The Zen, the Physics, and the Art of Brace Carving

While carving the braces for Ryan’s guitar I got to thinking about why this is my favorite part of guitar building. It really does have a Zen quality.

Brace carving requires the kind of focus that lets me empty my mind of all life’s distractions. This begins with honing the chisels. I zero in on the edge until it is sharp enough to shave hair off my arm. Then the chisel slices effortlessly into the soft quartersawn spruce of the braces that are already glued in place. Together the chisel and wood send feedback to my hands, telling me just the right angle and amount of pressure to apply.  When doing other guitar-building tasks I often listen to music. But when carving braces I listen only to the whisper of the wood and tool.

The longest braces of the top are the X braces, so named because they run diagonally and cross each other with a joint that laps in the middle. The X braces run to the edges of the sides. They are shaped like elongated pyramids that  taper down to a tenth of an inch at the outside edges. The brace that transverses the upper bout is also tapered to a tenth of an inch, as are all four braces on the back that run perpendicular to the neck.  The ends of all of these braces will fit into notches cut a tenth of an inch into the sides.

There are six more top braces that get carved into pyramids. These include two tone bars and four short finger braces. These get tapered down to about a tenth of an inch to meet the X braces and  tapered to nothing just before they reach the rim of the guitar.

If you haven’t glazed over yet, chances are you are wondering what all these pyramids and tapers and notches are for. All this carving stems from the fact that a guitar is a balancing act between two conflicting goals: One goal is to make the top, and to a lesser extent the back, flexible enough to resonate freely when you activate the strings. The other goal is to be strong enough not to collapse when you put about 180 pounds of pressure on the bridge by tightening the strings to standard tuning. To achieve this balance, braces need to be tall for strength and narrow for resonance. The pyramid shape maximizes the narrowness. The tapers add more flexibility and take advantage of the fact that the top and bottom need less support as they move closer to the rim.

The orientation of the grain in the brace wood is also important to the yin and yang of resonance versus strength. Quartersawn wood is straight-grained. Orienting the grain perpendicular to the top and bottom make the braces as strong as possible for their size and weight.

When I begin carving, the shavings are relatively thick as the braces take on their rough shape. Then I use a thumb and index finger to hold the plate to my ear as I tap it with the other index finger. Do I hear a clear note? How long does it resonate? I flex the plate along its length and width while my muscle memory judges the stiffness. I take a bit more off all the braces. And I listen again. Zip off rice-paper-thin wisps. Listen again. At a certain point only selective braces will need slight refinements until finally experience and intuition tell me it is time to stop.

And when I am done and step back, I am always amazed at how beautiful the shapes are. Yes, I shaped them carefully but I was focused on the sound not the look. After all, I’m the only one who will see the top braces other than some future repairperson who hopefully isn’t born yet. I sign my name and the date in a soon-to-be hidden corner of the top, just to say hi to that future luthier. Then, almost reluctantly, I glue on the bottom and top.