[tikicarver]

I ordered some new bulkheads from Van's to rebuild my tail section.
The F411 bulkhead is two pieces riveted together.
As you can see in the photo, they don't fit very well together because of the bends on the flanges at the ends. The center of each is pretty flat, so I'm afraid that if I start using a fluting pliers on the flanges that will put a curve into the center section of the bulkheads.
So how do you rivet these things together and keep the hole thing straight?

 

[flion]

I would try putting the bulkhead on a back rivet plate, web side down, and using a flat rivet set around those flange bends to get it to lay flat. If you've got a plain flat set (not the kind with the rubber around it) you should be able to get right up to the flange. Then, once the parts are together, go back and address the flanges themselves.

 

[N184DA]

It's been a number of years but from my recollection,,
Fluting the flanges was all that was necessary.

Just as with the wing ribs, fluting the "correctly" flanges will not distort the overall shape, or flatness and in fact should improve the fit.

 

[noelf]

Each rib need to be fluted...

...to get it to lay flat. Be sure to check the fluting diagram in the construction drawings to get the flutes in the correct location.

 

[N999BT]

Flute it

Flute it, just remember to miss where the rivets go.

 

[C-GRVT]

fluting, plus

the fluting will work - you need to flute because the edges where the flanges are are rigid, and these edges need to be straight.
Plus, you will find that the flanges at the curved part of the bulkhead do not make a smooth curve, there will be raised areas ("bumps") at the base of the flanges that if not filed down will cause the skin to not lie smoothly around the bulkhead curve when it is pulled down. But you probably already know to file those bumps down....
Bill Brooks
Ottawa, Canada
RV-6A finishing kit

 

[tikicarver]

Thanks for the tips. I'll give it a try.

 

[az_gila]

After you have fluted...

...the two pieces, riveted them together and installed them, lay a straight edge fore and aft along the center of the bulkheads where the side skin will lay.

You will probably find that a shim is needed on one of the flanges of the pair. A lot of RVs don't have this shim (including the QBs) and have a "wiggle" in the side skins right over this bulkhead. The flanges could also be "reformed", but a shim is an easier solution.