More CC vs RC questions was RE: Killer Octave & Pitch Raise

[Stéphane Collin]

Hi David.

I thought in a CC board, the under side (the one where the ribs are glued 
on) is compressed due to the opposite changes in dimension of the ribs and 
the pannel when stabilizing the moisture, while logically, the upper side is 
tensionned, for the very same reason.
Is this correct ?  Does that come into play ? (Or did I miss something ?)
I would believe, for a RC board with same curvature, the underside of the 
board is less compressed, as the ribs dont tear on the pannel.

Best regards,

Stéphane Collin.



----- Original Message ----- 
From: "David Love" <davidlovepianos@comcast.net>
To: "'Pianotech'" <pianotech@ptg.org>
Sent: Wednesday, February 16, 2005 4:35 PM
Subject: FW: More CC vs RC questions was RE: Killer Octave & Pitch Raise


>
>
> Maybe this is a better way to ask the question.  Does this make sense?
>
> R = rib stiffness under load
> P = panel stiffness under load
> A = total assembly stiffness under load
>
> R + P = A
>
> In an RC board R contributes more to A than in a CC board where P
> contributes more, at least proportionally.  That would mean that in a CC
> board the panel is more stiff relative to an RC board.  If that is
> correct, and if the bearing is the same in both systems, then the
> compressed panel must be stiffer than the uncompressed panel to begin
> with.
>
> David Love
> davidlovepianos@comcast.net
>
> -----Original Message-----
> From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On
> Behalf Of David Love
> Sent: Wednesday, February 16, 2005 6:28 AM
> To: 'Pianotech'
> Subject: RE: More CC vs RC questions was RE: Killer Octave & Pitch Raise
>
> Well this is an important point.  Why doesn't compressing the panel make
> it stiffer?  It seems like it must?  Even if compression and stiffness
> are not synonymous in this discussion, then the question is does
> compression itself change the physical and acoustical properties of the
> panel?
>
> David Love
> davidlovepianos@comcast.net
>
> -----Original Message-----
> From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On
> Behalf Of Ron Nossaman
> Sent: Wednesday, February 16, 2005 4:53 AM
> To: Pianotech
> Subject: RE: More CC vs RC questions was RE: Killer Octave & Pitch Raise
>
>
>>I didn't want this discussion to dry up too quickly as I still have a
>>few--at least--unanswered questions.
>>
>>So let's amplify this point a bit for my own clarification (forgive me,
>>I'm a bit slow sometimes).  It stands to reason that the uncompressed
>>panel is less stiff than the compressed panel, I think we agree on
> that.
>
> Apparently not. Compressing the panel doesn't make it stiffer. it makes
> it
> more compressed, which makes the assembly stiffer because of the
> geometry
> of the assembly.
>
>
>>The overall stiffness of the entire assembly (CC vs RC&S), however, is
>>relatively the same because the ribs in the RC&S board are stiffer than
>>in the CC board and the way the panel and ribs combine produce an
>>overall stiffness measured in terms of the whole assembly.  But if the
>>panel in the RC&S board is somewhat less stiff than the compressed
> panel
>>in the CC board how would you not expect that to have some effect on
> the
>>tone?  While the assemblies may both move up and down at the same rate,
>>might the overall stiffness of the panel, as opposed to the overall
>>assembly, have an effect, say, on which partials are damped and which
>>are not and the balance of those?  So if the slightly less stiff panel
>>has a greater damping effect, then the perception would be a somewhat
>>less lively or expressive, for lack of better words, tone.  I guess
> that
>>was a question.
>
> If the stiffness of the panel changed with compression, I would agree.
> Since it doesn't (how could it?), it's the assembly that is doing the
> work.
> Since the RC&S board will almost certainly have different degrees of
> stiffness and different spring rates in different parts of the assembly
> to
> a greater degree than does the CC board, they will likely not sound
> identical. Compression levels in the panel are not, however, the reason
> they sound different. Opinions will always vary on this point.
>
> It was never the intent of makers of RC&S boards that they should sound
> exactly like CC boards. We want them to sound good, and the many CC
> boards
> out there that don't sound good are what drives the desire to try and
> eliminate the down-side. Dale said it well. We're trying to keep the
> best
> features of the CC board without their inherent problems and
> inconsistencies.
>
> Ron N
>
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