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PostPosted: Wed May 13, 2020 7:42 pm 
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Walnut
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Hi there.
So I've got this classical guitar here, where the owner put a steel string on (one singular steel D-String only, the others were nylon strings), which apparently resulted in the bridge popping off.
I was asked to reglue it, which, given that it's a rather inexpensive guitar anyway, is fine by me.

Looking at the debris, I noticed that the bridge came of very cleanly, ripping of an entire layer of wood off the top. Also, it appears that the bridge wasn't glued with it's entire surface, as there is a small edge around it, where no glue went.

So I was thinking, given that the old glue held strong, and both surfaces are wood, couldn't I just glue it back on the way it is? It would slip right in.
Alternatively I could clean the bridge, flatten the spot where it's supposed to go, even widen it a little, so the entire bridge would make contact with the top, and glue it on. Plenty of work. Furthermore, by taking off the wood remains off the bridge, I would effectively lower the bridge, which would most likely result in the need of a higher saddle (or a shim to raise it back up). It's a cheapo guitar, so I'm not sure if it's worth that amount of work.

Have a look at the image, do you think, gluing it simply back on could work? I'd glue wood on wood, no contamination by old glue, so I would assume it should be fine. It'll look more or less like before, there will be a small gap at the rear edge between bridge and top, but by the looks of it, this gap was there before anyway...

Thanks guys! Don't let Corona bite you :)
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PostPosted: Wed May 13, 2020 8:25 pm 
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Looks clean, I would glue it in. Perfect match. The original was a great glue joint. The ledge was probably by design.

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PostPosted: Wed May 13, 2020 11:21 pm 
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Brazilian Rosewood
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It looks like a Cedar top which needs care in fitting and gluing the bridge. My guess is that they glued that bridge directly to the top with the finish on it and probably scribe a line around the bridge for some reason. It definitely appears that there was a scribed line. Doing that in cedar can cause a bridge to lift away like that taking wood with it.

The irony here is that that is so perfect in its failure that I would consider just gluing it back in place. In the end it will be a lot better off then it was right out of the factory.


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PostPosted: Thu May 14, 2020 6:58 am 
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Koa
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Same thought here. Looking at the offset of the “scribe line”, I wonder if they scribed where tape was during finishing.


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PostPosted: Thu May 14, 2020 8:42 am 
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Walnut
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Hey guys, thanks for your feedback. I'm just a tinkerer, who learns as he goes. But it's reassuring that I wasn't completely wrong on this :)
I wonder what the hole in the middle is for. Just a locating pin? At first I thought there is a screw, but upon close inspection there is none. Anyway... Let's get glue and clamps ready :)


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PostPosted: Thu May 14, 2020 12:15 pm 
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Koa
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Ironically most bridge to top failures are along the glue line and occur because the top wasn't properly prepared - often finish is left on the top and glue doesn't adhere to finish very well. Classical guitars usually have the bridge glued right to the top and then finished over - I can't tell if that was done with yours or if finish was removed. However, the good news (I guess) is that the glue joint was much stronger than the cedar and the failure is completely in the wood.

The other good news, as others have pointed out, is that it is a very clean failure. Often I spend a lot of time cleaning little bits of top wood off the bridge and trying to make the interface fit as well as I can - you shouldn't have any trouble gluing that back together. Make some good cauls for the inside - ideally it will be notched to fit over braces (I'm guessing that has fans). Get at least three deep clamps and practice getting everything in place. Often a bridge will skate around on the top while clamps are being applied - the little hole was probably for a locating dowel (where is it?). AR or HHG will work fine for this, clean up will be easy.

Let us know how it goes


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PostPosted: Thu May 14, 2020 2:51 pm 
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Old Growth Brazilian Rosewood
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It's been said that the word Cordoba which is an inexpensive brand of classical guitars stands for "bridge reglue" in Spanish.

Good going for your original though that if the fit is perfect from the clean way that it came off AND if it's all clean wood-to-wood get some Titebond original, proper clamps to reach the center and wings and glue that sucker back on and call it a day. Be sure no errant fibers are preventing that "snap" fit that we really want if we are not preparing the bridge bottom and bridge patch traditionally.

It's rare that we would consider this but we have and we have done it before when "it's appropriate for the instrument" and the wood on the bridge bottom will "key" well (fit perfectly) into the bridge patch.

