Help for New Owner - Aileron Trim Tab

Dear RV Friends,

As the new owners (not the original builders) of a beautiful RV4 my partner and I are sorting out a few issues. Specifically...

The left aileron suffered some hanger door damage with the previous owner and that damage resulted in a very heavy wing we can not trim out with the installed manual trim.

We intend to build a new aileron once the Northeast USA "nice flying weather" season ends in late December so this is a temporary fix.

I have read the Van's document "How To Diagnose And Fix A Heavy Wing".
But at this point we want to fly, not experiment with a permanent fix to the damaged aileron which will be eventually replaced.

A ground adjustable (bendable) aileron trim tab seems to be the quickest and easiest temporary fix.

So My Questions:
1) What thickness of aluminum to use for the trim tab;
2) The best location on the aileron for the tab;
3) What initial dimensions (length/width) to use as a starting point.
(We would initially secure the trim tab with Mach 1 tape for flight testing, then reduce the size of the tab to the minimum required through flight testing before permanent installation with cherry max rivets.

Your answers to the three specific questions above are greatly appreciated.

What I would do

Hello John,
I have a -4 that I built, and installed an electric aileron trim tab. I also have elec elevator trim and elec flaps, all on the stick..great set-up for future planning. In the interim, I would recommend doing a "wedge" tab simply double side taped to lower side of light wing aileron. You wont see it, it can be removed later when permanent fix is done. get some balsa trailing edge wedge from hobby shop or similar, 1" wide taper and make it about 4-6" long. May take a couple tries to get it trimmed, but it will do the job...no tab hanging out or rivets. How bad is your current aileron damaged? I would bet it could be re-skinned and made back true, saving the headache of building the spar/hinge points ect. I have a pics of my electric tab set-up if you need.

Another easy fix

John,
The balsa wedge and tape suggested is a good solution. Another is a Gurney flap, google it. They are very powerful nearly invisible. I have one on an aleron and rudder. The aileron is only about .124? tall and 2-3? long. Taped on with 3/4? masking tape under the aileron for over a year . FWIW.

The easiest temporary fix is to drop the heavy wing flap a degree or two.

My experience has been that making flap rigging changes to adjust roll trim has very little effect.
The flaps are so far inboard that the roll moment they are able to induce is small unless you make a huge deflection change.
A much smaller deflection change induced by a trim tab or some other means on the aileron has has a much large influence.

fixnflyguy said:

Hello John,
I have a -4 that I built, and installed an electric aileron trim tab. I also have elec elevator trim and elec flaps, all on the stick..great set-up for future planning. In the interim, I would recommend doing a "wedge" tab simply double side taped to lower side of light wing aileron. You wont see it, it can be removed later when permanent fix is done. get some balsa trailing edge wedge from hobby shop or similar, 1" wide taper and make it about 4-6" long. May take a couple tries to get it trimmed, but it will do the job...no tab hanging out or rivets. How bad is your current aileron damaged? I would bet it could be re-skinned and made back true, saving the headache of building the spar/hinge points ect. I have a pics of my electric tab set-up if you need.

Click to expand...

Thanks for giving me the rough dimensions on this. Just installed a wedge that was 1" x 6" made from trailing edge stock, and on the first try it brought my trim back to neutral (with me aboard and equal fuel in both tanks).

I coated the balsa with epoxy first for better adhesion of the tape. Once the tab was in place I put a piece of aluminum foil tape on the leading edge to smooth the transition. I finished it off with touch up paint, and I consider it to be a permanent fix.