Compression ridges was :Do you dry the ribs, along with the board, prior to gluing ?

[Greg Newell]

Dean,
	I had not heard Del's assertion from your first sentence before.
That is very interesting. Why wouldn't the greater flexibility in the high
treble also absorb the energy being transmitted there? If Flexibility is NOT
desired in the bass then it would seem that Thump may have a point about the
usefulness of an old panel, yet I still wouldn't trust it in a CC rebuild. 
	Regarding your last statement do I understand that you wish to tie
the high treble bridge into the case? How would that help? If stiffening the
high treble is something that you wish to avoid it would seem that this
would do that quite handily. If stiffening the high treble is something to
be avoided then what exactly does the treble fish provide?

Greg Newell
Greg's Piano Forté
www.gregspianoforte.com
216-226-3791 (office)
216-470-8634 (mobile)

-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Dean May
Sent: Friday, February 01, 2008 1:49 PM
To: 'Pianotech List'
Subject: RE: Compression ridges was :Do you dry the ribs, along with the
board, prior to gluing ?

>>Stiffness is desired in the high treble
>>but what about the bass where flexibility seems to rule? 

According to Del (and I believe it) high mass and high flexibility is
desired for treble. High stiffness and low mass is desired for bass. Low
bass frequencies require a very rigid moving panel. If the panel is not
rigid it absorbs all the energy before pumping out the fundamental
frequency. 

Which leads me to an epiphany I had the other day, thinking about an earlier
comment of how the soundboard panel is flexible across the grain. It seems
to me that running the ribs perpendicular to the grain in the extreme treble
does the very thing you wish to avoid, it stiffens the panel. What about
designing a rib, perhaps the last one (i.e., most extreme treble) that came
off the next to last rib and followed the bridge to the rim. This would give
the bridge support and add mass. Yet it would maximize the flexibility of
the extreme treble area of the board. I may experiment with that on the next
junker I get in. 

Dean

Dean May             cell 812.239.3359 

PianoRebuilders.com   812.235.5272 

Terre Haute IN  47802

 


-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Greg Newell
Sent: Friday, February 01, 2008 1:04 PM
To: 'Pianotech List'
Subject: RE: Compression ridges was :Do you dry the ribs, along with the
board,prior to gluing ?

Thump,
	You bring up a good point. The board would
lose crown due to compression set and therefore bearing which is no doubt
why some "rebuilders" drop the plate to achieve it. Or would that be to
re-achieve it? It seems to me that it's better to achieve the stiffness you
want as a product of design rather than a byproduct of age. Do you feel that
any compression set or at least that which results in compression ridges is
an inadequate design which did not support or resist downbearing?
Specifically in a CC designed board what could be done to design in more
support or resistance? Certainly size, shape and placement/orientation of
ribs, but is there something else? Since in a CC board the board itself
takes much of the load should the board be thicker in order to
resist/support better? That would seem to inhibit the bass movement
dramatically. I maintain, at least by my thinking, that the reuse of an old
board in a CC arrangement is a detriment however much and not a feature. I
could be less potentially problematic in a RC or RC&S board but I still
don't see how it could be better. 
	As an aside, wouldn't the age reactions that you wrote of earlier
which cause the board to become more brittle, however much, lend towards
easier and/or earlier cracks or ridges?  

Greg Newell
Greg's Piano Forté
www.gregspianoforte.com
216-226-3791 (office)
216-470-8634 (mobile)


-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Prof. Euphonious Thump
Sent: Friday, February 01, 2008 12:21 PM
To: Pianotech List
Subject: RE: Compression ridges was :Do you dry the ribs, along with the
board, prior to gluing ?

Compression set, combined with stiffening of the wood
through aging,  would make those areas stiffer, not
less stiff, hence more inclined to augment higher
frequencies, would it not ?
    The only problem I see is that the compression set
has caused the board to lose crown, hence bearing. If
the board was designed in the first place with
inadequate restance to down bearing, well, that's
another problem entirely.
 Thump



--- Greg Newell <gnewell at ameritech.net> wrote:

> David,
> 	Said much better than I. Thank you.
> 
> Greg Newell
> Greg's Piano Forté
> www.gregspianoforte.com
> 216-226-3791 (office)
> 216-470-8634 (mobile)
> 
> -----Original Message-----
> From: pianotech-bounces at ptg.org
> [mailto:pianotech-bounces at ptg.org] On Behalf
> Of David Love
> Sent: Friday, February 01, 2008 10:31 AM
> To: 'Pianotech List'
> Subject: RE: Compression ridges was :Do you dry the
> ribs, along with the
> board, prior to gluing ?
> 
> The problem of determining the extent of damage to
> the panel goes beyond
> what is visible in the form of pressure ridges and
> may be much more
> extensive than what you can see.  The issue is
> whether the extent of the
> damage compromises the panel's ability to achieve
> the requisite stiffness to
> vibrate at certain frequencies, mostly high.  Since
> the cost of replacing
> the panel is negligible when you factor in the labor
> costs of removing the
> panel in one piece undamaged, removing the ribs (you
> would be smart to
> convert this to a rib crowned assembly), repairing
> the obvious areas of
> damage to the panel, it just doesn't make sense to
> me to not replace the
> panel--especially when you can't be sure of the
> outcome.  Unless you are
> clinging to the romantic notion of old wood being
> better, I see no reason to
> go this route and I don't see evidence of old wood
> being better.  If you are
> hoping for performance which is just adequate or
> slightly compromised, then
> it just doesn't make sense.  
> 
> 
> David Love
> davidlovepianos at comcast.net 
> www.davidlovepianos.com
> 
> 
> 
> 
> 
> 



 
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