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A couple of weeks ago I posted asking for opinions about using WRC tops for steel string guitars. My third WRC build (*almost* finished, but now currently back on my bench) developed some very strange cracks just after spraying (see pic). I've been letting it sit aside while I decide what to do about it. The finish cracks are very obvious. I had just about decided to sand the top back to bare wood and start over.

But while buffing out the finish (to see if it was salvageable) I noticed a more bothersome *development". There are three hairline cracks that run longitudinally down the lower bout. Two of them are about 1/2" on either side of the center line. The third is about 1/2" to the right of the High E bridge pin hole. The small amount of moisture involved in wet-sanding made them become obvious. Now they are just barely apparent, but they are definitely there

So my latest idea is that I should just bite the bullet and re-top the guitar. There would be a good deal of time involved in sanding back to wood, refinishing, attaching the bridge, and setting up the guitar, and if I did all of that only to have to take it all apart again later, I'd be pretty bummed. I'm thinking that I've either used an inferior piece of wood, or thinned it too much, or that the temperature stresses of going in and out of the house into the mud room for spraying have caused a failure in the wood (I was pretty careful to acclimate the room, and let the guitar acclimate as well, but... ). The back, sides, and neck assembly turned out fine.

I guess what I'm looking for is confirmation of my plan. Would re-topping the guitar seem to be a wise course of action at this point?

TIA,

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Ken Mitchell
Durham, NC

Before doing anything check your humidity levels, it sounds like the top has dried out and cracked.

Fred

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Fred Tellier
http://www.fetellierguitars.com
Facebook page http://www.facebook.com/pages/FE-Tellier-Guitars/163451547003866

What humidity did you build at, and what has it been at since then? Temperature means nothing, other than how it effects relative humidity.

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Eschew obfuscation, espouse elucidation.

I'm pretty vigilant about humidity. It was built at around 45%. The air coming through the house and into the mud room (pulled through by an exhaust fan in the outside door) should have been about the same.

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Ken Mitchell
Durham, NC

There aren't many things likely to cause cracks like that other than humidity. Whether built moist then brought down to normal, or built normal then made dry, or green wood that is still shrinking and seasoning, somehow that wood has shrunk in width compared to when it was braced and glued to the rims. Not many other things will cause cracks like that.

Was the top built with a radius, and does it still maintain that radius right now?

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Eschew obfuscation, espouse elucidation.

Thanks for the insights, David.

It was built to a 25' radius, and has held it. The weather was pretty wacko during the week that I spent spraying this fellow. I was probably more focused on temperature than humidity. I build in one end of the house, where I keep the humidity pretty constant, and the spraying was done at the other end of the house. There are open doorways in between there, and I was assuming (probably incorrectly) that the humidity was at least somewhere near the same level, but it probably was *not*.

So... knowing the cause helps me for future builds. What should I do for this one? Will the longitudinal cracks close up and cease to be an issue with proper humidity? Will refinishing this top be sufficient, or should I start over and re-top the guitar?

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Ken Mitchell
Durham, NC

I would repair the cracks, sand the top a little and shoot more finish at least in the repaired area and finish the build. A good chance to improve your repair skills. If you are using lacquer the new finish should blend together with the old.

Fred

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Fred Tellier
http://www.fetellierguitars.com
Facebook page http://www.facebook.com/pages/FE-Tellier-Guitars/163451547003866