R,C&S question

[Richard Brekne]

Hi Jude

    Jude writes:

    Still, doesn't an RC&S panel experience similar high compression
    loads when it's humid out also leading to the accelerated aging. I
    hear what you're saying about wood, but if we're going to be
    consistent, why should there be accelerated aging on any type of
    panel if it's kept in a relatively stabile environment.

    I'm just trying to get a sense of that interchange of stiffness from
    compression verse rib support. I guess the hybrid covers the in
    between range, but I think the variations might be fascinating,
    soundwise.



This basic question is of course at the heart of my querie about 
calculating how much compression is created when a soundboard must 
deflect downwards RC&S designed ribs to the degrees necessary.

 From a general perspective, a soundboard gets subjected to relatively 
known amounts of down bearing. This is more or less independent of 
soundboard type.  The panel has to take on most of this load in terms of 
compression.  But thats  going to vary somewhat depending on how much 
compression there was at the outset vs how much pressure it takes to 
deflect the ribs.  CC ribs are easier to bend... but one has significant 
amounts of compression already in the unloaded panel... RC & S panels 
dont have any real compression in the unloaded state but the ribs 
themselves are harder to deflect.  To some degree these two systems 
counter act each other in regard to how much end compression there is in 
the panel.

We've heard much about how much compression builds up in the CC and RC 
boards as it takes on humidity and how destructive it is.  But how much 
compression builds up when downbearing is applied is not more 
specifically addressed then simply saying it just increases the matter.  
I asked this same question a couple years back about CC boards and 
simply got told  "I dont know and it doesn't really concern me" by the 
RC&S camp.

In any case... Showing how the three types of boards line up with each 
other in this regard by describing in quantifiable terms how much 
compression builds up in each when the piano is strung, up to pitch and 
at nominal RH levels seems kind of more then appropriate at this point.  
If someone indeed can do exactly this... its time for a journal article 
on the matter.

Cheers
RicB