Spurlock shimming method.

[Ron Nossaman]

>While I agree with you Ron N, I can see where Roger is coming from 
>here. There must be some minor contribution made by the crowned 
>('arched') sound board being attached to what we hope is a relatively 
>rigid perimeter (rim). 
---------------------------------
>It is interesting just how flexible seemingly solid objects can be. 
>Try placing a magnetic base dial guage ball-end on the bridge with 
>the base attached to the adjacent plate (we adjust plate set bolts 
>using a dial gauge in this position). Then lean on the edge of the 
>rim and watch the dial gauge indicator move. Even with a heavy 
>concert grand rim the movement will amaze you.

This is exactly my point. In any discussion of the basics of soundboard
structure, the minutiae is dragged out and presented as if it was in
important factor - before everyone understands the basics. Then everyone
abandons the basic concepts in favor of all these interesting little
conflicting thoughts that muddy the waters and don't really mean anything
in practice. The creep rate of the spruce will render any infinitesimally
present rim support of crown null and void almost immediately after
installation. There probably is some side pressure against the rim from the
panel, but that still isn't what is forming and maintaining crown. How much
pressure does it take to spread a rim the same distance as the difference
between the chord of the crown arc segment and the arc segment of the crown?



> They expect about 
>half of the down bearing to be lost when the piano is strung and at 
>pitch.

So do I, or rather I expect the crown under downbearing load to be about
half of what I built in.


Ron N