Need help with 1915 Gibson Mandolin

[Ian Davlin The Looth Group]

I’ve got an idea, but it’s a pain. Do what the violin folk do and separate the block and shorten the sides. It was put together with hide glue and that block may respond well to a damp sponge to get it going like a bridge plate.

[Bryan Parris Parris Guitars]

that does sound like a sticky wicket. 🙂

[Ian Davlin The Looth Group]

It is. When I was at Gruhns we had a few guys who would “bag” instruments like this. It means sealing the instrument off in a garbage bag with wet paper towels at the bottom and then hanging the guitar for a while. In essence, over humidifying.

There are a bunch of problems with this approach, mainly that if the instrument isn’t maintained at that new moisture content, it’s just going to try to wander back into the position it had achieved before the repair.

This is going to either break the new glue joint, or if you get a wicked strong glue joint, probably break something else. In the case of the gaping chasm on this tinkler, I’d say cracked sides.

So if you do try to swell it, I’d say use hide glue so nothing crazy happens if it spits the repair back at you.

[Tony Lewis Skypilot Guitar Repair]

Soak the bottom from the inside (so as not to hurt finish) from lower half middle out to within a couple of inches of the edge, keeping the edge dry, hoping the bottom swells enough to line up? If swells too much, monitor until it goes down just right and glue? Just an off-the-wall thought ……🪐

[Tony Lewis Skypilot Guitar Repair]

I should have been more specific. I was thinking of swelling direct, specific area. Not bagging the whole thing, which sounds crazy. I was thinking of putting the mandolin on it’s back, adding moisture directly to the area (half the mandolin bottom near the area that needs to grow) and swell that area hoping to swell enough to close gap which looks to be about 1/8 plus? It looks like the mandolin back is arched. I was thinking you could take a couple of fairly damp sponges and apply them an inch back from the split where the arch dips hoping to swell enough but keeping area at split dry so you can glue. This way your isolating swelling so as not to cut loose a bunch of joints. You could try this before surgery. What can it hurt?

[James Roadman]

I had a similar one many years ago, I did what Ian suggested. I made a cradle for it with pushers to manipulate the sides. I removed the tail block and removed a small amount of material from the sides.

[James Roadman]

[Mike Hoenerhoff Elderly Instruments]

Man I feel like I’ve done more of these than I care to remember. Most come together great, others, meh.

The first thing I do is bag it up and humidify it really well for a week or so. This will swell the back closer to its original shape. The back shrinkage over the last 100 years is definitely a contributing factor. Then I have two cauls; one that fits around the neck joint and hugs the shoulders, another that cradles the bottom. Two long clamps to crank it into place, Bob’s your uncle.

I’m not in the shop today, but when I’m back I’ll post a pic of the cauls.