SB failure

Well, this isn’t the most pleasant post to write, but it’s the way things are. Upon reviewing the work I’ve done so far on this service bulletin, the long and short of things is that I’ve ruined some parts and I’ll be substantially rebuilding the horizontal stab.

I mentioned in the last post that I’d had a few holes that got enlarged in the spar web, due to using a dull bit in the angle drill. At that time, I figured I could just replace those with 5/32” rivets and be fine. But I took a closer look at those holes tonight, and while two of them that are oversize can be safely opened up, the other two are far too large. I thought briefly of asking Van’s support about the possibility of doing another doubler repair here, but some reading on VAF reveals other builders who have gotten some very direct guidance on this topic, and that guidance is that any hole that can’t be fixed by opening up to #20 calls for replacement of the spar. Since I damaged both spars, I’ll be replacing both of them.

There are also some edge distance and hole spacing issues with the doublers I drilled, but that’s kind of beside the point right now, as the doublers will need to be re-drilled with the new spars anyway. While I’m at it, I’m also going to replace both reinforcing angles and all four of the inboard ribs. This is basically all fo the inboard/center structure in the stab. It’s possible that the ribs could be salvaged, but at this point I figure I might as well go all-in on using post-SB parts.

At the moment, my plan is to hold off on ordering anything until after I’ve done all the disassembly required for this replacement work. This is to allow for the possibility of damaging other parts beyond repair; better to make one parts order instead of two. I thought about going ahead with that disassembly work tonight, but I think it’s better that I take the rest of the night off and let this sink in before jumping into more work.

The good news is that the financial damage isn’t horrible. Replacing the parts listed above will cost about $140. Things only start getting significantly more expensive if I have to replace parts of the rear spar or the skins. I don’t think saving the rear spar will be a problem, but the skins might be a different matter – there are a lot of rivets to drill out carefully. Then again, my fancy new rivet removal tool will hopefully make this go better.

At this point, I think my goal will be to complete disassembly by the end of this weekend, and order the parts early next week. A stretch goal might be to get disassembly done tomorrow night and order the parts Friday, that’d save me a few days waiting, but again, rushing disassembly is likely to just make things worse.

Anyway, that’s it for tonight.

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