Official Luthiers Forum!

Hello everyone,
I have a braced top in my shop from an unfinished acoustic guitar that's been leaning against the wall for several years. The student (actually a day-job work mate of mine) was super busy at the time, buying a house, having a kid, and just wasn't able to dedicate the time required in order to finish the guitar. And once the window of opportunity passed, he never inquired about it. I'd like to resurrect this project, finish the guitar, and offer it to him as a gift.

It's a perfectly good top, plus, it's the one that HE built. Only problem is that it's lost it's radius, and is fairly flat.

What I'm wondering is... if I lay it in a radius dish for a couple of weeks, with some weight in the center, I'd like to think that I could re-induce the radius, and go ahead and use the top. Worst case scenario... if after a couple of weeks the top ends up still being flat, with zero radius... do you all think it will still work OK? As a true 'flat-top' guitar maybe? I guess it would be more at risk regarding changes in humidity, but beyond that?

Thanks for any thoughts or experiences folks could share.
Ken

_________________
Ken Mitchell
Durham, NC

If it was braced with a radius in a properly controlled RH area and is now flat, that’s a dehumidification issue. First give it some time at the RH it was braced at and see what happens.

I feel your plan is not a good one.

Thanks for the feedback, Ed. Yeah, the back and sides are together, and this top is finished, but there's still a lot of work to do, and I'd probably be better off just bracing another top for him.

_________________
Ken Mitchell
Durham, NC

...or removing the current braces, and re-bracing this top.

_________________
Ken Mitchell
Durham, NC

My thought is the same as Ed, and this is from harsh personal experience. Was it at a good RH when it was braced, and what RH is it experiencing now? If it is just unusually dry now it will probably get its radius back when returned to a mid-range humidity. More problematic would be if it was braced in conditions of high humidity. I did this once before I understood the issues and I braced a top on a wet and humid day when the RH was probably >80%. It looked great, but then went completely flat at RH 50. If that is the case for your friend’s top then it would be wise to take those braces off the thing and do it again in appropriate RH conditions.

Indeed. This is a case where saving a bit of work could cost a lot of work…

If it has some radius, once it is strung up the top should "pull up" some, so it might be O.K. Some people build with flat tops anticipating that the strings will pull a radius in them.
But.... Once you take on the task of finishing it for him, its success or failure will be a reflection on you.
You could shave the X brace down and laminate it back up (a la Fred Carlson) adding some arching back in as you do so. This might be one way to put the dome back in without completely re-bracing the top.

I would be reluctant to use it because so much time has gone by that it has likely taken a set. When I compare the difficulty of bracing up a new top in proper RH and with proper handling vs. possibly dealing with a continuously variable neck angle on this guitar every time the wind blows I'd go with a new top.

I've posted a tale of taking a braced top on my back deck with a nice scotch and water and in 20 minutes the sucker went flat. It came back in a few days but the lesson was learned that these things move a lot until they are attached to the rim and even some after that.

We deal with badly deformed necks a lot and you can heat press them straight again but once they took a set it won't last they will revert.

Thanks, everyone, for your thoughts and experiences. This top was braced in proper RH conditions, but over the past few years it has spent time in several places, with a wide range of humidity. I think I'm going to play it safe, take these braces off, and re-brace the top. That way my friend will still see his top and rosette, but I'll be confident about the bracing.

_________________
Ken Mitchell
Durham, NC

Wise!

That sounds like the best of both worlds, good idea Ken.

you can rebrace it

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

I would retrace it. I once took a braced top from Hawaii to Spokane, WA it had a reverse concave within 15 minutes. This was before I understand the importance of RH. I was taking the top for my Uncle Pat to evaluate. Well I retraced it when I got back home

_________________
https://www.instagram.com/fostinoguitars/
https://www.facebook.com/PuraVidaUkuleles/

Retrace the heritage of the tree? Just kidding.