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Wing Stand/Twist Question

ConAgraPilot

Active Member
Ok I have a question on the plans/instructions on my -8 wings. I have the wing structures in the wing stands and need to remove any twist and hard mount the rear spars. The question is do I do this with just the top skins on or top and bottom?
 
Really You could do tops, bottoms, none or both to set for twist. But obviously having a set if skins on will help. Having skins on will really help to take any sag out of the middle more so than taking out twist. But, it is an airplane so if you can, cleco up both sides. I ran a fishing line along the front and rear spars and then diagonal from front to rear spar. Clamp forward spar, adjust and clamp rear spar when all is equal. Really pretty simple to get it perfect. You'll want a secure clamping mechanism because when you rivet the tops, none of the bottoms will be on. I checked the twist periodically throughout the build and riveting to make sure nothing moved.
 
I did basically the same thing. Once I got the wings in the jig, I clamped in the front spar and moved the rear spar as needed as I checked the alignment/twist. Once the spar was in the right place, I clamed it down. I hung a plumb bob at each end of the wing and one at the middle of the wing. I also ran a fishing line across the front spar to make sure I didn't have any sag.

I did my aligning without the skins on. Once I had it where I wanted it and clamped in, I skinned it and the skins went on nicely. Every so often, I will still check my plumb bobs and fishing line to confirm I still have no twist and/or sag in the wings.
 
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Thanks!

Thanks for the replies!! I was just excited to get all the skins on last night and found that there was a little twist and it was very hard to remove it with them on. I think I will remove the skins and remove the twist and clamp. Then re-skin and make adjustments. Thanks again!
Michael
 
plumb bob

I did basically the same thing. Once I got the wings in the jig, I clamped in the front spar and moved the rear spar as needed as I checked the alignment/twist. Once the spar was in the right place, I clamed it down. I hung a plumb bob at each end of the wing and one at the middle of the wing. I also ran a fishing line across the front spar to make sure I didn't have any sag.

I did my aligning without the skins on. Once I had it where I wanted it and clamped in, I skinned it and the skins went on nicely. Every so often, I will still check my plumb bobs and fishing line to confirm I still have no twist and/or sag in the wings.

Yes, i forgot to mention in my post... plumb bobs at each end to check for twist.
 
The question is do I do this with just the top skins on or top and bottom?

Yes and Yes. I left the plumb bob in-place even during riveting. I was surprised to find the wings and other parts would move or twist very slightly every time I re-clecoed the skins. Even after match drilling and dimpling. Not much but enough that I could measure it so I always checked it after moving something to make sure it was as close to twist-free as I could get it.
 
Yes and Yes. I left the plumb bob in-place even during riveting. I was surprised to find the wings and other parts would move or twist very slightly every time I re-clecoed the skins. Even after match drilling and dimpling. Not much but enough that I could measure it so I always checked it after moving something to make sure it was as close to twist-free as I could get it.

I'm finding this to be the case as well, and I'm just getting all the skins clecoed onto the right wing. My "jig" is very sturdy, but not to floor and ceiling because of the garage door. I put the top skins on, then wrestled the corrugated tubing through for wires, and as expected, found that I had moved things a little. I unclamped the outboard rear spar and everything goes back to square. So my question is this: How do you introduce twist on a pre punched kit? I'm going nuts every time I check the measurements and it comes out just a little off. I'm far from an expert, but it seems like the only control over twist that I have is when I get around to drilling the W-408 leading edge rib and the W-423 joint plate, which are not pre drilled. Would it not be OK that as long as the parts fit together (skins to ribs, etc.) nicely to square it up initially, move on through it, then when I get to the point of drilling these parts, make sure everything is perfect? I think I'd be out of my league with a non pre drilled kit.
 
How old is your kit? With the pre punched skins etc. you do not NEED a jig of any sort. I built mine on the work bench and have no twist etc.
Nordo
 
Hey Al, This is Kevin, one of the KSP pilots you met at KFFT a year or two ago. My kit is just a few months old. I still haven't clamped the outboard rear spar to the stand. I've drilled all the main skins and am getting ready to drill the leading edge. Everything was square when I put the skins on. I'm going to double check the measurements before I drill that inboard nose rib with no pre drilled holes. I might not bother clamping it all down and forcing some kind of twist into it. I did notice yours appeared to fly just fine!
 
Tolerance for wing twist?

Yes and Yes. I left the plumb bob in-place even during riveting. I was surprised to find the wings and other parts would move or twist very slightly every time I re-clecoed the skins. Even after match drilling and dimpling. Not much but enough that I could measure it so I always checked it after moving something to make sure it was as close to twist-free as I could get it.

How much difference in the measurement from rear spar to plumb line, inboard vs. outboard, is considered acceptable when it comes to wing twist?
 
Twist

Not sure about tolerance but I'll bet it would be a suprise. I was suprised bow much a wing would twist even after top skins were riveted. It would be interesting to see how one ended up buikt on a bench.
I did just as others posted. Ended up dead nuts on one wing and 1/64 on the other.
 
Not sure about tolerance but I'll bet it would be a suprise. I was suprised bow much a wing would twist even after top skins were riveted. It would be interesting to see how one ended up buikt on a bench.
I did just as others posted. Ended up dead nuts on one wing and 1/64 on the other.

Thanks Larry,

I was seeing about 3/16" difference with just the top skins attached. I just went down and put the bottom skins on as well and re-measured. Now they're "dead nuts". I can't measure any difference. I think I'll stop worrying about this.

-Ted
 
When I built my 7, the plans showed measuring the twist with plumb bobs, etc. Mine were within the width of the plumb bob string--couldn't tell whether or not there was any twist. Then I noticed there was no tolerance on the plans. Called Vans and was told that how to measure the twist on the plans went back to the undrilled skins and with the pre-punched should be ignored. Or better yet, removed from the plans. I think they said if it was within a half inch, it was good.
 
Ok i know this is an old post but i wanted to comment on my experience clecoing the top skins on my 8 for the first time. I put the wing on the stand and leveled the main spar then used a plumb bob to check for any twist. It seemed to be about 1/16" inch off so rather than clamping the rear spar with a strain on it to remove that I just clamped the spar down so it wouldn't move. I was actually pretty amazed at the straightness of the wing. its a testament to the quality of the kit.

Then as I was clecoing on the top inboard skin i realized that my wing was racked a bit and had to unclamp the lower spar and let it swing freely. The top skins were still a bit of a struggle (bottom spar holes) to get fully clecoed in every 4th hole but not too bad. I've learned that if things aren't going together pretty easily then I'm probably not doing it right.

Anyway after getting the top skins clecoed i checked for twist and now its about 3/16". I can't see how that can be improved as the wing is so stiff now, but if vans says 1/2" and pre-punched kits don't need to be plumb bobbed etc then that makes me feel better. I'll probably confirm with Vans though.

Actually i will cleco the bottom skins on to see if that makes any difference. I guess its best to have all the main skins on prior to any match drilling.

** update ** after clecoing on the bottom skins the wing is straight as an arrow.
 
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