>What I said is that the crowning process does not damage the panel as long >as it is kept within the elastic range. Your putting the ceiling at 11% >(witch is equivalent ot 60% RH) is exactly what I said earlier. My figures put the panel at 1% compression. The elastic limit is somewhat less than 1%, so at 11%MC by my figures, the panel is already damaged. Also, assuming that a panel at slightly under the elastic limit will remain undamaged is not realistic. Compression damage accumulates relative to the level of stress, and time under load. >Of course once this damage start to happen in will have more serious >effects on the PC board than the RC board. The damage begins immediately with both assembly methods. And the fact that damage is both less severe, and of less consequence in an RC board than a CC board is the point of all this. >But even so I think deterioration will be incremental not catastrophic. No one ever made any claims to the contrary. The concern is the rate of incremental deterioration and resulting effect on soundboard performance. >The miracle of non linear compression? Discussing proportional limit in compression perpendicular to the grain, Hoadley says: "Beyond these limits, however, as the piece is compacted more and more, the resistance increases and no meaningful maximum load is reached." Since the panel of a CC board is very likely at or above the proportional limit when it's initially loaded with string bearing, non-linear compression is not an unreasonable expectation - and that's what I found in empirical tests. Also, I didn't find anything in the reference materials indicating that compression below the proportional limit is linear. Beam deflection is, so it's not unreasonable to presume that compression is too. Do you happen to have a reference for this, other than a line chart? Ron N
This PTG archive page provided courtesy of Moy Piano Service, LLC