how should I fix these cracks in the back of my Gibson acoustic

[Sir Ricardo]

Hello all - -

 

I've got a 1970s Gibson acoustic - a Southern Jumbo - and the back has some cracks. There are 5 cracks, all running in the same direction, in the same part of the back.

 

These cracks range in size from 3" to 10".

 

In between each crack - - - running along the crack - - is a strip of wood about 1/2" to 1" wide.

 

The wood running along the cracks flexes a bit, you can push down on the wood "strips" and get them to go into the guitar body around 1/4".

 

Even those these cracks / wood strips flex somewhat, you can play it in its current condition.

 

How should I fix these cracks? Apply glue from the outside, or do I apply it from the inside of the guitar?

 

Any thoughts on technique, type of glue, etc. etc. would be much appreciated.

 

thanks in advance - Richard

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[cjsinla]

I would be tempted to just flow a little of that yellow woodworker's glue into the cracks. It cleans up with water and I would have a moist rag to wipe down the outside if any comes through. That should stabilize it I would think. If that cracks are too wide I would consider using some small strips of wood or 1/64 ply or something for strength. I assume you know that the cracks will always show as you probably do not want to do a refin on it.

[duluthdan]

"In between each crack - - - running along the crack - - is a strip of wood about 1/2" to 1" wide.

 

The wood running along the cracks flexes a bit, you can push down on the wood "strips" and get them to go into the guitar body around 1/4"."

 

I don't understand? By wood strips are you perhaps referring to the actual back braces, which run perpendicular to these cracks? If so, and those braces are loose, I would take it to a luthier to fix. Have these cracks meandered or grown at all since you've had the guitar? Is the guitar drying out? A qualified luthier would probably glue and cleat those cracks to prevent them from growing. I wouldn't just hit it with yellow glue if you want to keep this for a few more years.

[Sir Ricardo]

"In between each crack - - - running along the crack - - is a strip of wood about 1/2" to 1" wide.

 

The wood running along the cracks flexes a bit, you can push down on the wood "strips" and get them to go into the guitar body around 1/4"."

 

I don't understand? By wood strips are you perhaps referring to the actual back braces, which run perpendicular to these cracks? If so, and those braces are loose, I would take it to a luthier to fix. > SEE BELOW

 

Have these cracks meandered or grown at all since you've had the guitar? > NO, but I've not owned the guitar long

 

Is the guitar drying out? > I don't believe so, it sustained damage before I got it

 

A qualified luthier would probably glue and cleat those cracks to prevent them from growing.

 

I wouldn't just hit it with yellow glue if you want to keep this for a few more years. > I'd like to do the work, whatever it is, myself. Any thoughts on what that work would be?

 

What I mean by 'wood strips' is that in between each crack, the wood flexes. The wood that flexes is the back of the guitar, which effectively has been 'cut up' into strips, due to the cracks.

 

I've modified a photo to illustrate this. It is not a brace, or anything internal. It's simply the back of the guitar, which now is in 'shards' or 'strips' due to the cracks.

 

[jedzep]

A quarter inch is a lot of movement, so merely glueing it won't stabilize the wood given humidity, handling, vibration etc. Just playing it will cause glue to be stressed. The following link should get you to Stewmac part # 1024 which is spruce patching to help keep the separate strips from moving.

 

I use painters (blue) tape applied to the outside to keep the glue mess from oozing out as you press it into the cracks, as wiping excess off will cause movement and screw up your work. The tricky part will be knowing where to lay your cleats and getting them secure without disturbing your delicate repair. I like the Titebond hide glue or dark glue for color blending.

 

However...my little guitar shop would charge me less than 20 bucks to fix this. Bet yours would be a cheap fix. Well worth having the pro do it.

 

 

http://www.stewmac.com/shop/Bodies,_necks,_wood/Acoustic_guitar_braces,_blocks,_and_blanks/Spruce_Patching_Wood.html?actn=100101&xst=3&xsr=350632

[Sir Ricardo]

.

 

well, I'm about ready to start gluing

 

I think given the tight fit of these cracks (they flex, but there is no space between the cracks and the wood), I'll use low-viscosity CA glue

 

I've prepped the first crack. 1) taped it off. 2) put a little walnut stain on it, as you could see the light-colored cracked wood just a bit.

 

So it appears ready for the CA tomorrow. I think the trick will be to just apply a little bit.....my understanding is that the low-viscosity CA glue penetrates cracks very easily, and dries fast. I want to put enough on for it to get into the crack, but not so much that it builds up on top.

 

Any last thoughts?

 

thanks much - Richard

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[jedzep]

Good luck! Don't know anything about that adhesive, but if it's a super glue type product it might adhere too tightly to the tape when you pull off, and won't allow you to wipe off excess.

[Sir Ricardo]

Good luck! Don't know anything about that adhesive, but if it's a super glue type product it might adhere too tightly to the tape when you pull off, and won't allow you to wipe off excess.

 

Update. First, thanks for this comment. I took the tape off prior to applying the superglue.

 

So.....it's not finished yet, but holy smokes, this superglue penetrates the cracks so effectively that I almost glued my left hand into the inside of the guitar! Let me explain. I had my right hand applying the glue, and the left hand inside the guitar body, through the soundhole, stabilizing one of the cracks. I finished putting on the glue, and then attempted to withdraw my left hand. It was stuck to the inside of the back of the guitar! Some of the glue had gone through the back (as it should), and then stuck to my middle fingertip. I had about 1 second to decide what to do, before it REALLY got stuck. I just pulled hard, and fortunately, no skin got left behind. I've applied acetone to my fingertip and now all is well. That was a close call, however........

 

.

[retrorod]

I guess it was close....! Nothing like being 'up to your elbow' in guitar....