---------------------- multipart/mixed attachment As long as we are debunking dogma, how about this: loading a soundboard does not simply put soundboard into compression, as has been implied in several recent posts. I am no mechanical engineer, but I have questioned several over the years on this topic in order to understand some observations I have made on pianos. In order to put an arched system into compression, the load must be _uniformly distributed_ across the arch. This is not the case in pianos. If we consider a cross-section including rib, board, and bridge, the load applied to the bridge is a _point source_. This type of loading does not produce simple compression. It causes the bridge to sink into a valley with bulges on both sides. The greater the loading, the deeper the valley and the more pronounced the bulges. Of course, real soundboards are not cross-sections, but have an extremely complex shape in 3-dimensions. Real soundboards can have bulges on either side or both, and the side of the bulging can change in different areas of the same piano. This sounds a lot like "bridge roll", doesn't it? Do we need another explanation of bridge roll? This valley/bulge creates a "wave" shape in the board. The resulting pattern of tension and compression is complex. Sometimes it can cause a charateristic pattern of compression failure and cracks. It can cause paradoxical cracks on the bottom of a soundboard. It can also make measuring the crown on the bottom of a board inaccurate. Bob Hohf Wisconsin ---------------------- multipart/mixed attachment A non-text attachment was scrubbed... Name: not available Type: application/ms-tnef Size: 2740 bytes Desc: not available Url : https://www.moypiano.com/ptg/pianotech.php/attachments/52/ec/40/4e/attachment.bin ---------------------- multipart/mixed attachment--
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