soundboardinstal again

[Joe And Penny Goss]

my opinion entirely ?
Joe Goss
imatunr@srvinet.com
www.mothergoosetools.com
----- Original Message ----- 
From: "Danny Boddin" <danny.boddin@pandora.be>
To: "Pianotech" <pianotech@ptg.org>
Sent: Monday, July 21, 2003 2:28 PM
Subject: Re: soundboardinstal again


> Excuse me, what is the meaning of  the 'MOE' ?
> Danny.
> ----- Original Message -----
> From: "Delwin D Fandrich" <pianobuilders@olynet.com>
> To: <oleg-i@noos.fr>; "Pianotech" <pianotech@ptg.org>
> Sent: Monday, July 21, 2003 7:39 PM
> Subject: Re: soundboardinstal again
>
>
> >
> > ----- Original Message -----
> > From: "Isaac sur Noos" <oleg-i@noos.fr>
> > To: "Pianotech" <pianotech@ptg.org>
> > Sent: July 21, 2003 2:30 AM
> > Subject: RE: soundboardinstal again
> >
> >
> > >
> > > The inserting under tension of the soundboard seem the only way to
> > > have some tension in the panel, in the rib direction (across grain)
> > > the modulus of elasticity is said to be 3 Kg cm2 vs. 100 Kg cm2 in
> > > direction of grain.
> > > So if we wish to have some tension in the panel that looks like a
> > > convenient method, more than compression crowning.
> >
> > Do you mean tension as in "a pulling force, or stretching something
> tight?"
> > Or compression as in, "pressing together by an applied force?"
> >
> > Generally soundboard panels are under tension only after some period of
> > having been subjected to compression-set and then finding themselves in
a
> > very dry environment.
> >
> >
> > >
> > > Stephen have forced back some boards with shims on the straight side
> > > with good results he say, when we see the dimensions involved, that
> > > looks like a possibility.
> >
> > The problem with this practice is that it works--but only very
> temporarily.
> > The physical structure of the wood we use for piano soundboards and ribs
> is
> > simply incapable of resisting the stresses created with these
techniques.
> > Entire theories have been built based on the assumption that wood is a
> > perfectly rigid and non-compressible material. But it is not. Even along
> > the grain it is a fairly readily compressible material.
> >
> > The mechanical characteristic involved here is actually compression
> > parallel to grain, not the MOE. This value, for spruce (it varies with
> each
> > specific species) is approximately 5,600 psi to 6,000 psi (36 000 - 40
000
> > kPa). This is not very much considering the small
> > cross-section--approximately 0.25 in2 (160 mm2)--of the typical
> > feathered-out rib end.
> >
> >
> > >
> > > The panel is said to be shaped with 1 cm more than the internal size
> > > of the rim, was said. If possible a soundboard that should be pinched
> > > in the rim should work better from an acoustical point of view (a very
> > > good joke to future rebuilders !)
> >
> > A good joke on the builder as well, I think. Make a sketch of a grand
> piano
> > rim, sketch in the ribs and the soundboard grain angle and then think
> about
> > the stresses involved with the proceedure you describe. Compare those
> > stresses with the known physical qualities of wood and you'll see what I
> > mean.
> >
> >
> > >
> > > Idem on the belly rail, while some brands have stopped the insertion
> > > there (Seiler for instance).
> > > But I seem to understand that in the actual conception in the USA the
> > > soundboard assembly is viewed as an auto supported device is not it ?
> >
> > In the end they are all auto-supported devices regardless of how they
were
> > installed. A few years of compression-set insure this.
> >
> > Del
> >
> >
> > _______________________________________________
> > pianotech list info: https://www.moypiano.com/resources/#archives
> >
> >
>
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