How Flat Is Flat?

[Doc]

I've had to pull the bridge off of my FT-79 Epiphone. It had sunk down on the neck side and pulled up on the bottom side enough so that it cracked near the saddle. I've kept a wet sponge inside the guitar for a month and it has flattened out a little. How flat does the top need to be? It now is sunken in on one edge about a 1/16 and is raised up on the other about a 1/16. It doesn't seem to be moving anymore. I can get inside and pull the plate and replace it but I'd rather not if I don't have to.

Any advice?

[orgmorg]

Doc, have you seen this before?

bridge doctor

It is designed to correct the problem you are having.

I've only messed around with acoustic guitars a little bit, but I have a feeling that even if you get the bridge put back right, it will just happen again. As far as the question of flatness goes, most guitars actually have a domed top, in a 25 or 30 foot radius-barely noticable, but gives it a bit of extra strength.

[JohnJohn]

Also check the bracing at the X.

If the bridge is dipping on one side it could be a brace has pulled slightly throwing off the top tension.

[Doc]

Thanks for the replys guys.

I have to get in there and replace the plate 'cause when I looked closer it's cracked along the line of the string holes.

I removed the 1/2" diameter brass inserts by putting a 3' long bolt in them one at a time. I wrapped the body of the insert inside the guitar with a piece of leather to protect the threads and clamped a small vice grip to it. I heated the bolt with a small torch until the glue softened. then I backed the little sucker out. This way the threads cut in the wood of the top didn't get trashed. I going to make a new bridge using the old one as a template. I've modified a couple of butter knives that I'll heat up on a hot plate and work under the old plate to lever it out.

The do-dad from Stew-Mac looks neat but I wonder how much it will affect the sound. When it's right this is a really wonderful sounding instrument. This was made back when Gibson seemed to still be motivated by things other than the bottom line alone.

I tried to force a thin palette knife under all of the bracing and it all appears to be solidly glued, so that problem isn't there.

I'm going to make clamping cauls out of some 1/4" aluminum and see if gluing in a new plate flattens out the top.

[JPL]

The do-dad from Stew-Mac looks neat but I wonder how much it will affect the sound. When it's right this is a really wonderful sounding instrument. This was made back when Gibson seemed to still be motivated by things other than the bottom line alone.

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I have that do-dad installed in an old Wurlitzer acoustic and not only did it bring the top down flat and fixed the intonation problem, it also made a nice sounding instrument into a great sounding one. Breedlove puts them into all of their guitars.

Edit: I just saw that this is an old Gibson so you might want to think about the vintage thing but there is a bridge doctor that does not need holes drilled or anything sacreligious like that.