soundboardinstal again

[Isaac sur Noos]

Stephen P. affirms that a table which is glued constrained will tone
better that one which is not.
As food for thoughts he say that for instance the elongation of high
treble string is very small (0.3 - 0.4 mm), but the tone difference is
going from 0 to 4000 Hz at the same time.


That the outside of the board does not help much in keeping the crown,
that make sense if we see the load as being carried vertically only ,
but it is not totally, and there is also the stiffening effect John
Hartman tells about.
When humidity changes the crown change should be less without a rim is
not it ?

When shimming the long side of the board , compression is placed under
the neutral fiber, but tension also, above it. Are you saying that the
material (the ribs) can't stand that added pressure ?

Stephen .P pretends that have done that (as a last chance repair) on
some pianos, and the results are there 15 years after he say (not as
good as a full replacement board indeed) under dry conditions he say
(mean, no cracks appear, the crown did not dissipate, etc...

Did not see that by myself.


If so why should we glue the soundboard, just screw them there, it
will be easier to change !

Joke apart, the truth may be using a bit of each of these

Neutral fiber is said to be the place where the fiber is not under
tension, nor in compression, depending of the crowning method and the
amount of crown -  more or less of the rib's height is then under
tension.

This neutral fiber idea is a new to me, but makes sense.


Back to holidays (no no, later !)

Isaac OLEG

Entretien et réparation de pianos.

PianoTech
17 rue de Choisy
94400 VITRY sur SEINE
FRANCE
tel : 033 01 47 18 06 98
fax : 033 01 47 18 06 90
cell: 06 60 42 58 77

> -----Message d'origine-----
> De : pianotech-bounces@ptg.org
> [mailto:pianotech-bounces@ptg.org]De la
> part de Delwin D Fandrich
> Envoyé : lundi 21 juillet 2003 18:43
> À : Pianotech
> Objet : Re: soundboardinstal again
>
>
>
> ----- Original Message -----
> From: "David M. Porritt" <dm.porritt@verizon.net>
> To: <pianotech@ptg.org>
> Sent: July 21, 2003 7:52 AM
> Subject: RE: soundboardinstal again
>
>
> > Ron:
> >
> > It looks like Mason & Hamlin did a fantastic marketing
> job with that
> > little strip of spruce on the fixture with the business card!
> >
> > dave
> >
>
> Yes, they did. But has anyone ever pushed down on the top
> of that arch to
> see how much pressure is required to flatten the thing out?
> I have--and it
> ain't much! And that's with the grain running lengthwise.
> As well, has
> anyone left one of these setups with the pseudo-ribs in
> place for a few
> weeks? Again, I have. And it settles out pretty fast.
>
> Like statistics, experiments can be set up to prove most
> anything--even
> outright misrepresentations. (Well, that's kinder than what I was
> thinking....)
>
> Del
>
>
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