<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META http-equiv=Content-Type content="text/html; = charset=iso-8859-1"> <META content="MSHTML 6.00.2800.1226" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY bgColor=#ffffff> <DIV><FONT face=Arial color=#800000>I don't deny for a moment that I = may be missing the ball here entirely - I'm really just trying to kick this = around, I think much like yourself. That being said ......</FONT></DIV> <DIV><FONT face=Arial color=#800000></FONT> </DIV> <DIV><FONT face=Arial color=#800000>When you have a CC soundboard = with no load on it, the rib is stressed in that it is trying to straighten out at all = times. The panel is compressed - that is what makes the rib bend, panel = compression. When a load is applied to the top of the soundboard downward, the panel compresses more and the rib is returned to a state closer to straight = and thus lessens stress on the rib.</FONT></DIV> <DIV><FONT face=Arial color=#800000></FONT> </DIV> <DIV><FONT face=Arial color=#800000>I don't understand the logic of = "...<FONT face="Times New Roman" color=#000000>the underside of the panel will = want to expand when down bearing is applied...<FONT face=Arial = color=#800000>". What leads you to that conclusion? Why would the underside of the panel = want to expand? The entire thickness of the panel would compress I should think.</FONT></FONT></FONT></DIV> <DIV><FONT face=Arial color=#800000></FONT> </DIV> <DIV><FONT face=Arial color=#800000>Maybe I'm all wet here, but = that's what makes sense to me. Anyone else care to chime in?</FONT></DIV> <DIV><FONT face=Arial color=#800000></FONT> </DIV> <DIV><FONT face=Arial color=#800000>Terry Farrell</FONT></DIV> <BLOCKQUOTE dir=ltr style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; = BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px"> <DIV style="FONT: 10pt arial">----- Original Message ----- </DIV> <DIV style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: = black"><B>From:</B> <A title=Richard.Brekne@grieg.uib.no href="mailto:Richard.Brekne@grieg.uib.no">Richard Brekne</A> </DIV> <DIV style="FONT: 10pt arial"><B>To:</B> <A = title=pianotech@ptg.org href="mailto:pianotech@ptg.org">Pianotech</A> </DIV> <DIV style="FONT: 10pt arial"><B>Sent:</B> Monday, October 06, 2003 = 5:40 PM</DIV> <DIV style="FONT: 10pt arial"><B>Subject:</B> Re: RC vs CC = again</DIV> <DIV><BR></DIV>  <P>Farrell wrote: <BLOCKQUOTE TYPE="CITE"> <FONT face=Arial><FONT = color=#008080>Comments below - I need some clarification to address these issues.</FONT></FONT></BLOCKQUOTE> <P><BR>Rather then copy over all this let me just re-word and see if = that helps. <P>A crowned CC panel, in addition to whatever else it is... is a = curved peice of wood. And as such the convex side will be stretched relative to the = concave side.  The overall levels of compression in the panel make no = difference in this regard. When downbearing is applied, then the convex side = <I>will be</I> compressed, and the concave side <I>will stretch </I>relative = to their condition before downbearing is applied. . But the ribs resist this = stretching tendancy, they will resist any stretching tendancy on the part of the underside of the soundboard. <P>In otherwords... the underside of the panel tried to expand when it = took on humidity... the ribs resisted this and crown was induced and the ribs = were bent. Pushing down on the board will increase the panels pressure on = the ribs because the underside wants to expand even more. <BR>  <BLOCKQUOTE><FONT color=#3366ff>So as stated above, when you apply downbearing, yes, the concave side of the rib stretches, but only = with reference to its curved compressed state - it doesn't stretch = relative to when it was straight. I think it is more appropriate and more clear = to state that when downbearing is applied, the concave side of the rib = experiences a reduction of its compressed state.</FONT></BLOCKQUOTE>Terry.. I = think you misread something here out of what I was saying ...yes ??  = Applying downbearing will stretch the concave side of the <I>panel.. </I>the = convex side of the <I>rib</I> will see this tendancy to expand just as it = sees any tendancy to expand on the part of the panels underside.... it will = resist the expansion. Hence the rib will experience an increase in stress,... = ergo it has to be supporting the crown against downbearing.  Just because the = the rib is a bit flatter, and there is an apparent lessening of the = compression in the lower half of the rib,  doesnt mean we can ignore this increase = in stress on the rib as a whole... or what ? <P>I dont see at this point how we can get around that, except by = refuting that the underside of the panel will want to expand when down bearing = is applied... and I dont see how we can get there at all. <P>I hope I've made clear where I'm getting hung up accepting this = "ribs dont support crown against downbearing" position. <P>Cheers <BR>RicB <P>-- <BR>Richard Brekne <BR>RPT, N.P.T.F. <BR>UiB, Bergen, Norway = <BR><A href="mailto:rbrekne@broadpark.no">mailto:rbrekne@broadpark.no</A> = <BR><A = href="http://home.broadpark.no/~rbrekne/ricmain.html">http://home.broad= park.no/~rbrekne/ricmain.html</A> <BR><A = href="http://www.hf.uib.no/grieg/personer/cv_RB.html">http://www.hf.uib= .no/grieg/personer/cv_RB.html</A> <BR>  </P></BLOCKQUOTE></BODY></HTML>