(Another) top belly question : when to worry?

[Inconnu]

Ok, so I want to stop worrying about that so I’m trying this post. My Norman B18 cedar top seems to have a slight bump just behind the bridge, a slight lifting. I’ve emailed the manufacturer who confirmed the top is a bit angled to begin with (not 100% flat) so I guess the lifting I see is not too bad. The action feels right. Sound is good.

But... what worries me now is that looking at the bridge sideways, it seems the pins are leaning towards the neck slightly (don’t know if they should, I’m not too knowledgeable of acoustics) and I can slide a piece of paper between the bridge and body, but only a little.

Should I worry?

[DenverSteve]

Since you are asking, you should have it looked at. Photos would help.

[The Bard Rocks]

I shouldn't say this without seeing pictures, but it looks like some trouble is heading your way. Have you kept it properly humidified?

[Wade Hampton]

I agree with Steve, as usual. A bit of bellying is okay, and the bridge pins angling a little bit towards the headstock is not necessarily worrying. But it’ll help to see some photos to see how far it’s gone.

In other words, it might be a problem, it might not be. We can’t tell until we see it.

Incidentally, if the top is bellying some and any kind of gap has opened up between the top and the bridge itself - in other words, if you can slide a corner of a business card between the top and the bottom of the bridge - the guitar needs to get looked at by a pro.

Hope that makes sense.


Wade Hampton Miller

[Inconnu]

Originally Posted by Wade Hampton

I agree with Steve, as usual. A bit of bellying is okay, and the bridge pins angling a little bit towards the headstock is not necessarily worrying. But it’ll help to see some photos to see how far it’s gone.

In other words, it might be a problem, it might not be. We can’t tell until we see it.

Incidentally, if the top is bellying some and any kind of gap has opened up between the top and the bridge itself - in other words, if you can slide a corner of a business card between the top and the bottom of the bridge - the guitar needs to get looked at by a pro.

Hope that makes sense.


Wade Hampton Miller

It makes sense. I'll try to post pictures later (phones dead right now). Currently, I can slide a piece of regular computer printer paper just a little bit under the bridge, in the middle of it (a business card surely wouldn't fit, the paper itself barely does).

Hmmm... guitar repair shops are all closed right now around where I live because of the Covid-19. Is there anything I can do to prevent things to go real bad?

Typically, should I boost or cut humidity?

[Jobe]

I'm not sure where you live but if it was me I would boost the humidity and loosen the strings just a bit. See if she will come into her own. You will still need to find a guitar tech down the road. If the bridge wants to lift she is asking for attention.

[FoxHound4690]

Originally Posted by Inconnu

Ok, so I want to stop worrying about that so I’m trying this post. My Norman B18 cedar top seems to have a slight bump just behind the bridge, a slight lifting. I’ve emailed the manufacturer who confirmed the top is a bit angled to begin with (not 100% flat) so I guess the lifting I see is not too bad. The action feels right. Sound is good.

But... what worries me now is that looking at the bridge sideways, it seems the pins are leaning towards the neck slightly (don’t know if they should, I’m not too knowledgeable of acoustics) and I can slide a piece of paper between the bridge and body, but only a little.

Should I worry?

Sounds like it's been exposed to hot conditions for too long i'm assuming you live in a hot/humid climate... you need to go into your local music store and get yourself a multi utility dessicant (an object that basically sucks up humidity), leave that and your guitar in it's case for a couple days straight and it should be fine after that. I use one for my Maton and it seems to do the job just keep it and the guitar in its case whenever its not being played.... I live in NSW, Australia and the summers here are torture.

[Wade Hampton]

Inconnu, if there’s room to slip some paper underneath the bridge between it and the top, the safest thing you can do is slacken the strings and put the guitar away until it can be looked at. Humidifying the guitar won’t reglue the bridge for you.

Do you have another guitar you can play in the meantime?

If you have no other instrument to play, if you’re somewhat handy at this stage the problem is fairly easy to rectify. You’ll need some deep throat C clamps, a couple of pieces of wood to protect the bridge and bridgeplate from getting marked up by the clamps, and some wood glue like Titebond or Elmer’s wood glue.

Take off all the strings, remove the bridge pins, put some leather between the wood pad and the top of the bridge, squirt a little glue into the space underneath the bridge, then gently clamp things down. Don’t over tighten the clamps, just get them dialed in where they’re firm and exert enough pressure.

Allow the glue to cure at least overnight, then when you think it’s cured enough restring the guitar and see whether you’ve fixed the problem.

