<!doctype html public "-//w3c//dtd html 4.0 transitional//en"> <html> Hey Dale... So you actually gave that a try then eh ??? Good for you... nothing like good old hands on experimentation to make things clear in ones mind eh ? Actually I did it both ways myself. Never really thought about the difference between arc lengths and chord lengths before. The math is easy enough for sure... but it left me personally scratching my head saying like you seemed to do... "nahhhhh... can THAT be ??"  So I took a thin piece of molding (easy to bend) about a meter long and dinked around afterwards... then got to wondering just how much it would take to get a .05 inch difference and was suprised at the result. "Doing the math" is of course a virtue a lot of us could persue more then we do, but then that doesnt always contribute much to understanding or perception of a thing. I suppose thats because we all think differently and thats really a fascinating thing in itself me thinks. Now, tho I suppose some few may mind... I will ponder a bit more about why this and a few other facts we've seen makes it meaningless to view the panel as a buttressed arch in any sense. I wonder, if you had absolutly rigid supports, and no ribs at all, how much support such a mild arching piece of wood like our generic soundboard would have for any given load over a given period of time. Thanks for the posting Dale. Cheers RicB     Anyways that Erwinspiano@AOL.COM wrote: <blockquote TYPE=CITE>In a message dated 5/3/2002 6:18:31 AM Pacific Standard Time, RNossaman@KSCABLE.com writes:     <blockquote TYPE=CITE style="BORDER-LEFT: #0000ff 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5px">Subj:Re: Crown, was RE:Curve on Bridge Bottom Date:5/3/2002 6:18:31 AM Pacific Standard Time From:<a href="mailto:RNossaman@KSCABLE.com">RNossaman@KSCABLE.com</a> Reply-to:<a href="mailto:pianotech@ptg.org">pianotech@ptg.org</a> To:<a href="mailto:pianotech@ptg.org">pianotech@ptg.org</a> Sent from the Internet          Rick</blockquote> , Ron   Well it does seem doeable at first thought but, it's not.  I toook a long rib (60 ft. radiused) unattached to any thing and simply bent it down flat as an experiment. Imperceptable change in length to the eye. No more argument from this casual observer>   >>>>Dale >>>>>>>>>   <blockquote TYPE=CITE style="BORDER-LEFT: #0000ff 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5px">  >Just trying to figure out why Dale got the notion that the panel would >spread by >0.05 " (1,27mm). Just eyeballing, it seems a reasonable enough first guess - until you check the math. It's just another of the 7.3 billion things that aren't what they seem to be at first glance, traditional wisdom, or intuition. Of course, it's just a matter of opinion that the math is right, and we haven't heard all the expert estimates yet. Ron</blockquote>  </blockquote>     -- Richard Brekne RPT, N.P.T.F. Bergen, Norway <A HREF="mailto:rbrekne@broadpark.no">mailto:rbrekne@broadpark.no</A> <A HREF="http://home.broadpark.no/~rbrekne/ricmain.html">http://home.broadpark.no/~rbrekne/ricmain.html</A>  </html>