>The other thing which fades in and out of the discussion is that the EMC >at assembly time determines the ceiling of RH which the piano can >comfortably live under without suffering compression damage. Certainly >there are many pianos with CC boards, living in situations over the >decades where they're never driven through this ceiling by seasonal >humidity maximums. There are also Climate Control systems which rein in >this annual roller coaster. But there are also many situations in which RH >rises to levels which will damage a CC board, but not an RC board (with >its higher assembly EMC). > >Bill Ballard RPT And the thing that seems to fade out of the discussion immediately is the understanding that compression damage occurring in a RC board doesn't mean loss of crown and tone to nearly the degree it does in CC. Panel compression at high levels is all the CC board has available to it to support crown against string bearing and to provide stiffness. Panel compression damage under these conditions makes a relatively big difference in stiffness and load capacity of the assembly. An RC assembly designed such that the ribs are carrying the bulk of the load will suffer considerably less than the CC board even with similar panel compression damage simply because the panel condition isn't as critical to the structure in a RC assembly. Sure, the RC board's panel won't be damaged as readily by MC swings because it was assembled at a higher MC than the CC board, but panel damage is far less critical to function in the RC board in any case. Ron N
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