RC vs CC again

[Ron Nossaman]

>       As you say It doesn't seem the panel is going to compress 
> significantly with these minor increases from downbearing. I typically 
> dry Sitka  panels before ribbing between 5.5% to 6% EMC out here in 
> Calif. Many go to the bay area with higher average moisture levels than 
> the central valley where I am. I have followed many of these pianos over 
> timed see no sign of compression ridges, cracks bulging etc. With other 
> kinds of spruce with less strength across grain , or containing too much 
> soft spring/early wood, it could be a problem.

But then neither you nor John are building compression crowned soundboards 
with flat ribs, so the comparison isn't of much use.


> >>> So then it looks like a safe level of E.M.C for panel crowning could 
> range from 5.5 % to 6%emc

In purely compression crowned boards, the overall compression is the 
problem, not the starting MC. Similar panel compression levels can be 
gotten by either severe drying, or pressing the assembly in a deeper dished 
caul. If the resulting crown is the same, the panel compression is the same 
no matter how it was arrived at.



>    If anyone has had the idea that only a highly modified board is an 
> exceptable and legitimate attempt at quality piano rebuilding just isn't so.

And as far as I'm aware, not a living soul has made that claim, so I can't 
help but wonder why so many people repeatedly and specifically make this 
point against a claim that was never made.

I also note that my original request for an explanation still hasn't been 
approached. John said that the ribs of a compression crowned soundboard 
supported most of the crown, and the panel supported very little. I'd still 
like to know how that can be when it is panel compression that is bending 
the rib in the first place, thus supporting both the rib and the bearing to 
retain crown.


Ron N