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PostPosted: Sat Jan 10, 2015 1:42 pm 
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Hey everyone,
I'm in need of some advise on how to go about fixing this racked soundboard. As most of you here in the U.S. know, we've been having some major weather fluctuations. Here in Florida, we were in the mid 80s with humidity in the 70-60% range last week and this week it's been in the 40-20s with humidity in the 30-20% range. I keep my shop as climate controlled as possible with the use of an Air conditioning system. With that said, I've never had a need for a humidifier because I've almost never had the humidity level drop below 40%. Well yesterday day the humidity level In my shop was 25%, so I brough the guitar in the house for safety overnight. This morning I woke up to find the the soundboard had split along its seam from the tailblock up to the soundhole. (Turns out the house is at 28%...)

Is there an elegant solution to this issue? I know I need to rehydrate the wood in order to get the pieces to come back together. (I tried using a large clamp to squeeze the poses back together, but no go) my concern is how can I fix it without affecting the sound of the top, and while insuring that this doesn't happen again once the customer takes delivery in a couple of months. Would putting the guitar in a bathroom with the shower running work? And once I get the pieces back together, how do i re-glue them? The good news is that the guitar is still in its unfinished state, so Im working with bare wood here.

I'm kicking myself in the a## for this one, because I know better.
Thanks for any help! And check your humidity levels people!


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PostPosted: Sat Jan 10, 2015 2:07 pm 
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I don't think you will like the answers you get. I would recommend a re-top since this is for a client. I would also revisit your jointing technique because you should not be able to see the joint and yours appears as a dark glue-filled line even where the joint is not open.



These users thanked the author Barry Daniels for the post: Hesh (Sat Jan 10, 2015 2:25 pm)
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PostPosted: Sat Jan 10, 2015 2:14 pm 
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Brazilian Rosewood
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Well sir, that is a real drag. I suppose it's too much to hope that you used HHG for the joint? That would be the only way I could see any chance at all of salvaging that top. Otherwise I'm afraid I can't see any way around a retop. Yellow glue will not rebond to fix that. It's probably peeled off the braces in that spot too.

I know you know this but...next time stuff it in a case with a soundhole humidifier.


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PostPosted: Sat Jan 10, 2015 2:16 pm 
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I could see how it looks like there is a visible seam in the photo, but thats not the case. The dark that you're seeing is the split. its runs the entire length, even over where the bridge plate is and all the way to the bottom. I spend a great deal of time joining my tops and the line is always invisible once glued together. I will say that this particular piece had a light stripe of grain that ran right down the seam. I wonder if this was a problem, or if it was bad glue.
Ive never re-topped a guitar, but I assume its no fun? I recently restored a HD-28 for a client that required a re-backing... Is that kind of the same process?

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PostPosted: Sat Jan 10, 2015 2:20 pm 
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If you google Greven guitar retop, you'll see a sweet uncomplicated method that allows you to salvage you bindings and abalone too...


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PostPosted: Sat Jan 10, 2015 2:22 pm 
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Hi Chris and sorry this happened to you. For the rest of us mere mortals we have to keep strict RH control regardless of what it's doing outside and this is so very important to guitar building, well you now know what can result....

Going forward there are two approaches to this repair that I can think of. First there is rehumidifying and gluing and cleating and the other alternative is to fill the center seam with top wood.

I suspect though that if you can get this crack to close all the way (a must for option one) that if you glue and cleat and the instrument encounters low RH again it will split again somewhere else. This would not be much of a fix and more an exercise in kicking the can down the road.

Filling and refinishing the top would help prevent future splitting but likely would show... It's also on my mind just how seasoned this top is as well. If it's a seasoned or not wood issue future upptiness from this top is highly likely.

Hopefully this is not a commission or to be sold if any of these things are in question because it may be a time bomb if it can't withstand low RH for a day or so.

Filling the void has other advantages too such as the ability to clean out most of the old glue before adding material. If simply raising the RH and the crack does close you still have the issue of old glue in the joint. It's not a big deal if you joined it with HHG but if not it can be a big deal.

On FRETS.net there are articles on filling a split like this and I would suggest that you check out the resources on Frank's excellent site for this one.

