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<DIV><FONT size=2></FONT><FONT face=Arial>Hey Richard,</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>I'll stick my neck out - not that I am any =
authority at
all on this subject - but perhaps it will stir something up. I figure if =
I say
something outrageous enough, then someone that knows what they are =
talking about
will chime in.</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>On a compression crowned soundboard, like a
Steinway, the rib acts as something to keep the one side of the =
panel from
expanding when the panel takes on moisture upon removal from the hot box =
- that
is what makes the panel crown. The ribs will be of constant thickness so =
that
the soundboard develops crown evenly. The ribs are thinned only at the =
end to
keep the soundboard flexible at the perimeter.</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>A rib crowned soundboard will have ribs that are =
more
evenly tapered over most of their length, such as the taper you =
describe. That
is because such a shape better supports a load when applied to the =
middle of the
rib, such as downbearing on the bridge. That is what I think, but you'd =
really
need input from an engineer type to say more about that =
subject.</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>Now all other manufacturers use the =
Steinway-shaped rib
because that is what Steinway does.</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>Is your soundboard crowned? Compression crowned? =
Rib
crowned?</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>Terry Farrell</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>----- Original Message ----- </FONT>
<DIV><FONT face=Arial size=2>From: "Richard Brekne" <</FONT><A
href="mailto:Richard.Brekne@grieg.uib.no"><FONT face=Arial
size=2>Richard.Brekne@grieg.uib.no</FONT></A><FONT face=Arial
size=2>></FONT></DIV>
<DIV><FONT face=Arial size=2>To: "Newtonburg" <</FONT><A
href="mailto:pianotech@ptg.org"><FONT face=Arial
size=2>pianotech@ptg.org</FONT></A><FONT face=Arial =
size=2>></FONT></DIV>
<DIV><FONT face=Arial size=2>Sent: Friday, January 23, 2004 10:18
AM</FONT></DIV>
<DIV><FONT face=Arial size=2>Subject: Rib =
Tapering</FONT></DIV></DIV>
<DIV><FONT face=Arial><BR><FONT size=2></FONT></FONT></DIV><FONT =
face=Arial
size=2>> Ok soundboard makers of the nett... Question.<BR>> =
<BR>> I
have re-ribbed this old square grand soundboard, and used more or less =
<BR>>
the ideas Joe and I exchanged, and I am ready to finish off the ribs =
<BR>>
now. On most of these oldies the ribs are very gradually thinned from =
<BR>>
the middle to the edges of the board. On newer instrument types the ribs =
<BR>> are the same thickness for most of the width of the =
panel, then
tapered <BR>> suddenly.<BR>> <BR>> So... what is the functional =
difference and what would be the <BR>> recommended type of tapering =
for this
case. It is a very low tension <BR>> affair and probably will not be =
able to
exert so very much down bearing <BR>> if that means anything. =
If I had
to hazard a guess I'd wonder about how <BR>> tapering effects the =
flexibility
at the edges. But thats just guessing.<BR>> <BR>> First time out =
with a
soundboard rebuild.... finally have my fingernails <BR>> a bit dirty =
with
this kind of work. So any good advice is muchly <BR>> appreciated. =
The panel
was dried for 2 weeks in my shop to the lowest RH <BR>> we get in =
these
parts... roughly 26 %. The panel is about half the <BR>> thickness of =
a
modern panel, and the ribs in question are about 1 cm <BR>> =
thickness, 2 cm
wide, and 2 of them are 60 cm long the third about 45. I <BR>> can =
post a
picture if that would be of help.<BR>> <BR>> Thanks muchly<BR>> =
<BR>> RicB<BR>> <BR>>
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