Official Luthiers Forum!

Sorry, no pics as this is just coming to mind as I sit here at work (sighhh). Anyway, one of us is about to attempt his
first acoustic build (now, let's not go name dropping, ok?) using Sapele for the back and sides. I found some pre-bent sides, as I thought bending wood might just push me over the edge so I cheated. Anyway, from a gracious gift, I've picked up the back & soundboard pieces, along with some bracing, a fretboard and trussrod. Yay me! The soundboard just came out of the "clamps" from joining as I was about to apply the same to the back, I realized that Florida humidity has caused both pieces to warp up in the middle.

Now, I'm very limited in my woodworking knowledge, to the point that the very first piece of "woodworking" I've ever done was a Les Paul build. So bear with me where I lack the proper background and information. But it seems logical it to me, to try and get the wood back to it's "flat" state and I did so by using a billet of Maple, a little under the size of each piece, stacked atop the two pieces, whic are on top of each other, ALL topped off with an extra battery (i.e. car battery) I had in the shop. Will this be sufficient to get it back to where I want it, or should I be doing something different? THis time of year we can go from 88degrees and sunny with 85% humidity, to 65 degrees and misty pretty much in the same day and I'm assuming this is what's caused it.

So, what should I really be doing and when will it be safe to join those pieces? Thanks in advance, by the way. I learn a lot around here!

Hey - welcome to the obsession... lots of fun ahead of you.

So, if I get your right, you've joined the top, but haven't glued any braces yet.. and still it's warping a bit. So... you're going to have some challenges if you get swings in humidity as you build. Anything you can do to stabilize the humidity in your shop will be good. Temperature swings are less of an issue - certainly within the range you're describing. I think what you've done is fine.

At the end of the day, the real challenge is when you brace the top and back. If you do that when humidity is relatively high, then it drops, you're going to have real problems. braced top will look like a potato chip.

You want to try and glue the braces, and close the box (glue the top and back to the sides) when the humidity is either stable or on the lower side (in Florida that's never going to be very low, I'd imagine, unless you get a cold snap and your heat goes on for a couple of days.) I think if you can get a hygrometer, and a dehumidifier, run it for awhile, and let the wood acclimate, then try and get the box built while it's in the 50 - 60% range, you'll be ok.

I don't think that any of the other steps in building are as sensitive to humidity (well, except finishing, but that's a different story) as gluing the braces and closing the box.

Eric,
Welcome from a fellow Floridian. For what it's worth, I do most of my cutting and sanding in the garage or outside, but I've learned to do my gluing inside on the dining room table (when my wife is not around) or the pool table. I, also, keep most of my back, side and top woods inside in old cedar chests.
Marty

Hi right back!

I haven't joined the back yet. I was about to when I found the two pieces bowing up in the center. I figured if I could get
them flat again, then once I joined them I would add the braces to hopefully prevent a re-occurance.