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| Help! Flattening a cupped veneered panel http://www-.luthiersforum.com/forum/viewtopic.php?f=10101&t=43837 |
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| Author: | MikeyV [ Fri Jul 18, 2014 1:05 pm ] |
| Post subject: | Help! Flattening a cupped veneered panel |
Greetings! On my current (slow) build, I'm trying laminated sides and back. (trying out the Martin thing of laminating D. nigra onto some red spruce.) So, I veneered both back halves, one side came out perfectly flat, the other cupped (longitudinally). If you put it on a flat surface, the middle is about 1/8" up. Unfortunately, it's warped the opposite way that would had been useful (the way the back is arched when built.) I have a lot vested in this veneer…the sides and back are all matching, and I'd hate to have to revenuer the back to get it flat. Question: Can I flatten this somehow with heat or moisture? It's glued with titebond I. I thought of wetting the concave side and clamping it flat…nothing. Next, I thought of clamping it between some metal plates or something similar and baking it at like 200F so the glue would soften and then let cool. My last drastic thought was to soak the veneer off and re-glue it when dry. YIKES! Any help would be greatly appreciated. You guys always set me straight. Thanks! Mike |
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| Author: | Lonnie J Barber [ Sat Jul 19, 2014 12:21 pm ] |
| Post subject: | Help! Flattening a cupped veneered panel |
Well Mike it looks like your not getting much response. So I'll give you my what I'd do not holding the thing in my hands. I've learned a saying over the years. There's never enough time to do it right. But there's always enough time to do it over. That sorta says do the last thing you said. Be careful soak it off there and redo. Good luck buddy. Not much help but it does amount to a bump. I'm always wrong so you'll probably get more response now. Good luck and good night. Lol Sent from my iPhone using Tapatalk |
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| Author: | johnparchem [ Sat Jul 19, 2014 12:46 pm ] |
| Post subject: | Re: Help! Flattening a cupped veneered panel |
I have never worked with laminated plates so take my advise with a grain of a salt. If you are talking about a smooth curve the length of the plate I am wondering If you can leave it. Join the laminated plates. The plates are going to be braced for the back and then glued to the rims. I am not sure bending the wood to deal with the extra .125" across the length of the back would make that much of a difference. The radiused sides should hold the correct arch. With two different wood laminated together you made a hygrometer. The woods react differently to moisture causing the curve. |
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| Author: | MikeyV [ Sat Jul 19, 2014 1:06 pm ] |
| Post subject: | Re: Help! Flattening a cupped veneered panel |
Lonnie, much appreciated. Thanks for the advice. John, I've thought that I could just go ahead and build with it. It's really thick right now, like over 0.150". I usually take backs down to at least .100", and often less. I think this could go down to .090" at least, being that it's adirondak and laminated (stiff). One thing I'm worried about is that once thinned, it will warp even more. Thanks guys! |
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| Author: | Lonnie J Barber [ Sat Jul 19, 2014 1:30 pm ] |
| Post subject: | Re: Help! Flattening a cupped veneered panel |
See I told you:0) Sent from my iPhone using Tapatalk |
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| Author: | wbergman [ Sat Jul 19, 2014 2:08 pm ] |
| Post subject: | Re: Help! Flattening a cupped veneered panel |
I concur with the approach to just go ahead with it. I think that a 1/8" gradual warp will not "fight" against the arch that you will impose with the bracing. I have had a lot worse result by bracing at the wrong humidity, which had to be redone--but that is another issue. |
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| Author: | James Ringelspaugh [ Sat Jul 19, 2014 2:40 pm ] |
| Post subject: | Re: Help! Flattening a cupped veneered panel |
Yeah, 1/8" over the length of a back is nothing and it will certainly be easy to work with once thinned to final thickness. I wouldn't sweat it one bit. |
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| Author: | SteveSmith [ Sat Jul 19, 2014 2:46 pm ] |
| Post subject: | Re: Help! Flattening a cupped veneered panel |
Yep, I would just join it and sand it to thickness. I would expect it to be just fine once it is braced. Nothing to lose anyway, I think trying to remove and re-glue would be hard to pull off and could leave you worse off than you are now. |
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| Author: | MikeyV [ Sat Jul 19, 2014 4:23 pm ] |
| Post subject: | Re: Help! Flattening a cupped veneered panel |
I guess my worry is that the glue lamination line and veneer is what's holding it into the cup, not humidity. And when the spruce is thinned, the veneer/glue will pull even more cup into it. The guitar is not for anyone, just a build for me. So I'm willing to roll with it. Does anyone think that I could clamp the piece between two cookie sheets and put it in the oven at 175 degrees to soften the tite-bond, then let cool? Does Titebond work like that? Where is re-hardens after being heated? Or would this just destroy the glue? At least it's not a structural joint. I'll report back at some point. Cheers! |
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| Author: | MikeyV [ Sat Jul 19, 2014 4:24 pm ] |
| Post subject: | Re: Help! Flattening a cupped veneered panel |
Lonnie, you crack me up. Thanks man! |
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| Author: | RusRob [ Sun Jul 20, 2014 12:39 pm ] |
| Post subject: | Re: Help! Flattening a cupped veneered panel |
Mike, You just learned the advantage to using HHG for laminating veneer. On veneering you usually apply the HHG to both sides and let it set. When you are ready to laminate the two together you would position them and run a hot iron over them to re-melt the glue. If you did end up with a bow in it then you can just heat it up again and flatten it out or put a slight reverse bow and you will have a flat panel. Titebond is not so great for re-do's. The main reason is it will not stick to itself once it is separated. You need to scrape all the glue off back to bare wood before regluing. HHG can be heated, separated, heated again and will hold like the original joint. I would tend to agree with the others that when you brace it you will be just fine as long as there are no buckles between the braces and you get a smooth surface. But I don't have any first hand experience and that. I do have some veneering experience with HHG so that part is what I do know. Hope it works out for you but next time think about using HHG. Cheers, Bob |
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