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| 3 piece back http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=24697 |
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| Author: | clutch [ Fri Nov 20, 2009 8:13 pm ] |
| Post subject: | 3 piece back |
Hello, this is my first post. I recently started building my first acoustic guitar (standard dreadnaught) My problem is this. I glued up the 3 piece back then glued in the bracing in a radius dish. Everything came out fine, but after about 2 weeks ( working on other parts) I find that the radius has flattened somewhat. Any body ever had this problem & is there any solution short of starting over? p.s. back is curly maple & yes, bracing was pre-radiused Thanks, Clutch |
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| Author: | woody b [ Fri Nov 20, 2009 8:38 pm ] |
| Post subject: | Re: 3 piece back |
I suspect the humidity was high when you glued it up, or it's low now. |
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| Author: | Steve Saville [ Fri Nov 20, 2009 8:41 pm ] |
| Post subject: | Re: 3 piece back |
Clutch, You have just learned a very valuable lesson about humidity. The wood movement is due to changes in wood moisture content. You have to learn how to control that before you try building. You need to keep your wood working/storage environment near 45% RH or you will have major trouble. |
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| Author: | truckjohn [ Fri Nov 20, 2009 11:44 pm ] |
| Post subject: | Re: 3 piece back |
As stated by others -- you probably glued up the bracing while the Relative Humidity was higher... Once it dried out some... the back shrank more than the bracing and Ka-Boing... you have a cupped back! Chisel off all those braces and then figure out how to dry things out real good before you glue again. One solution is to do work like this indoors in the AC or heat... bring the parts inside and let them acclimate for a couple weeks... then go for gluing.. Another solution is what Cumpiano states for a non-climate controlled shop: Wait till the weather is going to be fairly stable for a couple days. Have things ready so that you can glue the top or back to the rims within 24 hours of bracing it up... The Old Luthier's solution was to do all of your top and back bracing and box closing during the Winter heating months... and don't turn the shop's heat off... This ensures you are gluing braces and closing boxes only during the times of year when your shop was dryest... So far, I haven't had any trouble with Option #1 -- I like to keep my tops, backs, and sides in the house in AC space. Seems to help quite a bit with humidity control... so I don't have to rush like the dickens getting things braced up and glued to the rims.... or limit my Box Building work *Only* to our short South Carolina wintertime. Thanks John |
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