Big OOPS

Well after soliving the dimpling problem I mounted the QG tank that came with my wing kit to find out that the holes in the tank did not line up exactly with the counersunk holes in the main spar.
I thought it was just a tight fit to butt up against the leading edge so I got some screws installed as I figured they would pull the tank into alignment. Net result was that I have now elongated some of the dimpled holes in the tank and some have small cracks in these dimples (4 of them to be precise).
I am now stuck on how to solve this problem, my first thought was to throw myself off a tall building however I have decided there must be a better solution. One thought is to replace the countersink screws with pan head screws or maybe rivet a thin strip under the tank skin. Both will not be as neat as the original design.
Any brilliant suggestions??.
With the right wing I will of course check the alignment of the tank with the spar before I countersink and mount and simple everything.

mine looked like a "tight fit" also, so here's what i did. i clecoed on the leading edge and placed the tank on the spar. there was ~3/32 "gap" between the tank and the leading edge, and the tank's leading edge was about the same amount higher than my leading edge. i used ratcheting tie-down straps (with wood blocks to keep from deforming the edges of the skins) to pull the tank horizontally to meet the leading edge. then i put some 2x4's under the rear spar and again used ratcheting tie-down straps to pull the tank onto the spar. then the holes lined up. (i sort of stole the idea from the orndorff tape, but i don't recall him doing it horizontally, just vertically).

hth,

john


> Well after soliving the dimpling problem I mounted the QG tank that came with my wing kit to find out that the holes in the tank did not line up exactly with the counersunk holes in the main spar.
I thought it was just a tight fit to butt up against the leading edge so I got some
screws installed as I figured they would pull the tank into alignment. Net result was that I have now elongated some of the dimpled holes in the tank and some
have small cracks in these dimples (4 of them to be precise).

First piece of advice is step back and take your time coming up with a fix. I've made tons of mistakes over the years (yes, years) on my project and what seemed huge then seems very minor in hindsight. The best way to deal with these setbacks is to mull it over for a good long while before making a move. As far as this particular problem goes, have you considered abandoning these holes and drilling new ones to the right or left? The defective ones could easily be filled prior to painting and nobody would ever know. I'd give Van's a shout too since they've seen it all.

Steve Zicree

Too late to help but maybe someone else can benefit. When you have a gap (especially if the gap is not equidistant across the entire tank/leading edge) between the leading edge and the tank AND when the holes don't line up, part of the problem is the main spar is sagging. You will find that a lot of trouble can be saved if you jack the middle up under the rear spar, run that fishline across the length of the wing and THEN fit the tank.

You will find the proces will be much, much easier.

This is EXACTLY what happened to me. I puzzled over the fact that the tanks didn't fit anymore, but rather than try and force it (which I have been known to do on occasion ;-) I asked my buddy his opinion. He suggested we stretch a fishing line along the spar and that is when we discovered the sag. I jacked the rear spar up a bit and VOILA, it fit.

Man, I was sweating that one for a while.

Cheers

Mark

Bob Collins said:

Too late to help but maybe someone else can benefit. When you have a gap (especially if the gap is not equidistant across the entire tank/leading edge) between the leading edge and the tank AND when the holes don't line up, part of the problem is the main spar is sagging. You will find that a lot of trouble can be saved if you jack the middle up under the rear spar, run that fishline across the length of the wing and THEN fit the tank.

You will find the proces will be much, much easier.

Click to expand...

Dave,

I gave a bit more thought to your problem and looked at my own wing. If you decide to relocate the holes and give up on the old ones, here's a way to fill them so as not to cause too much trouble. Use a nice big flush rivet with a very short length to fill the hole in the tank skin, and provide a relief hole in the spar behind it. This way you can fill the resulting rivet head area with a bare minimum of filler and you won't need to worry about it popping off if you ever have to remove the tanks. I would use the soft type of rivet for this, since it is kind of a big guy and the soft ones are way easier to squeeze.

Steve Zicree

The holes in the tank skin are off by about 1/16 to 3/32 horizontaly (i.e the tank needs to go outboard a bit), yet the gap between the outboard tank edge and the leading edge is only about 1/16. I tried to move the tank closer to the LE without success (I did not try the strap approach suggested in the earlier email). The spar is supported in the middle ( the fishing line trick) but it is possible it has moved with all the work I have done to date so I will check that tonight. I am concerned about the deformed holes and am not sure what to do about them but there is only 4 of them, if I could get the rest to line up I could probably reform (redimple) them. The gap between the tank and the wing skins on the spar line is about 1/16 +, is this about right?

Another thought I just had is to recheck that the spar is not twisted in any way. I did check before but things may have shifted.

You might try flattening the dimples with a flush rivet set before re dimpling. I have missed a little on a few dimples & almost refilled the holes doing this.

Derrell

Man do I feel dumb, I checked the spar alignment and the center had dropped (I do not know how) a couple of turns on the screw jack and lo and behold all the tank screw holes lined up. I wish I could figure out how to ask the question here before I screw things up.
Thanks guys (and gals)

uk_figs said:

Man do I feel dumb, I checked the spar alignment and the center had dropped (I do not know how) a couple of turns on the screw jack and lo and behold all the tank screw holes lined up. I wish I could figure out how to ask the question here before I screw things up.
Thanks guys (and gals)

Click to expand...

Welcome to my nightmare ;-) I can't count how many times I thought the same thing.

Cheers

uk_figs said:

Man do I feel dumb, I checked the spar alignment and the center had dropped (I do not know how) a couple of turns on the screw jack and lo and behold all the tank screw holes lined up. I wish I could figure out how to ask the question here before I screw things up.
Thanks guys (and gals)

Click to expand...

Don't feel bad. When I was in this position, I was very upset and I searched the arvhives and even found a guy whose solution it was to grind down the z-brackets to make the tank come back into line. There was nothing about checking the spar. And when I told Van's about it, they said that they had never heard of it before. So hopefullyw hen they're getting tech calls about the situation now, they're telling people to check the spar.

I remember when I jacked up the middle and the "mislaigned tank" was sitting up there, there was a llittle pop on the second pump and the thing was sitting pretty and I thought, "geez, how simple was THAT." Problem was, it came 24 hours later and lots of wasted time worrying.

It taught me the value of taking walk when things don't fit right and really thinking it through and trying different solutions because, sure as shootin', no matter how many of these things have been built, everything about constructing them hasn't been learned yet.

And so the value of sharing what you learn is quite important too. We've all been in your spot. Don't beat yourself up.