PS: Shortly after I joined the OLF a fellow posted about his nearly completed guitar that at 3:00 AM he and his wife were woken up to hear a loud crack coming from his basement shop.... He also posted that he knew at once what it was. He had just finished the last coat of finish and was waiting a month to buff...

This story scared the heck out of me and was the reason why I took RH control while guitar building as serious as a heart attack from then on. Being the nag that I am since then when asked I always suggest to people that before you buy that killer bandsaw or source beautiful wood that you first do what ever it takes for where ever you are to be capable of maintaining a safe guitar building RH range. I often call it Job one... Remember too: What do politicians and hygrometers have in common? They both lie....


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PostPosted: Sat Jan 10, 2015 3:18 pm 
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Thanks for all of the advise. This is a commission for a local customer, so unfortunately I need to make a permanent repair here. I like the retop method mentioned from Greven guitars and I'm hoping I can make that work. My only concern is that the guitar will lose structural integrity with the loss of pocket joints with the new x braces after routing off the old top.

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PostPosted: Sat Jan 10, 2015 3:44 pm 
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Get a regular old sound hole humidifier and give it a few days. It'll probably come back together. Assuming it does, I would then just work some tite-bond into it. After there is plenty of glue in the crack, I would run a plexi-glass caul down the seam and clamp gently from the inside to align. Then stick a clamp around the hips for good measure.

Personally, I think this should be a pretty adequate solution. You could also stick some cleats in there for good measure.


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PostPosted: Sat Jan 10, 2015 4:13 pm 
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Before retopping you might try adding a splint of wood in the crack. Adding a splint can give the additional wood needed to withstand low humidity conditions, and if well done can be a good inconspicuous fix (especially on new unfinished work). If you don't like the way it turns out, then retopping is still an option.


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PostPosted: Sat Jan 10, 2015 4:52 pm 
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if this is a commission re top and redo

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PostPosted: Sat Jan 10, 2015 5:18 pm 
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It's a shame. That's a nice looking top,love the bearclaw but if I were paying for it I would want it re-topped.


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PostPosted: Sat Jan 10, 2015 5:56 pm 
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Combing both lines of advice, start an entire new guitar for the client. Fix this one with a sliver of wood or other method and use if for something else.


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PostPosted: Sat Jan 10, 2015 6:29 pm 
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wbergman wrote:
Combine both lines of advice, start an entire new guitar for the client. Fix this one with a sliver of wood or other method and use if for something else.


This...

And don't kick yourself too hard, every one of us could do the same thing, and with our 100th guitar.

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PostPosted: Sat Jan 10, 2015 6:34 pm 
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Just asking not recommending -- This seems like the perfect application to take advantage of the capillary action of CA -- re-hydrate to close the gap tight, drizzle thin CA along the seam (I think 100 times more effective than rubbing HHG or PVA into an already closed gap), install some cleats using strong rare earth magnets as clamps. Some makers actually use cleats on the seam as their regular construction method. Likely scraping and completely refinishing the top would be required.

This reminds me of why I do not take commissions or do repairs for $$

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PostPosted: Sat Jan 10, 2015 8:50 pm 
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Tomorrow I'll start the re-top as many of you have suggested. The only reason I can justify a "repair" is because it's faster or easier, and that's no reason to keep me from doing what's right. I don't think I'll be able to pull off the method that retains the binding and pearl, so I'll be removing the top, pearl, and binding in order to acheave as accurate to original top in strength and rigidity as possible. I don't like the idea of not being able to notch in the x braces into the sides and I have enough abalone on hand to do it right. In fact, I have another top that has already been thicknesses and has a double abalone rosette installed from the same tree, so that saves me a day or two of work right there.

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PostPosted: Sat Jan 10, 2015 9:27 pm 
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Great to hear!


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PostPosted: Sat Jan 10, 2015 9:47 pm 
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I just want to chime in and say,
make sure you know what went wrong with this one before you do another.
I think a top that was braced and glued to the rims at proper humidity should have survived a short round of 28%.
Also, it should have split the wood not the joint.
Before you do anything, come up with a way of measuring humidity you can believe in and do a destruction test of your edge gluing technique.
Hot hide is the way and the light. beehive


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PostPosted: Sat Jan 10, 2015 10:26 pm 
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Good point David, I'm a little worried about my plate joint on the top I plan on using to replace it. But what I think happened here is that I braced the top at way two high of a RH level. To my recollection, it was in the high 60% range. I didn't think twice about it because this guitar will live in FL in a beach house once complete, but that would make the drop into the 20% range, a 40% difference, and that would cause the problem.

