Top crack repair - Spanish guitar 1970's

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Top crack repair - Spanish guitar 1970's

Postby Simon Magennis » Wed Sep 19, 2012 3:30 pm

First off let me say that I may get this done professionally for two reason - time and saleability.

I have a 1978 Spanish guitar with a 4 inch crack. When strung up to tension it is almost invisible. I noticed it first when I took the strings off to inspect the inside. It lifts up and becomes obvious - now that I know where it is I can see it easily enough. As far as I can diagnose it does not go through at any point - i.e. I can't feel any trace of a crack when I run my fingers along the inside.

The crack runs along the end of the bridge from about 2 inches in front to about inch back towards the end and is held by a very light bridge pad and by one of the braces. With the strings off the top rises slightly to a very slight ridge making the crack obvious. I am not sure what the finish is. The top is spruce with an 1970's "Spanish Orange". I suspect its nitro though I would really have expected shellac on the guitar in question. It is fairly well used so invisibility isn't an issue. My main concern are cleats.

If I do it myself, this is what I am thinking:
1) tape each side of the crack
2) warm it up with a hair dryer
3) work in thin hhg with my finger or a very fine brush or both pushing up from the inside to open it up
4) use two big pairs of magnets to press it flat and closed. Clean up. I don't think a clamp is needed but I would do a practice run before I glued and make sure the magnets had enough power to close and hold it flat.
5) once dry put in one very small cleat on the longer bit of the crack in front of the bridge using either a magnet or a clamp.

The last bit is the stage where I have most concerns. How many cleats should I use? The bridge pad and one brace are in place already so its reasonably stable as it is. Would one be enough or should I have maybe two on the longer stretch (2 inches) in front of the bridge and one on the shorter bit behind the bridge? Naturally on the top, "less is more" in terms of not affecting the sound. Forgot to say the crack is on the treble side.
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Re: Top crack repair - Spanish guitar 1970's

Postby Barry Daniels » Wed Sep 19, 2012 3:40 pm

Could this be a finish crack that does not penetrate the wood? If the wood was cracked, you should be able to feel it inside.
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Re: Top crack repair - Spanish guitar 1970's

Postby Simon Magennis » Wed Sep 19, 2012 6:12 pm

Barry Daniels wrote:Could this be a finish crack that does not penetrate the wood? If the wood was cracked, you should be able to feel it inside.


Hi Barry. Yes, that is possible. Maybe I am jumping to the wrong conclusion partially conditioned by the fact I got it through eBay and tend to assume the worst. I re-inspected it just now and I still can't see/feel any crack on the inside. Looking at the outside more closely I see that the crack is running down along the middle of a wider growth ring and there are tiny zig-zags in few places when I look really closely. However, what makes me think it's the top is the movement when press the top with my finger beside the line at one point. Seems like a bit too much just for the finish but I don't have the experience to really recognize the symptoms. I don't know a definitive way of telling the difference. Getting a pro to look at it is sounding more and more like a good idea.
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Re: Top crack repair - Spanish guitar 1970's

Postby Wayne Brown » Wed Sep 19, 2012 8:16 pm

Putting a light inside the guitar body may help you determine whether the crack is all the way through the wood (or not) if the light shines through.
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Re: Top crack repair - Spanish guitar 1970's

Postby Thomas Dooher » Fri Sep 21, 2012 3:14 pm

X2 on the light comment...
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Re: Top crack repair - Spanish guitar 1970's

Postby Simon Magennis » Sat Sep 22, 2012 5:20 am

Thanks for the suggestions. My conclusion is that I need to get a pro to do it or at the very least to diagnose it. My only other experience with a top crack was in a cedar top I build. I bumped it against something and it got what I called a "pressure crack" - it was tight but had moved on the growth rings and was clearly visible and easy to feel both inside and outside even though it was only half an inch or an inch long.
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