RV-12 rudder trim tab evolution

My wife and I built our empennage kit at Synergy Air in 2016. Recently I got the rudder out and installed it. Last night I was in the garage and noticed a missing rivet (bottom most, aft most rivet on the left side of the rudder). I check my section 7 and noticed it called out all holes to be 4-3's. My section 7 is an original version 0 section 7. So I put a rivet in this hole.

Later it struck me that my rudder does not have a trim tab installed. So I looked at the section 7 I have on my laptop - and it calls out the trim tab, a bunch more rivet holes on the left side of the rudder skin plus some new structure under the skin (R-01211). When I looked more closely I saw that section 7 has been completely updated as of 1/26/18. This is apparently the new section 7.

Scratching my head a bit I went back and looked at all of the files I have from Van's thumb drive - and found section 7A. It seems as though I am missing this section from my original set of plans. Presumably the folks at Synergy were smart enough to not put that rivet in as part of the original construction knowing the trim tab was going to be installed there (the hole had black sharpie around it - I should have dug deeper before installing the rivet). If it had shipped as part of my empennage kit we certainly would have installed it it seems to me.

I'm completely capable of drilling out that rivet and following the instructions in section 7A, but I am curious about the history here. Did empennage kits like mine ship without it back in 2016? Should I be worried about not having the R-01211 in my rudder?

There is an old thread discussing this topic here that states the trim tabs weren't part of the original kits: https://vansairforce.net/community/showthread.php?t=105014

As another point of reference, I received my empennage kit May of 2017 and it didn’t have the trim tab yet either. I purchased later and drilled out the rivets.

The rudder trim tab wasn't standard in the earlier kits.

A while after it's introduction as an optional part, enough service experience was gained to determine that the designed bend angle was ideal for most all RV-12's and those that it wasn't, required just a very small adjustment, so it was added as a standard part to the kit.

Mine was built in 2014 - 2015 (not by me).
It does not have a trim tab, why do current models need one?
My ball is centered in cruise, and out to the right on climb out.

seagull said:

Mine was built in 2014 - 2015 (not by me).
It does not have a trim tab, why do current models need one?
My ball is centered in cruise, and out to the right on climb out.

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The common standard is that an RV-12 will require a yaw trim input in cruise flight (there is nothing in the aircraft design like offset vertical stab., etc., to do this)

I fixed rudder trim tab adjusted for cruise flight will only provide the correct amount of yaw trim in one flight condition so it will be normal to still need pilot input for any condition other than cruise such as climbing, descending, etc.

If an RV-12 is in yaw trim in cruise flight with no trim tab installed, there is likely some other yaw trim influence present.
A common one would be a slightly distorted rudder trailing edge, some times caused by the rudder getting slammed in strong gusty winds when the gust lock wasn't installed.

I consider my RV-12 to be in good rigging. I have adjusted the flaperons for hands-off level flight in cruise with pilot and full fuel. Ball is centered with factory rudder trim tab. Approx 2 lbs. force is required on right rudder in climb, and some lesser amount of left rudder in a descent, if ball to remain centered. Application of flaps in descent is hands-off level flight.

The RV-12 experiences yaw upset in turbulence. Yaw is the lease stable axis in turbulence.

Absolute joy to fly…

rvbuilder2002 said:

A common one would be a slightly distorted rudder trailing edge, some times caused by the rudder getting slammed in strong gusty winds when the gust lock wasn't installed.

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Would this be visible? This plane has always been hangared and treated like a queen.

seagull said:

Would this be visible? This plane has always been hangared and treated like a queen.

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If it is enough to effect yaw trim, it should be visible.

rvbuilder2002 said:

If it is enough to effect yaw trim, it should be visible.

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Are you saying it would be visible like a bend in the skin?
I will look closely, I have had it for a year, flown it 200+ hours and it has flown straight as an arrow from the start. The finish is gloss paint and I have never seen anything bent.

Piper J3 said:

I consider my RV-12 to be in good rigging. I have adjusted the flaperons for hands-off level flight in cruise with pilot and full fuel. Ball is centered with factory rudder trim tab. Approx 2 lbs. force is required on right rudder in climb, and some lesser amount of left rudder in a descent, if ball to remain centered. Application of flaps in descent is hands-off level flight.

The RV-12 experiences yaw upset in turbulence. Yaw is the lease stable axis in turbulence.

Absolute joy to fly…

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My experience flying in slight to some moderate crosswinds aloft the past 6 weeks with the windy Santa Ana wind conditions here lately, has been that I'd really rather have the weight of my instructor on board, too.

Flying solo requires more rudder input, for sure, to keep the plane straight and the ball centered, and the ride is considerably more bumpy when the wings are loaded even less than at max gross. It's very noticeable. More weight is much smoother.

My plane does have a trim tab built and attached on the left side of the rudder. It looks like a little 12" long "wedge" that has been attached with maybe a 7 -10 degree add on of deflection, a little over 1" front to rear? It flies hand free, easily, with me in it and a full tank of fuel. Previous owner weighed about 295# and it flew straight for him, also.

If it is not broke, don't fix it.

Agreed. Mine's been less than half-a-ball out since I built it. While testing I added a temporary rudder trim tab four inches long stuck with 3M double-sided tape. It's still there!