Top wing skin shrinkage?

[SgtZim]

This is a little disconcerting. Everything fit fine when I match drilled the top skins. I did the countersinks in the spar flange, dimpled the ribs and rear spar flange, touched up the flange with my countersink. Now I clecoed every thing together again - starting at the leading edge - spar holes, worked toward the trailing edge and those holes/dimples no longer line up. They are off by at least 1/32 - the rivets will not lay down straight - which means the dimple and countersinked dimple on the spar are not nesting.

So, the plans have you start riveting in the middle and work outward. I worry that riveting won't restore any of the shrinkage caused by the dimples and I won't have a good fit at either the leading edge or the trailing.

Any tips gentlemen????

[60av8tor]

Hard to say exactly without seeing the structure. However, I have had a few similar instances that left me head scratching. I removed all the clecos, started over, and everything fit the second time...

[Louavul]

Bruce: The skins on my -7 did exactly the same thing. The farther outboard I got the holes could not even be clecoed.

As I recall, it's been awhile, I removed the skins, verified the rigging in the jig with fishing line, etc. Clecoed the skins back on clecoing in a random shotgun partern then riveted the same way. It all worked out fine.

Suspected that working from one end to the other allowed for an accumulation of tolerances resulting in the outboard mismatch. I put up a message here on the site back then but that may have been when this site was email based not web.

P.S. got a favorite for the Derby? I miss my bluegrass this time of year.

[wirejock]

Maybe my wife washed the top skin. Sorry.
I don't think anything is shrinking. It sounds like some dimples aren't nesting completely. They can be very obstinate. Remove the clekos and recleko. Try different patterns. It will fit but don't start riveting till it fits. I assume you have a jack under thd aft spar to support the wing mid span.

[DaleB]

I found it helpful in most cases to start putting clecos in at the center, and work out toward the edges. On the wing skins I'd put 3-4 of them along the top edge (main spar) to "hang" the skin, then put half a dozen in the middle of the wing spanning two ribs, remove the spar clecos and work my way out from the middle. Perfect fit.

[longranger]

Wing skins are easy compared to fuselage top skins...

[fixnflyguy]

Heat it with halogen lamps and start getting clecoes in every 3rd hole or so. You would be surprised at how much it will "grow". I heated mine purposely while drilling so it would be tight.

[F1Boss]

Originally Posted by fixnflyguy

Heat it with halogen lamps and start getting clecoes in every 3rd hole or so. You would be surprised at how much it will "grow". I heated mine purposely while drilling so it would be tight.

The heat trick might work if your holes were getting closer as you clecoe'd 'em down. Your problem sounds like they are seemingly 'stretched' out?

So: Start in the middle and cleco every 12th hole in one direction, then the other, then every 6th, then every 3rd (you will have two open holes side by side in your line up).

START RIVETING IN THE MIDDLE - fill every 6th hole in one direction, the restart in the other direction, again with the 6th hole.

Then every 3rd using the same process. The take your clecoes out and finish 'er up.

I do this on almost every rivet line during assembly unless there are only 3 rivets in any particular line..

Carry on!
Mark

[SgtZim]

I really appreciate your support and suggestions. It is looking better now - I took them all out and tried working from aft spar forward - came up short on the front by the same distance. Took it all apart again - clecoed the front spar first, working from the center out, then clecoed to the ribs starting with the center rib and working both left and right as I went aft - looking like a flattened arrow as I went down. I still came up apparently a little short, but I tried putting clecoes in the aft spar, working from the center out again and I am much closer now. There is some flex in that aft spar it seems. I can relax and get over the "panic attack". It is really very reassuring to hear you guys sort of verify that I didn't make up some new problem.

So, by the time I'm done - I'll have a killer handshake from the cleco-cises.

Thanks again.

[SgtZim]

Originally Posted by longranger

Wing skins are easy compared to fuselage top skins...

I'm not scared,

I'm not scared,

I'm not scared...