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Wrong solutions for a warped 12 string top

Q: I have a 12 string guitar which has a distorted soundboard at the bridge. The bridge has rotated toward the fretboard due to string tension. This means that the soundboard dips on the string side of the bridge, and rises up on the other side. I am guessing that I could solve the problem by propping inside the guitar using "miniature pit-props" which work in the same way as mini-versions of what are used in mines. Clamps and/or weights could then be used to force the top panel of the guitar back flat. I then intend to fit a "trapeze" tailstock so that string tension is transmitted to the end of the guitar.


A: First let me express horror at the idea of "pit props" and tailpieces. Your guitar worked fine before your current problems. Returning it to its original condition is all that is required. Get a good light and an inspection mirror and take a long hard look at the under-side of your top. Check for loose braces: Press on the top, look for gaps between the braces and the top. Loose braces will allow a top to distort. Check for a loose bridge: As a bridge slowly works loose, the glue footprint gets smaller and smaller, putting more leverage on the top. A loose bridge can distort a top. You don't need a fancy system of block and tackle to straighten the top. Just reglue the brace or bridge and everything will fall into place. But, what you will probably find is that the braces and the bridge are tight.

Guitar tops are not flat. Some are arched by the pull of the strings; some are intentionally arched at the factory. I find that people notice that their guitar is getting very hard to play and, looking for an explanation, see that the top is arched. Their actual problem is that their neck needs to be reset, or maybe they just need an action set.

Anything made out of wood changes shape every time the weather changes. If it warps backward it will pull straight again. If it warps forward, it has 180lbs of string tension holding it warped. So guitars slowly collapse, over many years. After twenty or thirty years the only way to realign everything is to take the neck off, refit it and put it back on. Sight down the edge of the fingerboard using the strings as a straightedge. Adjust the truss rod until the neck is straight, and then look for a "ski jump" where the fingerboard meets the body. The ski jump part, or fingerboard tongue, is right. The rest of the neck must be aligned with it.

Steve Mason