>The discussion of spruce's ability to compress 1% without damage is >interesting, but is at most only half the story. Does anyone know how far >healthy spruce can stretch without failing? > >Bob Hohf >Wisconsin Dear Bob, If you mean tension parallel to the grain, then according to Hoadley wood is stonger than steel on a weight-for-weight basis when tension is parallel to the grain. He also says the tests are hard to conduct and are of a limited use. Stretching along the grain occurs when the treble bridge is glued to the soundboard and forces and end-to-end deflection. I would hate to *hear* the point of failure of that stretch which could really ruin a soundboard and your day. This stretch under crowned conditions is different than what the book talks about in a simple tug-of-war effect. There seems to be a definate amount a soundboard will allow to be stretched when gluing on the bridges. The dynamics of all the forces in a soundboard assembly under pressure seem gigantic. Tension, compression, stretch, you name it. Understanding the strengths of wood and differences in comparison to seasoning times would an interesting experiment. Did you hear on NPR about a venture to raise thousands of logs from the bottom of (I think) Lake Michigan? Apparently left over from the logging days there are all these prime oak, sugar maple and other species lying on the bottom in great shape. The owner plans to mill it and sell it to woodworkers and the like. Too bad there problably won't be much spruce. Brent Brent.Fischer@ASU.EDU Arizona State University/Tempe
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