Horizontal stab disassembly begins

Finally got started on tearing this thing apart tonight. Over the past few days, I spent a fair amount of time thinking through this process. The main outcome of this was that I decided to go ahead and order my replacement parts after all, rather than waiting until after disassembly like I said last time. I figured it’d be better to get the parts in hand sooner, to minimize downtime. I can find other things to do while waiting on stab parts, but I’ll be limited in what I can do some I’ll have a workbench full of stab parts.

I also decided not to go ahead and replace the inboard ribs after all. After reviewing the stab assembly procedure, I was reminded that those ribs don’t come predrilled, and have to be drilled in assembly with the skin. That seems like an opportunity to cause problems, as well as being more work, so I’m going to use the ones I have – after all, there’s nothing wrong with them

Anyway, all that stuff shipped today and should be here middle of next week. In the meantime, back to disassembly.

My basic plan here is to reverse the assembly procedure – first, drill out all the rivets to the rear spar and extract it, then drill out the rivets between the skin and ribs and remove those, and finally remove the front spar. Tonight I figured I’d just see how far I could get on the rear spar. The answer was “pretty far.” I started by drilling out the solid rivets securing the structure together. Then there were the four Cherry blind rivets that secure the rear spar to the center ribs. Getting the heads off those was surprisingly easy, I was kind of expecting some drama, but it didn’t happen.

Next were the skin rivets.I got all these drilled out and removed fairly efficiently – instead of my usual painstaking three-step process, this time I just center-punched and drilled, being careful to try and keep the drill centered. It didn’t go perfectly, but I got all the rivets out without any major damage. There are a couple holes where I may need to go to a NAS oversize rivet, but mostly things went great.

At this point, I was ready to extract the rear spar, declare victory for the night, and retire inside. Except I couldn’t seem to get the spar to come out, it seemed hung up in the middle of each side. Right…oh, right where I took the heads off those Cherry blind rivets. The shafts of those rivets were still in place, and once I thought about it…of course they’re probably still holding things together, the whole idea with them is that they grip the sides of the hold really well. “Shaft” is really not a great word, what’s actually left is just a thin metal tube. One of them had its edge bent a bit, and I was able to get a punch on that one and drive it through, at which point that part of the spar got looser. That confirmed my theory – I just need to knock out the other three shafts. Well, first I need to figure out how.

I started trying to use a punch to catch the edge of the sleeve in one hole, then thought about the possibility of damaging the hole. I also thought about how I might be bending the rib flange inside the stab by doing this – I should really be backing that up with a wood block or something. The bottom line was that rather than trying to force this issue, it was better to just call it a night, let the problem marinate in my head, and revisit it tomorrow.

So that’s what I did. I’m happy with the progress I made today, even if it was sort-of backwards-moving progress. Tomorrow we’ll keep it going.

Update: I got the spar off after all. It suddenly occurred to me that all I needed was something to use as a punch that would fit snugly in the rivet hole. I didn’t have an actual #21 punch, but I did have a #21 drill bit. And it did a bang-up job of driving the rivets right out. Easy peasy.

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