Thank you, Terry, for the informative answer.
Actually, no, I remember not from whence the
statement originated: only that somewhere in the
barrage of info on this list it was stated that a
rib-crowned board should have ribs taller in
cross-section than wide. And that any piano with wide
( rather than tall ) ribs is inherently CC. That this
Packard was rib crowned there is no doubt: the contour
is readily visually observed as cut into the ribs
themselves. Also that it has an extremely full, rich,
round tone there is no doubt, though the damage to it
is significant ( it lived beneath an air-conditioner
and the whole board is white with water-damaged
shellac. ) And the aforementioned cracks. Quite a
testimony to RC construction, I do believe !!!
Thummmmmmmmmmmmm
P.S. Anyone have definitive dope on a Packard-
automotive, and Packard-piano link ????
--- Terry <terry@farrellpiano.com> wrote:
> Assuming you mean me, I don't believe I have ever
> said any such thing. I
> recall that I did mention that two Knabes that I
> have taken apart had
> crowned ribs but that I didn't know if the crown was
> cut into them or if
> they had just warped that way (although my
> assumption is that the crown was
> cut into them). I know nothing about rib designs on
> Ivers and Pond or
> Packard or any Knabe other than the ones I have in
> my shop.
>
> I believe RC, which stands for Rib Crowned, means
> that the crowning of the
> soundboard is produced by a combination of crowned
> ribs and panel
> compression (the panel is dried down sufficiently
> prior to ribbing so that
> significant panel compression occurs and crown is
> formed in the soundboard
> additional to that formed by the crowned ribs).
> Downbearing in a RC board is
> supported in part by panel compression and part by
> rib crown. RC&S is Rib
> Crowned and Supported - simply meaning that panel
> compression is
> insignificant as a factor in forming crown or
> supporting downbearing.
>
> Realize that there is much of a continuum between
> the two. Ron N., Del and I
> all dry our panels down to somewhere between 6 and
> 6.5% MC prior to ribbing.
> So even here in panels we describe as being RC&S,
> there is some panel
> compression (although maybe not at the tail end of a
> really dry spell) and
> hence some small amount of support produced by panel
> compression (at least
> when they are new). Perhaps Ron O is the only one
> that is building a pure
> RC&S soundboard with his laminated panels (but even
> those panels get
> compressed a bit when the piano is strung!).
>
> Terry Farrell
>
> > Most of the great old pianos I have, with plenty
> of
> > crown remaining, have very substantial ribs which
> are
> > wider than they are deep. It has been said that an
> RC
> > board should have ribs which are deeper and wide,
> and
> > it has been said ( by Terry ) that thesse old
> pianos,
> > such as mine: Knabe, Ivers and Pond, Packard, ARE
> RC.
> > So why do contemorary RC builders invertthe
> formula
> > which has held these pianos so well? My Packard
> > ( free ) has about 10 cracks in the board, but
> still
> > has plenty of crown and sounds like rolling
> thunder. )
> > Also: My previous question was ignored:
> "What, in
> > terms of construction, is the difference between
> an RC
> > and an RC&S board!
> > Thanks in advance,
> > G
> >
> >
> >
> >
> > --- Richard Brekne <Richard.Brekne@grieg.uib.no>
> > wrote:
> >
> > > Ah but it is another matter.
> > >
> > > The RB&S board will by its design nature
> maintain a
> > > more stable
> > > stiffness to mass relationship with variances in
> RH,
> > > and the CC board
> > > will vary more across the grain with those same
> > > variances.
> > >
> > > RicB
> > >
> > > >/ but achieving that and at the same time the
> same
> > > stiffness to mass
> > > />/relationships is another matter.
> > > /
> > > It is not a 'another matter'. If you have
> determined
> > > a certain spring
> > > rate but would like more mass you can use more,
> > > lower and wider ribs,
> > > and your mass will be increased at a given
> > > stiffness. If you want
> > > less mass for the same stiffness (spring rate)
> you
> > > can use less,
> > > deeper and narrower ribs. Its a simple matter to
> > > arrive at the spring
> > > rate and mass relationship required, using RC
> > > construction.
> > > Furthermore, I believe that the stiffness of
> ribs
> > > should ideally be
> > > varied along their length. The rib should be
> stiffer
> > > under the
> > > bridges (where most CC boards collapse in short
> > > order), getting
> > > gradually weaker as we move from the bridges to
> the
> > > ends of the rib.
> > > The tapering of rib strength is a cake walk when
> > > building an RC& S
> > > board. While the CC building school can contour
> the
> > > panel thickness
> > > to increase the stiffness under the bridges, it
> is
> > > more of a 'blunt
> > > instrument'.
> > >
> > >
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