As for plate joining, I use a Stanley #7 joint plane with an upgraded Veritas blade and ensure a good joint by looking for any light in the seam. I glue them together by wedging the pieces between two lines of nails that are narrower then the width of the two combined pieces, thus forcing them together. Where could I be going wrong?

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PostPosted: Sat Jan 10, 2015 10:54 pm 
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DriftwoodGuitars wrote:
Good point David, I'm a little worried about my plate joint on the top I plan on using to replace it. But what I think happened here is that I braced the top at way two high of a RH level. To my recollection, it was in the high 60% range. I didn't think twice about it because this guitar will live in FL in a beach house once complete, but that would make the drop into the 20% range, a 40% difference, and that would cause the problem.

As for plate joining, I use a Stanley #7 joint plane with an upgraded Veritas blade and ensure a good joint by looking for any light in the seam. I glue them together by wedging the pieces between two lines of nails that are narrower then the width of the two combined pieces, thus forcing them together. Where could I be going wrong?



That the joint failed and you say the two halves were joined properly, it's got to be the glue I would think.
The joint obviously was the weak link as the top didn't crack elsewhere, correct?


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PostPosted: Sun Jan 11, 2015 4:18 am 
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You don't say which type of glue you have used but this is a fine example of where HHG has a distinct advantage. If the joint fully closed with correct humidity it would simply be a matter of introducing fresh HHG and allowing the new glue to solve the old. If anything it makes for a stronger joint because it has already been effectively sized.
If you've never used HHG before practice before doing it on a soundboard joint. Use the tape method, it's simple and very fast.


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PostPosted: Sun Jan 11, 2015 8:07 am 
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Although you have decided to retop the guitar, you might try your hand with splinting the crack, to give yourself some experience doing splints. It is a valuable skill to learn, especially when working on older instruments where retopping is the last resort. Some have mastered this technique to make repairs that are undetectable.
Because of the way guitars are built and the conditions they live in they all eventually crack.


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PostPosted: Sun Jan 11, 2015 11:06 am 
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bluescreek wrote:
if this is a commission re top and redo


I agree here. I've done the split repair and it will never be invisible and while it may be acceptable on a pre-existing guitar, you are presenting your customer with a new guitar. Anything shy of a full re-top is poor care for your customer IMO.

Edit: Sorry I didn't read much past John's post. Glad to hear you're going to re-top.

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PostPosted: Sun Jan 11, 2015 11:24 am 
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I used LMI glue to join the top, but it was a while ago when I did that. I had a bottle of the LMI glue that went bad and was recalled, and there is a good chance that I might have used that bad glue to join this top, but I have know way of knowing for sure. This worst part about this whole experience is that I'm now second guessing myself on several fronts. This is both a good and bad thing I guess. IT's good to go back and review all of my methods, but this type of damage leaves me with a few unknowns as far as the cause. The damage was only at the joint and nowhere else.

A question that remains is this: Would bracing the top at a relatively high RH (60%) cause damage like this if it suddenly dropped down to 28-35% RH for a 48 hour period? I keep leaning toward this idea that my main mistake was assembling under higher than normal humidity (so the wood was swollen) and this caused the top to be much more susceptible to RH changes than if it had been assembled under average or lower than average levels... Is there any validity to this thought?

You guys are such great help and I appreciate it.

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PostPosted: Sun Jan 11, 2015 11:36 am 
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In my opinion, yes -- you are correct assembling/gluing the sound board and any other the thin parts together in such high humidity is asking for trouble. And it is not uncommon for the top or back seam to fail before an actual crack in the plate material, I've see this even on high end guitars.

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PostPosted: Sun Jan 11, 2015 11:52 am 
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I glue up at around 45% RH. I start to get a little worried if it drops below 35%. That's a 10% drop. Yours has gone down by 30%, that's quite a drop and it's going to introduce a lot of stress. If this was an old Guitar I'd be happy that the centre seam gave way. I think I'd rather have that happen than a great big long crack somewhere else on the soundboard.


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