If caught early enough this will generally do the trick. I’ve had this quick, easy (and inexpensive) repair done a few times and it’s always solved the problem and never needed to be done over.

But if you wait too long and the distortion caused by the bridge being yanked upwards becomes more extreme, the entire bridge will have to be replaced. That’s a much more expensive repair to have done, and whenever a bridge has to be pulled off the top there is inevitably some damage to the top underneath, with wood fibers from the spruce getting pulled off.

So it shouldn’t be allowed to get worse because the longer you wait, the structural risk to the guitar becomes exponentially greater.

Short version: your safest course of action is to take the string tension off and wait until you can get the work done by a pro. If that’s not an option, you can try fixing it yourself. Be cautious.

But it’s not safe to allow the bridge to pull up any further. Trying to correct this by adjusting the room humidity is a forlorn hope that won’t do any actual good, but might cause the guitar to become more damaged if you decide to wait and see whether that works first, and continue to keep the guitar up to tension.

So loosen the strings while you decide how you’re going to proceed.

Hope this helps.


Wade Hampton Miller

[Inconnu]

Thanks to all for your replies. I’ll try to answer to most of them in a single reply:

- I live in Montreal, Canada. Winters are cold (last one wasn’t all that much) and heating does dry air, summers are hot and can get humid. I do use a dehumidifier in the summer and have AC. I keep my instruments in the basement in the winter, where the humidity remains a bit more constant on its own, the house as it’s air exchange system and I monitor humidity (got a humidifier if there’s any issues). My other instruments didn’t suffer problems, even the old classical guitar standing next to the Norman. I still can’t figure out if it’s the lack of or the excess of humidity that caused the issue.

- I just tuned the guitar down a whole step to reduce possible problems. Will de tune more if necessary. I can stop playing it until I get it looked at or decide to reglue on my own (don’t know when luthiers will reopen around here).

[Wade Hampton]

Iconnu, the bridge pulling off of the top isn’t necessarily humidity-related at all, and it puzzles me that that’s been the general thrust of this thread so far. This kind of problem generally has a LOT more to do with string tension and sometimes with adhesion problems - particularly with cedar tops. Western red cedar has a substance in it, an oil of some kind, that helps it repel insect depredation when the tree is alive.

Unfortunately, this same naturally occurring compound also makes it more difficult for glues to work. So if this guitar has a cedar top, the bridge lifting is probably at least partially because of that.

So, again, seriously - don’t assume humidity is the source of this. It might be part of the problem here, but usually that causes splits in the vibrating plates like the top and back rather than causes the bridge to lift.

Hope that makes more sense.


whm

[redir]

Some makers cut a very small rabbet joint around the bridge foot print so that it extends over the finish giving a very nice clean looking appearance along the bridge edge and the top. I always argue against that preferring to use the strength of the entire foot print and now I realize I have another argument against that, so people don't worry about it

IDK if that is the case with your guitar but it could be. We really need to see pics. And it would help if you knew the design of the bridge.

[jonfields45]

Norman is a Godin brand. I've owned a few over the years and they all had their bridge edges not glued. I had one removed and glued on an A6 Ultra; ladder and tone bar braced (maybe it should be called V braced these days?) Cedar top with Koa veneer with the nearest cross brace to the bridge on the neck side of the bridge plate. The repair shop let me keep the old bridge. The replacement bridge they ordered from Godin was machined to be glued to the edge. Sweetwater to their credit paid to have the repair done at my favorite local shop, Brothers in Wind Gap PA.

Here are the pictures I took at the time. I think (this was some time ago...) we concluded after it was over that the repair was not structurally required but hard to justify not doing given the visuals. The top of that guitar had some rotation at the bridge.

[Inconnu]

Originally Posted by jonfields45

Norman is a Godin brand. I've owned a few over the years and they all had their bridge edges not glued. I had one removed and glued on an A6 Ultra; ladder and tone bar braced (maybe it should be called V braced these days?) Cedar top with Koa veneer with the nearest cross brace to the bridge on the neck side of the bridge plate. The repair shop let me keep the old bridge. The replacement bridge they ordered from Godin was machined to be glued to the edge. Sweetwater to their credit paid to have the repair done at my favorite local shop, Brothers in Wind Gap PA.

Here are the pictures I took at the time. I think (this was some time ago...) we concluded after it was over that the repair was not structurally required but hard to justify not doing given the visuals. The top of that guitar had some rotation at the bridge.

That’s a relief! I didn’t any glue! I guess it’s case closed then!