Buttressed Arch. Question for Ron N.

[Ron Nossaman]

>  and is there any advantage to trying to make that rim
> immoveable, and is there a consequence to it moving with respect to the
> soundboard?

Another recent observation along these lines, for anyone 
interested. I've read for years how a soundboard doesn't boom 
much when it's first glued in, and develops a boom after a few 
days. With the RC&S board I put in the B I'm currently trying 
to get done, I was playing with the boom, or ring tone of the 
board to see what it did. With the F clamps just on, and 
Titebond still dripping on the floor, I thumped the mid tenor 
bridge with my fist. Got a good solid boom with a bit over 
three second ring time! Thump tone changed frequency up and 
down scale just as I'd expect, but the ring duration really 
stood out as extraordinary. Next day, I removed the clamps and 
thumped it again. Still a good boom, but the ring time was 
half of what it was before I took off the clamps. Now, 
"conventional wisdom" would say it had "something" to do with 
the fit at the rim, and the clamps supplying added coupling 
between the panel and rim, but that ain't it. As I was leaning 
on the curved side pounding away, it struck me that the rim 
was vibrating like a palm sander against my stomach, which 
wasn't nearly as dramatic with the clamps on. Even with that 
"iron fortress" rock maple rim, it was absorbing more 
soundboard energy because I had removed the MASS of the clamps 
from the rim. When I got the plate bolts installed, the plate 
in, and tightened down the cap nuts, the board ring time came 
right back courtesy of the plate mass. Sooooo, it seems to me 
that this could be something else to add to our arsenal of 
possible field modifications in our never ending quest to make 
pianos seem better than they were either designed or built to 
be. Addition of mass loads to inner rims to improve sustain in 
otherwise functional soundboards should be worth a try in some 
situations. It would be easy enough to clamp on test loads to 
diagnose problems and potential improvements, and quick and 
cheap enough to implement if it helped and you had a need.

To whomever,
Ron N