Be absolutely sure though that it's completely down everywhere and test it with a piece of paper poking it around the joint area to be sure it's all the way down. Do a dry run with the clamps even though Titebond Original (only use the original Titebond for this one) has lots of open time. Dry runs give us practice and unmask issues down the line that we may not know about until we encounter them.

For the record it is almost always a good practice to clean all old wood and glue from the bridge bottom and clean up and expand the bridge patch to very close to the perimeter of the bridge. We don't like taking it to the perimeter because pro quality work should not only last like pro quality work it should look like it too.

Regarding how it failed I think you nailed it too. A single steel string greatly increases the tension on a classical bridge.

Lastly leave the clamps in place for 12 - 24 hours. Do not restring for at least 24 hours. Hot water and a paper towel (we like Bounty it won't scratch guitar finishes) will clean up the old glue but do try to clean all the squeeze out you can get to right after setting the clamps to make your life easier tomorrow.

Good going for taking this one on you checked all the boxes in my mind with presenting the facts, pics and well reasoned speculation with a proposed fix, two actually. That's unusual on this forum or any forum for a person new to repair to get so much right. You have some natural ability for this stuff. Good on you.

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These users thanked the author Hesh for the post: yelemusic (Tue May 26, 2020 7:39 pm)
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PostPosted: Thu May 14, 2020 10:08 pm 
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Cocobolo
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So THAT's why we need to be real careful about cutting away the bridge footprint in the masking tape! Learn something every day.

Than s for sharing.

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PostPosted: Sat May 23, 2020 7:52 am 
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Walnut
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Hey guys, thanks a lot for all your great input.
I've glued everything down yesterday, went without a hitch, but of course I'm nervous about restringing now :) Will it hold up?
I'm sure it will, as everything sits nice and tight, and I know how strong titebond is :) But it still is a bit nerve wracking :)
I'll let it sit for another day and restring it tomorrow.

Special thanks to Hesh! Very nice feedback, thanks :)



These users thanked the author yelemusic for the post: Hesh (Sun May 24, 2020 8:46 am)
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PostPosted: Sat May 23, 2020 8:31 am 
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A good Titebond glue joint will be stronger that the wood.

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These users thanked the author SteveSmith for the post: Hesh (Sun May 24, 2020 8:46 am)
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PostPosted: Sun May 24, 2020 6:37 pm 
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Koa
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Yes, there was the increased tension of a steel string, but there was also a scribed line through the finish at the rear of the bridge — western redcedar is quite intolerant to that. I’ve reglued several classicals that fail like this. If the factory worker has been less zealous with his Xacto knife, the joint probably would have held.

Like others, I would focus on making sure the cedar-to-cedar fit is perfect. Nothing wrong with Titebond here, but I switched to hot-hide glue for those just because the cleanup is so much easier.


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These users thanked the author Tim Mullin for the post: edstrummer (Fri May 29, 2020 1:11 pm)
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PostPosted: Tue May 26, 2020 7:43 pm 
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Walnut
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So far the guitar is stable, it stays in tune, the glue joint is solid, so for now I declare: mission accomplished :)
We'll see if the owner comes back after 2 years because the bridge has snapped again :) I doubt it though, as long if she doesn't put a steel string on it again!



These users thanked the author yelemusic for the post: Hesh (Wed May 27, 2020 10:58 am)
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PostPosted: Wed May 27, 2020 10:58 am 
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Old Growth Brazilian Rosewood
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yelemusic wrote:
So far the guitar is stable, it stays in tune, the glue joint is solid, so for now I declare: mission accomplished :)
We'll see if the owner comes back after 2 years because the bridge has snapped again :) I doubt it though, as long if she doesn't put a steel string on it again!


Good job, pat yourself on the back for a job well done.

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These users thanked the author Hesh for the post: yelemusic (Wed May 27, 2020 9:16 pm)
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PostPosted: Fri May 29, 2020 8:29 am 
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Brazilian Rosewood
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Cordoba means "Bridge Reglue" well ya learn somethin' every day. LOOL

laughing6-hehe



These users thanked the author jfmckenna for the post: Hesh (Fri May 29, 2020 1:47 pm)
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PostPosted: Fri May 29, 2020 1:48 pm 
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Old Growth Brazilian Rosewood
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jfmckenna wrote:
Cordoba means "Bridge Reglue" well ya learn somethin' every day. LOOL

laughing6-hehe


I laughed my butt off the first time I heard that, so true too.

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