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Old 09-15-2021, 05:17 PM
Alan Carruth Alan Carruth is offline
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Join Date: Feb 2011
Posts: 3,768

As somebody who doesn't use deflection testing as an acoustic indicator I couldn't say. I use a vibration test to determine the Young's moduli along and across the grain, and the associated damping factors. I use the modulus along the grain to determine the proper thickness for structural reasons, and then use Chladni testing to optimize the brace profiles for the best acoustic response. You can, of course, use static deflection tests to get the Young's moduli, and use that data for structural determinations, but IMO stiffness and mass distribution are important, and that's what the patterns are about.

David Hurd does use static deflection maps of tops to guide him in brace shaving, and says my system gives deflection results that are similar to his, but that's a fair way from simple wood property testing. He loads the top at the bridge, and then measures the deflection at a grid of points across the whole lower bout, looking for smooth contour lines. Again, it's about how the stiffness is distributed, not just how stiff it is.
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