Fixing a Warped Bridge...

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Fixing a Warped Bridge...

Postby Ryan Mazzocco » Sun Oct 21, 2012 3:20 am

Can it be done?
I'm working on an Alvarez with a really bad bridge belly. as usual the bridge is pulling off so I went ahead and removed it. When it came off it was extremely warped and twisted. (Imagine the St. Louis Arch after being hit by a tornado. I exaggerate of course, but you get the idea.) I wanted to see if I could save it rather than having to replace it. so I clamped it to a straight caul on the bottom to get the warp out and clamped each end flat to take out the twist... then put it in the oven for a couple hours at 225F. Took it out and it was flat as a pancake. after looking at it for just a minute I quickly put it back in the clamp set up to set overnight and hopefully get the wood to fix it's memory in that position.
I just made this up on the fly as I was doing it. Has anyone else ever tried something like this? If so can I expect long term results or will it just go back after I let it out of the clamps? or does that all depend on how long I wait to put it back on the guitar?

IMAG0308 20.JPG


While I have your attention: this may be a job for the bridge doctor, but I would like to see if I can get the belly out of the top. it's a laminated spruce top. all the bracing seems good and solid, none loose or broken. the bridge plate is ply-wood. Would it help if I replaced that with maple and then applied heat while clamping the top flat? Or maybe try to flatten it before I put in the new bridge plate... To be honest, with everything looking to be in such good shape inside, I'm a little puzzled how it got so much belly to begin with.
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Re: Fixing a Warped Bridge...

Postby Mark Swanson » Sun Oct 21, 2012 8:49 am

I have flattened bridges with heat before, and it works. We bend sides, and expect them to stay put...why not a thicker bridge? I heat and clamp it, and then will sand and scrape the bottom level, that gives me a fresh surface for gluing too.
I'm a little puzzled how it got so much belly to begin with.


As far as that bellied top, it isn't surprising when you look at how the top and bridge plate are made. These laminated guitars have the inner layer as the thickest of three layers of wood. And of course the inner layer is the least quality piece too because it doesn't show- and more importantly, that inner layer has a grain direction at 90 degrees to the outer layers- that worst possible direction for a guitar! The grain direction goes from side to side, and not in the direction of the strings and so it really makes bellying much more likely, The bridge plate is made in the same way, so these guitars really have very little support against the belly problem.
I think I'd just replace the bridge plate and re-glue the bridge and that will get rid of most of it, the rest should be manageable. Avoid heating the whole top.
    Mark Swanson, guitarist, MIMForum Staff
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Re: Fixing a Warped Bridge...

Postby Ryan Mazzocco » Sun Oct 21, 2012 1:07 pm

Mark, sounds great! Your answer helps make my whole world make a little more sense. Of all my guitars only two have laminated tops and they both have really bad belly while all my solid tops are laying nice and flat.
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Re: Fixing a Warped Bridge...

Postby Ryan Mazzocco » Wed Nov 21, 2012 11:09 pm

so, I had a little time this evening and came back to this guitar....
Mark, first I just want to say that I am so sorry for not listening to you.
So here's what happened. I decided I wanted to try to flatten the top if I could. I took a couple of wood cauls and spanned them over the area from where the top dipped closest to the sound hole and out past the point where it had the most hump past the bridge. I used my soundhole clamps to put pressure on the two points (since they have the leveler I used that second clamping foot to add pressure to both the front and back end.) It appeared that I got it pretty flat, but I knew that as soon as I took the pressure off it would just go back where it was (and I was right about that as we will later see...) So, I thought I would try just a little gentle heat. Nothing really crazy I thought... I just put a blow dryer on low to it and walked away for a few minutes.... about 30 actually...
So when I came back to check on it I noticed 2 things that I didn't like at all.
1) the area where the heat was most concentrated looks almost bleached or blushed. and
2) it only had very little, if any, affect.

I know, I did a bad thing. You were right, I was wrong. You are smart, I am dumb. You are good looking, I am not attractive.... so now that we've got that out of the way,
What happened? Why did the finish discolor? is there a way to fix it?
at50.JPG
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Re: Fixing a Warped Bridge...

Postby Ryan Mazzocco » Thu Nov 22, 2012 12:30 am

or here's another thought...
could it be possible that the heat combined with the clamping pressure caused the polyurethane to separate from the wood? I mention this because it seems to start where the edge of my cauls were and then flows out from there.
I don't really know... just an idea.
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Re: Fixing a Warped Bridge...

Postby Mark Swanson » Thu Nov 22, 2012 1:56 am

Hmmmm...well, sorry about that!
I might be smart, wise and good looking too :? but I don't know what happened to that! It seems like your guess about the finish separating from the wood is as good as any guess I might make. I think if I was going to heat the top and try to flatten it, I would have moistened it well inside first. But who knows, that might have messed it up too! It can be very risky trying to flatten a top like that. So sorry for your bad luck, you might have to live with that guitar the way it is.
You could replace the top, you know! A nice solid top would solve ALL of the issues.
    Mark Swanson, guitarist, MIMForum Staff
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Re: Fixing a Warped Bridge...

Postby Ryan Mazzocco » Thu Nov 22, 2012 2:37 am

eh... it's actually worth more to me as is than if I did do all kinds of extensive work to it. I was going to try to keep it minimal anyway. I bought the guitar for $50 at a local flea market. you can see all the cracks and dents in the picture. It is a survivor of the May 22, 2011 EF-5 Tornado that hit Joplin, MO. I think I mentioned it in a different post at some point. My wife thought I was crazy to not totally refinish it altogether, but I wanted to preserve the damage. That mile-wide tornado missed our house by about 3 blocks so there was more to it than just getting another guitar to me.
Ultimately, I just wanted to get it playable. Someone had got ahold of it before I found it and made some really sloppy repairs which I had to fix. but someday she'll be a player with a great story.
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Re: Fixing a Warped Bridge...

Postby Michael Lewis » Thu Nov 22, 2012 2:50 am

Ryan, I think you should have gone with the Bridge Doctor to get the hump out of the top. it will take most of the stress off the bridge and lower the hump.

Take a good look at the finish under strong light to determine if it is separation or discoloration. Try a drop of naphtha at the edge of the finish in the bridge area to see if it wicks under the finish. That should tell you if it has separated or not.
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Re: Fixing a Warped Bridge...

Postby Steve Senseney » Thu Nov 22, 2012 10:35 am

When I have tried to flatten a hump in the soundboard, (on low quality insturments only!!!) I have used a clothes iron. Put some clean t-shirt material with a little moisture over the area you are working, and place the iron on the t-shirt.

You will probably mess up any finish that you have on the surface with the use of effective heat, whether it is from a clothes iron or hair blower.

There are several things happening as you apply heat. It makes the wood more bendable, dries it out if you don't add moisture, and can soften glue (depending on the type of glue used).

It is hard to heat the bracing underneath adequately, so it may stay deformed.

After you have it in a better shape, you need to put some weight or clamps on it to maintain that shape until it is cooled down again.

Then you get to refinish it again.
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