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<DIV><BR><FONT face=Arial size=2>> I'd restate my question... but it seems
like really no one knows how to <BR>> figure how much compression is imparted
to a panel for a given <BR>> downbearing with known starting values for rib
strength and orientation <BR>> and panel compression for a constant
RH. And if THAT be the case... <BR>> then how on earth can
we be certain of just how much compression is in <BR>> an RC&S panel when
loaded ? Those ribs are stiff suckers... downbearing <BR>> forces compression
in the panel as it strains against the ribs.... its a <BR>> fair
question.<BR>> <BR>> <BR>> Cheers<BR>> RicB<BR>> </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2><STRONG>Ric,</STRONG></FONT></DIV>
<DIV><FONT face=Arial size=2><STRONG></STRONG></FONT> </DIV>
<DIV><FONT face=Arial size=2><STRONG>Symantecs aside, it seems like a fair and
interesting question to ask to me.</STRONG></FONT></DIV>
<DIV><FONT face=Arial size=2><STRONG></STRONG></FONT> </DIV>
<DIV><FONT face=Arial size=2><STRONG>I've built my rib data spreadsheet to
calculate the sag by entering the pressure of the string bearing force, rib
dimensions, modulus of elasticity of rib material, bending and resisting moments
& moment of inertia. Many of these factors come from static
tables in old industrial standard texts for the given material (ie sitka
spruce, sugar pine etc.) and are based upon some sampling once upon a time. I
know it's been brought up that the modulus of elasticity, for example, will vary
from rib to rib even with the same species and dimensions (this by the way
is definitely one of the advantages of the laminated ribs in that the elasticity
coefficient is averaged out). </STRONG></FONT></DIV>
<DIV><FONT face=Arial size=2><STRONG></STRONG></FONT> </DIV>
<DIV><FONT face=Arial size=2><STRONG>Here are some potential
drawbacks:</STRONG></FONT></DIV>
<DIV><FONT face=Arial size=2><STRONG></STRONG></FONT> </DIV>
<OL>
<LI><FONT face=Arial size=2><STRONG>Even with all this data, some of the
static values and constants are averages or
aproximations. </STRONG></FONT></LI>
<LI><FONT face=Arial size=2><STRONG>Everyone I know, including
myself, uses the formula for center loaded beams, which isn't
exactly the case in the piano, where there may be two to
three different loads on a given rib and even when there is only one load
it is not necessarily in the center. This does make a good case for the
symetrical design though, if for no other reason than to make the math
easier.</STRONG></FONT></LI>
<LI><FONT face=Arial size=2><STRONG>A judgement still has to be made as to how
stiff you want your assembly to be. </STRONG></FONT></LI></OL>
<DIV><FONT face=Arial size=2><STRONG>Nevertheless, it's still a pretty good
tool, a point of departure shall we say. I don't know how much compression this
translates into but I would sure like to know. And I would like to experience
how this affects the sound. All in due time I hope, unless this is my Moby
Dick.</STRONG></FONT></DIV>
<DIV><FONT face=Arial size=2><STRONG></STRONG></FONT> </DIV>
<DIV><FONT face=Arial size=2><STRONG>Ron N. makes some very good points about
staying out of the "swamp of details" and staying aware of the diameter of
the hair we are trying to split (definitely goes in the Ron N. Greatest Hits
of List Quotes), but there's no harm in asking
questions.</STRONG></FONT></DIV>
<DIV><STRONG><FONT face=Arial size=2></FONT></STRONG> </DIV>
<DIV><STRONG><FONT face=Arial size=2>Cheers,</FONT></STRONG></DIV>
<DIV><STRONG><FONT face=Arial size=2></FONT></STRONG> </DIV>
<DIV><FONT face=Arial size=2><STRONG>Jude Reveley, RPT<BR>Absolute Piano
Restoration, LLC<BR>Lowell, Massachusetts<BR>(978)
323-4545</STRONG></FONT></DIV></BODY></HTML>