Guitar bellying out

[DarkHorseJ27]

I was playing my Parker and noticed that the soundboard beneath the bridge looked higher that the soundboard above the bridge. I held a ruler against the soundboard to confirm that diagnosis.

 

The guitar was severely dehydrated when I bought it, but has been properly humidified since I've owned it, if that makes any difference. It came with a one year limited warranty, but its already been over a year.

 

So far it is minor, so I'm wondering what I can do to help stop it. Switching to a lighter gauge string is one thing (currently has .12's on it). The JLD Bridge Doctor (http://www.stewmac.com/shop/Tools/Special_tools_for:_Bridges/JLD_Bridge_Doctor.html) is another possible option, but it requires surgery. Any other options?

[S~R~O]

This is from; http://frets.com/FRETSPages/General/faq.html#Bulge

 

I've had a hard time trying to find information regarding top warp (behind the bridge). From what I understand acoustic tops are never flat, but I've noticed on my guitar that it is warping behind the low E & A and not behind the High E and B area

behind the bridge. I use light gauge strings and I was wondering if this was normal warpage, and if this will worsen in time.

- - - Scott Blanchard, Harrisburg, PA

 

Hi, Scott.

 

Well, it is possible that you have some real trouble there. In a healthy guitar, the "bulge" behind the bridge usually takes the form of an overall "dome" rather than having a lumpy appearance when viewed in reflected light. Now, sometimes the bracing inside simply "translates" through the top to reveal the location of brace ends, where there's no damage or difficulty. Where there is a pronounced "wrinkle" in the top behind the bridge, it's often a sign that the top has become loose from the X-brace in that area. As far as I know, there is only one cause of this looseness: excessive heat. In a hot car, the temperature can get to about 175 degrees Fahrenheit, and most guitars are made with glue that loses strength at 120, failing completely around 150 degrees. If you'd like to see some detail on this subject, I have an article posted here on FRETS.COM entitled "The Loose Cross Brace Top Wrinkle."

 

Lots of musicians bring me their guitars, fearful of the top bulging too much. Most of the time I can assure them that their guitar has a normal appearance. But these things can be subtle, so I suggest that you get in to see a competent luthier for an examination and opinion. (http://frets.com/FRETSPages/pagelist.html)

 

FF, 12/3/99

[Freeman Keller]

 

I was playing my Parker and noticed that the soundboard beneath the bridge looked higher that the soundboard above the bridge. I held a ruler against the soundboard to confirm that diagnosis. The guitar was severely dehydrated when I bought it, but has been properly humidified since I've owned it, if that makes any difference. It came with a one year limited warranty, but its already been over a year. So far it is minor, so I'm wondering what I can do to help stop it. Switching to a lighter gauge string is one thing (currently has .12's on it). The JLD Bridge Doctor ( http://www.stewmac.com/shop/Tools/Special_tools_for:_Bridges/JLD_Bridge_Doctor.html ) is another possible option, but it requires surgery. Any other options?

 

 

The quote from Frank Ford says a lot, but I'll add my experience.

 

Tops on acoustic guitars are built with a slight dome - usually about 25 foot radius. A straightedge at the bridge will have 1/16" or so clearance at the sides of the lower bout.

 

The top on dry guitar tends to sink in, conversly, an over humidified guitar might bulge slightly.

 

Loose braces or bridgeplate might contribute - tap on the top and listen for rattles or look inside with an inspection mirror. Fairly rare, however, but it does happen

 

All guitars are trying to "bend in half" under string tension - the saddle acts as a lever to pull the lower bout up and push the area between the soundhole and bridge down (in fact, that is how they "make sound"). Lightly braced guitars more than over built ones (and their is a tendency with modern guitars to brace them lightly to get instant gratification out of them).

 

Guitars that need neck resets frequently have bellied lower bouts. My old D12-28 had a big belly which mostly when away when the neck was reset. Your guitar seems awfully young for this, however.

 

The JDL might bring the top down but it might also introduce all sorts of other problems. It was a disaster when I tried one on my D12-28 (before the reset) and there was a long discussion over at UMGF where NONE of the Martin luthiers and repair techs had anything good to say about them. If you want more info, let me know.

 

12's are considered "lights" - each step of gauge will change the top tension by 10-20 percent. You can also down tune (each half step is about the same tension as on string gauge). You will loose volume by going to lighter strings. Personally I would look elsewhere.

[DarkHorseJ27]

I know there is always some bulge. But the bulge is higher south of bridge and higher north of the bridge, with the bridge tilting towards the soundhole. I don't believe that is normal. But I will check for loose braces.

[Guitar Hack]

Hows the action on the guitar? If too high that might be causing it.

[DarkHorseJ27]

 

Hows the action on the guitar? If too high that might be causing it.

 

 

The action is rather low. Upon investigating further I believe the mistake may be mine. With the way I was measuring combined with the bass balanced bridge made it look like the guitar was bellying higher on one side of the bridge than the other.

 

But I'd rather be wrong than to have something {censored}ed up on my guitar.

[boxorox]

A little bellying is built in. A little bellying over time is natural, and taken into consideration by builders. If it looks like asymetrical warpage or interferes with your ability to set the guitar up to be playable, see your tech.