Top crack

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Mike Sandor
Posts: 65
Joined: Sat Jan 07, 2012 9:13 pm
Location: wisconsin

Top crack

Post by Mike Sandor »

I need some guidance on this problem. A crack just developed on a newly assembled guitar. First, a little history on this body. I build it a little over a year ago, sprayed the lacquer, but did nothing with it until 2 months ago, at which time I buffed it out, fit and installed the bridge, installed the neck and set it up. I originally had it strung up with Lite strings, rated at 163 in./ lb.
The guitar sounds real nice, played it every day, hung it up when not playing it, stayed in tune real well. All in all, real happy with it. A week ago, I decided to try a bit heavier string set, went to mediums, rated at 173 in./lb. Yesterday, I see the top cracking.
I am stumped and more than disappointed.
Before even thinking about a repair, I would like to understand the cause. I remember well reading about the importance a perfect glue joint. I took extra care with this. I used Tite bond, and interesting enough, the glue join appears to have held, but the cracking appears to follow the grain, starting at the joint line. This is a piece of slightly bear clawed sitka spruce.
I would have thought that if there was internal stress due to pulling in a joint, that would have shown up before now. The humidity is pretty steady at my place at right around 50 %.
Any one care to beat this up. I sure would appreciate it.
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Michael Lewis
Posts: 1473
Joined: Thu Jan 12, 2012 1:22 am
Location: Northern California USA
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Re: Top crack

Post by Michael Lewis »

Wood shrinks across the grain when it loses moisture. I would put one (1) damp paper towel in the guitar and put the guitar in a plastic bag for a day or two and then look at it. If the towel is dry then dampen it again and close it up again for another day or two. It may take 3 or 4 cycles of doing this to get the crack to close, but it is much better to sneak up on it than to over do it. The seam needs to be reinforced on the inside or it may reopen when it dries again.

Mike Sandor
Posts: 65
Joined: Sat Jan 07, 2012 9:13 pm
Location: wisconsin

Re: Top crack

Post by Mike Sandor »

Thanks Michael, I bagged it up before leaving for work this morning. We will see what the next couple of days brings. Still struggling with the cause how ever. Going back through my prints, the top was finished to .125 before is was attached to the body. This is a large body guitar, and followed the bracing pattern from purchased prints, I wonder if there was to large a span between the tail block and the first brace. The tail block was angled down slightly to eliminate a possible pressure point at that area.
Thanks again for your suggestions.

Shawn Strickland
Posts: 5
Joined: Thu Apr 18, 2013 12:53 pm

Re: Top crack

Post by Shawn Strickland »

Any positive update so far?

Mike Sandor
Posts: 65
Joined: Sat Jan 07, 2012 9:13 pm
Location: wisconsin

Re: Top crack

Post by Mike Sandor »

I have been following Michaels,s advise, guitar has been bagged with a moist towel inserted in the sound hole since the first post. I put the towel in a resealable baggy, opened just a bit. With in 4 days I could see the cracks closing. As of now, they are totally closed. Will be installing a Sitka patch soon. I am thinking that I thinned this area of the top a bit to much. This guitar was built along with two similar ones. I did a bit of experimenting with the bracing and top. I can deflect this area farely easily witn my thumbs. Hopefully a patch will do the job.

Mike Sandor
Posts: 65
Joined: Sat Jan 07, 2012 9:13 pm
Location: wisconsin

Re: Top crack

Post by Mike Sandor »

I figure it was time for a update. I probably will be chastised for my repair technic, but my eye was drawn to the tell tail signs of the crack. I decided to do a inlay. This was a very interesting little project. The inlay pocket in the guitar was cut out first. .050 deep. I then made a walnut piece to fit but in a reverse image. I used a piece 3/4" thick but only cut to a depth of .100. I then inlay-ed the pearl into the walnut at .05. deep. You can cut so precise that you will not need filler. Actually, if you do not oversize the pocket just a bit, it can be a struggle inserting the pearl. I used abalone for the smaller inside pieces and bordered with mop. Then sliced off the piece with a band saw and glued them in. Once dry, I scraped down to the guitar top and just before reaching the top the pearl started to show through.
The body is on the drying stand after spraying lacquer, but I kinda like it. Lots of possibilities.
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Simon Magennis
Posts: 452
Joined: Sat Jan 07, 2012 7:51 am
Location: Menorca. Spain.

Re: Top crack

Post by Simon Magennis »

Neat.

Beginners make mistakes, journeyment learn how to fix them but masters merely have features.

Warren May
Posts: 246
Joined: Fri Aug 10, 2012 7:00 pm

Re: Top crack

Post by Warren May »

Neat looking inlay and a nice fix for a nasty crack. I think a pickguard with a similar motif but smaller would be interesting?

AL Lombardo
Posts: 11
Joined: Sun Jan 08, 2012 10:20 am

Re: Top crack

Post by AL Lombardo »

Personally, I think your inlay is highly creative and gives the guitar great look ...very different. I like it. My very first guitar about 10 years ago, now has developed that exact same crack. I hope you won't mind that when I get enough motivation, I 'borrow' a similar idea!

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