Soundboard mass

[John Delacour]

At 11:40 -0600 24/11/07, Ron Nossaman wrote:

>If you're talking about loading to failure, it's a moot point in a 
>bridge, since the flexural loads aren't anywhere near the limit of 
>strength. Stiffness is exactly the quality in question.

Yes, that goes without saying.

>I'm talking about in general, a lesser bridge height can be 
>effectively compensated for by increasing the number of load 
>supporting ribs. If these ribs are shortened through the treble with 
>cutoffs, considerable stiffness can be obtained with a net reduction 
>in mass, if that's what you want. Ribs can also be reconfigured to 
>be deeper and narrower, again increasing stiffness without being 
>locked into any particular mass as a result. They can also be made 
>wider if you want more mass.

Yes, I must say that I've never understood why for a long period 
makers with very few exceptions used, and still do, ribs of more or 
less square cross-section rather than taller and narrower bars 
providing the same or better stiffness for less mass.  There was a 
time, however, in the very early days of the modern piano, when some 
makers did so, especially on uprights.

>  The whole point of redesign with rib crowned and supported boards 
>is that you get to make these decisions consciously and deliberately 
>rather than taking what the 150 leave you stuck with. This isn't 
>smoke and mirrors. A number of small shop rebuilders are currently 
>doing this stuff quite successfully.

I'm sure they are, and I have at no point suggested it's anything 
like smoke and mirrors, but my thoughts tend always towards design 
from scratch although I'm a rebuilder and although one of my main 
current projects involves the lowering of the level of the (new) 
soundboard to accomodate a 40mm tall bridge.

It's hard to generalize about "150 year old approaches and 
assumptions" let alone 110 year old ones because there were quite a 
few makers who had very individual insights, and the more time goes 
on the more I tend to think there is no new thing under the sun. 
However when I read a man like Wolfenden, who was probably very much 
in the main stream, and incidentally built pretty good pianos, it is 
clear that quite a lot regarding the soundboard and vibration in 
general was not considered as deeply as it might have been and 
tradition and empiricism were allowed to rule.  And though Wolfenden 
may speak of a 38 mm bridge I think he did not actually use such a 
tall bridge and very few makers did, with exceptionally good results.

JD