<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD><TITLE>Re: Soundboard crown</TITLE> <META http-equiv=Content-Type content="text/html; = charset=iso-8859-1"> <STYLE type=text/css>BLOCKQUOTE { PADDING-BOTTOM: 0px; PADDING-TOP: 0px } DL { PADDING-BOTTOM: 0px; PADDING-TOP: 0px } UL { PADDING-BOTTOM: 0px; PADDING-TOP: 0px } OL { PADDING-BOTTOM: 0px; PADDING-TOP: 0px } LI { PADDING-BOTTOM: 0px; PADDING-TOP: 0px } </STYLE> <META content="MSHTML 6.00.2800.1106" name=GENERATOR></HEAD> <BODY bgColor=#ffffff> <DIV><FONT face="Comic Sans MS" color=#000080></FONT> </DIV> <BLOCKQUOTE dir=ltr style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; = BORDER-LEFT: #000080 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=fordpiano@earthlink.net = href="mailto:fordpiano@earthlink.net">Phillip Ford</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> August 17, 2003 10:23 = PM</DIV> <DIV style="FONT: 10pt arial"><B>Subject:</B> Re: Soundboard = crown</DIV> <DIV><BR></DIV> <BLOCKQUOTE cite="" type="cite"> <BLOCKQUOTE><BR>I was also speculating about what would happen to = this board if it was subjected to a drier or more humid = environment.  My thought was that in a drier environment the board would want to = move up.  My thought was that the board is describing an = arc.  As it dried this arc would have to get shorter, so the board would want = to flatten out, which in this case would mean moving up.  You = seem to think it would move down.  Why do you think that?<BR></BLOCKQUOTE></BLOCKQUOTE> <BLOCKQUOTE cite="" type="cite"><FONT face="Comic Sans MS" color=#000080>Good question. You'll have two forces fighting each = other, but they'll not be equal forces. I think the stress interface will win. = At least until the panel self-destructs.</FONT></BLOCKQUOTE> <DIV><FONT face="Comic Sans MS" color=#000080></FONT><BR>Do you = think this panel will be any more likely to self destruct than a rib crowned = soundboard with positive crown?<BR></DIV></BLOCKQUOTE> <DIV dir=ltr type="cite"><FONT face="Comic Sans MS" = color=#000080>I've no idea. It depends on the MC of the panel when the ribs were glued on, I should think.</FONT></DIV> <DIV dir=ltr type="cite"><FONT face="Comic Sans MS" color=#000080></FONT> </DIV> <BLOCKQUOTE dir=ltr style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; = BORDER-LEFT: #000080 2px solid; MARGIN-RIGHT: 0px"> <BLOCKQUOTE cite="" type="cite">....I was making the assumption = that any board (whether RC or CC) with positive crown and having downbearing = would have compression in the panel.  But I can see that this gets = back into the arch behavior territory again.  I presume your position = would be that with positive crown and downbearing on a RC soundboard there = would be no compression in the panel because the panel can't support it and = all the load is being resisted by rib bending.</BLOCKQUOTE></BLOCKQUOTE> <DIV dir=ltr><FONT face="Comic Sans MS" color=#000080>There might = be some. Or there might not be any. It would depend on what the MC was at any given = moment. If it is above 6.5% there will be some nominal amont of compression. If = below 6.5% there will be some nominal amount of tension.</FONT></DIV> <DIV dir=ltr><FONT face="Comic Sans MS" = color=#000080></FONT><BR> </DIV> <BLOCKQUOTE dir=ltr style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; = BORDER-LEFT: #000080 2px solid; MARGIN-RIGHT: 0px"> <BLOCKQUOTE cite="" type="cite"> <DIV>Perhaps I can explore that in my experiment as well.</DIV> <DIV> </DIV></BLOCKQUOTE></BLOCKQUOTE> <DIV dir=ltr><FONT face="Comic Sans MS" color=#000080>But I = suppose we shouldn't hold our collective breaths....</FONT></DIV> <DIV dir=ltr><FONT face="Comic Sans MS" = color=#000080></FONT> </DIV> <DIV dir=ltr><FONT face="Comic Sans MS" color=#000080>Del</FONT></DIV></BODY></HTML>