More on soundboard crown

[Ron Nossaman]

>snip.... Given a panel crowned assembly with a severely dried
>panel, and one rib crowned with a non dried panel, both to identical crowns
>at room EMC, the one with the higher panel compression level will have the
>steeper spring rate gradient, and will be stiffer.
>
>
>Now correct me if I am wrong.. but I understand this to mean that a CC 
>board will be stiffer, both unstrung... and increasingly so when 
>downbearing is applied.

Wrong. As we've discussed specifically and often, the RC board can be made 
much stiffer, both unstrung and strung, though the CC board will often have 
a steeper spring rate progression under deflection, at least while the 
crown lasts.


>Assuming that is correct, and putting aside all other compression damage 
>discussion for a second or two... I have a question about this long term 
>so called compression set.

It's not so called. It is a real thing, backed by that real science that 
you so often peripherally refer to lately. See "Understanding Wood" by R. 
Bruce Hoadley, for a start. Reading up on some of that real science you 
recommend will answer your questions.


>On the side of this... and please forgive whatever lack of knowledge I 
>display in the asking,  if compression from ribs being glued cross grain 
>to the panel is such a problem...even in RB boards.. is there no way of 
>contriving a rib such that it is a bit less constraining ?
>
>Just musing again
>
>RicB

Yes, if you design the ribs to support the crown without needing panel 
compression to do so, and don't dry the panel to extremes, panel 
compression is no longer a problem. This should start sounding familiar 
about any time now.

Ron N