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How Should I Go About This Repair?
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=32080		 Page 1 of 1
Author:  WilliamS [ Tue May 03, 2011 1:03 am ]
Post subject:  How Should I Go About This Repair?
I was asked to repair this guild classical whose bridge has sheared off and was just wondering how you guys with more repair experience would go about it (my repair experince so far has mostly involved fixing my own mistakes on builds, not trauma like this).
Sorry for the poor picture from my phone.
Image

A couple of things:
-I've repaired/cleated the huge crack since I took the picture. It actually closed up pretty nicely.
-This damage isn't particularly recent and, while the bridge didn't take a huge amount of wood with it, the layer on the bottom isn't what I'd call whisper-thin in all areas, either.
-The bridge on this guitar is very narrow (much more so than my classical bridges) which, in my mind, may have contributed to its having sheared off.

My inclination is to clean up and patch the bridge area then make a bridge slightly wider than the original. But if you guys with more experience think that's not really necessary then I'm more than willing to listen.

Thanks,
William
Author:  bluescreek [ Tue May 03, 2011 6:17 am ]
Post subject:  Re: How Should I Go About This Repair?
it appears to be a classical. You need to clean off all the fibers and make a small sanding block to sand the bridge foot print. I also think you need to re hydrate that guitar. before you do anything. Set a small cup of water inside the guitar and lay somthing over the sound hole . You will see the cracks tighten up.
Once the crack close you can use hot hide glue or tite bond and work the glue into the cracks. Using a deep throat clamp, lay lexan on the top and clamp things up. Use a cleat on the inside. I would try and make the cleat about 1 inch long and diamond shaped. Put 2 or 3 along the seam. Also check for loose braces.
Reglue the bridge and you should be fine.
Author:  David Newton [ Tue May 03, 2011 8:21 am ]
Post subject:  Re: How Should I Go About This Repair?
Ditto on John's advice, but I always try to figure out: why? And learn from it.

It looks like the glue held, and the wood sheared, and I think it sheared because when the top finish was removed for bridge gluing, it was cut around the perimeter with a knife, and it was cut too deep, and sheared along the depth of the cut.

To me, it means "don't cut down into the wood, if you are only wanting to remove the finish".
Author:  WilliamS [ Tue May 03, 2011 8:44 am ]
Post subject:  Re: How Should I Go About This Repair?
So it's ok for the bridge to be sitting slightly below the plane of the top after the reglue?

And, as stated in the original post, the crack has already been closed up and cleated. And, yes, I did rehydrate the guitar before doing the repair on the crack-I took the picture right after receiving the guitar, well before my post. I'm just getting around to tackling the bridge and, since the only bridges I've reglued to this point are ones that I carefully removed myself and took few/no fibers with them I wasn't sure what the best course of action would be.
Author:  WilliamS [ Tue May 03, 2011 8:51 am ]
Post subject:  Re: How Should I Go About This Repair?
David Newton wrote:
Ditto on John's advice, but I always try to figure out: why? And learn from it.

It looks like the glue held, and the wood sheared, and I think it sheared because when the top finish was removed for bridge gluing, it was cut around the perimeter with a knife, and it was cut too deep, and sheared along the depth of the cut.

To me, it means "don't cut down into the wood, if you are only wanting to remove the finish".


Yeah, I've seen pictures of bridges that sheared from cutting too deep when scoring before removing finish. I'm not so sure that that's the case here, though. First, the bridge did hold for around 40 years (I believe it's a 1960's guild). Second, and more importantly, though it did shear in a relatively straight line the shear line isn't perfectly straight and it is nearly 1/16" inside the perimeter of the bridge.
Author:  theguitarwhisperer [ Tue May 03, 2011 8:52 am ]
Post subject:  Re: How Should I Go About This Repair?
I have a classical guitar of my own that did the exact same thing, the top split and the bridge sheared off with most of the fibers intact.
Since the glue didn't fail but instead the wood failed, after closing the top as you did, I just glued the bridge right back down without cscraping anything off. That was15 years ago, it's still intact and sounds great.
Author:  Laurent Brondel [ Tue May 03, 2011 8:55 am ]
Post subject:  Re: How Should I Go About This Repair?
This looks like WRC. Not uncommon for bridges to lift like that on WRC as WRC has no shear strength compared to spruce. Try to clean up the top as well as you can, and to remove the finish (not the wood) under the whole footprint of the bridge. It looks like you should be able to do a very clean and invisible repair.
Author:  WilliamS [ Tue May 03, 2011 8:59 am ]
Post subject:  Re: How Should I Go About This Repair?
I thought about that for a bit but the break is a couple years old at his point so the gluing surfaces would not be at all fresh.
Author:  jac68984 [ Tue May 03, 2011 9:01 am ]
Post subject:  Re: How Should I Go About This Repair?
I don't build classical guitars, but isn't it common practice to glue the bridge on a classical prior to finishing? The photos don't show the top of the bridge, but if it has finish on it, I'd say the sheared wood is not due to scoring the finish.

Aaron
Author:  Laurent Brondel [ Tue May 03, 2011 9:02 am ]
Post subject:  Re: How Should I Go About This Repair?
WilliamS wrote:
I thought about that for a bit but the break is a couple years old at his point so the gluing surfaces would not be at all fresh.
And???
Scrape or sand the bottom of the bridge clean without removing unecessary wood, ditto for the bridge footprint on the top. As I wrote before, remove the finish under the whole footprint of the bridge, heat some HHG and clamp the thing.
Author:  WilliamS [ Tue May 03, 2011 9:21 am ]
Post subject:  Re: How Should I Go About This Repair?
Laurent, we must have been typing at the same time. My response about the gluing surface not being fresh was directed at the suggestion that I glue it back as is. I will try to flatten the bottom and see how much material is left. I think you may be right.
Author:  WilliamS [ Tue May 03, 2011 9:27 am ]
Post subject:  Re: How Should I Go About This Repair?
Thanks, Filippo. I've been building classical guitars for seven years (have even sold a few) so the bridge glue up will be no sweat.
I just have very little repair experience.
Author:  Barry Daniels [ Tue May 03, 2011 9:29 am ]
Post subject:  Re: How Should I Go About This Repair?
Even though the exposed wood surfaces are not fresh, they would make very good mechanical contact if left as is. Normally, I always prepare fresh surfaces on bridge reglues, but I would probably also glue this one back as is. Either way should work fine.
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