Bottom skin troubles

I'm ready to rivet the inboard bottom skin to my first wing, but I'm in trouble trying to line up the holes.

When I match drilled the skin to the structure, it was on the wing jig and I had no problems lining up everything. The top skins has been riveted without any problem.

If I cleco the skin starting from the rear spar, all the holes on the ribs are ok, but I have the holes on the main spar of center of something about 1/32". If I cleco starting from the main spar, it goes better but the holes on the ribs and the rear spar are off center of something like 1/64. I can cleco the skin but the rivets head doesn't lay flat in the dimple. I tryed different ways to cleco the skin (starting in the middle and so on... ) but the result is always the same.
The rib flanges are square to the web.. the holes on the ribs are lined up.... I can't find a solution!

Help please!!!!

My bottom skins were tight going on too, with the holes at the rear spar being the toughest. However, once I started riveting the situation seemed to improve.

Just a thought... You're top skins could have contracted in cooler temps and could be pulling on the rear spar. You could try warming the top skins, bottoms, or both with a heat gun (or out in the sun) and see if the fit improves.

Sorry I'm not more help.

Hi Brad, thank you very much for your answer. (Your web site is my first source of help, good job!! )

I match drilled the skins in the winter (around 12-15?C) and riveted the top skin last month (23-25?C). Now we have 27-30?C so I don't think the top skin have contracted.

By the way, I'm sure that riveting will improve a little bit the fit but I'm afraid it will not.... Since I'll start riveting from the rear spar as suggested in the instruction I don't know how I'll solve in the event the misalignment on the main spar will still be present. I hope to find a solution before star riveting to at least improve the fit even if not perfect.

Where are the wings?

I had a misalignment problem when I tried to cleco on the bottom skins while the wing laying up side down on a bench. When I placed the wing in the wing cradle everything lined up. Could this be the problem?

Have you dimpled everything yet? Sometimes the dimples will help everything line up better. Good luck.

@Jake
Yes, my wing is on the bench... I'll try to put it back on the wing jig or in the cradle... maybe it slightly bents under its own weight

@Steve
The holes are already dimpled.

mototopo said:

@Jake
Yes, my wing is on the bench... I'll try to put it back on the wing jig or in the cradle... maybe it slightly bents under its own weight

Click to expand...

I think you found your problem, the wing seems to relax under its own weight laying on the bench. I disassembled my wing jig as soon as I took the wings off so that wasn't an option for me. I think Van intended for the bottom skins to go on while they were sitting in the cradle.

Thanks Jake. Tonight I'll put the wing back on the jig.. fortunatelly it's still there! Hope it'll work!

Similar problem on bottom skin

I just finished riveting my bottom skin today. I kept it in the cradle and was able to do the riveting myself. I was little nervous about it but it really turned out to be a non-event. I clamped the spar to the cradle to keep it from moving while riveting.

Before I started riveting, when I would cleco the bottom skin on, I had a similar problem like yours. I had a tough time getting the clecos in the main spar.

Starting in the center of the skin, I riveted the skin to the rear spar outboard, then inboard. Staying in the center, I then riveted outboard then inboard on the ribs working my way to the main spar. When I reached the main spar, it all lined up nicely. I was able to slide the rivets in without any problem.


Doug
RV-7
Wings - closing up
Fuselage - inventoried

Doug, didn't you followed the suggested riveting pattern (starting on the inboard portion of the rear spar and working in an L-shaped pattern along ribs and outboard) ? Can you reach all the rivet holes trough lightening holes and inspection access without pull up the unclecoed skin?

Similar problem on bottom skin

No, I didn't follow Van's suggestion of moving it to a workbench and riveting in an L pattern.

Working in the cradle, I had to pull the skin back a little when I was near the rear spar. As I worked my way closer to the main spar, access was much better through the inspection and lightening holes. It helps to have long skinny arms.

Mhmm.. probably I'll rivet the skin the same way as you... hope my arms are long enough!

I'm just still worried about the hole misalignment. I put the wing back on the wing jig and even if slightly better, the fit is still not perfect. I'll try again moving the wing on the wing craddle.. maybe with the wing upside down it will change again....

I'm thinking to star riveting even if the fit is not perfect hoping it will improve while riveting. But what if it not improves??

Same issue here

Did this issue work itself out after riveting mototopo? I am seeing the same thing, only the rivet holes at the main spar are off nearly half a hole if I cleco from rear spar to front.

Hi,
first, try different clecoing pattern starting from different point on the skin.. it will make some difference. In my case I still had some misalignment so, before start riveting, I contacted Scott @Van's to explain my issue and he told me is not uncommon. He told me to start riveting along the main spar/inboard rib and working down to the rear spar and ouboard. It worked well, but first make sure your rib's flanges are perfectly square (also a little touch up will make a huge difference). I left my wing in the craddle instead than on the workbench. As pointed out by other people, it helps.

While riveting, you'll see the skin seating well in the dimples on the ribs and the fit going much better.

Following this riveting pattern I ended up with some unreachable rivets along the rear spar (between the 3rd and 4th bay) that I was unable to buck ( I work alone, maybe with an helper it will be easier). Scott told me to enlarge the holes to #30 and use CS4-4 pop rivets. Don't care about the edge distance, it's just a little bit under specs (Scott was confident it was ok and I trusted him).

On the second wing the initial fit was better. I started riveting in the middle of the skin (even if I initially had a little misalignment on the main spar) but the holes aligned well once started. On a few holes I had to slightly enlarge them with a #40 reamer (just a little touch up without any visible hole elongation).

At the end, I'm satisfied with the result.
Contact me again if you need further infos.