laminated ribs

[Ron Nossaman]

> Just to revisit this for a moment--on an RC&S board do you find a
> significant tonal difference between a board loaded at 250 and one loaded at
> 800 lbs?
> 
> David Love

That's a pretty wide range for one board type, and I suppose 
it depends on what is considered significant. I find a 
moderate bearing change makes some slight difference on an 
RC&S board, but a similar change is considerably more dramatic 
on a CC or RC and panel supported board. I think that's 
because because the spring rate doesn't change appreciably in 
the RC&S board as it's deflected, but it does in panel 
supported boards. Spring rate is, I think, key here. But then 
some of that could well be back scale length too, since I 
haven't made bridge position and plate modifications on 
anything but RC&S boards, I don't have direct comparisons. I 
also don't load RC&S boards lightly, or panel supported boards 
heavily in the first place, which complicates comparison.

It goes back to what you said about balancing soundboard 
stiffness to the scale, with bearing load being a necessary 
component of the scale for soundboard design consideration, 
and spring rate is much less variable on a RC&S board after 
it's built and in the piano than in panel supported boards. 
This also means that the tonal character of panel supported 
boards will change more with humidity swings as varying panel 
compression levels change the spring rate.

Ron N