<!doctype html public "-//W3C//DTD W3 HTML//EN"> <html><head><style type="text/css"></style><title>Re: Unusual rib structure?</title></head><body> <div>Hi Sarah,</div> <div><br></div> <div>Its an interesting piano you have.</div> <div><br></div> <blockquote type="cite" cite><font face="Arial" size="-1">OK, there's something about my piano (1933 Wissner 9') that seems odd (in my limited experience), and I've just got to ask.  My soundboard ribs have an unusual structure (I think), and I'm uncertain as to the purpose.  Most of the ribs are "tied" together with one of two small cross-braces.</font></blockquote> <div><br></div> <div>I can't see how the ties can do anything to either enhance the structure of the board or its function tonally. They remind me of the tie strap across the bass corner ribs of a model B Steinway, which also are of doubtful benefit.</div> <div><br></div> <blockquote type="cite" cite><font face="Arial" size="-1"> Counting from the keyboard, high treble end of the soundboard, the first brace starts around the center, keyboard-end of the soundboard at rib 8 and continues leftward and towards the tail through rib 13.  Then from the other end of rib 13 (right side of the piano), another brace starts and extends towards rib 17 in the tail.  Ribs 1-7 and rib 18 have no cross-braces.</font></blockquote> <div><br></div> <div>An 18 rib design, while the D has 17 in the latest offerings at least.</div> <div><br></div> <blockquote type="cite" cite><font face="Arial" size="-1">  Here are some photos:</font></blockquote> <blockquote type="cite" cite> </blockquote> <blockquote type="cite" cite><a href="http://www.wonderfulhome.info/soundboard1.jpg"><font face="Arial" size="-1">www.wonderfulhome.info/soundboard1.jpg</font></a></blockquote > <blockquote type="cite" cite><a href="http://www.wonderfulhome.info/soundboard1.jpg"><font face="Arial" size="-1">www.wonderfulhome.info/soundboard</font></a><font face="Arial" size="-1">2.jpg</font></blockquote> <blockquote type="cite" cite><a href="http://www.wonderfulhome.info/soundboard1.jpg"><font face="Arial" size="-1">www.wonderfulhome.info/soundboard</font></a><font face="Arial" size="-1">3.jpg</font></blockquote> <div><br></div> <div>Looking at what appears to be the fifth rib from the bass Sarah (the rib which in jpg 3 runs to the top LH corner of the image), the rib appears to be quite deep in the centre. They look suspiciously like they are rib crowned. Would you mind measuring the overall rib depths at their centres? I'd be interested to know what they are.</div> <div><br></div> <blockquote type="cite" cite><font face="Arial" size="-1"> </font></blockquote> <blockquote type="cite" cite><font face="Arial" size="-1">The ribs on the cross-brace end are not smoothly tapered the way I think of most ribs being.  Rather, they are reduced in tiers, and the cross-braces run across the tiers.  The rib ends without cross-bracing are tapered in the conventional manner.</font></blockquote> <blockquote type="cite" cite><font face="Arial" size="-1"> </font></blockquote> <blockquote type="cite" cite><font face="Arial" size="-1">So...  Why was this done?  Was it a way of stiffening the soundboard?</font></blockquote> <div><br></div> <div>I would speculate that the designer was interested in achieving a graduation in the sudden reduction of the rib section modulus of a conventionally feathered rib. The stepped feathering would probably cause the panel deflection to be somewhat more progressive. Mind you, this may not necessarily be desirable. For me at least, the 'jury is still out' on this matter.</div> <div><br></div> <blockquote type="cite" cite><font face="Arial" size="-1">.  The bass on this piano is incredibly rich, powerful, and mellow, and the sustain is unbelievable.</font></blockquote> <div><br></div> <div>The tiered feathering should allow quite a substantial impedance reduction in the panel behind the bass bridge. I would expect this piano to have quite a dark tone in the bass.</div> <div><br></div> <div>I'll be interested to hear other observations of others re the feathering.</div> <div><br></div> <div>Ron O.</div> <div><br></div> <x-sigsep><pre>-- </pre></x-sigsep> <div>_______________________<br> <br> OVERS PIANOS - SYDNEY<br> Grand Piano Manufacturers</div> <div><br></div> <div>Web: http://overspianos.com.au</div> <div>mailto:info@overspianos.com.au</div> <div>_______________________</div> </body> </html>