Another issue that can cause this is moisture content of the wood. These issues tend to show up often on imported guitars. Even if the wood was well acclimated and the instrument manufactured in a controlled environment. Not all are.... they still are shipped over sea.
Perhaps high end or custom instruments may get the luxury of air shipment, the rest come in container boxes on cargo ships. These shipping containers do not always stay dry inside. And if they do not leak then they are airtight and will have a terrarium type effect inside them. So either way for their journey here they get pretty moist. The reason why they are shipped with rods slack perhaps.
So what happens is what I have called hydroshock over the years. The RH rises rapidly in the container causing all the wood to expand, perhaps as much as 5-7% in volume. Finish handles expansion quite well. It stretches easily in most cases. So when the container arrives and the guitars come out everything still looks like it did when it went in.
But now the wood will dry back out and shrink back to its nominal size. The faster this happens the more trouble there will be.... This is the real reason I think most shops installed RH controlled rooms for acoustic guitars only. But even if dried out slowly there will most likely be some type of finish issue. While finishes stretch easily, they do not tend to retract quite as well. Couple that with a bit of uneven movement between the two different pieces of wood and enough stress develops in the film to cause it to break and delaminate at the joint.
IME overzealous truss adjustments usually either break the cheap rod or pop the FB end off the neck.
|