Old Gibson Mandos - Back and side separation

[Matt Bradford]

Hey Frank and Friends,

I've got two early 1900s Gibson mandos in the shop, one A and one F, with the back and sides separating.  I have to apply a ton of pressure just to get part of it lined up, and even getting as many clamps on as possible, they don't line up great.  I get one part flush and the side is bulging someplace else.  

Are there any cool little tricks to get this to go back together right?  Or is it just build a jig and hope the glue holds.  Seems like a lot of sideways pressure pushing against the joint.  Any experience would be appreciated.

Thanks,

Matt

[Thomas James]

Sounds like the back(s) may have shrunk? 

[Frank Ford]

Here's what works for me:

http://www.frets.com/FretsPages/Luthier/Tools/BenchClamps/benchclam...

[Ned Knepp]

I've dealt with this by using a setup something like the one Frank documented here .

His setup is MUCH better than the one I came up with but both worked the same way. I found that I needed to stabilize the mandolin on a small framework so that I could apply pressure to the side I wanted to push into place. It turned out to be much harder to push the side back where it was supposed to be than I expected and I ended up using some moisture and time to get it back onto place. 

The idea of the  braces is to allow you a way to focus pressure across the whole curve. I made a cork lined strip to put between the screws and the side. Once I dampened the side, I put some pressure in the side and left it to dry. I repeated this process 2 or 3 times before I got it all back into alignment.  I used HHG to glue it up and left it over night. Just remember to put some wax paper between the cork and the side when you glue it up. 

I didn't have to do it this way but I suppose you could use more of the brackets and strips to support the other sides if they are bulging .  Take a look at the link on frets.com.

[Matt Bradford]

Thanks guys.  Yeah, the backs have shrunk.  Frank, thanks for the link.  I was think right along those lines.  Thank you all for your insight and experience. 

[Ned Knepp]

Matt, if the backs have shrunk, I think you might want to consider humidifying the instruments before you try to glue them to see if the edges line up better.