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Double flush rivets in Fuselage?

Rick RV-4

Well Known Member
Page 28-12 calls for "double flush" rivets in seven places in order to fit the gear weldments over those rivets (along the bulkhead). I'm a little confused as to where the shop heads of those rivets are supposed to sit, as I can't find any guidance on countersinking the tops parts of the bulkheads there. The bulkheads are already countersunk on the bottom in order to provide a fit for the lower dimpled skin. Don't want to weaken the flange there with a "double countersink" without knowing that's what you are supposed to do.

So, are you supposed to countersink both sides of the bulkhead flange there? Is there something I'm missing?

Thanks in advance!
 
Page 28-12 calls for "double flush" rivets in seven places in order to fit the gear weldments over those rivets (along the bulkhead). I'm a little confused as to where the shop heads of those rivets are supposed to sit, as I can't find any guidance on countersinking the tops parts of the bulkheads there. The bulkheads are already countersunk on the bottom in order to provide a fit for the lower dimpled skin. Don't want to weaken the flange there with a "double countersink" without knowing that's what you are supposed to do.

So, are you supposed to countersink both sides of the bulkhead flange there? Is there something I'm missing?

Thanks in advance!

Yes you are supposed to countersink that flange to accept the double flush rivet shop head and no it doesn’t call out that step. I distinctly remember this step (even though it’s been a few years) because when I asked I got the response of “you’ve now entered the phase where you’re a builder, not just a plans follower and you have to start thinking on your own”. I’d already built an rv-8, so I thought that was a little much of a response in asking a clarifying question.

I personally think this is one of those little things they’d benefit from adding the missing callout to the plans, but alas. Neither you no I were the first to ask, and we won’t be the last.
 
I agree. I’ve built an RV-4 so understand being a builder. But when they walk you by the hand on the easiest steps it’s a little odd to leave you hanging on a step like this, where you need to double countersink a critical part like a fuselage bulkhead. Oh well.
 
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