NAGD : The battle of the bulge

Flink_Poyd · June 2016

I picked up a cheapie beater acoustic off Ebay, a Grant F-120 (pics to follow). Apparently MIJ around 70's 80's probably a company rebadging them on import. It looks pretty nice apart from a few knocks and one poor repair but its just for around the house so Im not to fussed.

I knew it had a bulge behind the bridge before I bought it but its made the action so high its difficult to play.

Ive seen all sorts from damp rags left in the soundhole to gadgets that pull it back to shape. Bearing in mind this is a cheapie Im not going to spend £100's fixing it.

Are there any methods that actually work to reduce it?

octatonic · June 2016

Take some pics and post them.

There are several causes and it will be easier to diagnose if we have pics.

Often you remove the bridge, shave it down and glue it back down.

This isn't that expensive, especially if you don't need a finish repair.

Flink_Poyd · June 2016

octatonic · June 2016

Ok, all acoustic guitar tops will have a bit of a curve in them- that is a function of the design (the soundboard and back work a bit like a pair of bellows) but that looks to be a pretty extreme example.

It is a common problem though- does it still such when the strings are off?

First thing you need to see inside it and make sure there are no braces that have come off and the under bridge patch is still in one piece.

I use an endoscope for this, but a mirror on a stick works too.

Hopefully nothing is missing or loose- if it is then you will have to repair them, which is a tricky job.

A damp cloth inside the body can help- put down some sort of barrier for the back, like a plastic lid.

Seal up the sound hole somehow- I use a yoghurt lid.

Leave it a couple of days and see how it fares.

Flink_Poyd · June 2016

octatonic said:

Ok, all acoustic guitar tops will have a bit of a curve in them- that is a function of the design (the soundboard and back work a bit like a pair of bellows) but that looks to be a pretty extreme example.
It is a common problem though- does it still such when the strings are off?

First thing you need to see inside it and make sure there are no braces that have come off and the under bridge patch is still in one piece.
I use an endoscope for this, but a mirror on a stick works too.

Ive loosened the strings to see if it settles any but so far nothing. I cant see anything thats obviously broken so far.

octatonic · June 2016

Flink_Poyd said:

octatonic said:

Ok, all acoustic guitar tops will have a bit of a curve in them- that is a function of the design (the soundboard and back work a bit like a pair of bellows) but that looks to be a pretty extreme example.
It is a common problem though- does it still such when the strings are off?

First thing you need to see inside it and make sure there are no braces that have come off and the under bridge patch is still in one piece.
I use an endoscope for this, but a mirror on a stick works too.

Ive loosened the strings to see if it settles any but so far nothing. I cant see anything thats obviously broken so far.

Try the damp rag approach first.

It will need a couple of days.

Flink_Poyd · June 2016

octatonic said:

Flink_Poyd said:

octatonic said:

Ok, all acoustic guitar tops will have a bit of a curve in them- that is a function of the design (the soundboard and back work a bit like a pair of bellows) but that looks to be a pretty extreme example.
It is a common problem though- does it still such when the strings are off?

First thing you need to see inside it and make sure there are no braces that have come off and the under bridge patch is still in one piece.
I use an endoscope for this, but a mirror on a stick works too.

Ive loosened the strings to see if it settles any but so far nothing. I cant see anything thats obviously broken so far.

Try the damp rag approach first.
It will need a couple of days.

OK. Just watched a video suggesting similar from some bloke called Bob Taylor, we'll see what happens in a day or 3

Lewy · June 2016

octatonic;1106310" said:

A damp cloth inside the body can help- put down some sort of barrier for the back, like a plastic lid.Seal up the sound hole somehow- I use a yoghurt lid.

Leave it a couple of days and see how it fares.

How will that help? Isn't excess belly often a symptom of excess humidification? Tops sink when they're too dry, not belly....?

earwighoney · June 2016

Lewy said:

octatonic;1106310" said:

A damp cloth inside the body can help- put down some sort of barrier for the back, like a plastic lid.Seal up the sound hole somehow- I use a yoghurt lid.

Leave it a couple of days and see how it fares.
How will that help? Isn't excess belly often a symptom of excess humidification? Tops sink when they're too dry, not belly....?

Yes, I can't see the guitar would be in need to be humidified as a soundboard that has bellied is a sign of excess humidification.

What is the action at the 12th fret? Is it possible to give a measurement of the difference between the fret and the string at the 12th fret?

Is it possible to get a side on picture of the bridge and saddle? Depending on how much free saddle is, if you want to bring down the action sanding down the saddle could be the easiest way to make the guitar more playable.

AliGorie · June 2016

guy's are correct - a SLIGHT dome is built into the acoustics top but this looks to have gone 'pregnant' - if there's enough height on the saddle to take it down (by sanding the saddle underside) to achieve a reasonable action that's the way to go on an inexpensive guitar. Otherwise it can get expensive having 'structural' work done.
Alternatively - u could take up slide playing.
Oh, Grants had shops in Edinburgh and Glasgow
I recall getting strings there when visiting friends in Glasgow West End Byres Road area.
He imported Grant badged guitars from Japan (Fujigen (also made Ibanez, Greco, Antoria, CSL etc) or Matsumoko (Aria)).

Flink_Poyd · June 2016

Has anyone used the JLD bridge doctor? It's looking like the only option at the mo.

TheBigDipper · June 2016

I managed to spoil a solid spruce top guitar by leaving it in a hot, sunlight room for a couple of months outside its case, on a stand. The belly bulged (without lifting the bridge off the top) and left me with a very high action. It wasn't worth spending lots of money on, so I just got the saddle lowered (as per earlier posts above). Looking at your pix, you appear to have a lot of saddle height available for removal.

The result is I have a decent action again - just as it was when I bought it. The top E is almost touching the bridge as it leaves the saddle, so I can't do this again. However, the top has been stable for the last 3 years so I probably won't have to.

FWIW, trying to see if drying it out with silica gel bags didn't work for this guitar, but I did try that first, to improve things if I could.

If you Google the Bridge Doctor, it seems that people experiences have varied.

Gru · July 2016

I have used a bridge doctor on An old Lorenzo acoustic with good results.

The top bulged due to too much moisture (a constant issue with my parents old house).

Before using, the guitar had a high action and sounded dead. After, the action was improved and it had life back in the sound.

I would certainly use one again on a cheaper guitar that needed some help.

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NAGD : The battle of the bulge

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