Recently, I spent some time doing two of my favorite things: using a hand plane on a premium spruce soundboard (Engelmann this time, still from Old Standard Woods) and dreaming about the next guitar. Using a sharp plane on a perfectly quarter-sawn top with almost no runout has got to be one of those tasks that zen masters describe to their students. The wood tells you what it wants to do, and you learn a lot about the piece of wood you’ve selected for your top.
I graduate the top of every guitar I build, in response to the way the wood behaves under a plane and how it flexes under hand. Generally, I leave the bridge area slightly thicker, and the outer wings of the lower bout end up thinner. The idea is that the thinner outer edge of the lower bout will move a bit more in response to the vibration of the strings. And, the perimeter of the soundboard is naturally stiffened by its proximity to the linings and sides. However, after building many guitars, I still don’t have a target thickness; if anything, my target range is getting broader. The tops vary from board to board, end to end, center to edge. It takes a hands-on approach to get the best results.
I attended a workshop at the shop of Robbie O’Brien earlier this spring that focused on the classical soundboard. In the two-day class, we talked about how classical soundboards work, then thicknessed, graduated, braced and tuned the braces. It was a great experience, and I left with a completed, ready-to-install top. I’ve chosen to keep the sample top in the shop as a yardstick against which to compare future tops.