I am not sure how much wood you have on either side of the break, but you might try some dowels and slow setting epoxy. This glue has some gap filling properties.
You will likely have to make some interesting cauls so you can get some pressure on it to hold it while the glue drys. keep a close eye on the squeeze out so you do not have to scrape forever in the contours.
Good luck. I be interested in hearing how you finally resolved it.
Good questions.I wil have to defer to teh finish experts around here. I do not use stain very often and when I do I tend toward dyes. I have never had a problem with a clear coat however. But as said, I will defer to the experts. They will chime in soon.
Got a couple of thoughts, and a couple of 'gasps' on your problem. Some people may not like a couple of the idea but I'm working under a couple of assumptions. First and foremost, I'm assuming you aren't planning on pulling the covering. It also looks like the curl is where the back structure is connected. Third is you're wanting it together but hidden things aren't that important.
With those assumptions, I'd first align the pieces and come in from the back with a forstner to counter bore and come in so I could get maybe 2 or 3 particleboard screw (maybe 2 1/2" - 3") that can pass through the break. Finish with a pilot hole for the screws so they don't split the arm. Take yellow glue, thin if necessary to get it to flow through the joint. Pull it together and screw it together. Plug the holes when done. Fill as necessary, touchup as necessary.
Neither bondo nor expoxy will take stain, you'll have to tone it instead. I don't like to use expoxy except as a last resort. Such a problem to get off it you ever have future work to do. Same with doweling or biscuits in this case, You'll have a hard time getting them in unless you come through the side. If you're going that anyway, why not just use some good particleboard screws.
Here's my current plan, based on your input:
1) Make cauls & verify clamping procedure.
2) With it unclamped, work yellow glue thoroughly into the break.
3) Clamp, wipe down any excess glue & let it dry overnight
4) Using forstner bit, create 2-3 holes for screws at whatever points give best access & least notice (sofa is away from wall in the middle of the room, so the backside isn't any less visible)
5) Drill pilot holes through the arm and sink in screws
6) Sink dowels into holes about .25-.50 inches deep.
7) Trim & sand down dowels to match contours of sofa arm
8) Stain & finish area
New to the forum, but am really hoping for ideas...
I have a sofa that has a broken arm (photos below). Doesn't affect stability, only appearance. Even with moderate pressure (when sitting on the sofa & leaning on the arm), it doesn't separate from the wood but maybe 1/4" max. My primary concern in reattaching it is fit & durability...I'm betting that in 5-6 years, I'll forget it broke & pick it up by the arm to move it...or that someone will lean/sit on the arm before I can stop them.
It seems like the best I can do is fill the gap with glue, use dowels and/or screws to reattach it, and cover the holes with wood plugs. Does anyone have a better idea on this? (or can you affirm I'm headed down the right path?)
Pics that follow are:
-- sofa overall (2 pics)
-- front break (3 pics)
-- rear break (4 pics)