How much belly bulge is acceptable?
 

And just a normal part of owning a guitar that is not brand spanking new?

It really depends on the construction of the guitar - when the top bellies, it can lead to loose braces, a popped bridge (had that one happen), etc. On the other hand, I kinda like a bit of belly on an older guitar - I wish I could say it definitively adds to the vintage tone, but sometimes it feels like it does ;).

I typically have my guitars checked out once over 1 - 2 years - a key checkpoint is the health of the internal structure, given any bellying going on. So - I don't think there is a "correct" answer as much as the fact that bellying has its pros and cons and if you like the guitar, just make sure you get it checked out periodically to ensure that the bellying isn't translating to a big structural issue any time soon...

When the instrument is structurally compromised or it raises the action beyond the available saddle adjustment.

No, it isn't a given with every non-new instrument. How much - or if - depends on the instrument.

depends on how much - a little bit is not unusual , lighter bracing attributes to this somewhat . It scares alot of people , what scares me are older guitars that don't have any -
Can you post a picture ?

Look at any guitar built by Dana Bourgeois, right off the assembly line. Quite rounded.

Yet my Flammang L-40, built in 2005, is almost dead flat, no doubt because I had tapered bracing done instead of scalloped, along with a 24.9" scale.

HE
http://howardemerson.com/music2.html

LOL! When I first read the title of this tread I thought it referred to the player, you know, "belly bulge!" My wife is always on my arse about that. I thought, "Oh no, not here too!" :D

Somebody....
 

Somebody on here or somewhere on the internet, said something to the effect that "I don't trust a guitar that doesn't have some belly buldge". I'm certain these were not the exact words, but you get the idea.

I was not aware that this happens, but it makes sense that the 'pull' of the strings over time create a bit of bulge behind the bridge. My old guitar, a 2009 Taylor didn't have any bulge AFAIR, but my current 31 year old Yammie has a bit of a wave close to the corners of the bridge. I wonder if this has been there all the time, or it has gotten worse as humidity spikes (as it does here now)?

I bought a used Martin D12X1 with what looked like to me to be just a little bit of bellying. Fortunately it appears that I was right. It had not been humidified for the previous year and after I had it consistently humidified for a few weeks I had a set-up done and it seems to have stabilized. What this leads me to think is that to some extent the belly doesn't matter as much as the relative stability of the top related to humidity. Of course, there's no real answer to the OP's question, but this is my recent and limited experience.

Older Gibsons were built to include a bit of 'belly bulge', or in other words the tops were not braced to be completely flat under tension even as new instruments. Still the case with Gibson flattops from Bozeman IME. Every Gibson I've had has had 'belly bulge'. My HD-35 and a host of other Martins had the same thing, from vintage to newer stuff.

Too much is too much and I've rarely encountered it except in a guitar that had loose braces or something else going on.

'Top sink' = the top sinking above above the bridge toward the soundhole also happens but is not planned into the build and generally not a good thing at all compared to 'belly bulge'.

Pretty sure that's a Norman Blake quote. I think somebody here has it in their sig.

My D28 Marquis has a bit of bellying going on. It's not visable, but taking a thin, soft cloth and feeling the whole area below the bridge, I can feel some bellying. It seems pretty even though, almost like it was built that way (I hope). It feels very symmetrical, about 1-1.5" from the edge of the guitar, all the way around the lower bout, it starts a gentle rise to the bridge. Scared the crap out of me the first time I felt it. :)

Anybody else out there with a pregnant Marquis? Should I start crying now? :lol:

Had a guitar years ago that was developing what I considered to be an unacceptable bulge. Popped in a JLD Bridge Doctor and the bulge receded dramatically. Guitar sounded markedly better as well. Dunno if the JLD product is still available, and YMMV.

My first thought as well. Funny.

Well the guitar at issue is my HD28V. So as to one poster, yes it has scalloped, light bracing. As to one of my favorite AGF helpers, yes it is just a little bit of bulging behind the bass side of the bridge.

Also, the action is perfect, so that is not an issue.

I will try to send photos tonight. FYI, I live in a very humid neighborhood (underground springs everywhere) with constant humidity in the house at 60+%. Since noticing this (which may have always been there), I have been keeping it in a case at 50% humidity and tuned down a half step. I really wish I could just keep the thing out and tuned normally because it cuts down significantly on my random playing time.

Thanks everyone.

