evaluating sdbd. crown & bridge downbearings in a new piano

[Ron Nossaman]

 the
>latter has a photo of spruce originating in China, while not citing species or
>any properties, the sample _looks_ very tight-grained.
>
>The soft, summer growth wood indeed is more easily compressed to failure and
>expands more, and the wood shrinkage figures I have are averages generalized to
>all applications; specifically, however, the wood with medium grain density is
>what this thread focuses on, since controllable expansion should be an
issue for
>CC boards and strength and lightness is for both CC and RC boards (see Del
>Fandrich, "Soundboard Technology," Text for PianoTalk #2, Feb. 1995:
>http://www.olynet.com/users/pianobuilders/soundboards.html) [...I am in no way
>associated or affiliated with...].

* Actually, for RC boards, growth ring count in the 10-12 per inch range
work just fine. Since you can control the stiffness so much better with the
ribs in this system, a more flexible panel is not only allowable, it is
benificial. 



>As for my own understanding of the subject, the unshaped CC ribs as Frank
Weston
>describes are considerably more _deformed_ to accomplish the same profile of an
>RC assembly; while the glue holds and the cellular structure of the soundboard
>panels remains intact, this should present little problem. But as failures
>progress, the tendency of these flat ribs is toward flat where the shaped ribs
>maintain crown longer.

* Exactly, and in the CC crowned assembly, panel deterioration progresses
much more rapidly.



>I seem to be adept at killing threads, but I hope not to do so with this one
>since I'll be rib-crowning my first piano soundboard in the next week or so.
>
>Clark "the Thread-Killer" 'Pianaccione'

* Great! I hope you'll have some details for us.

 Ron N