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Hi, as of a few minutes ago I am new to this forum. I have a Martin kit that I purchased about 15 years ago, and have finally decided to build. All of the wood looks to be in good condition, except the rosewood back panels are somewhat warped. I am thinking of soaking and clamping them between some melamine shelving to flatten them, any suggestions? They have both slight twist and bow which I think would be flattened when the back is braced, but I would like to correct before joining-there will be a herringbone strip between them which has a twist of its own...

Thanks, Bob

First when you say warped do you mean bowed as in across the grain or warped as in in both plane, bowed and twisted. My guess is it is bowed. If so lay it dry cup down on a concrete floor for several days. Then sticker it between 3 1x1 spacers for about a month and all should be fine. If in deed it is both bowed and racked the I would do the sane thing the concrete will draw out most of the bow and stickering will help relieve the racking if not too bad.

Welcome to the forum, Bob.

I wouldn't soak them. Maybe lightly spritz with water then put some weight on them for a couple of days. You need to sticker them so air can circulate around them, otherwise they might mildew. You don't want to get them too wet, and then have to wait for them to thoroughly dry again. A few days under weight should flatten them well. Someone else will chime in here, but seems like they only recommend spritzing one side, but I forgot which one.

You might get by without any water if you can leave them alone for a few weeks. Build the neck, or cut braces, etc. while you're waiting.

What part of the country are you in, Bob?


Ronold man39078.7375810185

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OLD MAN formerly (and formally) known as:

Ron Wisdom

Somewhere in the middle of Arkansas......

Two methods to consider:

If they are dished, lightly dampen the concave side and lay them on a concrete floor concave side down and place a weight on top. It rarely takes more than overnight for them to flatten.

If they are more stubborn get nine stickers, (strips of wood) three the width of the backs and six a couple of inches longer.   Make layer of long stickers, back, short stickers, back, long stickers, have the two concave faces on the outside. Then place a cable tie over each pair of the longer stickers and tighten, lightly spritz the outside concave faces. As the wood flattens gradually tighten the cable ties. Leave them for a couple of weeks to really set flat.

You stack should look like this ( except not in Mad Rose!)



ColinColin S39078.7453935185

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

How thick are the back pieces? You probably don't have a drum sander? IF you have access to a drum sander take it down to say .140 inches, joint and join.

It's not uncommon for wood to get that way, cupping too. By sanding you can sometimes eliminate some excess warpage, and it thins the boards which makes them less strong than when thick rough back pieces.

Seems like my Martin Kit didn't need much sanding on the back. Wetting and stickering is a way to go though, if you have a few days to spare. What the heck, it's been fifteen years, eh?

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http://www.dickeyguitars.com

Hey Wirebender (electrician?)

I forgot, but I heard it here once, get a clothes iron out and iron the panels flat, no kidding.

You might want to take a spray bottle and hit with a light coat of water, then just iron 'em.

Before you laugh too loud, think about this, the sides get ironed into a curve, so why not iron a curve flat? Good luck and oh yeah, welcome to the OLF.

Great suggestions everyone.Bruce Dickey39078.7530324074

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http://www.dickeyguitars.com

cupping comes from one side being drier than the other. the drier side naturally shrinks relative to the wetter side leaving the cupped effect, the drier side concave whilst the wetter side is convex.

by placing the wood cupped(concave) side down on a concrete floor the concrete will impart a certain amount of moistur to the wood bringing it bach into moisture balance.

the spritz or a light wipe with a damp cloth can do the same.

Hey, ironing with a clothes iron works like a charm. It takes a while because they really need to get thoroughly heated up, just like bending a side.

I put a piece of 3/4" plywood on top of my table saw and start ironing one of the top halves on it. Work slow and keep the iron moving. No real need to add moisture. Have the iron turned up quite high. After a bit, flip the piece over and work from the other side. After a few flips it will magically relax and start to flatten out. This can take 10 minutes or more, so don't give up too early. When it gets where you want it, quickly slip it under the plywood sheet and the cast iron top on your table saw will act as a heat sink and cool it down while you iron the other half.

I consider a clothes iron a very important tool in my shop

Grant

Grant!

I knew I'd heard that somewhere. Based on what I'd heard, the old house iron made it down to my shop. Hey I like the plywood and table saw heat sink idea too. Plus, moisture driven from the wood into the plywood is added to the other side sort of equalizing the moisture of both sides.

I believe it was Taggart who I saw first using the concrete to straighten Brazilian.... well.. he shared it online.

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http://www.dickeyguitars.com

Wow, thanks everyone. Of course after 15 years I'm looking for the quickest way to get started so I'll probably try the iron unless someone vigorously objects. I had thought of something similar, clamping the plates to the tablesaw extension and heating the table from below, but preheating with the iron sounds less fraught with unintended consequences.

My family is infamous for unfinished progects, and at Christmas dinner my brother challenged everyone present to commit to finishing something and presenting it next Christmas. The guitar is my progect, and I intend to finish it and several more before the deadline...tomorrow the boxes of tools from LMI will be delivered...I will keep you posted!

By the way, Ron, I live in Big Bear City, CA, up in the mountains above San Bernardino

Bob

Bob, just don't use an iron that your significant other is attached to. Things will not go well for you. Bad mojo using it and then there is the couch issue.

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Aoibeann

[QUOTE=Aoibeann] Bob, just don't use an iron that your significant other is attached to. Things will not go well for you. Bad mojo using it and then there is the couch issue.[/QUOTE]

Well, If you are any kind of a decent guy/gal, buy her/him the fanciest new one that you can find and "dispose" of the old one in the shop. Maybe get her/him one with an operator if you want to really shine

Grant