rib radius

[Delwin D Fandrich]

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  ----- Original Message -----=20
  From: Erwinspiano@AOL.COM=20
  To: pianotech@ptg.org=20
  Sent: July 11, 2002 6:35 AM
  Subject: Re: rib radius


  In a message dated 7/11/2002 4:31:37 AM Pacific Daylight Time, =
mfarrel2@tampabay.rr.com writes:

          Dittos Terry.=20
      I Know of no on using less crown in the treble. At least many are =
using 60ft. thru out and many of us increasing radius into  the treble. =
I think the confusion is that a 60 ft. curve on a 40 inch rib appears to =
have proportionally more crown (7-8 mm) than a 15 inch rib with a 25 ft. =
curve ( 1.5mm) when observed visually.=20
  >>>>>Dale Erwin>>>>>>>>

Dale & Terry,

Let's define our terms here. When talking about increasing or decreasing =
crown we're generally referring to the amount of visible curvature in =
the system -- a particular rib or the whole board. So an increase in =
crown means the system has more visible curve and a decrease in crown =
has less. It's the radius of the curve that is changing. Now, if we're =
talking about radius then a rib cut to a 40' radius has more crown than =
does a rib cut to a numerically larger 60' radius. Regardless of length.

We use ribs of smaller radius (larger crown) in the treble and ribs of =
larger radius (smaller crown) in the bass.

At least I think that's what Terry was referring to?

Del

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