How to repair a gap between back plate and binding on 1914 A3

[mjbee]

I just acquired a very nice 1914 A3. The seller said that the back had shrunken and it had been "professionally repaired", yet it still has a 1mm wide, 2.5" long gap between the binding and the back plate to the left of the end block/tailpiece. All appears stabile: no rattles etc., no movement at all in the sides, binding, and back. But I suspect that some repair now will prevent a problem in the future. Is this an easy fix? A spline of some sort? I appreciate any guidance out there!

[Skip Kelley]

One thing to check, is push the binding tight and see how that lines up. Does it sit recessed in the binding channel or is it flush with the side?

[rcc56]

No, this is not an easy fix.

The correct way to repair it is to open the joint in the mis-aligned area, clean out old glue, fix any loose linings, and see if it will pull back into shape with a cleverly thought out clamping system that will hold everything in line after new glue is applied. Sometimes, the rib will not pull back into position without applying so much pressure that the rib will crack. You don't want that.

If the rib cannot be pulled back into alignment without excess pressure, a trick from the world of violin repair is to carefully be loosen the rib from the tail block, shorten it slightly, and re-glue it. Not an easy job, and not one for a beginner. For those who do not want to attempt such a technique, a spline can be added instead, but the repair will be clearly visible.

This is a job for a seasoned professional. Some other tricks may be necessary to make everything work. This type of repair has to be worked out as you go. Pictures cannot reveal the exact procedures necessary for a case like this.

[sunburst]

When old Gibson mandolin backs (and more rarely tops) have shrunken so that they will no longer line up with the rim all the way around I generally "split the difference" so that the ledge of rim outside of the binding (or edge of the back) is the same width all the way around. In this case, that might not be worth doing if it is securely glued the way it is. There is no structural problem with leaving it as is if it is all glued securely, it is just an aesthetic issue that probably could have been done better and can be corrected if it comes loose again in the future.
I don't like seeing that binding sitting out there on it's own like that because it is susceptible to damage from catching on things or even bumping against things, so I might consider releasing the binding from the rim and attaching it to the back. That would leave the top edge of the rim exposed outside of the binding, but that is less prone to damage.

[pops1]

What John said, or you could make a piece and fit it in to keep the binding supported. Should the back come off in the future that piece could be removed and the back reglued differently.

[rcc56]

I don't know, gentlemen . . . after another look at the second picture, I think someone should stick a probe, a pin, or even an .016" guitar string into the gap parallel to the rib to make sure there is not a loose lining or a loose joint at the tail block.

[HoGo]

I don't know, gentlemen . . . after another look at the second picture, I think someone should stick a probe, a pin, or even an .016" guitar string into the gap parallel to the rib to make sure there is not a loose lining or a loose joint at the tail block.

Agree, it looks like full separation from block and/or back. Lining may still be attached to top or side but the binding was stuck to side well so it took it with. If it is glued together in this state I would try to open it and push it back into place (hopefully HHG was used and not modern glues to "fix" it).

[pops1]

I think you might be right Bob and Adrian, when I blew it up it looks like the lining is loose.

[mjbee]

When old Gibson mandolin backs (and more rarely tops) have shrunken so that they will no longer line up with the rim all the way around I generally "split the difference" so that the ledge of rim outside of the binding (or edge of the back) is the same width all the way around. In this case, that might not be worth doing if it is securely glued the way it is. There is no structural problem with leaving it as is if it is all glued securely, it is just an aesthetic issue that probably could have been done better and can be corrected if it comes loose again in the future.
I don't like seeing that binding sitting out there on it's own like that because it is susceptible to damage from catching on things or even bumping against things, so I might consider releasing the binding from the rim and attaching it to the back. That would leave the top edge of the rim exposed outside of the binding, but that is less prone to damage.

Thanks John. It IS securely glued at the moment: I can press on the binging and the side and barely get any movement toward closing the gap. I hear what you're saying about "catching" with that gap, and my original thought was a spline, as I was more worried about the end grain of the bottom being exposed to humidity. Is that a concern?

Thanks also to Pops1, Hogo, RCC6: I peered into the gap with a light and magnifier: it looks like maybe there is a piece of lining missing (or perhaps glued to top and I can't see it I need a dental mirror!). Again, everything is glued solid at the moment despite that gap.

I'm heeding RCC6's advice, and will not attempt this fix myself. In the 70's I tried to fix a rusted fender (fender on my car, not a fender guitar!) on with my own with "bondo" (the car equivalent of plastic wood): not pretty! Won't even think about applying my ham-handed skills to this.

[j. condino]

The all too often used vintage Gibson alignment torture device might be of help:

[Mike Buesseler]

The all too often used vintage Gibson alignment torture device might be of help:

Why is it used “all too often”? Looks like a great tool.

[Greg Mirken]

Indeed, it is a very useful fixture. Not only on mandolins, I might add. He simply means this type of damage happens too often, and often heat and humidity are factors.

[Mike Buesseler]

Indeed, it is a very useful fixture. Not only on mandolins, I might add. He simply means this type of damage happens too often, and often heat and humidity are factors.

Thanks, Greg! And thanks, James. That was all I wanted to know!

[sunburst]

Gibson's tendency to use flatsawn (less stable than quartered) wood for backs also contributes to the problem.