Repairing a 20 year old Martin acoustic wont stay in tune

[Gavin1393]

A seasoned performer brought in this 20 plus year old Martin guitar. It has been well used over the past three decades and has become tired! Essentially what has happened is that the soundboard has split from just below the bridge all the way through to the bottom side of the guitar. This has been a problem for some time for this musician, and he has taken the guitar to a number of luthiers but the problem and indeed a solution was not found.

When he brought the guitar to me to have a look at, the general comment was that the guitar wouldn't stay in tune. Now this can point to tired tuners, but i noticed that the action was plain horrible. the guitar was really difficult to tune and the spilt in the soundboard wasn't clearly presented.

It was only once I ran my fingers over the soundboard that the split in the soundboard could be felt ( with the strings at full tension) but most alarming was the bulge that could be felt on the treble side of the bridge. Alarm bells went off because, as the guitar was being tuned the bridge was raising up like a DRAW-BRIDGE and simultaneously raising the action of the guitar something awful.

Because the split was hardly noticeable, but split all the way down, getting glue into the crack was going to be difficult but necessary. There was just too much weakness and instability at the bridge that to not get this glued up would mean the guitar was not fixable. Further, the prolonged issue had left the structures weakened even though the braces and such were all fine. With the lateral stability improved I needed to improve the longitudinal stability by effectively building a bridge TRUSS-ROD! Yes, you read right!

I will be stringing this up tomorrow, but here are some pictures!

[Gavin1393]

Here are the 'after' installation pictures of the Bridge truss Rod.

I have drilled a hole in the bridge between the third and fourth string. There is a screw that attaches to a block of wood beneath the bridge. The block is shaped to lend support to the bridge area. Beneath the bridge is that block (2nd picture) attached to a length of dial that rests up against the end block (where the strap lock is attached). The dial is then tightened up and this tension counteracts the tension of the strings and will prevent the bridge from raising which will improve action and keep the strings in tune!
I have also carefully removed the pick-guard and re-flattened it according to Brendan's method as it was curling at all the edges.

[stan]

wow gav, great to see repairs like this and how they are done

[ihasmario]

First picture is a classic. Really nice solutions for a workhorse.