Acoustic Soundboard split down the middle

[Gavin1393]

Ok, so I get the call about fixing a Chinese made acoustic guitar. Apparently a copy of some special edition put out by Martin. The back sides look like they are are a composite of something purporting to be Indian Rosewood and the soundboard is sitka spruce but a very low grade. so the reason I got the call was because the bridge has pried itself loose from the soundboard, the soundboard has bellied AND split down the middle from the sound hole to the bottom of the guitar. Now understand that this guitar has hardly been played. It still has the manufacturers ticket attached to the tuners.

At first look, it is clear that the builder hasn't a clue about attaching a bridge. A soundboard is usually radiused at around 28 feet and hence the bridge needs to be shaped accordingly. This one is dead straight which possibly explains why is has ripped itself free from the sound board on the bass side. Now it seems like someone had a go at filling the crack with super glue but this hasnt worked possibly because there is really a simpler way of gluing the two halves of a soundboard back together but that is for another time. In short the prognosis is that we need to remove the nitro from the soundboard, clean the split of the superglue residue and then shape the bridge and repaint with Wudtone!

So I get going with the removal of the nitro using my trusty Makita when suddenly i notice something that really shouldnt be the case....the soundboard which should be approximately 2.6 to 2.8 mm thick (5mm if a Cole clark!!) is actually less than 0.5mm along the split. Further checks reveal that around the whole bridge area, this is the general thickness of the soundboard. No flippin wonder the guitar had bellied. and there was I thinking someone stuffed up by gluing the guitar when the humidity was all wrong. This would be the usual reason for a bellied guitar this soon after manufacture.

Hence, back to the drawing board because what needs to happen now is nothing short of a heart transplant! Namely to get a piece of sitka spruce and graft this on top of the very thin piece and to make it look like one piece again!

Here is the progress so far...

[johnnychronic]

What is the point of putting all the work of artistic inlays on a disposable guitar? Why do people still think that buying a copy of an expensive article will be the same?
When you are finished Gavin do you feel your customer will have paid, in total, less than the value of the guitar?

[Gavin1393]

Its an interesting question. Funny thing is that the ornate mother of pearl is nothing more than a transfer of some description! I have been very generous in terms of my costs and he really has me at slave labour rates!

[AJ]

/<\\/p>[]<\\/p>/Quote from Gavin1393 on December 2, 2013, 00:09
Its an interesting question. Funny thing is that the ornate mother of pearl is nothing more than a transfer of some description! I have been very generous in terms of my costs and he really has me at slave labour rates!

The wife bought me (a while ago) a cheapie from the reject shop.. (bout $20). I tried to play it just the 1 time, but with a string action at the neck joint where you could just about drive a mack truck between the fret board and the strings... well.( I am musically challenged at the best of times lol) And to boot, the belly has the battle of the bulge going on from the first time the strings were pulled up to tune..

Quick Q tho, can the string height be dropped at the bridge by sanding the bone ? And would you suggest removing the bridge to see if I can rid it of the bulge? (Point is I don't want to upset the apple cart with the boss of economics at my place)

[stan]

interesting fix Gav!

[Gavin1393]

AJ, the problem is to determine WHY the thing has a bulging belly. For a better quality guitar it could be to do with moisture in the wood when the wood was glued. This is why it is so important to make sure the humidity is at around 40-50% when you glue! The fix here is to either reduce the bridge and the nut so that the obvious resulting high action on the guitar can be normalised. However, the issue comes in when it has more to do with the soundboard not having enough support at the bridge plate . Very often a split soundboard will cause this issue. The tell tale sign is that as you tune up the guitar on each string it places the guitar under more tension and hence all the other strings go out of tune as you tune each string. The reason for this is that as the guitar is placed under pressure, the belly bulges and the bridge bends towards the sound hole raising the string height and shortening the string length!
The way to solve this issue is usually with matches and gasoline....

[Gavin1393]

I am now attempting to match the colour of the new piece with the rest of the soundboard. Brendan dropped by this evening and after a discussion around the colour matching suggested the vintage amber which seems to have worked very well. This is the first coat.

[wokkaboy]

looking good Gav, hope this isn't Kev Bloody Wilson's axe ? haha. The colour match is pretty good, just need to sand back where the join lines are

[Gavin1393]

Haha, no fortunately for KBW it isn't his!
Have some work to do on his one though.

[stan]

nice work, i would have thought replacing the top would have been the go here