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From: Ross
Remote Name: 76.101.10.109
Date: 18 Jul 2007
Time: 08:17:41 -0400
Luthier’s Weblog 7/18/07 Getting back to the work of bracing design, the robot luthier sees that he must address the problem of brace abutment. The problem that arises is that, when one brace butts up against an X-brace member, an area of exaggerated stiffness results. This can be adjusted by trimming the brace butting up against the X-brace member to two - five thousandth s thickness and tapering to a gently rounded maximum height. This maximum height “peak” should be about 1/3 to 1/5 of the length of the brace from the abutment point. A sharp peak should be avoided, as this concentrates stiffness in a specific area. The builder aims at a smooth, linear graduation from stiffness near the bridge to flexibility at the perimeter. Graduation of brace height, and profiling of the braces’s cross section is made as gradual and smoothly rounded as possible. The need for bracing to keep the top from deforming due to string pull is pronounced at the strings’ anchor point, and minimal at the perimeter, due to greater load sharing surface area and load dispersion by the braces. It’s a beautiful thing, made visible by logic. The builder has largely given up on the concept of tap tuning. He has surely tried to make a connection between tap tones at various points of the braced top and end result instrument tonality. Conclusions have eluded him, however, and he instead adjusts the top by trying to achieve a particular degree of flexibility and weight. If the top is too heavy, but the right flexibility, he often removes material from the bracing closest to the center. If the top is a comfortable weight, but too stiff, he removes brace material closer to the perimeter. If the top is too light, or too flexible, he hasn’t been paying attention. The penalty is high: the top is discarded. The builder has been reading good books again, bathing in the washing waves of light thrown up by James Salter and William Faulkner. He idly speculates on the feasibility of accurately recycling the light into the form of sound waves, cast by a wooden plate. Ross Teigen 8:45 am