The final brackets to go into place were the inboard ones that will be accessible from the wing root. These are slightly different from the other bracket in that they don't have any nutplates riveted to them. The nutplates used here are riveted to the spars instead, a job I already accomplished back before I riveted the skeletons together since they were way easier to access back then.
As it turns out, Van's has you wait to install these nutplates for a reason. The holes in the spar aren't full size, meaning two things: 1) I would need to enlarge the holes in the spars without damaging the nutplates behind them, and 2) there was no way I would be able to back drill the brackets to #12 with the nutplates in the way. The first issue was easily overcome with a #12 bit, a slow drill speed, and a steady hand to avoid drilling into the nutplates themselves after enlarging the holes. The second issue required a bit more thought.
Since there was no way I could use the #12 bit through the nutplate I decided to use the largest bit that would fit to keep the new holes centered, which ended up being #19. I could then drill the initial matched hole through the nutplate and into the bracket, take the brackets off of the spar, and finally updrill the holes to #12 for the bolts. This worked better than I expected, even if I was a little concerned about damaging the threads of the nutplates with the drill bit. I'm not sure I'd recommend this method over the plans method though.
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| It was a good thing I was able to cleco the brackets through the nutplates. This would have been way more difficult if I couldn't. |
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| See that top part of the bracket sticking out past the baffle? That's gonna be an issue. |
As I went to cleco the rear tank baffle to the brackets, I came across an issue with the inboard bracket I had just drilled. The line where the rivet holes were supposed to be on the inboard bracket wasn't even close to lining up with the holes in the baffle. Even with the rest of the brackets lining up almost perfectly with the baffle in the correct place, I couldn't get the inboard brackets to work.
I took a look at the undrilled angle for the other tank and realized that it would have the same exact issue. There was no way to have good edge distance on both the rivet holes and the bolt holes, even with the bracket positioned exactly halfway between the two sets of holes.
Reading the plans again, I realized that I had made the mistake of drilling the bolt attach holes first and then moving on to the rivet holes for the baffle. What I was supposed to do was cleco the angle to the baffle using the 1/8" hole I had drilled in the angle, then match drill the bolt holes in the angle. Doing it per the plans still wouldn't have worked though since I would have had bad edge distance on the bolt attach holes instead of the rivet holes, so the matter became moot.
As an experiment I took some duct tape and pretended I had a Z bracket with a slightly longer bottom flange for the bolts. After slipping it into place and marking the holes I discovered that this would be a perfect solution to the problem.
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| Now that looks a lot better. |
I soon ordered a section of Z-angle with this longer flange from McMaster-Carr. The longer flange won't interfere with anything else here and will guarantee that all holes in this piece have adequate edge distance, so it's a no-brainer to me.
