NEEDED: airplane tail rib brake

[akrotodd]

Been using a store-bought brake to bend 4130 steel sheet, .025" thick, into ribs for airplanes for decades now. Every time, the taper of these ribs (7/8" or 3/4" wide at one end, 3/8" or 1/2" at the other end) gets in the way of the last bit of bend because of the nosepiece thicknesses of all brakes I've tried.

Since usually the tails on these airplanes taper, it's not smart to make a press brake die set because each rib pair is a new length. And since most of these tails are covered in fabric, there's a 20-30 degree "kink" along each rib's edges to make sure you don't chafe the covering.

Sheet 4130 has a good amount of springback, too.

All this means there's no great cool way to fab these bent-up ribs, without having to go back and hand-straighten or close up the narrow ends when you're nearly done. That's so amateur-time.

What's needed is a brake with a very thin nosepiece (like 1/4"?) but this nosepiece only needs to reach in about 3/4"-1" max after the 90 degree bends. If there was a secondary operation like a set of roller dies to run along the length of the tapered bent ribs to do the fabric-proofing-kink, that'd be OK.

[C-Bag]

How long of a bend are you wanting to do at one time or can you do like you've been doing and just have something that get those end spots?

I'm one of those people that when there is a problem I get a "hit" that's a mental pic. My mental pic was for " touch up" of those narrow spots and was my old valve spring compressor with an angle iron as the anvil set as a v and 1/4" flat plate welded to the screw side of the compressor edgewise to meet at the bottom v. The plate could be whatever width would clear the sides of formed rib. I'd probably take off the flat washer thing that's swedged to the screw end of my valve spring compressor right now and weld the 1/4" plate to a piece of pipe that could fit tight over end of the screw to give it enough support.

I don't know if any of that makes sense or helps.

[akrotodd]

These ribs go from the leading edge tube to the spar tube, and from the spar tube to the trailing edge tube of the horizontal stabilizer, vertical fin, elevator, and rudder. So, they can be from 5-6" long to almost 24" long, depending on where they go.

The hand tweaking at the end of the process isn't a problem, except that it can make a beautiful rib look crappy.

I can't picture what you have in mind. But don't sweat it.

Let's see who's already solved this with a rigid yet narrow magic nosepiece design for a brake, so I can try to push these ribs out in one shot. If nobody, then I start getting nuts with adjustable pressbrake die sets and so on. THAT would be a complex little mechanism, for sure.

Thanks.

akrotodd