laminated ribs

[Ron Nossaman]

> Ron:
> 
> I just want to revisit this for a moment.  Do you mean your typical load is
> 900lbs?  And if so, what kind of deflection are you building your ribs for,
> i.e. what percentage of the original crown do you figure is remaining after
> the board is loaded?
> 
> David Love


David,

Somewhere in the vicinity of 900, in a big piano. I'm figuring 
1° in the bass, up to something between 1.5° and 2° at the 
top. I calculate for about 40% deflection in design, and wind 
up between 40% and 50% in reality. I'm happy with at least 50% 
of the original crown remaining. A smaller piano with fewer 
ribs might get more like 600 or 700 lbs, with bearing angles 
adjusted accordingly. Since the spring rate of rib supported 
boards is much more nearly linear than in panel supported 
boards, small changes in bearing angles don't have dramatic 
effects on tone, so the whole thing becomes more structurally 
and less tonally oriented.

Ron N