M

Michael Brown

Active Member
During the building process I check my wings for twist, everything was straight. Today I clecoed the skins back on after dimpling and checked again. I found about 7/16 inch twist in my right wing. I removed the skins and the tank and checked again. Now I have less than a 1/16th. Installed the tank and skins again and it remained the same. Started riveting and it is not moving. What is acceptable?

Also, I am checking this with two plumb bobs hanging on a cleco at the main spar and the measuring at the rear spar.

My left wing is perfect.

Thanks,
 
Rivet all skins in the jig

I can't answer the "what is acceptable" question, but if you haven't riveted the bottom skins on yet, you can clamp the rear spar to remove all twist before riveting the bottom skins on. I riveted the bottom skins of both wings when the wings were in the jig for exactly this reason. Before riveting the bottom skins on one wing, one wing had ~3/16 twist if the rear spar was unclamped. It only took a small amount of force to untwist that amount and clamp the rear spar in the correct position. Once the bottom skins were riveted on, they're rock solid. Both wings turned out to have less than .015 twist over the entire length.

If you remove the wings from the jigs and rivet on the bench, there's no control of how much twist will be built in.

Good luck!
 
How do you measure .015, I am trying to figure out how to measure twist to that precision. I will build on and see what I can do when it comes to the bottom skins. Thanks!
 
Just an update

Today I had some time to think about what was going on. So I loosened all the screws on the tank and removed about half the clecos in the top skin. Then I just gave the rear spar a little push in the direction it needed to go and it popped right into place. Tightened the tank up and installed the clecos. Start riveting tomorrow. Wing is straight.... Whoo Hoo
 
Michael Brown said:
How do you measure .015, I am trying to figure out how to measure twist to that precision. I will build on and see what I can do when it comes to the bottom skins. Thanks!
Click to expand...

I used a dial caliper to measure from the rear spar to the plumb lines and had .008 on the right and .012 on the left. (yea, a bit anal):D

Dave
 
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