Thermos

Thermos

Well Known Member
Patron
Hello all,

I'm in the process of finishing up all the match-drilling and prep work on the fuse center section, and have already match-drilled the F-776 center bottom skin to the F-704 bulkheads.

Before I yank everything apart, I must decide whether to countersink or dimple the F-776 and F-704 where they'll be riveted together. Van's FAQ says you can either countersink or dimple those holes...I'm probably over thinking this, but does one way work better than the other? If the -704s are dimpled, how much extra "machine countersinking" (Vans' words) is required to make those skin dimples sit flush in the bulkhead?

One other question...reading ahead in the plans, the F-772 forward bottom skin should be match-drilled to the center bottom skin and bulkhead, but it seems a little too late to do that once the center skin and bulkhead have been dimpled and the center section riveted together. If you're already past this point, how did you match-drill that skin?

Thanks,

Dave
 
I dimpled all three layers on mine except where countersinking was required to fit the gear weldments on my -7A. The .040 thick flanges of the F-704 didn't need any touchup after dimpling with my Cleaveland dies.

The prepunching is so good that there's really no need for "match" drilling here. You could just run the drill through them individually and they would match up just fine.

Good luck.
 
I countersunk mine and if I were doing it again I think I would dimple them. I have a number of "smokers" on the bottom forward sheet. The rivet heads are pretty much perfectly smooth with the skin surface so maybe I should have countersunk a tad less.
 
Dimpled

I dimpled mine. I had read somewhere that it makes it slightly stronger? Plus I never bothered with the double flush rivets on the end of the front spar carry though as I have no intention of of it ever being a nose wheel RV.

Peter
 
Dimple everything that you can

I dimpled mine as well. Again, Cleaveland springback dies and enough pressure to fully dimple the 040 and leave the skin nice and flat around the dimple.
 
Aircraft Assembly 101

"Dimple where you can; machine countersink only when you have to."

Repeat as necessary.

Carry on!
Mark
 
YEP! I agree!

Dimple whenever there is an option. Machine countersink only when necessary.
 
Countersunk mine but that's only because I figured it was the same width as the wing spars, which are countersunk.

It'll probably all come unzipped on first flight.
 
Message received on the dimpling, I appreciate the response!

I've been using Cleaveland dimple dies for most of the project, it's good to know that they work well on the 0.040" spar flanges, and that I can get by without removing material from the flanges or skins.

Thanks everyone!

Dave
 
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