Buttressed Arch. Question for Ron N.

[Erwinspiano at aol.com]

Ron
  I find that with tight bond glue  it takes about 3 days for the  glue joint 
to get quite hard & then the boom really comes alive.   With the Bolduc glue 
it's the next day.

>  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


 
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