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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoPlainText>Not wasted, it's allowed me to formulate more clearly many of my questions and some of the answers. For that I'm appreciative. You could work on style though FWIW. <o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>There is a practical side to this. As I said, I believe the differences between CC boards and RC&S boards are, on a practical level, one of degree not of kind and the differences are characterized by where the bulk of the load is focused. On one far end of the continuum is a complete compression system in which there are no ribs at all. The crown is formed as I mentioned by drying the panel down and gluing it into the rim and allowing it to expand. Any load then that’s put on the board via the string scale will be supported by nothing more than the compression of the panel. Not very practical for obvious reasons but that's a pure compression system. On the other end is the pure RC&S system which calculates the rib scale as if the panel isn't there at all and the ribs are designed to take the entire load of the string scale. I've heard it expressed that way on more than one occasion. But there's a problem. The panel does go there eventually and will contribute to the load bearing properties of the system unless you do one of two things: not include the panel (can't do that) or minimize or zero out the load. Because as soon as you start to load the board you start introducing panel compression and it now becomes a factor in the overall stiffness and impedance characteristics. Very quickly that system will become too stiff and will have all the acoustical characteristics that go along with that. The rate at which the stiffness of the increases in stiffness may differ (you've talked about linear versus non linear systems) but linear, in my view, is not the case. The systems are the same. The rate of deflection looks something like this. A system that starts without compression simply starts farther left on the x axis and the initial rate of change is greater, more linear if you will, than one that starts already with some compression. But I digress.<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText><!--[if gte vml 1]><v:shapetype id="_x0000_t75" coordsize="21600,21600" o:spt="75" o:preferrelative="t" path="m@4@5l@4@11@9@11@9@5xe" filled="f" stroked="f">
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</v:shapetype><v:shape id="Picture_x0020_23" o:spid="_x0000_s1026" type="#_x0000_t75" alt="cid:image007.png@01CC376C.19134270" style='position:absolute;margin-left:0;margin-top:0;width:321pt;height:192.75pt;z-index:1;visibility:visible;mso-wrap-style:square;mso-wrap-distance-left:9pt;mso-wrap-distance-top:0;mso-wrap-distance-right:9pt;mso-wrap-distance-bottom:0;mso-position-horizontal:left;mso-position-horizontal-relative:text;mso-position-vertical:top;mso-position-vertical-relative:text'>
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</v:shape><![endif]--><![if !vml]><img width=428 height=257 src="cid:image002.jpg@01CC421F.E7D4E3D0" align=left hspace=12 alt="cid:image007.png@01CC376C.19134270" v:shapes="Picture_x0020_23"><![endif]><br clear=all><o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>So the next question is how important is loading the assembly. I’ve heard it argued that in this system it's not that important. A very light load is ok. Well, I would say that a very light load is not just ok, it's necessary, but it's not without tonal consequences. If you believe that loading the board is necessary for effective (acoustically effective that is) transfer of the string load to the panel load then you would be SOL. Further, if you believe that loading the board in order to maximize the potential energy in the system (something that's been discussed) is necessary you would also be SOL. If you don't believe that or are willing to live with the acoustic outcome of a relatively unloaded board (or a board with very high impedance characteristics when loaded) then fine. I'll give that that's an esthetic choice. For me personally, having built boards like that, I don't prefer it but I accept it as an option. <o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>Now those are two extreme examples that in the real world don't happen (hopefully). In fact, for most soundboard builders (that I know) there is some attempt to balance the amount of load bearing support of the rib scale along with a manageable amount of compression, commonly in our discussions referred to as a hybrid system. My point is that in practice all systems are hybrid systems. But the emphasis on focusing things at one end of the continuum rather than the other forces certain other choices that affect not only stability and longevity, but the tonal envelope itself. I am more and more inclined to think that there is a somewhat narrow sweet spot in which those factors are in balance and discussing the issue as if it's one or the other and neither the twain shall meet neither represents the reality, practicality or the broader acoustic esthetic that gives us some leeway to manipulate the tone in one direction or the other with some guarantee of success. <o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>David Love<o:p></o:p></p><p class=MsoPlainText>www.davidlovepianos.com<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>-----Original Message-----<br>From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On Behalf Of Ron Nossaman<br>Sent: Thursday, July 14, 2011 10:13 AM<br>To: pianotech@ptg.org<br>Subject: Re: [pianotech] Measuring Crown Radius<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>On 7/14/2011 10:15 AM, David Love wrote:<o:p></o:p></p><p class=MsoPlainText>> You haven't<o:p></o:p></p><p class=MsoPlainText>> adequately answered the question, at least not to me and I am open to it.<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>Then the failure is mine. Since I'm obviously not able to get across to <o:p></o:p></p><p class=MsoPlainText>you one extremely simple mechanical concept on the fundamental <o:p></o:p></p><p class=MsoPlainText>difference between the function of ribs in CC and RC&S boards, I'll quit <o:p></o:p></p><p class=MsoPlainText>wasting your precious time trying and you can find for yourself a more <o:p></o:p></p><p class=MsoPlainText>capable teacher who can.<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>My apologies for your wasted efforts so far.<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>Ron N<o:p></o:p></p></div></body></html>