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Gluing spruce top to solidbody guitar


GregP

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Background:

I have a guitar that I'm frankensteining into something new. The original plan was to strip the old guitar's finish, possibly run the body through a quick pass on a planer or router jig to "true up" the top, and then glue a 2.5mm thick sheet of sitka spruce (a ukelele top, actually) for decorative purposes. I'm not expecting the top to actually have much if any of a contribution to tone. It's just that I wanted a natural wood top of some variety, flat not carved, and couldn't find appropriate veneer in my area. This is a thicker veneer surrogate, really. ;-)

So I used the heat gun method of stripping the guitar body, and I discovered that this body had already been finished and refinished a second time at the factory... it must've had a bad first time of it, so the factory earmarked it for refinishing with a graphic application. The graphic application came off easily, and the top layer of paint as well. But then...

It has a noticeably thick and durable coat of... something... underneath. An epoxy resin maybe? A durable layer of polyurethane? In any event, it is resisting heat gun work.

 

Proposed solutions:

1. Despite the legwork with the heatgun, run it through a router jig after all. Ie. continue with the ORIGINAL plan. The router should have no problem reducing height by a mm or so, exposing bare wood. I should note here that I'm not that keen on using a power sander... I've done that before and I know that I seem to have a tendency to leave a less than even surface behind.

2. Figure out what solvent will work on this exposed layer and try to chemically finish it off.

3. I halt the stripping process (leaving the poly/resin layer intact) and glue the spruce directly to this currently-exposed layer.

 

This is where my questions come in:

1. Which method would you go with? I'm leaning towards lazy (ie. option 3), because this is meant to be a cheap getting my feet wet frankenstein project, not a perfect build.

2. If chemical is recommended, any guesses as to what this layer might be (poly seems most likely?) and what chemical to use?

3. If I go with method #3, I don't suspect wood glue will work... the exposed layer is plasticky and non-porous. But would I be able to get away with something like 2-part epoxy? The spruce has no structural significance and is literally just a decorative layer.

 

Thanks in advance!

 

 

 

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  • 2 weeks later...

The router jig worked. The crusty crap was no challenge for the high-speed router bit. Nice and clean and true both front and back. The only issue was that my plunge router doesn't have awesome capabilities for micro-adjustments. I wanted to go like... 1/10 mm deeper, so I ended up having to set my bit flush against the surface and lock it in place, and then raise the surface by 3 printer papers. ;-) Worked as expected.

Made the jig with a decently executed design and a bit of serendipity (had some extruded aluminum beams that were PERFECT for the job... it's not like most people just have that stuff lying around). Will post photos.

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I was in the same boat stripping a body that I'm currently making into something completely new. Paintwork went off beautifully from the heatgun and then some weird pink stuff showed up underneath that didn't really care about the heat. 

Also went with router-thicknessing the thing :)

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