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I'm building this 'Experiment' Guitar, for the sides and back I used Walnut, everything was looking good until I pulled the sides out of the mold last night to do some sanding on the kerfing...

I guess while sitting in the mold they developed a lump around the middle part of the body, you can't see it but you can feel it. So now I'm unsure what to do about it, I have some bracing around the sides and can take the sides to the belt sander and get them flat without removing too much material (I hope). But if I do that

I'm worried they will warp again, any ideas on how to approach this one?? I was thinking of making some small plywood slats, pressing the sides together with a heating blanket (to get them flat) and then applying some heat to see if they will straighten out. It would be easy if I had caught it before the stupid kerfing was on..

HEEEEEELLLLLPPPPPPP!!!!!

-Paul-

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-Paul-

Patriot Guitars

Hey Paul I am having a hard time envisioning this, Got any Pics?

OK here is a closeup of the side:



And another shot:



Here is the kerfing and bracing:



It's flat in the cutaway, at the heel and mortise (of course) and seems to be pretty good at the waiste...

-Paul-

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-Paul-

Patriot Guitars

Paul,

I had this problem with some maple sides once, (I put it down to not running enough hot/cold cycles in the bender) I cured it by spritzing, then heating the side up with the blanket and clamping it using some sections of steel slat and wood blocks. I ran the cycle a couple of times, then left it 48 hours and it worked fine.

Hope that helps, the sander should be the very last resort!

Colin

PS I don't know if this is less likely to happen with solid sided moulds? Just a thought.Colin S38420.2010763889

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

I got a bit of this kind of thing happening in the set of Khaya (African Mahogany) sides I bent. Less than here, and I could sand it out, but I blame it (in part) on the fact the mold I've got isn't completely solid; the 'wave' lines up. The new ones will be fully solid for this reason. It's marginally more work, but I feel full support can only be a good thing.

Paul,
What type of walnut is it? How thick are the sides right now? Does it flatten out where your side braces are?

   You didn't way how you bent. I do see this happen with rift cut and when people use too much water or not enough heat.
   You want the heat to be about 275-300 for about 3 minutes . If you soak the wood , then the outside dries and the moisture inside will warp on its way out.
    looking at the nice quarter you have I suspect not enough heat , or the bending method. If you go the
http://www.bluescreekguitars.com
   there is an article there that will explain how I bend. Every now and then wood will warp and that is the nature of the business , but that set looks too good for the wood to warp on its own
john hall

I bent this set just like all my other ones, this is the first set that did this, I left each side for at least 6 hours in the bender and ran them through multiple cycles of heating and cooling. They came out with very little springback so I assumed they where fine.

I like Colins idea and will try that tonight, it's only in the lower bouts that it did this.

Brian it's just standard CA Walnut, I got it from AC Woods, it was a nice quarter sawn set.

All I'm interested in now is how to fix it, I don't want to start over on this one...

-Paul-

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-Paul-

Patriot Guitars

I bend alot of sides. Sometimes this is the nature of the beast. It you over cook the wood you will end up making it too dry and it will split down the road.
   Good luck. Support the sides well. Use .025 stainless or springsteel slats. Also here is a hint for next time if you are using a machine , don't set the waist first. Let it about 3/4 " off the pattern till the bouts are set , then set the waist , this pulls the wood and sets the wood under a little tension with the compression.
   

I thought it might be Claro, not because of the look but moreso because of the "warping". Until Claro is very dry it leans toward being a lesser stable wood. Even when dry it can present some challenges and it may not be a bad idea to lightly seal the inside of the guitar. Might want to think about some extra side braces also (just a thought). It is a pretty wood. I do agree that sanding is not the answer.....you might be opening up a whole new can of worms with that.

Thanks for the tip John, I'll give that a try. I used to use two sets of steel when bending but found I can get better tension by using just one with the wood over the blanket and the blanket over the steel.

I'm going to try getting them flat tonight with a small blanket and see what that does...

Thanks

-Paul-

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-Paul-

Patriot Guitars

Well I fixed it but by taking it to the sander, it's pretty stable and not too thin, I like my sides a little thick so there was some room to flatten it down. I'm thinking about adding more bracing to the sides but I'm not sure it will make all that much difference, Kenny Hill once told me that wood's a pretty strong force when it want's to move....

I was nervous at first, but the paper on the sander was a little old so I was able to go slow...

Seems fine now...

-Paul-

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-Paul-

Patriot Guitars