Rib Crowned Hamburgs ?

[Overs Pianos]

At 2:38 PM -0500 20/6/05, Ron Nossaman wrote:
>
>And rib crowned is not necessarily rib supported, as we have so 
>exhaustively and repeatedly described. Most pianos these days seem 
>to be rib crowned, but bloody few, if any, are rib supported. 
>Calculating loads and deflections from string scale and rib 
>dimensions will tell, for those who truly care to know.
>
>Also, if the ribs ends curve more after feathering, that can only 
>come from panel compression. Either the panel is dryer than ambient 
>room RH% on assembly, or it's pressed into a caul of tighter radius 
>than the ribs when the ribs are glued on.

I totally agree. The factory line is often just the factory spin. How 
many folks check the actual product for conformity to the spin which 
surrounds it? Very few. If the board crowns up more at the feathering 
it is compression crowned regardless of any claim to the contrary. 
Rib supported boards just don't crown up more at the feathering. I 
know this to be a fact because I build rib supported boards, as do a 
few others on this list. And I've also built compression crowned 
control panels which always have a smaller radius at the feathering.

Very often the factory line doesn't match the actual product. How 
often have we heard about the tapering of sound board panels from 
S&S. They may have done it at some time but . . . The original board 
which I pulled from a 1962 Hamburg D last year had a 8 mm thick panel 
everywhere. I still have the original panel at the workshop.

Ron O.
-- 
OVERS PIANOS - SYDNEY
    Grand Piano Manufacturers
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Web http://overspianos.com.au
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