Old Gibson A - sinking top/loose brace

[deadonkey]

Hi all,

I have a pre truss rod era Gibson A that I've had for a few years. It already had a badly sunken top and loose brace when I acquired it for a low price. I had the brace reglued and a taller bridge made and all seemed stable for a few years. This mandolin has an exceptionally fine warm tubby tone and I'm very fond of it despite its condition.

I was jamming with some friends the other night and heard a popping sound and upon removing the strings and putting an inspection mirror in I saw that the lateral brace had come loose across half its length, so my questions are as follows:

Does this mean the top is sinking again and this movement is what caused the brace to pop?

Can it be stabilized in the short term by reattaching the brace and clamping it through the oval hole? If so, any thoughts on how much time this would buy me?

Would removing the back and old brace and carving and fitting a longer and slightly wider brace restore stability to the top? Would this negatively affect the resonance and beautiful tone of the instrument? I am confident in doing this work myself so economics are not the issue here, just whether there is any hope of whether this work could be successful for keeping this instrument going.

Am I better off shopping for another old Gibson A model that is in better condition that will not give me any trouble? I am based in Ireland and they are quite rare and more expensive than the US market here.

Thanks for any help or insights you can give.

John.

[mandocello8]

Same story here. Went to Mandolin Brothers on Staten Island, played every mandolin,
walked out with the best sounding one, an A4 with a sink hole in the top, very good price.
Played well with light strings, was stable for years, until.

Took it to the shop for repair with a very good local magician (a member here). Bottom
line, top wood is too thin, not strong enough. Back comes off, Gibson single brace comes off,
X-braces go in. (plus new fingerboard with correctly placed frets and a carbon fiber insert
in the neck). Not cheap, like buying it all over again.

That was about 3 years ago. The newly X-braced top is stable and it takes medium strings.
I play it with a wegen pick and it is very loud, much louder than before. loud enough
for bluegrass jams and irish sessions, with room to spare. The tone may have changed
slightly, without blind test, hard to tell.

So, good for another 100 years. If your repair man suggests same thing, my vote is "yes".

[sunburst]

Some old oval Gibsons have tops that are too thin, others do not.
A brace glue joint failure can easily cause sinking of a top that is fully thick and strong enough otherwise, and re-gluing the brace properly will often restore full height and function to the top.
You will need someone experienced to look at it and determine the condition of the top and what repair path to follow. If it is determined that the top is thick enough, the joint needs to be thoroughly cleaned and the brace re-glued with high quality glue. I would use hot hide glue, and many other repair people would make the same choice.
Once again, if the top is plenty thick, working through the sound hole is not a big deal for a competent, experienced repair person.

If the top is too thin, it might be best to go shopping rather than go to the heroic measure of installing an x-brace.

[rcc56]

In my experience, glue joint failure at the brace is much more common than a weak top.

If the brace has already been reglued once, the joint may have failed again because new glue does not stick to old glue as well as it sticks to clean wood.
I have also seen braces develop a split. On an oval hole mandolin, a split brace can usually be repaired unless it is chewed up.

The first thing that I would do would be to clean off both surfaces of the old glue joint as best as I could. I would probably use a combination of pulling sandpaper through the joint to clean the brace surface, and gluing some sandpaper to a feeler gauge or other probe to clean up the top surface.

If a new repair won't hold and you decide to open the instrument, be aware that Gibson installed a 1/4" long piece of nail in both the tail block and the neck block to use as locating pins to hold the back in position when the instrument was originally assembled. Those nails will still be in there. They are no problem to negotiate if you know that they are there, but it is a need-to-know. It will explain why your opening tool will suddenly stop and go no further when it hits the nail. The solution when you reach that spot is to start working from a different angle.

[deadonkey]

Thanks all for these informative replies

John.