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| HELP : Warped Back and Sides http://www-.luthiersforum.com/forum/viewtopic.php?f=10102&t=4677 |
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| Author: | peterm [ Mon Jan 23, 2006 4:26 am ] |
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I was about ready to thickness sand a set of figured walnut back and sides when I dicovered one of the backs and one of the sides is warped!  they're both bowed straight down the middle. 
Very strange....one side and one back!! Does any one have an idea how to get them straight enough to sand in a short period of time so I can start my guitar? Thanks for any input! |
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| Author: | Michael Dale Payne [ Mon Jan 23, 2006 4:37 am ] |
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I have never had to do this but I believe I heard you cand set it on concrete cup side down overnight and the concrete will draw it down. I assume that the concrete is drawing out the extra moisture from the wood. Typicaly I sticker warped wood with several equally spaced sticks for several months and it takes care of it self over time. |
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| Author: | Colin S [ Mon Jan 23, 2006 4:49 am ] |
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I cured this once by spritzing, then stickering (sticker, side, sticker, side, sticker)and using cable ties on the ends of the stickers to pull the whole pack flat, use four sets of stickers on the backs and five on the sides. Leave for a week and they should straighten out. Take them out only when ready to thickness. Shouldn't be a problem once you have taken them to thickness. Colin |
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| Author: | RussellR [ Mon Jan 23, 2006 5:02 am ] |
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Hi Peter Colins suggestion is a good one I would spritz, Lay on a flat hard surface with the center part of the bow sticking up and then put some weight on top. |
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| Author: | tippie53 [ Mon Jan 23, 2006 5:20 am ] |
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warping is a state of wood. If it isn't stable warping will happen or if you have a moisture problem. The setting on concrete is not a good idea as you want to take moisture out not put it in. If I am prepping wood for building I will see that the moisture content is at least 8% or lower. You can flatten the wood using a hot iron without steam and the heat will help. Start on the high side and as you dry it and make it "flexible" this will take about 10-15 minutes , keeping the iron moving. WHen this happens you should be able to press it flat overnight , then process it. Once you bend it and get the backs glues and bracing things should hold. john hall |
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| Author: | LanceK [ Mon Jan 23, 2006 5:21 am ] |
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I have set a really warped set of india back plates on my cement shop floor and the next day there were flat as a' um - board 
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| Author: | Don Williams [ Mon Jan 23, 2006 5:27 am ] |
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Heat blankets & heavy aluminum plates....works great. |
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| Author: | peterm [ Mon Jan 23, 2006 5:30 am ] |
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Thanks guys! I'll try the cement floor and if that doesn't work I'll iron it like John suggested! |
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| Author: | Shane Neifer [ Mon Jan 23, 2006 6:17 am ] |
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Yup, you got some ideas Peter, I wouldn't suggest adding water, better to just dry the other side. One side has probably picked up more moisture than the other. These thin bits move around like CRAZY!! You could even use a hair dryer or heat glue, carefully, on the convex side and I bet it would start to flaten out. Shane |
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| Author: | Grant Goltz [ Sat Jan 28, 2006 10:54 am ] |
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Just saw this post (I have been gone to the wilds of northern Manitoba for a week and just got back). It sounds like what you have is a set that is the first two slices from the outside of a case hardened board. The cupped half is the first slice and the flat one, the second. The cupping is not related to a moisture difference, it is wood cell damage during too rapid drying. What happens, and some woods are more prone to this than others, is that when boards/planks are dried too fast, the outside dries way faster than the inside of the board and tries to shrink. This also tries to compress the wood cells on the inside of the piece (which have not begun to shrink since they are still at a high moisture content). At a later stage of the drying these inner cells will shrink as they dry, but since the outer "skin" of the board has already taken a set from drying, the inner cells end up smaller than the outer cells. This sets up stresses in the board which shows in the cupping of the outer slice. Hope this is not too confusing
You can sometimes temporarily relieve this with heat, moisture, etc., and can often flatten the slice so that you can thin it (and keep it fairly flat because it is then more flexible), but you have not really eliminated the basic problem which is wood cell damage. There is no quick fix that really gives you stress free wood. Two things that are longer term solutions seem to work. First, if you suspect case hardening, you can rehydrate the board and then dry it again slowly. One thing that I almost always do when I suspect case hardening (for example when I get cocobolo that I know or suspect has been kiln dried - almost always has some degree of case hardening) is to store the boards for a couple of years under conditions of high seasonal moisture. The boards shrink and swell over a few seasons and pretty much even out. I let them slowly air dry another 6 months or so and then resaw, most of the problems are gone. The other fix is one for after the case hardened wood has been resawn and you have the cupping. In this case, I soak both slices until they are back to green moisture content. This may take a week and the surface may get a real ugly color. I then sticker and dry slowly and things usually come out fine. You cannot just treat the cupped half because you need to restore both slices to the same condition. Now, this does not solve your problem of wanting to get on with your guitar build, but hopefully gives some information that might be useful in the long run for folks. Grant |
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