RV 12 Prop Balance, "get er done"

[Walt]

Every RV12 I've done has benefited significantly from balancing, if you haven't done this yet you need to!
(recommended by Rotax as well).

This one was a little bit of a challenge, took 5 runs to get it (could have stopped at run 4 but I like to see them less than .05 IPS).

Went from 0.544 IPS down to 0.019 IPS.
Owner said it appeared to need less throttle for the same RPM.

Hopefully JJ will post a picture of his plane with a fresh paint job, it looks awesome!

 

[yankee-flyer]

Southern Ohio group

Anyone interested in a group balance somewhere here in Southern Ohio? That includes someone to do it, of course.

Wayne 120241

 

[Dave12]

I had mine done 2 months ago and am very pleased with the results. The tech stated that it was not terribly far out compared to the Bonanza he balanced just before mine, but I did notice a nice change. I did a thorough carb synch. just prior to the job. It is worth doing.

 

[rvbuilder2002]

Walt, when you do a dynamic balance on an RV-12, do you use a digital protractor to compare the pitch of the blades to each other first?
A couple tenths of a degree difference between the blades (easy to have), will make a significant difference in how smooth it runs, and it will induce errors into the balancing process.

 

[Walt]

Walt, when you do a dynamic balance on an RV-12, do you use a digital protractor to compare the pitch of the blades to each other first?
A couple tenths of a degree difference between the blades (easy to have), will make a significant difference in how smooth it runs, and it will induce errors into the balancing process.

I do not do any pitch checking or adjusting. However, I do advise owners that they should have the prop pitch where they want it prior to doing the balance. If I started checking/adjusting pitch on every one that may open up a whole new can or worms, but I am open to suggestions.

 

[rvbuilder2002]

I do not do any pitch checking or adjusting. However, I do advise owners that they should have the prop pitch where they want it prior to doing the balance. If I started checking/adjusting pitch on every one that may open up a whole new can or worms, but I am open to suggestions.

Not really suggesting that you do, just offering the FYI that blades at even very slightly different pitch angles can have a significant effect on prop track and smoothness (A lot of RV-12 builders/owners are not aware of this).

It will induce errors into the balancing process.

 

[Walt]

Not really suggesting that you do, just offering the FYI that blades at even very slightly different pitch angles can have a significant effect on prop track and smoothness (A lot of RV-12 builders/owners are not aware of this).

It will induce errors into the balancing process.

From my experience I have found that an aerodynamic imbalance behaves differnently than than a mass imbalance. I can always correct a mass imbalance, but an aerodynamic imbalance (may be caused by different prop angles, bent blades or out of track) will not balance down to the typical low levels I get. The slightest RPM change will cause the polar aerodynamic imbalance to move so you end up chasing a moving target that you can never catch.

A "precision" prop protractor is quite expensive and would be very hard for me to justify.

 

[rvbuilder2002]

The slightest RPM change will cause the polar aerodynamic imbalance to move so you end up chasing a moving target that you can never catch.

I am well aware of the problems it can cause. I have done a dynamic balance a number of times on RV-12's

Just offered the info in the interest of helping out RV-12 owners.

BTW, an expensive prop protractor is not needed. Do a search here in the RV-12 forum.

 

[Walt]

Just offered the info in the interest of helping out RV-12 owners.

All excellent points, RV12 owners should take special note on the importance of proper blade angle adjustment and then getting your setup dynamically balanced.