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<DIV><FONT face=Arial size=2>Hi Ron,</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Thanks for the feedback. Rib =
crowned?
Interesting. What characteristics suggest that? (I know very =
little
about soundboard/rib structure.) I gather that rib crowning is a =
more
recent development in piano technology? Is there some place I =
could read a
brief history?</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>I measured the ribs for you. I =
wasn't
perfectly exact in my measurements (didn't have the time), but if you =
want more
exact measurements, I'll get them for you later. Aside from the =
tapered
ends, the dimensions are constant throughout the length of each =
rib.
The bottom of each rib is rounded slightly I didn't measure =
the
lengths of the tapers. The height and width of the ribs (in mm) =
are as
follows (in order from treble to bass):</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>rib =
h
w</FONT></DIV>
<DIV><FONT face=Arial size=2>1 difficult =
access</FONT></DIV>
<DIV><FONT face=Arial size=2>2 =
19
19</FONT></DIV>
<DIV><FONT face=Arial size=2>3 =
21
21</FONT></DIV>
<DIV><FONT face=Arial size=2>4 =
21
23</FONT></DIV>
<DIV><FONT face=Arial size=2>5 =
25
24</FONT></DIV>
<DIV><FONT face=Arial size=2>6 =
25
25</FONT></DIV>
<DIV><FONT face=Arial size=2>7 =
26
26</FONT></DIV>
<DIV><FONT face=Arial size=2>8 ? =
26
(difficult access)</FONT></DIV>
<DIV><FONT face=Arial size=2>9 =
28
26</FONT></DIV>
<DIV><FONT face=Arial size=2>10 =
28
26</FONT></DIV>
<DIV><FONT face=Arial size=2>11 =
28
26</FONT></DIV>
<DIV><FONT face=Arial size=2>12 =
27
26</FONT></DIV>
<DIV><FONT face=Arial size=2>13 =
27
26</FONT></DIV>
<DIV><FONT face=Arial size=2>14 =
26
26</FONT></DIV>
<DIV><FONT face=Arial size=2>15 =
26
26</FONT></DIV>
<DIV><FONT face=Arial size=2>16 =
26
26</FONT></DIV>
<DIV><FONT face=Arial size=2>17 difficult =
access</FONT></DIV>
<DIV><FONT face=Arial size=2>18 difficult =
access</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>You are correct that the bass is rather =
dark.
Of course I like it that way.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Peace,</FONT></DIV>
<DIV><FONT face=Arial size=2>Sarah</FONT></DIV>
<BLOCKQUOTE dir=ltr
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000000 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=sec@overspianos.com.au =
href="mailto:sec@overspianos.com.au">Ron
Overs</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> Tuesday, May 06, 2003 =
6:43 PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: Unusual rib =
structure?</DIV>
<DIV><FONT face=Arial size=2></FONT><FONT face=Arial =
size=2></FONT><BR></DIV>
<DIV>Hi Sarah,</DIV>
<DIV><FONT face=Arial size=2></FONT><FONT face=Arial =
size=2></FONT><BR></DIV>
<DIV>Its an interesting piano you have.</DIV>
<DIV><FONT face=Arial size=2></FONT><FONT face=Arial =
size=2></FONT><BR></DIV>
<BLOCKQUOTE cite="" type="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><FONT face=Arial size=2></FONT><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 cite="" type="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 cite="" type="cite"><FONT face=Arial =
size=-1> Here
are some photos:</FONT></BLOCKQUOTE>
<BLOCKQUOTE cite="" type="cite"> </BLOCKQUOTE>
<BLOCKQUOTE cite="" type="cite"><A
href="http://www.wonderfulhome.info/soundboard1.jpg"><FONT =
face=Arial
=
size=-1>www.wonderfulhome.info/soundboard1.jpg</FONT></A></BLOCKQUOTE>
<BLOCKQUOTE cite="" type="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 cite="" type="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 cite="" type="cite"><FONT face=Arial
size=-1></FONT> </BLOCKQUOTE>
<BLOCKQUOTE cite="" type="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 cite="" type="cite"><FONT face=Arial
size=-1></FONT> </BLOCKQUOTE>
<BLOCKQUOTE cite="" type="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 cite="" type="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></BLOCKQUOTE></BODY></HTML>