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Hello, and thanks in advance for your advice.

What approach would you take to fix a terribly deformed plywood top with a plywood bridge plate?  The bridge lifted over the years, and a pronounced belly formed, leaving the top, under the bridge, quite sloped.  It is not a nice gradual slope.  If one were sledding on the guitar top, one would start at the back of the bridge footprint and slide to the front of the footprint.

The bridge lifted, and was successfully removed. The guitar is one from the 70's, the bridge has two bolts and an adjustable metal insert saddle.  The X brace has come unglued on the treble side near the bridge, where the deformation is the greatest.  The glue used has a white color.

I am quite reluctant to try to remove the bridge plate, as I am afraid the plywood top would come away as well.

Has anyone had success fixing one such as this?

Tags: belly, plywood

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Hi Elaine.  You are describing very severe structural damage in a cheap plywood guitar from the 70s.  It is likely that the top has delaminated in parts.  Between that and the bracing failure  the top sounds unfixable.  You could replace the entire top, if the rest of the instrument is OK.  But there is a strong chance on a beater like this that other problems coexist - bad neck angle, twisted neck, seized truss rod, worn frets, crappy tuners.  In short - probably not worth the time/cost/effort on this instrument.  At this point the question of sentimental value comes up ( “my dear departed mother played me and my 10 siblings lullabies on this guitar every night, I would do anything to fix it”).  So I could understand if you want to try a heroic rescue for this instrument - but the reality is that it sounds like time for a new guitar.  

Mark, thanks for your input.

The guitar indeed has sentimental value to the owner.  It seems to be in great shape aside from the deformed top, and has lovely binding, purfling, etc.  I think it will need new frets, however.  As I am fixing it for the sheer fun of the challenge, cost is not an issue.

So here is my plan, sans a better idea.  I am going to attempt to flatten the top, at least somewhat, by clamping a 2 X 5 heat pad inside the guitar between damp terry cloth and a caul over the bridge plate.  After that has "cooked" I will clamp it as flat as possible using the bridge plate caul and a cork lined board across the top.

Assuming this flattens it somewhat, I will re-glue the loose brace, and glue a piece of hardwood over the existing bridge plate, with the grain running parallel to the strings so it resists bending as much as possible.  Then I will fit the bridge to the perfectly flat top (ha ha) and glue it back on.  I will leave the bolts out (yes, it had bolts).

After this, I will install a JLD bridge doctor, 'cause, why not?  I fervently hope it doesn't need a neck reset after all that, but we shall see.  I suspect the action was pretty good because the front of the bridge had sunk down.

What do you think of that plan?

Cheers,

Elaine

Sounds like a plan. Getting the top wet and clamping until dry is also a way to straighten warped wood, but heat is probably more effective.

Hi, I have done this repair more times than I can remember, over the years. I have the whole process in photos of many guitars, but too many to post here. I will see if I can put it into words. It's pretty much as you explained in your plan. I have found that ply/laminated tops can be more difficult to correct as often the problem may have been caused by heat, so the top pulls up, and the glue resets in the laminations and holds the top in its new shape.

What I have done, with success, is to remove the bridge, and sometimes the bridge plate, apply heat with a hairdryer evenly over the affected area and a bit beyond. My heater is small enough to do the inside too. Then clamp a board over the humped-up area and let cool. Repeat until the top remains where you want it. You could dampen the exposed top in the bridge area and inside.

I would then fit a new bridge plate or add a lamination to the existing one, if not removed, it depends on the guitar. The grain of the plate I try to run at an angle. Many times I have found the need to add a brace to the top, along the back of the bridge plate. I would then cleanout under any loose braces and reglue them.

I do the same operation, in reverse, for the sunken area of the top in front of the bridge/soundhole area.

Don't forget to check the radius under the bridge itself, and correct if need be. It's not the full story but I'm sure you get the idea.

Good luck Taff

OK, sounds like you have nothing to lose from trying to flatten out that crinkly thing, and if that fails a re-top is not out of the question.  Life in the old girl yet......

Thanks Mark.  I'm pretty sure a re-top is way beyond my level of competence.  I'd hate to give back a sad pile of wood.

Cheers,

Elaine

Taff -

Thank you, that's very helpful. 

I clamped it overnight after applying moisture and a heat blanket to the bridge plate, and it is somewhat better but still quite bellied.  I will do that again, add moisture to the top bridge area as you suggest, and heat the top in a larger area, perhaps with the heating pad I use for my own back as opposed to a hair dryer.

How do you clamp the sunken area?  Do you make a caul for the inside that goes between the X braces, or a larger one with cutouts that go over the X braces?  If you happen to have a picture of that it would be helpful.

Again, thank you.  At least now I know it can, and has, been done.

Cheers,

Elaine

Hi Again Elaine, here are a few photos from one of the jobs more recently. There are captions on the photos, but if not enough info let me know. This guitar was a Cole Clark, with a bracing system I have had to rework a few times.

The extra brace, in this instance, was used to strengthen the sunken area. I placed a bar across the top and pulled the face up to it with clamps. The brace I used to stiffen the one already in place, in this case, it was glued on top of the existing one.

The caul used to pull against would be as you suggested, whatever is best to apply even pressure from inside.

The action at the 12th was 5mm, prior. Hope this helps. Different guitars need a modified approach, this is just one. Cheers Taff

Thank you Taff, that is great!

Cheers,

Elaine

I have a guitar with a similar bellying issue, but not as severe as yours sounds. The bridge plate is plywood (with a mahogany veneer oddly enough). I used the TJ Thompson Belly reduce to flatten the top. Now I'm debating what to do with the bridge plate. I have no tools (or skills) to remove the plate, but I'm worried about adding a piece of hardwood and thickening it even more. Is this something I need to worry about? What was the thickness of the hardwood overlay you used? 

I don't really feel like buying another $80 tool to remove the bridge plate and also risking hurting the top more. 

Any help would be appreciated!

Thank you!

Hi Bob -

The overlay I used was Bubinga 1/16" - 3/32" thick.  I was dealing with a plywood top, and a plywood bridge plate, glued on with some strange thick and translucent glue.  Even after heating, it showed no signs of wanting to loosen, and I did not want to damage or destroy the top.

I also installed a JLD Bridge Doctor, which did the top deformation a world of good.

Bottom line, the guitar sounded better than ever (according to the owner), and he was thrilled.

Good luck!

Cheers,

Elaine

Hi Bob, I have a selection of plate removal tools that have worked well for me over the years. All shop-made. I always make what I need if I can, then buy the tool if I really have to down the track. More often than not the ones......I make are the ones I keep using. There is also an assortment of small block sanders in this kit too.

Hope this helps. Taff

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