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Bellying Tension vs. Humidity
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=25139		 Page 1 of 1
Author:  sprouseod [ Tue Dec 22, 2009 8:38 am ]
Post subject:  Bellying Tension vs. Humidity
Just curious if there is a way to tell if a guitar has bellying of the bower bout due to string tension vs. high humidity?

Thanks
Richard
Author:  Barry Daniels [ Tue Dec 22, 2009 9:38 am ]
Post subject:  Re: Bellying Tension vs. Humidity
Tension related bellying is usually seen as a hump behind the bridge. Humidity caused bellying is spread out over the whole top and is not directly noticeable. It is mostly observed by higher string action. There could also be a combination of the two.
Author:  sprouseod [ Tue Dec 22, 2009 10:30 am ]
Post subject:  Re: Bellying Tension vs. Humidity
The action is definitely higher, not unplayable, but noticeable. Also there is a faint crack in the finish along the center seam in the lower bout that starts at the bridge and dissipates as it approaches the back of the lower bout. It is most noticeable over the hump. I do know it is a water bases finish like KTM-9

Richard
Author:  Barry Daniels [ Tue Dec 22, 2009 10:56 am ]
Post subject:  Re: Bellying Tension vs. Humidity
The crack may be your problem. Are you sure that it doesn't extend into the wood? You may want to take the string tension off until you get it repaired.
Author:  sprouseod [ Tue Dec 22, 2009 2:30 pm ]
Post subject:  Re: Bellying Tension vs. Humidity
I looks like it is in the wood. I took the strings off and got inside, you can feel the crack from the inside as well

R
Author:  mhammond [ Tue Dec 22, 2009 2:31 pm ]
Post subject:  Re: Bellying Tension vs. Humidity
I have noticed that the KTM causes the hide glue on the center seam to swell up and show a little bit. I'm have not been able to figure a cure for the problem yet. I do know that it will become less noticable with time
Author:  Barry Daniels [ Tue Dec 22, 2009 3:18 pm ]
Post subject:  Re: Bellying Tension vs. Humidity
sprouseod wrote:
I looks like it is in the wood. I took the strings off and got inside, you can feel the crack from the inside as well R


Then you should repair it by working some glue into the crack. Then you may want to add some small spruce cleats in the open areas between braces to reinforce the joint.
Author:  sprouseod [ Tue Dec 22, 2009 3:34 pm ]
Post subject:  Re: Bellying Tension vs. Humidity
will do

thanks
r
Author:  Brook Moore [ Thu Dec 24, 2009 12:23 pm ]
Post subject:  Re: Bellying Tension vs. Humidity
If the glue joint itself has failed, then the real issue is what glue was originally used. If the top joint was glued with hide glue, then you are in luck as this is the easiest repair. If the top was glued with yellow or white glue, then you cannot just use more glue of that type and expect it to hold. CA is the only glue that I have found that will reliably stick to cured Titebond. Perhaps polyurethane will adhere, I have not tried it.
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