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trim tab

M

metalman

Registered User
Melbourne Australia
Hi all, I am just about finished the elevators on my exp supercub, I'm wondering if anyone has built them with a trimtab rather than the factory system, it would have to weigh less and be a lot less complicated, something like a cross between a Super Decathalon (the size and placement) and an RV7 (using either a vernier cable or electric) any thought or pics?
Mat
 
the Wag Aero Sportsman 2 plus 2 has the trim tab. I really like the way the Super Decathalon trim works. handy. The standard for Super Cubs is the jackscrew system. Check around for a set of plans.
 
Don't do it ... Stick with the jack screw. You can't beat a trimable stab. We have covered this subject before, use the search function to find the threads.

Jason
 
I have a Super D and a Cub. Both trim systems work fine. I do not believe the Cub system is that much of a weight penalty, and properly lubricated it never stops working. I have heard of a cable break on a Decathlon, and the pilot (a friend) said it was truly a handfull.
 
I have been flying a 2+2 with a trim tab and have not noticed any bad behavior other than running out of elevator when I am a little forward in CG. I am currently rebuilding and am thinking on going to the jack screw and the Bill Rusk electric motor to operate it. We will see how muck work I want to do when it comes time to do the modification and let that be the deciding factor.
 
Short of going to a flying stabilator, aka Piper Cherokee, a Cub type trimming stabilizer is the most aerodynamically efficient pitch trim system available. A trim tab on an elevator, when trimmed against a nose heavy condition, actually reduces the elevator effectiveness because the tab is down thereby reducing the elevator authority. You would have more elevator authority by trimming nose down. The tab would then be up, acting like an upside down flap on the elevator, increasing the elevator force. This would not be a comfortable condition as the pilot would have to apply a continuous up elevator force and defeats the purpose of the trim in the first place.
 
DUSTERMAN said:
How does the Huskies work? Feels alittle different.
Click to expand...

The Husky trim works well too. It is a bungy system (spring and cables,pulleys that do to it's ratio and geometry is quite effective. It gets a bad rap from those who've never flown one. It works suprising well. I find the Husky to be rock solid when it comes to trimming.
 
I hate the Husky trim. It trims the airplane but but no feel, just pulling against a spring. I think if you just want to fly a trim tab is a simple solution but as posted above the jackscrew is effective and is one of the things that makes a Cub better in my opinion.
 
I have a stretched pacer type and have gone with the 4deg down stab and two trim tabs on the ele, this is the same as the PA 15 and the Bearhawk, my reasoning is a more secure stab, and you can get more authority by having a greater range like 28 deg both up and down, and larger tail feathers. I made a chain system over a SS cable with a torque tube for a more fail safe system than a simple cable. I have always liked the Piper system for ease of use, but always found a lack of feel in caparison to a trim tab system.
 
Hi Jim,
I am trying to get input on the geometry of stretched Pacers that are flying and what the results are for trim and elevator effectiveness, etc. Did you put the tailpost of your build on the same HRL as the original Pacer? Also looking for Riblett wings on Stretched Pacers to see exactly what angle of incidence was used ie. the angle between the HRL of the fuselage and the chord line of the wing. Did you use a Riblett wing?
 
About the only thing that I would change on my J4 would be to get rid of the fixed stab and go with the J3/18 adjustable stab. One thing nice on the fixed stab on the J4 is that if you remove the stab fairing there are 7 vertical holes so that you can set the leading edge to carry the tail load for each planes weight. The POH recommends different holes for land and floats and they are about 1" apart.

Glenn
 
I once owned a J-4 that had a J-3 tail married to it with the adjustable stab (with a field approval!) It worked well. No complaints. Poor thing is languishing rotting away in a junk hangar, but I can't find the owner to buy it back.

I completed a Wag Aero SC this summer and used the trim tab on it. The trim tab is very effective, actually, a bit touchy. Much more so than a Champ or Citabria. However, it doesn't provide quite as much nose up trim as I would like. I may have to change the shimming for the leading edge of the stab to address that. Based on my experience, I honestly can't say that I prefer one over the other. They both work well. Seems to me that I have most of the parts for the jack screw system stashed somewhere in the hangar.
 
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