<!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 6.00.2800.1106" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY> <DIV><FONT color=#008080>Comments below:</FONT></DIV> <DIV> <SPAN id=__#Ath#SignaturePos__></SPAN> </DIV> <DIV>----- Original Message ----- <DIV>From: "Richard Brekne" <<A href="mailto:Richard.Brekne@grieg.uib.no">Richard.Brekne@grieg.uib.no</= A>></DIV> <DIV>To: "Pianotech" <<A href="mailto:pianotech@ptg.org">pianotech@ptg.org</A>></DIV> <DIV>Sent: Sunday, March 30, 2003 10:21 AM</DIV> <DIV>Subject: Re: Soundboard Torture</DIV></DIV> <DIV> <BR>> Farrell wrote:<BR>> <BR>> > I'm not 100% sure I = am understanding your comments correctly, but here goes: The board in my = picture has very thin (about 3/8" thick) ribs and offer little resistance to = bending. An unribbed panel will expand and contract with changing humidity without = crushing - because it can expand freely. With my MC gauge in the photo, the wood = is relatively free (compared to a piano soundboard in a strung piano) to = expand and contract, so little, if any, crushing is going to occur with my MC gauge = (likely no crushing because the level of compression force here is likely well = below the failure level of spruce).<BR>> <BR>> We are on the same page = here.<BR>> <BR>> > In the piano, when the soundboard panel is exposed to a = similar high humidity environment, the panel will try to expand as much as the = panel of my MC gauge. It will tend to crush though because the stiff ribs<BR>> = <BR>> Here's where my comment came in... I thought it (a real = soundboard) would start crushing without the addtion of the string downbearing... = especially if you are up to humidity levels as in your (very cool I might add) experiement.</DIV> <DIV> </DIV> <DIV><FONT color=#008080>If the ribs are more stiff than the = compression strength of the panel, it would certainly make sense.</FONT><BR>> = <BR>> > and the string downbearing pressure prevent it from expanding (of = course, it will expand a little bit, and that is why you might see a several = millimeter increase in crown - ! but not 8 inches).<BR>> <BR>> And then the = addition of string bearing would simply compound, exasperate... further damage = the cells with even more compression.<BR>> <BR>> I thought this is what Del = and Ron have been describing.<BR></DIV> <DIV><FONT color=#008080>I have little doubt that if Del and Ron state = that, it is likely true. </FONT></DIV><FONT color=#008080></FONT> <DIV><BR>> > Does that address your comment? Are you asking = whether panel damage can occur from the rib restraint alone? I don't know what the = numbers are, but obviously if the ribs were big and numerous enough, the panel = thin enough, and the humidity high enough, I'm sure you could set it up where = the panel would fail in areas.<BR>> ><BR>> <BR>> Yes, thats what = I thought has been argued... described by Del, Ron, and a few = others.<BR>> <BR>> ><BR>> > The panel will crush if it is restrained = enough. In a strung piano, I don't know what percentage of the restraint is from ribs = and how much is from string bearing. I suspect the ribs play a much larger = role.<BR>> ><BR>> > Terry Farrell<BR>> ><BR>> <BR>> I think we = are pretty much on the same page Terry. What I dont know is just what = combination of humidity and downbearing will push wood cells beyond their compression = limits in a traditional compression crowned board. I do know, that S&S claim = that as long as the humidity levels are kept within recommended tolereances the soundboard will perform and hold up well.  How they define this = exactly is another matter :)</DIV> <DIV> </DIV> <DIV><FONT color=#008080>Agreed. And I wonder about the same = thing.</FONT></DIV> <DIV><FONT color=#008080></FONT> </DIV> <DIV><FONT color=#008080>Terry Farrell</FONT></DIV> <DIV><BR>> <BR>> Cheers, and thanks for the clarification<BR>> = <BR>> RicB<BR>> <BR>> "Welcome to the Brave New World, may I see your = passport please ?"<BR>> Horiff Ikensaur Urlyf<BR>> <BR>> --<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>&= gt; <A href="http://home.broadpark.no/~rbrekne/ricmain.html">http://home.broad= park.no/~rbrekne/ricmain.html</A><BR>> <BR>> <BR>> = _______________________________________________<BR>> pianotech list info: <A href="https://www.moypiano.com/resources/#archives">http://www.ptg.org= /mailman/listinfo/pianotech</A></DIV></BODY></HTML>