but I shoot for them being the same.

My recommendation is that you call Sensenich and ask them your questions.

[DHeal]

My prop only required a couple of small washers to balance at 0.02 fps. Check the blade weights etched onto each prop blade stub to see if they are a closely weighted matched pair. Talk with Sensenich.

[bajapilot]

Since we're talking prop balancing, can anyone recommend someone to balance my prop in northern Ca. I'm based at PVF, btw Sacramento and Tahoe.

Thanks, Bill.