>My gauge has a full 2-5/8-inch crown. I was excited after a day or so >when it had a good 1/4" of crown, but I find it rather amazing that so >much crown would develop with an apparent change of only 3.5% MC. I'm sure >a large part of the large crown development is because all my dimensions >are reasonable for a real soundboard, except for my rib thickness which is >perhaps 1/3 of where it might be on a piano. I use the formula Len*0.043*((ToMC-FromMC)/0.28) to estimate expansion rates in new spruce. Len is length in inches, 0.043 is a constant for the approximate expansion coefficient for spruce, and 0.28 is the saturation MC. So 46*((8.4-5)/0.28)=0.240", which is how much an unrestrained panel of new spruce should have grown with that MC change. I would expect somewhat less from the old used panel, but that's one of the things I intend to measure with my little experiment. Figure the arc segment length on top of the panel against the length of the straight rib before assembly, and you can get a rough indication of how much compression is in that panel. >I'm looking forward to this gauge being of very good use after I get it >calibrated - which will occur after we get all this MC mucky-muck worked >out to some degree of satisfaction. > >Terry Farrell It should be quite useful (if it will fit in your hot box). <G> Ron N
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