laminated ribs

[Ron Nossaman]

> There was a discussion some time back about calculating the load per rib but
> I can't find it.  Do you simply average the number of unisons per rib in
> that section and calculate the load accordingly? 
> 
> David Love


I use the diabolically clever and highly sophisticated method 
of looking at where a line half way between and parallel to 
the ribs intersects the bridge and noting the unison numbers 
at those points. Using these physical observations, each rib 
is assigned the total bearing load of the unisons it will be 
carrying in the piano at the presumed bearing angle and 
calculated tensions from the scaling spreadsheet. Unison loads 
down scale of the line go to the rib immediately below the 
line, and unison loads up scale of the line go to the next rib 
up. In other words, I look at the layout and see which ribs 
are carrying which unisons and add up the unison loads for 
each rib. The deflection of each rib is then computed with the 
accumulated load for each, and that gives me some idea of the 
load capacities of every rib in the system. I then diddle rib 
dimensions, number, and/or bearing angles until I like the 
interrelated results of calculated deflection under load of 
the system, and build it. Every rib is doing a specific job, 
and I'd like some idea of what that job is for every single rib.

It's really not remotely mysterious or tricky. It just takes 
plain old time, thought, and work. Making sense of the outcome 
in terms of tone production is about the only thing that will 
take some accumulated experience and educated judgment - 
within the scope of what type of rib support system you're 
using (RC, or RC&S). The rules are different for each. I have 
no clue whatsoever how to design a CC board, so that one's not 
on the list.

Ron N