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flaperon hinge (rod end) adjustment

What is the effect on roll trim, of making a half turn OUT on the LEFT aileron hinge rod ends?

The reason I ask is that I have found the hinge rod ends are not equally set, and I have a slight roll. After reading a bunch of posts about roll trim, I've checked all the components and trailing edge of top wing skin. The only real assymetry I see is those rod lengths and the relative heights of the flaperons while in the neutral position (eyeballed with a straight edge running chordwise off the trailing edge of the top wing skin).

Flying RV-12 I didn't build. I don't know if the difference was unintentional or oversight.
 
It certainly will have an impact on roll trim. If you’ve got the build plans, section 18 is for the flaperons. See attached for the 11/32” dimension from center of the rod end to the flaperon skin.
 

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It certainly will have an impact on roll trim. If you’ve got the build plans, section 18 is for the flaperons. See attached for the 11/32” dimension from center of the rod end to the flaperon skin.
Thanks for the reply. Yes, I saw that in the drawings, and that's how I know these are out of spec. Mine are closer to 13/32. However, if I turn these into 11/32, then the other half of the hinge will impact/scrape the flaperon skin, so I sort of see why the builder chose not to turn them all the way in. I do know that some people have adjusted those to affect roll trim, but I've never seen anyone describe which direction, or how much. I also don't know the aerodynamic impact not having the flaperons centered in the slipstream--or even if they should be!
 
By all means, I’d go for spec, as they are primary flight controls!
When I built mine they did seem darn close to the skin, but should not be moving at all since they are Loctite’d in. (It might be a challenge breaking them loose to re-adjust.)
 
I bought my 12 from original builder and it had a small trim tab attached to bottom left flaperon with double sided tape. Did the job – plane flew hands off in cruise and straight with flaperons extended both notches. I flew the plane this way for about a year and then decided to fix. Pivots were set to KAI. Removed trim tab and right wing was severally heavy. I tried pinching trailing edges of flaperons and didn’t see much improvement. I also looked at top wing skins behind rear spar and that looked good.

So, I started playing with flaperon pivot rod ends and achieved desired result – straight and level flight (ball centered) in both cruise and slow flight with flaperons extended two notches. I don’t remember how many turns in/out. As I recall ½-1 turn on both wings. I also can’t recall which flaperon was raised and which was lowered. I do remember that it was not intuitive. You’ll need to experiment and test fly to discern correct adjustment. It took several test flights to dial in the change. Airplane continues to fly excellent. I fly two other factory built RV-12’s and they all fly exactly the same.
 
... should not be moving at all ...
The rod end forms the top half of the hinge. The flaperon does move in relation to the bottom half of the hinge. There is currently only about 1/64 between the bottom skin of the flaperon, and the bottom half of the hinge.
 
The rod end forms the top half of the hinge. The flaperon does move in relation to the bottom half of the hinge. There is currently only about 1/64 between the bottom skin of the flaperon, and the bottom half of the hinge.

The rod end should not be moving in relation to the flaperon skin at all. If it does, there is a big problem, and the Loctite has failed (similar to a loose jam nut). This would cause thread spalling and eventual failure. We definitely don’t want our flapperons falling off.
 
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... I don’t remember how many turns in/out. As I recall ½-1 turn on both wings. I also can’t recall which flaperon was raised and which was lowered. I do remember that it was not intuitive. You’ll need to experiment and test fly to discern correct adjustment. It took several test flights to dial in the change. Airplane continues to fly excellent. I fly two other factory built RV-12’s and they all fly exactly the same.

Concur with this. During my initial flight testing, there may be need to lower or raise the flapperons to achieve level flight/ball centered etc... if you are detecting a heavy wing. I found at the time the flight testing procedures did not explain that very clearly (may have been updated since). Until you flight test, you may not know for sure what the proper depth for each of the L/R rod ends so start with them set equally to the KAI values. There should be no need for an added trim tab on the flapperons once adjustments are taken during flight testing.
 
The rod end should not be moving in relation to the flaperon....
Agreed that would be a disaster. I'm just failing to convey my meaning here, and I'm sorry I do not have a picture or video to show you. Everything is solid, so no worries. If I find (or take) a close-up picture I'll reply here with annotations to explain.
 
You are probably doing something wrong. Here is a shot of my rod ends. They are set to 11/32” from bolt center to skin +/- .015. I set the rod ends by inserting a 3/16” pin into the spherical bearing and adjusting it’s height to just clear two ¼” spacers on either side (one half of 3/16” pin + ¼” spacer = 11/32”)
IMG_0925.jpgIMG_0928.jpg


The leading edge of Flaperon doesn’t sit flush to the top wing skin.
IMG_0933.jpg


The Flaperon bearing height is a setting, not an adjustment. Adjusting the rod end bearing height may fix the issue, but it’s compensating for other errors in the system. I agree with Brent, the PAP lacks a systematic procedure for addressing this common problem.
 
Solution - Roll Trim

I've fixed roll trim on several RV-12s so perhaps I can share my experience:

As far as the cause, there are so many factors involved in a small roll anomaly that it is essentially impossible to nail it down to one. Just a few include: the clocking of where the thread starts on the bearing, minor twist induced in the flapperon during assembly, twisting the wingtip when drilling the outboard skin, not aligning the torque tubes/flapperons properly when drilling the torque tube, and consistency of the trailing edge bend (This is addressed in section 5 of the build instructions.) If your goal is a perfect zero roll in cruise any anomaly in these will change your roll. Keep in mind also that your roll trim will also change depending on your lateral weight and balance (e.g. big guy in the pilot's seat flying solo will roll left vs. 95 pound guy flying solo will roll neutral or to the right)

Yes, changing the depth of the bearing has an effect on the roll trim. 1 revolution on both bearings in only one flapperon is roughly equivalent to 1 degree per second of roll. If you need more you can adjust the other flapperon as well. As long as you keep the bearing within... say 2 revolutions of the original spec, there should still be plenty of thread engagement to take the flight loads. This means that you can adjust up to 4 degrees per second of roll if you adjust both flapperons. Any more than that and I would say that there is something more seriously wrong with your flight control rigging than a normal roll drift.

I hope this helps,
 
I tried installing one MD3614M last night using MMiller's technique. I also ran out of room before the gap was down to 11/32" (head of MD3614M hit the skin). Are folks opening up the hole in the flaperon when this happens to allow for clearance?

It was a quick trip to the hangar, I'll try again next week at all 4 locations.
 
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