This week I completed the assembly and first round of finish sanding on the soundbox of Dan's Italian Spruce and Indian Rosewood Concert Nylon Crossover. I do a lot of the fine tuning of my guitars rather late in the building process. I like to leave the top just a little thick pre-assembly and then incrementally thin the top at various stages of construction. This being a nylon string instrument with lattice bracing, the top will be especially thin upon completion. In this case, I thinned the top uniformly to .095" pre-assembly. Once the box was closed up, but before routing the binding channels, I used a palm sander to thin the perimeter area of the lower bout to about .070", all the while paying close attention to the flexibility of the top and how it deflects under pressure. After installing the binding there's an additional bit of sanding to flush up the surfaces of the top, back and sides surfaces with the binding and purfling strips, and this removes just a little more material off the perimeter of the top, but it's still just a little thicker than what I'll finally want. After I've made the neck and bridge for the guitar and done a final round of finish sanding on everything but the top of the guitar, then I'll do a final round of finish sanding on the top paying very close attention to the deflection of the top and its thickness (which I can still measure with a Hacklinger gauge), and especially to the tap-tone, as I carefully thin various areas. In the end the top will range in thickness from about .080" in the area around the bridge and the upper bout to about .055" around the perimeter of the lower bout. More soon, Dan. :)
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