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<DIV><STRONG><EM> Ric</EM></STRONG></DIV>
<DIV><STRONG><EM> If you are looking for some kind of numbers I can't help
you but if you want my tactile experience. That's another. The
assumption that CC boards aren't strong would be incorrect. They are
extremely strong due to there non- linear compression rates. meaning as
they are compressed they become more resistant to compression by the bearing
load. Also Sitka spruce renders them even stronger because of its
strength. AS has been said before that drying the panel will create
compression as well as the steepness of the soundboard press/dish it is being
pressed in. </EM></STRONG></DIV>
<DIV><STRONG><EM> My Colleague Chris Robinson of Connecticut
still produces a C. C. Board & as you may know from the Mason & Hamlin
on display in the rebuilders gallery, his boards sound really good.
You may wish to ask him some general question but other than that he is
rightfully proprietary about his methods. I will tell you he uses different
radii cauls for different sized boards, if that tells you anything. If you think
about this a bit you'll figure it out.</EM></STRONG></DIV>
<DIV><STRONG><EM> If you get an opportunity to restring a C. C. board with
a fat crown try pre stressing it & you'll find out in a tactile sense just
how stiff they can become very quickly. Also I suspect it is this
predictable quality that makes it an easy method for the factories to use. In my
experience a C.C. board coming from the usual places will always sound better if
I can spot some compression or compression ridges in the panel. Ie. the Yamaha
C-7 F I tuned yesterday. I've worked on it 15 years & it's Best one
I've heard. It has significant and visible compression in the panel &
more than most Yam's</EM></STRONG></DIV>
<DIV><STRONG><EM> Dale</EM></STRONG></DIV>
<BLOCKQUOTE
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue 2px solid"><FONT
style="BACKGROUND-COLOR: transparent" face=Arial color=#000000 size=2>Hi
folks<BR><BR>One thing that keeps bothering me and makes it difficult to
resist <BR>buying right into the RC & S gangs reasoning is that we never
hear <BR>anything about how<BR>compression reliant boards figure load
bearing.. or much of anything <BR>else for that matter. I find all kinds
of references to how an RC & S <BR>board is actually designed... but
nearly nothing about how one figures <BR>basic things like just how darned
strong a CC board is. <BR><BR>It struck me the other day that perhaps there
isn't really much to begin <BR>with, that perhaps this all was started by a
more seat of the pants <BR>approach. If you dry a panel you can judge
its MC fairly accurately by <BR>knowing the beginning MC and how much it
shrunk after drying ... yes ? <BR>So.. reversing that logic if you have
a dried panel and inhibit by some <BR>mechanism it from expanding and you know
how much increase in RH you <BR>subject it too... then you know how much
compression the panel has taken <BR>on. Ribs are a way of inhibiting
this expansion yes ? Seems to me then <BR>that measuring the amount of crown,
knowing the bending strength of the <BR>ribs, and the change in RH gives you
then enough information to fairly <BR>accurately find the strength of the
assembly for any given amount of <BR>crown. From that point perhaps a few
decades of trial and error with <BR>regard to problems incurred with various
rib placements designs was more <BR>significant in terms of
<<design>> then any engineering in the usual <BR>sense of the
word.<BR><BR>Ok.. this is pure speculation on my part. But it
would REAAAAALLLLY be <BR>helpful if someone would do a basic review for the
benefit of the whole <BR>list as to how one goes about designing (by the
book... if there is one) <BR>a CC board, or any board that relies very much on
compression. It would <BR>most certainly make it much easier to
see <<the light>> as it were <BR>between the various methods
of building boards.<BR><BR>I've done two board replacements earlier... and got
quite a bit of <BR>advice as to rib placement / size... etc... and both these
were reliant <BR>on compression for crown... and no one could really give me
any good <BR>specific engineering reasoning's for any of their
advice.<BR><BR>Cheers<BR>RicB</FONT></BLOCKQUOTE></DIV>
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