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Hey all -

On a recent build, after two months of being "a guitar" my bridge decided to start pulling away from the soundboard, just a little in the center. Now the soundboard seems to be cracking between the bridge and tailblock. It's a shame since I just buffed it out recently and all. Sweet guitar, ugly problem!

Anyway, does anyone have a tute for doing a simple crack fix? It's not all the way through < I don't think>, and you can barely see it...I don't think a shim is in order, but one of you out there probably knows better than I! I'll be removing the bridge to re-glue anyway.

That will be the last time I use my wimpy old cam clamps for gluing bridges! Making a "through the string hole" jig for the next one.

Thanks,

Jon Simpson

Hi John.

I've frequently fixed cracked soundboard. It's not a difficult fix.

Once the bridge will be unglued, take a small plastic cup and stick a demp paper towel in it and put the cup in the soundbox. Leave the guitar in it's case (horizontally, of course). That will humidify the wood and the crack will close on it's own. Wet the towel every day until you can't see the crack anymore (can take up to a week, but according to how you describe the crack, more like 2 to 3 days). If you have a guitar humidifyer, that will do as well, if not better than the plastic cup and paper towel.

Once you are there, you are not done yet. Make sure your hand are clean and push some titebone glue in the crack using your finger. You can use one hand from inside of the box to push to wood up to open the crack, but be gentle. Once that is done you can clean the remaining glue from the top with a wet towel. Now you could stop there but an extra precaution would be to glue a small cleat under the crack, just to make sure it doesn't open again.

One last thing, the cause of the crack might not be the bridge that was lifting, but a lack of humidity. If the ambiant air where you store the guitar is a lot dryer than the environment where the guitar was built (say by 20-30%), then cracks can happen. So you might want to check that out.

Good luck!

_________________
Alain Moisan
Former full time builder of Acoustics, Classicals and Flamencos.
(Now building just for fun!)

Jon buddy do you have some pictures so we can see what is happening?

Here's a few pics....

The bridge is BARELY lifting in the center...maybe 1/64" at best. The split kinda looks like gluejoint failure, although it appears to be splitting all the way into the tailblock, and the top is glued pretty well to the topside of the tailblock.

Any recommendations for removing the bridge? Don't have the StewMac tool or "repair blanket".

Thanks for all the help!

Jon thanks for the pics. It does indeed look like the joint failed for the top. The bridge lifting is yet another joint failure.

A couple more questions for you if I may please?

1) What kind of glue and processes (candling, joining/clamping, etc.) did you use for joining the top plates and gluing on the bridge.

2) Humidity control: Was the guitar built with some humidity control AND at least where I live the furnaces are now on, things are drying out, are you in a cold climate and has the guitar been subjected to dryness?

Thanks

Hey Hesh! Thanks for the reply. I glue with Titebond, usually.

For joining tops, I run them across the jointer (clamped together so I shave the joining edges at the same time). I then "candle" them with a bright light and if all is well, then glue together in a jig similar to the one shown in attachment (don't have a pic of mine, but this is essentially the same), with four pipe clamps gently squeezing the joint together from the sides. Covering the joint in wax paper, I place a piece of scrap wood along the length of the joint and put 3-4 weights on it overnight. I've read the posts about sanding vs planing when it comes to joining tops ad such, but the jointer had been doing fine for me so far.

For gluing the bridge on, I scrape away the lacquer and lightly score the soundboard diagonally where I'm gluing. Titebond and three cam clamps via the soundhole. I'll be switching to a "thru the string hole" jig for bridge gluing from now on, though.

Humidity - I build in my basement (Iowa...getting colder here too!) which I try to keep around 50-55%rh all the time. This guitar in question showed NO sign of failure when it left my shop, and it started to do all this while innocently hanging on the wall of a reputable guitar store...where I presume they keep the humidity in check as well.

So if this is indeed a joint failure, would a cut-in splice be the remedy?

Forgot pic...here ya go:

That top crack is almost certainly a humidity issue.
Building at 55% humidity is looking for trouble...which is why builders take great pains to build between 40-45% humidity. This top dried out and pulled right apart. A couple years back I did some warranty repairs on three Maton guitars that had the same issue....built too humid to stand drier US conditions. My guess is the shop where yours was hanging had air conditioning but no humidifier in the room.
You have two options. Humidify the heck out of it and repair the crack (and pray it doesn't get dried out again), or replace the top under more optimum conditions. Good luck.

_________________
"I want to know what kind of pickups Vince Gill uses in his Tele, because if I had those, as good of a player as I am, I'm sure I could make it sound like that.
Only badly."

The humidity in the basement sounds at least a little high to me. Search of the archives indicate a prefered humidity of 42% - 48%. I have mine on the low end of that range.

Your trust/assumption about humidity control might be misplaced. Most of my local "reputable" music stores do NOT have a climate controled room for guitars. They hang on the wall in the wide open space. That air conditioned space (with no other de/humidification) where I live in NC is generally about 35-40%. So, if I built at 55% and it goes inside and up on the wall of an air conditioned building, that's a 20% difference.....Cold dry air and heating lowers the inside humidity even further

Just some thoughts.

Joe

I keep seeing those humidity numbers for NC. I live in Charlotte, and the AM average humidity is 82% and the PM average is 53%. It rarely goes below 50% except in the colder months of winter in December through February. What part of the state are you in?

_________________
Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

Yowch!

It's a battle for me to keep the shop below 45% in the summer months, it's usually right around 45-47. In light of the responses (thanks!) I see that I really need to dry it out even more. I guess a second dehumidifier is in order, even with the AC going! That, and I'll get a few more RH gauges and average out the readings...I doubt the calibration of my cheapo digital gauge.

Sadly enough, this is the same guitar with the severe blushing under lacquer problem I posted a few months ago. Obviously damp then, dry now. It all makes sense.

I'll fix the crack and hopefully sell it to someone that lives in a rain forest.

yeah...that's the ticket......

Jon my friend I think that Don nailed it.

Also scoring the top in preparation for bridge gluing with Titebond is not a good idea if you will pardon me for saying so. Titebond does much better with a good fitting, freshly planed if possible, wood-to-wood joint.

Jon don't be too discouraged by this...if it can happen to a big company like Maton, it can happen to anyone. Look at this as a learning experience and make changes to your environment to accommodate for the humidity stuff and move forward. You'll do fine.

_________________
"I want to know what kind of pickups Vince Gill uses in his Tele, because if I had those, as good of a player as I am, I'm sure I could make it sound like that.
Only badly."