aargh - Quickbuild wing bottom skin fit
 

Hi All,

I could use advice regarding the fit on my QB bottom wing skin. Basically, I've got nearly the whole skin riveted on and am finding the row of holes on the forward spar are all about 1/32" off, enough to not quite let a rivet be pushed in.

When I fit the skin, I had a similar issue. I worked around it by changing my cleco pattern, until I could get cleco's into every few holes. Thinking I had it lined up, I then drilled, deburred etc and and started riveting.

Now I've got the skin almost fully riveted, starting from the trailing edge, and things aren't pulling together again like they did clecoing. The weird thing is, the entire rear spar and ALL the rib holes line up just fine, the only misalignment is with the forward spar. I'm thinking that that bases of the wing ribs weren't quite fluted enough during the QB build, increasing the gap between the "foot" of the rib and the spar.

So, the question is, what now? The holes aren't very far off... my inclination is to redrill the holes to #40 (slightly enlarging them,) and then using the next length rivet in the holes to allow them to swell up a bit. I suppose my next thought would be to drill them all out to #30 and use AD4's, but, that seems like overkill. Thoughts from the VAF?

Thanks much,
Josh (very frustrated)

Hi Josh.. I had a similar issue on my slow build left wing (still working on the right wing.. hope i'll not have the same issue!)

I was lucky because I noticed the misalignment before start riveting and, contacted Van's, they told me to start riveting from the main spar down to the rear spar. It worked well (while riveting all the holes came to the proper position) except for a few rivets along the rear spar I couldn't reach with the bucking bar and, as per Van's suggestion, I used blind rivets on those holes.

In your case I suggest you to contact Van's and ask for a solution.. elongating the holes on the main spar doesn't looks to be a good solution. You can check for proper bend/flute of the ribs flanges and start clecoing form the middle of the ribs and proceding to the spars (or starting at the main spar and proceding to the rear one)... if you can cleco the skin, while riveting your fit will be better because the rivets will force the dimples in the proper position. But, again, a call to Van's will give you more usefull informations.

Thanks
 

Thanks for the reply. I am hoping to avoid drilling out every rivet in the skin, but I guess I need to suck it up and do it, if that's what needs to be done. I have an email into Van's, we'll see what they say...

Drilling out ALL the rivets in the skin will result in a LOT of enlarged holes.... I don't think it's the way to go.

Let me know what Van's says.

It's maybe 75% of them... I was hoping everything would pull together, should have stopped riveting sooner I supposed. One step forward and two back.

I say go with the drill the mis-aligned holes out and use the next size up on the rivets... if you drill all the others out, you'll probably do more damage than good by the time its all said and done with... thats just too many to drill out... another thing to try, I use a pin punch sometimes to help line up holes... on occasion, i have to push it in pretty hard to get it to line up. I have a feeling it slighly stretches the skin to the hole, but not by enough to obtain any kind of measurement. You could try that, starting at once side and working your way to the other? Here is the punch I use:



I just put it in the hole, and push it up to the tapered part, a little push and a twist or two puts the holes into exact alignment... take it out, drop a rivet in, and pull the trigger!

and here is where I got it:

http://store-planetools.com/pinpunch.aspx

You're going to think I'm crazy, but.....

The wing is on straight padded sawhorses perpendicular to the the spar, right? With the lower skin in place, flip it over, bottom side down. Make sure each sawhorse is under a rib. Have a buddy push down on the rear spar while you push down on the leading edge. Now crawl up under the wing and insert the clecos ;)

Dan - that's crazy enough that it just might work. The holes are that close.... now to round up a helper for this weekend....

The CNC punch at Vans didn't put the holes in the wrong place. Gravity has deformed your wing because, lacking one skin, it is currently an incomplete structure. Sitting on the sawhorse pulls the spar-to-rib flange a bit longer, like so (small arrows):



Flipping the wing puts that flange in compression, and lo, the skin again fits.

No more Alabama jokes from me!
 

....Dan has to be a Mensa member!:)

Thanks, Dan,