Ron Nossaman wrote: > This looks to me to entirely contradict your claim that building CC > boards with flat ribs does not put the panel at damagingly high > compression levels. Immediate compression damage seems to, instead, be a > realistically unavoidable consequence. 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. Any soundboard has about a 30% change of RH window that it can safely live in. The difference between a Panel crown (PC) board and a Rib crowned (RC) board is the difference in the moisture content they have at the time of ribbing. In every other regard the behave the same. They have the same stiffness they sound the same and they both increase and decrees in crown with changes in RH. The difference is that a PC board will start to develop damaging stresses at about 60% RH while a RC board will have the same thing happen at about 70% RH. Of course once this damage start to happen in will have more serious effects on the PC board than the RC board. But even so I think deterioration will be incremental not catastrophic. I am getting tiered of this discussion (I am sure most everyone else is too) so I guess you win Ron. You can finally get the last word in. I am looking foreword to further enlightenment on your favorite topics. The evils of compression, watch out that sound board could explode at any moment! The miracle of non linear compression? The BIG equation? and How the piano industry will be saved by a spreadsheet and a bottle of tight bond. John Hartman RPT John Hartman Pianos [link redacted at request of site owner - Jul 25, 2015] Rebuilding Steinway and Mason & Hamlin Grand Pianos Since 1979 Piano Technicians Journal Journal Illustrator/Contributing Editor [link redacted at request of site owner - Jul 25, 2015]
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