Compression Question

[Richard Brekne]

Delwin D Fandrich wrote:

> ----- Original Message -----
> From: "Richard Brekne" <Richard.Brekne@grieg.uib.no>
> To: "Pianotech" <pianotech@ptg.org>
> Sent: August 29, 2003 11:40 AM
> Subject: Re: Compression Question
>
> >
> >
> > John Patton wrote me a year or so back when I asked him about this and
> said
> > then that Steinway dries their boards down to about 4% and uses machine
> > crowned ribs. FWIW.
>
> That is, then, a change from their traditional "perfected" practice.
>
> >
> > Do I understand correctly that the rib crowned board will sooner or later
> also
> > surcomb to more or less the same self destruction, but that essentially
> it will
> > just take much more time for it all to happen ?
>
> Sigh. It depends on the MC of the soundboard panel at the time it is
> ribbed. If it is 4%, yes, the panel will still self-destruct even if the
> ribs are crowned. But the system will still retain most of the crown that
> was machined (or otherwise put) into the ribs. If the MC of the panel was
> up around 6.5% or 7% when it is ribbed it will still be possible to damage
> the board by leaving the piano in a semi-truck trailer somewhere in
> Tennessee during a summer heat wave for two weeks (every day well above
> 100º F) while the driver goes on vacation but it is far less likely that
> the panel will be damaged during anything resembling normal climate
> conditions.
>
> Never is a long time and even wood beams stressed in thier longitudinal
> direction will undergo some creep or compression set. At least in theory.
> But, assuming a normal string load, after some initial settling it will not
> be all that noticable over the lifespan of the piano or its owner.
>
> Del
>
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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