Custom Piano Restoration / SB Designing

[Ron Overs]

>Hi Dale.
>
>I'm curious about something that I dont think has really come up. I 
>hope you are up for an answer.
>
>In RC & S boards as they have been roughly described on the list so 
>far, the primary (or certainly one of the main) concerns is to view 
>the ribs as load carrying beams.  How does one go about avoiding 
>ending up with one or more strings somewhere along the bridge(s) 
>placed so that they can strongly excite a SB reasonant freq close to 
>its own ?  How do you go about dealing with where soundboard nodes 
>and nodal lines end up ?


Ric,

The problem you describe can happen to any soundboard, regardless of 
its construction method.

I use small brass weights, attaching them to the board at strategic 
places along the bridge (under soundboard buttons) to push any nasty 
resonances down to in-between semitones. I use weights anywhere where 
they might be required, as long as it works. Every piano will require 
a slightly different weighting regime, regardless of how carefully it 
is built.

A couple days ago in this space when there was brief discussion of 
soundboard resonant frequencies, there was some talk of the 
fundamental resonance. Someone called for an F.

When we were building no. 6 we had a high end instrument of similar 
soundboard width, in for a rebuild at the same time. Both were 
without plates. The resonant frequency of the other instrument was 
the bottom Bflt of an 88 note compass, while that of No. 6 was the F# 
above. It doesn't of course tell you that much, since its the overall 
stiffness verses mass relationship which will largely dictate the 
resultant resonant fundamental.

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