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On one of my recent builds, the top seam is starting to open up. I'm normally an avid hide glue user but, best I recall, this one was a quickie side project where I just pulled a top down and started looking at it, then - before I even knew what happened - it was joined. Didn't have a batch of HHG at hand, so I used some LMI white. The batch, come to find out, was bad. And I failed to test the offcuts on this one for glue failure, or I would have caught it. Luckily, this was a spec build that I've just been playing myself. It's been for sale and I've been carrying to my shows to stir up interest (of which it's done a great job). Now I'm glad it hasn't sold. Back under the knife.

Anyway, however it happened, this top wound up on a finished guitar. The back started showing issues, too, but I routed it on the completed, finished guitar and inlayed a new back strip to repair the joint.

So, any pointers on repairing this? I need to get ALL the old glue out. I'm thinking about using a knife and opening up the crack then inserting a tapered splice along the lines of what StewMac shows with their "power knife". I'm using HHG, of course, this time! Of course, I'll be removing the bridge, too, and repairing the crack right up close to the rosette, but leaving the rosette in place (which should leave plenty of support in that area. It's a fairly wide wood rosette.).

I would like to make the repair as invisible as possible. If it becomes impossible to do so, I guess it can be a candidate for a 'burst....

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Wes McMillian
Santo, TX
http://www.wesmcmillian.com

I've managed to get nearly perfect invisibility with these types of repairs but it's very difficult. You need to start by finding a piece of spruce that is very close in color to the top. If it's not too wide then you could just try and humidify the guitar so the crack closes and then message some glue into the joint and clamp the guitar. To clamp it make some cauls out of 2x4. Band saw the shape of the lower bout and line with cork. I also lay a piece of plexiglass over the crack along it's length and clamp that as well so the joint doesn't bulge up and out. Also if you do need to widen the slot then make the line in cross section V shaped. Then make your sliver V shaped as well. That way when you clamp from the top you get a nice tight joint without the sliver going through to the inside of the guitar.

Good luck.

Don't splint it if you can get it to close up. Add some humidity to the guitar for a few days and see if the crack closes. If so, you have a much better chance of a near invisible repair. Making an unseen splint repair is near impossible even for the experienced repairman.

If it was a HHG joint then, yes, I would just close the crack and reglue. Problem is getting the old PVA glue out of the joint. That's why I figured I would have to make the V-joint repair - in order to successfully remove all the old glue and get a clean repair.

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Wes McMillian
Santo, TX
http://www.wesmcmillian.com

The glue in the joint should be really, really thin if the joint was tight. No need to get too worked up about removing old glue. I have never had problems regluing open joints like this. Just get it humidified so the crack is tight. Work in some HHG and clamp it level with some plexiglass cauls. Remove when dry and wipe off the squeeze out with a damp rag. Place some small patches on the seam and call her done.

Hmmmm.....OK! I'm game to try it, nothing to lose. Worst that can happen is that I still have to open it up later. I was just thinking that good glue over bad wasn't a fix. We'll see what happens. Thanks!

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Wes McMillian
Santo, TX
http://www.wesmcmillian.com

was the top finished ?
This is actually an easy repair to do if you have an unfinished guitar. This happens when your top dried out . I like to brace tops at under 40% RH. I don't use the V notch bit inlay a piece up along the crack. I prefer hhg or fish glue for this repair as it can appear to look like a grain line. Figure you repair to start from the end of the guitar and finish out under the bridge for best results. If it is small opening you can make a thin sliver and work that in.
For best results don't rehydrate the top as the crack most likely may reopen when it gets dry again .

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

The guitar is finished, John. The seam started showing up a little under string tension. I build in a pretty tightly controlled humidity level, normally around the 43-45% range, and never more than a couple of points outside of this range. I understand the thought behind bracing dry, but I don't believe this guitar has ever been exposed to anything less than the humidity range it was built under. If anything, its been more since we moved to GA from TX.

It will definitely be a HHG repair. As I said earlier, I am normally an avid hide glue user but had a moment of weakness when I decided to join a couple of plates spur-of-the-moment without any HHG ready to go. Never again. Not saying there's anything wrong with the LMI glue but at least when I mix a batch of hide glue I know what it is and how old it is.

It is nitro finished, so the finish repair is not a problem. Looking again now at the crack, it shows up a couple of inches behind and before the bridge. The crack in front of the bridge has me a little puzzled now. It can't really be opening up between the bridge, bridge plate, and X brace in that area. Makes me think this was just a bad joint all along. And makes me wonder how I let it pass. Must've been a really bad day for me.

That is making me think again that I may have to bite the bullet and splint it. If the joint was bad from the get-go I don't think rubbing more glue in is the answer. It's not like I can get it to close up any better in the area in front of the bridge. Still strange to me that it never showed up before. You would think there was no way it could open up in that area unless it really had dried out and the wood shrank back, but I just don't see it. And the top was plenty seasoned.

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Wes McMillian
Santo, TX
http://www.wesmcmillian.com

I agree, it sounds like the seam was already parted when you assembled the components. I'd remove the bridge and splint it.

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Old growth, shmold growth!

[quote="Barry Daniels"]The glue in the joint should be really, really thin if the joint was tight. No need to get too worked up about removing old glue. I have never had problems regluing open joints like this. Just get it humidified so the crack is tight.

Hmm.. don't agree with this advice at all. Whether the join was thin or not is irrelevant; the issues
are 1) will the new glue stick to the present surface and 2) will the temporary artificially-humidified joint stay together over time.

yup this isn't a normal RH crack . you sound like you have it under control . If it is too lightly braced you will find that out soon enough. Things happen and you will learn more from a failure than a success. A thing like this can be a good learning experience.

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Now that we're back to the original splinting question - any advice from those who have done it? I'm assuming just some careful work with a good sharp knife or razorblade. Any other recommendations to get a good, consistent channel for a splint?

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Wes McMillian
Santo, TX
http://www.wesmcmillian.com

Wes, I've got a straight edge with one edge beveled. I use this straight edge as a guide for a sharp knife. (I use a utility knife, with a fresh blade) I cut a "V", using the beveled edge of the straight edge for the angle, as well as keeping the cut straight. I don't know what angle the edge of the straight edge is, I just use it to set the blade angle on my table saw. I make a "V" shaped splint, for the V shaped channel. Put it in with HHG. After it's dried trim both inside and out, and touchup the finish.

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I didn't mean to say it, but I meant what I said.
http://www.brackettinstruments.com/

So you are saying that you would splint a crack, even if you can get it to close up tightly with some much needed humidity? Then you are making a problem worse without trying a fairly non-invasive repair. Splint repairs are not easy to do correctly and are very difficult to touch up and not look very apparent. One should not do a splint unless it's the last resort.

I'm not sure if this was addressed in one of the many responses.

What are you planning to do with the guitar? If you are planning to sell it, consider if you would want to buy a guitar with a history of a crack and the repair is not certain.

I repaired a D28 year before last with a cracked top obviously due to low humidity. I did the repair by humidifying, re-gluing, and then adding patches for reinforcement. The following winter it was kept in a humidified room but taken out for gigs,rehearsals, etc. It cracked again. Probably won't do that again for something that is obviously a humidity crack.

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Steve Smith
"Music is what feelings sound like"

the only glues I would not be worried about removing is HHG or Fish. Tite bond needs to be cleaned out for a good reglue joint .

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it