Rib scaling question

[William R. Monroe]

Forgive me if I'm being obtuse here, but I'm not clear on how this answers
David L's question.  Not that you were addressing him here, Dale, but, the
question still remains for me, as David phrased it,

" If the danger of too much stiffness in the treble is as you describe, why
the fish?  Doesn't that increase stiffness and reduce mass?"

What say you all on the fish?  It seems that this would be counterproductive
to the, "that short sustain, screaming treble" that Ron N mentions that we
are trying to avoid.  Doesn't employing a fish reduce the mass that we would
otherwise intend to increase?

Respectfully,
William R. Monroe




----- Original Message ----- 
From: <Erwinspiano@aol.com>
To: <pianotech@ptg.org>
Sent: Saturday, January 07, 2006 8:32 PM
Subject: Re: Rib scaling question


>
> Mike /Ron
>    Mike, Thanks  for the kind comments of  appreciation.
>   Mike this stiffness question is surely relevant to  us all. How stiff is
> too stiff?
>   I've maintained that a too stiff system yields a  sustain that must be
> extricated by stiffer & stiffer hammers until it's not  retrievable. ie
too much
> bearing on an otherwise well supported belly  chokes the sound
>      I agree with Ron, usually a safe  thing to do, grin, and it's also
true
> in this  case the  extra ribs are primarily for crown support & turning
them
> perpendicular to  the bridge & obtuse to the grain angle of the sound
board
> increases  stiffness without adding mass.  Del's/Rons have been saying
this for
> years now & I finally proved it to myself.
>      The upper part of the treble board in  the last octave & half area is
> quite stiff simply because the  board spans an ever decreasing span
between
> belly rail and curve side of  case. Combine this with a stiff bridge on
top in the
> same vicinity ands  some short spruce ribs and this is going to drive the
> tone.  Of  course adequate down bearing assumned.
>     Sincerely
>   Dale Erwin
>
>
> >  Primarily for Dale Erwin, (who was generous enough to share his
thoughts
> > and his photos with us all through the PTG Journal) but  anyone please
feel
> > free to chime in if you've got thoughts on  this...
> >
> > Most rib scale modifications I've seen / heard about  involve additional
> > ribs, closer together, and perpendicular to the  bridge, in the treble.
> > Reasons:  maintain crown, increase  impedence for longer sustain.  I'm
> > wondering how critical it is  to get enough but not too much increased
> > stiffness.  Have you  ever gone too far?  What were the resulting
symptoms?
> >
> >  thanks
> >
> > Mike
>
> The addition of treble ribs is  realistically more important to crown
> support in the killer octave than to  high treble stiffness. The
> symptom of too much stiffness in the high end  is that short sustain
> screaming treble we talked about a couple of weeks  ago. The cure is
> mass to get the fundamental resonant frequency  down.
>
> Ron  N
> _______________________________________________
>
>
>
>
> Dale  Erwins Piano Restorations
> 4721 Parker Rd.
> Modesto, Ca  95357
> 209-577-8397 cell 209-985-0990
> Featuring Custom Restoration  Services
> & Sales Of Restored
>
> Steinway ,and Mason &  Hamlin Pianos
> www.Erwinspiano.com
>