Guitar bellying ?

[krauser2]

I know this is normal as guitars age, but what are ways to reducing this even if just by a little?

I use 11's, so they are still considered light, with a straight edge it looks like I could benefit from the belly being a little lower before I go and get the neck reset, refret and nut/saddle changed out

I know about the JLD bridge doctor, but what are other options, this seems to be a hard topic to find solutions to

 

[Scratch]

There's a couple of threads on here somewhere, Krauser. Several members have used the bridge doctors with success. My G312 had a bit of a belly when I bought it last October. I replaced the strings and with lights; swapped out the saddle, played it almost nightly for several weeks and the belly eventually disappeared. I'm not really smart enough to know why, but it worked!

 

[capnjuan]

The deck isn't built perfectly flat; it's supposed to have some crown to it. Gotta pic with the straight-edge on the deck?

 

[chazmo]

A little belly is pretty normal.

But, if it is possible that you might be over-humidified. That's a possibility for causing belly. I'd try loosening the strings for a few days and dropping the humidity a bit (to maybe 40-45% RH). See if that helps.

Yes, the JLD bridge doctor has gotten all positive reviews that I've read on the boards, except one guy cranked the thing too much / quickly and ended up breaking his bridge.

Breedlove guitars use the thing as standard equipment, and a couple that I've played are absolutely marvelous. *However*, if you use an under-saddle transducer, you may have issues with the placement of the thing. Keep that in mind. My luthier wasn't able to install a K&K pure western mini system in his Breedlove.

 

[krauser2]

i'll throw in a couple slica packs and keep the case closed

I checked the crown with a ruler i guess is all out of wack.....

i found a sturdier straight edge and its actually not that bad, I'll still keep on eye on it

it gets pretty toasty in the summers in SC and my AC is broke

 

[Mr. P ~]

Martin's don't start sounding good till they get a little belly.

A small amount of belly is good, but as it increases the action gets higher. If it goes too far braces start to come loose, and of course you don't want that.

Most guitars that do not have a problem will belly to a certain point and stop.

Lighter strings as you have done is the best solution.

 

[Mac]

I agree with all the above-- I've had and still have a few old guitars and some bellying is quite normal. As long as the instrument is stable then it's all right-- a point of balance has been reached, and yes, some guitars do need a bit of pooch to voice properly. IMO what to watch out for is a hollow developing at the bridge side of the soundhole, sometimes actually associated with a lowering of the action-- this is definitely Not Good.

Having said that, unless you have had a guitar from new you have no idea of the abuse it previously suffered. I have an '82 Yamaha L15A, handmade, all solid (if you see one of these for sale at least try it-- lovely instruments.) Anyway it's a lightly built guitar but the top has only a very slight belly, probably because I bought it new, never string it with anything heavier than 12s and ensure that it's slacked a couple of steps if I'm not going to be using it for a week or more. On the other hand I have had, to quote two memorable examples, a '69 Martin D18 and a '74 Guild F48 which both had been seriously overstrung for years with predictably severe damage to the top.

This is a long way of getting to say this: The JLD Bridge Doctor is a real saviour in cases like these. I sold the Marty and the F48 because the cost of neck reset and other work was just too much; I have been kicking myself for it ever since I discovered Bridge Doctors. Not only do they cure the problem, they actually improve the tone, partly by themselves but also because they let me confidently use 12's when I would otherwise go to 10's just out of sympathy for an older instrument.

Bridge Doctors are going on all my older acoustics now as a matter of course. My JF65-12 was the most recent recipient and now she is even more wonderful than she was before, which is really saying something, plus I can run the nice big strings that make her really sing with no worries. I really can't see a downside to this wonderful device except maybe that I didn't invent it!

 

[Mac]

Hi

I don't want to take this over but I was chatting about this to an engineer friend of mine last night and we made some (I think) interesting observations.

First, the string pull on a steel-strung guitar is 200lb or more. This is a pull parallel to the top. The dimension between the top of the bridge saddle and the table creates a lever, producing a turning effort or moment of around 65 inch-pounds about the bridge.

Conventional X-bracing has the effect of concentrating the stress on the top at a point between the bridge and soundhole. This is a very poorly supported area and it would appear that the unbalanced turning moment applied by the bridge acts on this as a fulcrum to hump up the top on the bridge side of the X and force it down on the soundhole side, leading eventually to the problems we are all familiar with.

The Bridge Doctor is a lever attached to the underside of the bridge attached to a thrust rod that acts on the end block; because this lever is much longer than the saddle-table lever, a relatively smaller force is able to cancel out the turning moment exerted by the strings on the bridge.

However, once the moments on the bridge are in balance the string pull has not gone away; instead, part of it has been resolved to a force acting at 90 degrees to the table, upwards, while the remainder is acting along the top. (If you draw this out in one of those wee drawings you did at school it's quite clear.) Therefore the result of the installation of a BD is NOT that the table becomes dead flat but that the table adopts an even upward curve or slight belly across the whole top of the guitar both in front of and behind the bridge--ie it adopts the shape it was designed to have! Because the bracing is designed to resist an upward stress rather than a momentary one, the top will quickly adopt the shape that balances the upward thrust and stabilise.

The vibrating effect of the strings is still transmitted to the top-- which is still under tension-- but in a more even and balanced manner.

This is why, I believe, the BD has the often reported, and in my experience too, effect of improving the tone-- the top is able to act as it is designed to act rather than responding to an unbalanced turning moment.

So-- according to my engineer friend, and I agree-- it appears that the X-brace, while sonically excellent, is structurally unsound without adequate resistance to the turning moment described above.

Interestingly I have a 1975 Ovation Legend, which is Ovation A-braced, and shows no belly in the top whatsoever. Not everyone likes Charlie's guitars but he was a very innovative and creative thinker, and his bracing developments deserve more attention.

 

[12stringer]

I used a JLD BD on my jumbo Tacoma 12 string with great success. Will be using one on my 71 F112 as well...they do take away the concern about using slightly heavier guage strings and leaving the 12er tuned up to pitch.:wink: