Soundboards: Thickness and Area

[Isaac sur Noos]

But Richard, the hammer produce resonnance of the board, at its own
resonnant frequencies, while certainly less efficiently than a
generator, so I believe that is the same effect and the same name for
the sand pictures .

Greetings



Isaac OLEG

Entretien et réparation de pianos.

PianoTech
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> -----Message d'origine-----
> De : pianotech-bounces@ptg.org
> [mailto:pianotech-bounces@ptg.org]De la
> part de Richard Brekne
> Envoyé : lundi 20 octobre 2003 22:41
> À : Pianotech
> Objet : Re: Soundboards: Thickness and Area
>
>
> No no no... we are not talking Chladni patterns here Cy. But you are
> right that they are dependant on the Frequency of the vibration.
>
> But in this case you are not providing the soundboard with
> a particular
> frequency per se... you are just hitting the bridge with a hammer or
> something... as in one time every second or two..
>
> A Chladni pattern require an input frequency that
> corresponds to one of
> the soundboards resonant frequencies.
>
> Cheers
> RicB
>
>
>
> Cy Shuster wrote:
> >
> > Don't these Chladni patterns depend on the frequency of
> the vibration?  See,
> > for example:
> >
> >
> http://www.kettering.edu/acad/scimath/physics/acoustics/imag
> es/chladni-dat.gif
> >
> > It's the last project on this page:
> >
> > http://www.gmi.edu/acad/scimath/physics/acoustics/projects-s.html
> >
> > Or is it different because the edge of the panel is
> already glued down?
> >
> > --Cy Shuster--
> > Rochester, MN
> >
> > ----- Original Message -----
> > From: "Richard Brekne" <Richard.Brekne@grieg.uib.no>
> > To: "Pianotech" <pianotech@ptg.org>
> > Sent: Monday, October 20, 2003 10:49 AM
> > Subject: Re: Soundboards: Thickness and Area
> >
> > Apprapoe freeing up the edges of the board Dale,
> >
> > One of the segements of Steingræbers lecture in Helsinki this past
> > weekend was about this. He showed a few pictures of how
> they go about
> > this at their factory and breifly discussed some of the
> goals in their
> > proceedure.
> >
> > They spread dark sand on the panel and then pound a bit
> on the bridge to
> > see where the sand settles. They remove material from the
> soundboard
> > until the sand accumulates in a very clearly defined thin
> boarder line
> > about the edges of the entire soundboard. They are particularily
> > concerned with the K point area which corresponds to the
> area in the
> > treble where the so called killer octave phenomena occurs. But all
> > around the edge of the soundboard they want a precisely
> defined line of
> > sand.
> >
> > Tho he didnt mention it, the pictures also revealed an
> accumulation of a
> > line of sand just at the leading edge of the bridge as
> well. I didnt get
> > a chance to ask him if that was done on purpose or not.
> >
> > Cheers
> > RicB
> >
> > > Erwinspiano@aol.com wrote:
> > >
> > >          Glenn
> > >   You're asking the hard technical questions. My
> engineer friend say
> > > that when his friends get picky with details the
> comment is "hey your
> > > not building a piano ya know" I take that as a
> compliment. In this
> > > case we are but fortunately board thinning isn't a
> mystery. It however
> > > helps to have an organized approach to thinning. If you
> ask 5 belly
> > > guys how they do it you'll get five different answers.
> > >    The amount of thinning depends on what your goals is
> & what you
> > > think is benifiacial to freeing up the edges of a
> board. The thinning
> > > in most regimines includes thinning along the
> spine(straight side), on
> > > around the tail around the curve and stopping short of
> the top treble
> > > area which needs no or little thinning.
> > > Some also thin along the belly rail up to the offset of the
> > > board ,which is sometimes desireable depending on the
> overal thickness
> > > of the board to start.
> > >   Thinning is mostly restricted
> > >
> > >
> >
> > --
> > Richard Brekne
> > RPT, N.P.T.F.
> > UiB, Bergen, Norway
> > mailto:rbrekne@broadpark.no
> > http://home.broadpark.no/~rbrekne/ricmain.html
> > http://www.hf.uib.no/grieg/personer/cv_RB.html
> > _______________________________________________
> > pianotech list info: https://www.moypiano.com/resources/#archives
> >
> > _______________________________________________
> > pianotech list info: https://www.moypiano.com/resources/#archives
>
> --
> Richard Brekne
> RPT, N.P.T.F.
> UiB, Bergen, Norway
> mailto:rbrekne@broadpark.no
> http://home.broadpark.no/~rbrekne/ricmain.html
> http://www.hf.uib.no/grieg/personer/cv_RB.html
> _______________________________________________
> pianotech list info: https://www.moypiano.com/resources/#archives