It's been my observation that as long as my arms can reach the neck and strings and my strap is long enough "belly bulge" isn't really a factor :ha:

Norman Blake said that---and he should know!;)

An old luthier once told me: "A guitar too stiff to bulge is too stiff to vibrate."

Actually, there is a standard: 1/4 inch. That is, hold a straight-edge across the lower bout just below the bridge. Anything up to 1/4'' on both sides out at the edge is just fine.

Jon Z.

I'm very interested in this as I was looking at a buying a second-hand guitar which should be well built (Cort Gold Edge Limited Edition) but had a Bridge Doctor installed by the owner as there had been some belly bulge after only a year or so of it being bought.

The price is good and the guitar plays nicely, but I was put off by the fact that the belly had bulged in only the first year or two, despite the guitar only being used at home and stored in the case, as the owner told me (he was very honest and up-front about it).

I have guitars that are 35 years old without bulge, so a guitar getting a belly bulge that needed a Bridge Doctor, stored at home and also very 'young' - that scared me off.

Am I being unreasonable or should I avoid it for that reason?

Love to hear the thoughts of others on this.

I've bought/traded into a few older guitars showing a small bit of bulge. As long as the volume/tone and playability were still there, I figured that at 30-50 years old, they weren't that bad yet.

- Big bulge? Pass.

- Slight bulge, great sounding guitar, unbeatable price and still plenty of room to work with the saddle? Perhaps.

Using custom light strings (11-52) I've never noted any new (or increased) bulge on anything I owned.

Trevor Gore (Australian luthier with two guitar building books to his name) measured a bunch of 'good' guitars and found they had up to two degrees tilt of the bridge with the string tension. The tension and rotation pulls up the lower bout. This is different from the dome that most builders build into the top and back. Obviously different gauge strings will give you more or less lift. Some guitars are built for light strings and you will not be putting 13's on them. A stiffer top will allow for 13's and would be more suited as a stage guitar as you can drive the top harder and will have less tendency to feed back. Depends on what you want out of a guitar. A responsive guitar or one that can be used in a bar fight. ;)

I would avoid it. I can think of two scenarios here.

(1) The guitar was under-built and is going to be structurally at risk, bridge doctor or not. Result: pass on the guitar.

(2) The previous owner didn't understand that most guitars are built with a top radius, and that lightly-built guitars can have some bulge and forward bridge tilt (1-3 degrees or so) without it being an issue. Result: bridge doctor has been installed for no reason. Pass on the guitar.

Reading the subject line, I thought the same thing LOL!

I was told by a luthier that too much belly buldge can be a result of over humidification for a long period of time. I could have bought a Froggy Bottom with quite a pronounced bulge in the top for a relatively cheap price, but ended up passing on it. It just bothered me too much. I've also read that there is a process where the buldge can be reduced under heat and pressure, but not many luthiers perform this process.

I use a strap even when seated to deal with my belly bulge.

Yup. Ask a classical luthier "can I put strings of such or so tension on my guitar" and he'll probably tell you to look at the saddle/bridge assembly whether the saddle visibly leans more forward.

Heh, I was going to reply that I also preferred guitars with a visible belly and at least a humpback ^^

THanks for that. The guitar is in as-new condition and only a year or two old (well, the owner bought it a about a year ago, and it doesn't have heavy strings on it. So yes, I'll pass. If i had more experience I might be able to get a 'feel' for how good/bad it is, but I think that if I did buy it, it would always be on the back of my mind, and would detract from the experience of playign it (which is more of how my mind works than the guitar may work, but I know how my mind works...)

Cheers, all!

I measured my 1 year old D-16 Special and my 1979 D-35 with a straight edge. Both were at 1/16 on each side and both sound great.

A big bulge isn't going to make the guitar sound better, it could cause problems later on.

My ‘04 D18GE has a bit of a belly behind the bridge. So does my ‘00 HD28LSV. It’s all part of the plan. The LSV had a neck reset last fall, just before the holidays. The GE seems to be years away from needing a reset.

@ChrisMartinMan: Have you considered a room dehumidifier? We live in the PNW, where low RH (30-35%) is only a concern for maybe a week or so each year. Our house is on a hill, and the downstairs is below ground on two sides. It usually sits at 60-70% RH. We run a dehumidifier to keep it at 45-50%. All five of our guitars live in the “music room” down there. They are quite happy and stable.