Soundboards: Thickness and Area

[Richard Brekne]

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/images/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
> 
> _______________________________________________
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-- 
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