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Aileron twist correctable?

HeliCooper

Well Known Member
I just finished riveting the bottom skin to the spar and thought I better take a look at where I stand. This is what I see with the right and left ailerons respectively.

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The right aileron was off on the end rib hole alignments. Using a punch I was able to line the holes up but even with the clecos in I have this twist. I am guessing the spar got twisted somehow, maybe from the counterbalance/nose rib assembly since that process seemed pretty hokey to me.

My question is can I fix this twist during the trailing edge riveting or do I need to do something else now to correct this. What can I do?

Thanks,

Jim
 
Any aircraft assembly becomes torsionally stiff along its span when any boxed section of it is closed.
In the case of the aileron, once the fwd "D" cell (box) of the aileron is closed, it pretty much locks in what ever span wise alignment you have.
It should be correctable if you un-rivet the bottom flange of the spar and then re-rivet while maintaining alignment.
 
Thank you guys. I guess my next question is how do I prevent this from happening again. I understand in the thread linked clecoing the TE in and then the spar/bottom skin should align the aileron (I will check it on my granite table again). My guess is that as soon as I uncleco the TE and get my ape arm in there the aileron will twist again while I am riveting. Is there a good way to hold the aileron in the cradle?

In the mean time I'll get going on those bottom skin/spar rivets.

Also forgot to mention. My twist ended up being 3/16" (I noticed in the picture the ruler is unreadable).
 
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Clecoe it together lined up as I describe, on your wing. Put it in the cradle,holding it in place with foam, etc, and do three or four rivets spread out along the spar. Take it out of the cradle and check on the wing. If all is well stick a few more rivets in. It is possible that your cradle is twisted and holding the aileron too tight. If it is cleoced together straight foam pieces wedged in the cradle should hold it from twisting. Make sure the cradle is not the problem.
 
Thanks Tom,

I'll give it another go. The weird thing is the left aileron came out perfect. Maybe just got lucky on that one.
 
Saga continues

I removed all bottom skin/spar rivets and right away noticed that without the bottom skin on the same twist is still evident. I decided to try and correct this by using a similar method to Tom's. I clecoed the TE and bottom and top skins. I then clamped the aileron to my table top and then clecoed the bottom skin to to spar. As soon as I remove the clamp the twist immediately returns to the aileron. I even went as far as putting in a negative (relative to the current) twist while it the aileron was clamped and then clecoing. The twist returns back to the same 3/16" every time.

The only idea I can come up with is to clamp the top skin/main ribs down with 0 twist and reach in and set some rivets to see if the rivets will hold out the twist. Does anyone have any better suggestions?
 
I removed all bottom skin/spar rivets and right away noticed that without the bottom skin on the same twist is still evident. I decided to try and correct this by using a similar method to Tom's. I clecoed the TE and bottom and top skins. I then clamped the aileron to my table top and then clecoed the bottom skin to to spar. As soon as I remove the clamp the twist immediately returns to the aileron. I even went as far as putting in a negative (relative to the current) twist while it the aileron was clamped and then clecoing. The twist returns back to the same 3/16" every time.

The only idea I can come up with is to clamp the top skin/main ribs down with 0 twist and reach in and set some rivets to see if the rivets will hold out the twist. Does anyone have any better suggestions?

If the L.E. is already riveted to the counter balance, it will also contribute some torsional stiffness.

What you are proposing is what I would do.
 
The LE is not riveted to the counter balance. I clamped the aileron down flat and put in 10 rivets along the span. I check where I was at and it looks like I still have a 1/8" twist. I'm at a loss of what to do with it now. I put bolts through the mounting holes and those are lined up. It seems if I try to negate the twist too much it pulls these holes out of alignment and the bolt wants to go in crooked. At this point do I need to just accept the 1/8" twist?
 
Did you mount it on the wing and check it there?

Tom,
I'm not sure i understand the reasoning for checking for twist with it on the wing?
The only reference at the inboard end is the flap which could also be slightly twisted and not be a valid reference.
You can check the alignment of the top spar flange rivets to the top skin trailing edge but I don't think that is as reliable as a known to be flat surface (I don't personally know if a granite counter top will always be guaranteed flat)

1/8" twist is not enough to have a negative influence aerodynamically (a lot of RV's are flying with worse), so at this point you will have to decide whether you are willing to accept it or not.
 
By mounting the aileron and flap together on the wing it is possible to see how things line up relative to the wing. I clamp a long straight edge to both surfaces. A long sting would also work. I suppose you could have a twist one way with a flap and the other way an aileron that could cancel out. The point is that, as you say minor differences will not affect flight, but minor differences are really obvious when you mount the wing tip on and sight from the tip inward. The "eye" will see a 1/8" difference when the wing tip, aileron and flap are lined up.
A very minor error in a table top will show up on the final rigged aircraft, that is why I like to verify the surfaces on the wing, not just on a flat table.
It is interesting that I would have had the same error on the same aileron had I not checked this on my wing first.
 
Aileron twist correctable

Hi , introducing myself for the first time as a builder of a rv14 down under in New Zealand. I have watched this forum for a sometime but now that I am building, thought it appropriate I participate. Thankyou Doug for a great forum.
HeliCooper I am just working on my ailerons at the moment and noticed my right aileron ribs that attach to the counterbalance are slightly off when lined up on a flat surface but the left seems o.k. Maybe your first assessment is correct that the counterbalance attach is throwing everything out of alignment.
I am redoing my right aileron counterbalance but luckily am not as far on as you are.
I am a first time builder and so feel your pain but I am very interested in the outcome of this thread.
 
I've decided to just accept the twist at this point. My reasoning being that in order to correct it (or hope to correct it) I would have to remove the 10 rivets for the second time and remove the top skin rivets. All of that removal takes time and possibly compromises the structure. If it drives me crazy down the road I will make a new aileron from scratch.

Thanks for all the help. Bummed out the bottom rivet removal didn't help solve the problem.
 
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