The fuel tank is attached to the front wing spar using Z brackets, and of course they all face different directions depending on the location just to be confusing.
The kit supplies a couple of templated drill guides to drill the first center hole in all of the flanges (minus the inboard spar flange, which gets drilled later).
I drilled all of the center holes in the Z bracket flanges, then measured and drew a line down each flange (to line up in the holes of the baffle when match drilling). The brackets were then drilled to match the baffle holes.
The last step for preparing the Z brackets was to upsize the hole in the flange that goes against the wing spar. The side of the bracket that goes against the baffle gets riveted on (pop rivets), but the side that attaches to the spar gets bolted on. Of course things were going great until I drilled the very last bracket. For whatever reason, my brain just disconnected and instead of enlarging the spar side hole, I enlarged one of the holes on the baffle side of the bracket. Oops. There's no saving this since these brackets have to get sealed as part of making the fuel tank leak proof. So I pulled one of the Z brackets for the other tank just so I could keep going. I'll have to order a replacement bracket from Van's so I have the parts when I'm ready to do the right tank. I looked it up and it's a whopping $2.50 part, but of course will be $10 to ship it here. At least it's better than messing up an expensive part!
I didn't get a picture of it, but the Z brackets don't actually get clecoed onto the baffle for the initial fitting with the wing spar. The clecos are too long and interfere with the fit against the spar, so instead I had to attach temporary pop rivets. Van's supplies some "soft" pop rivets that will supposedly be easy to drill out later once I'm done fitting the tank to the wing. I'm skeptical. I'm guessing they'll be harder to drill out than they say they are.
I laid the tank on the spar and clecoed the skin in place. Ultimately the skin gets screwed to the spar, but for the time being 1/8" clecos fit tight enough in the spar nut plates. The Z brackets were then match drilled to the holes in the spar.
The tank fit fine except for the outboard portion where it fits up against the other leading edge skin (where the joint plate is). It not only had an uneven gap between the skins, but the profile of the leading edge didn't line up well.
I did some digging online and it sounds like this is a pretty common problem. Since the gap was tight at the aft edge near the spar, I decided to take all of the spar clecos out (thankful for the pneumatic cleco tool at this point) and put a temporary shim under the inboard end of the tank to lift it up and even out the gap a bit and then start clecoing from the outboard edge in. I also gave the nose a tap with a hammer/block to push it down even with the outboard leading edge skin. Doing it in that order, I was able to even things up pretty well. From what I've read, this slight gap all but disappears once the wing is painted.
In reality, it's pretty tight when not looking at it from inches away - flush on the aft edge and maybe 1/32 on the front edge.
Even though there's very little likelihood of the wing having any twist because of the pre-punched parts, I need to check it to be sure. That requires putting the bottom skins back on and dropping a plumb bob from the front spar and measuring the distance to the rear spar. That'll be where I start tomorrow.
