No downbearing ?

[Delwin D Fandrich]

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  ----- Original Message -----=20
  From: Erwinspiano@aol.com=20
  To: pianotech@ptg.org=20
  Sent: January 02, 2004 2:20 PM
  Subject: Re: No downbearing ?


  In a message dated 1/2/2004 11:51:20 AM Pacific Standard Time, =
pianobuilders@olynet.com writes:
          I wonder if it was common practice to press boards on a flat =
deck which is what I've always heard.(I forget where) Perhaps no one =
really knows but even if they were pressed in a dished caul with ribs =
that long & usually not very tall how much crown could the panel really =
retain over time. I recently saw  1920 ish Knabe upright with very tall =
ribs & enough of them. I didn't check the crown at that time but I will =
when next I see it. This piano was very well preserved ,great sound. =
Thanks for the replies.
     Dale

>From what little I've been able to piece together in talking with some =
old bellymen both were common. The dished caul was introduced along with =
the crowned rib but was often used with flat ribs in the misunderstood =
hope that this would somehow reduce the stress on the panel.=20

In general relatively low, wide ribs are used with compression-crowned =
soundboard systems (they must be flexible enough for the expanding panel =
to force a crown) and taller ribs are used with rib-crowned systems =
(they must be stiff enough to support crown). At the risk of stirring up =
once again The Great Soundboard Debates of 2003, ribs do not support =
crown in a compression-crowned system. They must be relatively flexible. =
The last Knabe upright I was involved with had crowned ribs.

Del
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