Thorp Air Command - T18.net

As expected, my plane requires some aileron trim in order to fly hands off for long distances. I have the standard flap trim system, but I was looking more at the aileron trim option. I was also looking for a way to get aileron trim without cutting up my aileron and installing a true aileron trim system.

With that in mind, I bought a rudder trim tab from Avery tools. http://www.averytools.com/prodinfo.asp?number=9883

The dimensions are 6" long, 1.5" wide, and it tapers from 3/8" down to 0".

I applied the tab to the aileron and went flying. I couldn't tell it made any difference in the flight characteristics. I would have expected some effect, either good or bad.

Would you expect a rudder trim tab to have an effect if you applied it to the aileron?

As reported several times before in the old newsletters and this forum, the preferred way to correct roll trim is to slightly bend the trailing edge of the ailerons. It doesn't take much. Sliding the thumb and forefinger along the trailing edge while applying pressure will bend it enough to make a difference. Bend the trailing edge up on the heavy wing and down on the light one. I would check the rigging first, before making adjustments. The Thorp has differential ailerons and rigging to include the bell-crank angles must be right. Again, it doesn't take much. The rudder trim "wedge" isn't enough area to do much. A moveable trim tab should be the size of a dollar bill and needs to move at least a half inch up and down to cover the various lateral asymmetric loads you will encounter with different size/no passenger situations. Hope this helps.

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Bob Highley
N711SH
SN 835
KLAL

Thanks Bob. Guess it'll take a little more than taping on a trim wedge.

After disassembling and painting my bird I had a heavy right wing when finished. On the ground the ailerons looked to be rigged correctly. In the air it only required about 1/16" of aileron travel to level the wings. It took about two turns of rod end bearing to fix it.

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Bruce Finney
N18JF T-18C #262
Yelm, WA USA

Good info Bruce. That's about the same symptoms my ailerons display. My condition inspection is right around the corner so I may give the rod end a turn or two and see what happens. Thanks again.

Bruce: I have the same problem . I assume you corrected the right aileron ? Turned the rod bearing out ?

RB

The right wing was heavy, needed down right aileron, turned the right aileron rod bearing in.

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Bruce Finney
N18JF T-18C #262
Yelm, WA USA

Thanks Bruce ! I think I knew the answer , but after 3 days of mental un stimulation with the non existent radio problem I wanted to cry Mommy !

RB