repair advice needed

[octopu]

Hello everyone,

I have bought a Swedish Levin 55 mandolin from1955.
This mandolin supposed to have birch back and sides according to the Levin information pages but it looks mahogany to me.

Unfortunately the back has come loose from the sides.
It's a clean split so there is no wood split, just the glue let loose.





I don't know what type of glue was used on this mandolin.
The problem is that if want to reglue it the new glue cannot penetrate te wood because of the old glue.

For that reason I thought it might be an idea to glue it with a clear 2 component slow curing epoxy glue.

Is this a very bad idea?? (please be gentle with me i'm new here)


The other problem is that the neck is a little bowed.
Without strings.
A ruler on top of the first an last fret give a space 0.016 inch in the middle 0.4064 mm
A ruler on top of the first an twelfth fret 0.008 inch in the middle 0.2032 mm

Is this normal or should this be measured under full string tension?

Any ideas/thought are welcome.
Thanks in advance, Paul

[Jeff Mando]

you might try to remove the glue with something like a thin emery board or nail file or sandpaper wrapped around a credit card. Then use Titebond wood glue and clamp.

[octopu]

The problem is that it came of but with the inside lining still attached to the back, therefore it is impossible to sand because I would have to sand around the corner of the sides of the mandolin.

[rcc56]

If the mandolin was made in the '50's, it was probably originally assembled with hot hide glue.
Fresh hot hide glue sticks to old hide glue surprisingly well. Sanding is often unnecessary. I would try this first.

If this is not the first time the joint has come loose and somebody used a different kind of glue, you'll have to clean it up the best that you can. You can take a piece of steel, put a 90 degree bend in it, glue sandpaper to it, and get between the lining and the side that way. In such a case, Titebond Original might hold better than hide glue.

[HoGo]

+1 50's is very likely HHG.
look for blobs of dry glue inside, white glues are distinctively whitish translucent. If you dig into drop of dry glue with needle HHG will be hard while white will be more rubbery.
You can wash some of the glue off with vinegar and water (deionized), works both for HHG and white. You need to clean it form dirt before gluing anyway...
I've used CA succesfully on this kind of repairs when few previous attempts with various unknown glues failed and there was no way to clean the mess perfectly. But CA can be messy (if it gets on finish) and you will hardly get invisible glue line...

[Br1ck]

My feeling is if the separation is that much, the rest of the back is probably barely hanging in there. I have a 50s arch top, probably a rebranded Stella, and the whole back came off in about ten minutes. I was able to check for loose braces, clean off the mating edges, and reglue solidly clear around the guitar.

[Paul Busman]

If the OP isn't a luthier, hot glue might not be a reasonable option. I'd also recommend Titebond with a couple of dry runs clamping the separated pieces.

[Jeff Mando]

I think the OP is overthinking the repair. There is plenty of "lip" showing in the picture where the back will make good contact with the side edge. Just scuff the surfaces with sandpaper, original Titebond and clamp, wipe the squeeze out and you're done. I wouldn't worry about the inside kerfing. In this case, you are just resealing the popped back. Not a major structural repair. Should be fine for another 60 years.......

[Steve Ostrander]

I agree with Brick. I'm not a luthier, but I would check the integrity of the entire glue joint on the back, because I would only want to do the repair once.

[Jeff Mando]

Removing the back is easy -- getting it to line up perfectly again is very difficult without a jig and some experience. I would not recommend it if you haven't done a few. Plus you need a jig and a bunch of clamps.....

[Bernie Daniel]

Removing the back is easy -- getting it to line up perfectly again is very difficult without a jig and some experience. I would not recommend it if you haven't done a few. Plus you need a jig and a bunch of clamps.....

+1 Especially if it is an old instrument were stresses have been contained for a long time.

[Steve Ostrander]

See, that’s why Im not a luthier....