Soundboard mass decisions

[Ron Nossaman]

> When adding mass to the high treble, sometimes there is no access underneath the 
> board.
> 
> I assume that finding a way to attach some mass here is basically "by hook or by 
> crook".  Correct?

Correct, unless you installed the board and made arrangements 
for access or pre-loading before gluing it in. Still looking 
for a very strong hamster that's good with hand tools for 
those field repairs.


> For instance, since its relatively easy to access the front vertical surface of 
> the high treble bridge from the action cavity,
> would there be any reason not to apply a nicely fit piece of bar stock to this 
> surface?  

I've considered it a few times, but haven't tried it. I don't 
see why it wouldn't work.


>Or...is there any reason weight could not be mounted on the top 
> surface of the board, as close to the bridge as possible?

No guesses on this one. It would have to be tried. Except for 
the way it looks, a weight could be screwed to the bridge top 
easiest of all. Maybe we ought to be designing something 
exotic and intentional looking for that purpose. Make it 
mysterious enough, and everyone will want one on their piano too.


> This brings a second question to mind, regarding bridge mass and or stiffness, 
> as it relates to the seriously undercut bridge root often found in original 
> bridge roots. This undercut bridge root which results in mass removal and loss 
> of stiffness, combined with the tapered board up in the treble,  seems to be 
> chasing flexibility and low mass...something very different from what the thread 
> is discussing.  
> 
> What were they up to?
> 
> Jim I    

Flexibility. The undercut is to get the bridge footprint away 
from the belly rail and more into the functional part of the 
board. The configuration of a grand makes this tough to do, 
and something like about 25mm is all you can hope for in most 
cases. Thinning the panel is intended to get more soundboard 
movement and volume, I think, and it works well enough if it 
doesn't kill the required stiffness.
Ron N