SB00067 Mass Balance Weight Removal

[Jcurry]

Hey Guys,
I have a legacy -12. Evidently my stab was never balanced. While complying with SB67, I discovered my stab is nose heavy. Just trying to get an average amount of weight that was removed on the legacy -12 in order to obtain neutral balance if your stab was not previously balanced. Thanks.

[seagull]

I removed 9.52 ounces.

[rcarsey]

I did not measure how much weight was removed.. but I waited until the stabilator was painted before balancing. A few photos are attached here.

[Jcurry]

Thanks Walt and Rob.
Rob, what did you use to trim your weights?

[bobg56]

A hacksaw works fine.

[Skip12]

Originally Posted by Jcurry

Thanks Walt and Rob.
Rob, what did you use to trim your weights?

A drill also works well.

[Mich48041]

Since legacy RV-12s have flown just fine for hundreds of hours with a too heavy counterweight,
it is better to err on the side of too heavy, especially if the stabilator will be painted in the future.
RV-12iS plans page 11iS/U-11 says to err on the side of too much counterbalance

[hamblin10]

Im planning on just climbing into the tailcone with my drill and remove material until the counterbalance stays in a neutral position when moved. Seems like the fastest method to get to the same result.

[rcarsey]

Originally Posted by Jcurry

Thanks Walt and Rob.
Rob, what did you use to trim your weights?

I (actually the shop it was in) used grinding/sanding disc on a rotary tool. I didn't mind if they got lead shavings and dust all over their hangar . We thought about whether the trim servo should somehow be connected while we were balancing.. and decided against it. We trimmed until the stab (including the AST which we taped into a neutral position) was balanced. (we hung the stab from the ceiling with wire by its pivot bolts)

Once we mounted the stab in the plane and hooked everything up though, it seems we removed too much weight. So I guess my advice to others is to either trim it in place, or somehow account for the trim servo weight.

[Jcurry]

Originally Posted by rcarsey

I (actually the shop it was in) used grinding/sanding disc on a rotary tool. I didn't mind if they got lead shavings and dust all over their hangar . We thought about whether the trim servo should somehow be connected while we were balancing.. and decided against it. We trimmed until the stab (including the AST which we taped into a neutral position) was balanced. (we hung the stab from the ceiling with wire by its pivot bolts)

Once we mounted the stab in the plane and hooked everything up though, it seems we removed too much weight. So I guess my advice to others is to either trim it in place, or somehow account for the trim servo weight.

Going by the KAI, I placed weight on the stab until I reached neutral. This turned out to be 18 0z total. The KAI says to divide this by 2. This gave me 9 Oz to remove. I decided to only remove 8 0z to account for blade width material loss and to ere on the side of being a little nose heavy. Happened to work out
to be perfectly balanced.
Thanks for all the info everyone