<!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 5.50.4134.600" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY bgColor=#ffffff> <DIV> </DIV> <BLOCKQUOTE dir=ltr style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; = BORDER-LEFT: #800080 2px solid; MARGIN-RIGHT: 0px"> <DIV style="FONT: 10pt arial">----- Original Message ----- </DIV> <DIV style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: = black">From: <A title=rbrekne@broadpark.no = href="mailto:rbrekne@broadpark.no">Richard Brekne</A> </DIV> <DIV style="FONT: 10pt arial">To: <A = title=pianotech@ptg.org href="mailto:pianotech@ptg.org">pianotech@ptg.org</A> </DIV> <DIV style="FONT: 10pt arial">Sent: June 16, 2001 6:48 = AM</DIV> <DIV style="FONT: 10pt arial">Subject: Re: Soundboard = Evaluation</DIV> <DIV> </DIV>Ok Del.. lets see if I understand the essence of the = points in your reply correctly then... You saying the following..?? 1:  Compression crowning a board is basically synonymous with = or at least necessitates "fiber compression damage" </BLOCKQUOTE> Almost. I wouldn't use the = word 'necessitates.' It's a result. Compression-crowning a piano soundboard = assembly inevitably results in some amount of fiber compression damage within the = soundboard panel.   <BLOCKQUOTE dir=ltr style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; = BORDER-LEFT: #800080 2px solid; MARGIN-RIGHT: 0px"> 2:  Fiber compression damage will = probably have little effect, if any, on the panels performance as a diaphragm in a = rib crowned sound board assembly. </BLOCKQUOTE> The best evidence to date = points in this direction. It is certainly consistent with the theory of the rib-crowned = soundboard system.   <BLOCKQUOTE dir=ltr style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; = BORDER-LEFT: #800080 2px solid; MARGIN-RIGHT: 0px"> 3:  It is not the compression damage per = se that causes the loss of tone performance, it is the loss of crown in the = sound board assembly (the loss of stiffness) that results from that = compression damage that causes the loss of tone performance. = </BLOCKQUOTE> Yes.   <BLOCKQUOTE dir=ltr style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; = BORDER-LEFT: #800080 2px solid; MARGIN-RIGHT: 0px"> 4 The across grain compression strength  = that maintains crown in compression crowned boards is = inherently weak and will dissipate over time. (relatively short ??) (regardless of = such factors like such as climate ??) </BLOCKQUOTE> Yes. It is both time and = stress dependent. The more compression stress the wood fibers are under, the faster the = resulting compression-set will occur. The longer the wood fibers are under = compression, the more they will be permanently deformed. This is climate dependent to = the degree that during dry periods moisture will be drawn from the wood fibers and = the panel's internal compression will decrease. During humid periods the = wood fibers will absorb moisture, try to swell, and the panel's internal compression = will increase.   <BLOCKQUOTE dir=ltr style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; = BORDER-LEFT: #800080 2px solid; MARGIN-RIGHT: 0px"> I am not quite sure why a compression board is said to be "damaged" = (fiber compression damage) when in essence this damage is meaningless in as = much as all one has to do is re-rib and reconfigure for a rib crowned = assembly. </BLOCKQUOTE> Because, in essence, the = wood fibers end up being permanently damaged! And that's meaningful. As this damage occurs, the performance of the soundboard--in its original configuration--is permanently altered; crown dissipates, string bearing decreases, and tone performance diminishes. Is it meaningless that = compression damage--and the resulting loss of tone performance--can start showing up = in pianos that are only five and ten years old? Is it meaningless that = soundboard compression damage can even be found in pianos while they are still on = the showroom floor? I'd hazard a guess the owners of these pianos don't = consider it meaningless as their piano's tone performance gradually--sometimes not = so gradually--dies and who are now faced with some rather expensive choices = to get it back. Finally, it probably not = meaningless to the technician/rebuilder who will be taking on the task of = remanufacturing the piano to give it a voice once again. That we can take the fiber-damaged = panel, and by installing a rib system of a different design, make it functional = once again as a piano soundboard is a whole other issue. No, on the whole I'd say = fiber compression damage occurring within the soundboard panel is anything but meaningless. Del</BODY></HTML>