Buttressed Arch. Question for Ron N.

[Fenton Murray]

How about treating the inner rim with a penetrating epoxy?  Holes could be
drilled and filled. From another perspective there were also pianos with
rims that were not solid, Bosendorfer, I think I know of a Chickering.
"From a design novices perspective, ribbing the panel at a 60' radius
through
the panel and 6% emc seems inadequate to form enough crown especially in the
upper end of the piano. "
Thanks to Dave L. for suggesting I re-examine my emc.

----- Original Message ----- 
From: "John M. Formsma" <john at formsmapiano.com>
To: "'Pianotech List'" <pianotech at ptg.org>
Sent: Saturday, April 15, 2006 6:32 PM
Subject: RE: Buttressed Arch. Question for Ron N.


> Rons,
>
> So, bear with one of the guys who feels a little slow in getting all this
> through a thick skull...hitherto I've focused on servicing these pianners
> rather than making the design better, although it's always been quite
> fascinating.
>
> I think what you're saying is that mass in the rim and on the rim via the
> plate is good. Right?
>
> Now, the impedance under consideration is the ability to resist energy
from
> the board into the rim where it's dissipated, if I'm getting it. So, more
> mass = more impedance = more sustain, huh?
>
> OK, next. If more mass is good, what about the theoretical possibility of
> having the most massive, densest material as a rim to which the board was
> affixed somehow? Just for theoretical consideration, would that make it
> better theoretically?
>
> Practically, what better material could be used than what is currently
used?
> I mean, it seems like you could actually get about anything to work, but
the
> heavier you make 'em, the less likely they would be bought b/c they would
be
> so difficult to move.
>
> Thanks from someone whose head impedance is pretty high. <g>
>
> John Formsma
>
> > Following on from Ron N's comments on the mass loading of rims, and its
> > impedance benefits, I've suspected for some time that heavy plates help
> > sustain. I think its one of the reasons why the Baldwin SD-10 is such a
> > remarkable instrument. The benefit of using a denser timber such as rock
> > maple for the rim may have as much to do with the mass increase as
> > stiffness.
>
> I agree, both counts. Load 'em up.
>
> Ron N
>
>
>