Increasing Crown

[gordon stelter]

I am currently fiddling with the idea of gluing
auxilliary laminations to the spine of existing ribs,
while the two are flexed together, along with a
backing caul, by a jig secured to the back of the
piano. 
     I asked Terry Farrel to recommend a
laminate--perhaps 3mm thick, 3 ply, but have not heard
back from him yet. Anyone else care to comment?
     Thump

     
--- Michael Spalding <spalding48@earthlink.net> wrote:
> William,
> 
> I'm a relative newcomer compared to others who I
> hope will join in to
> clarify or refute.  My perspective is that of a
> mechanical engineer turned
> piano technician.  But as I see it, crown is a
> means, not an end.  In other
> words, what you need from a soundboard is
> appropriate
> stiffness/mass/impedence that endures for the life
> of the piano. ( Refer to
> archives about impedence matching SB stiffness to
> string wt/frequency in
> the different regions of the SB.)  Crown is a
> construction feature which,
> in combination with traditional materials and design
> features, tends to
> produce the desired effect.  There are other ways to
> achieve this,
> including Del's epoxy surface coating.  I have
> noticed, in my brief career,
> big improvements in treble power, clarity, and
> sustain in small pianos,
> without doing anything about crown.  What you do
> have to do:  re-attach
> separated ribs, shim or fill SB cracks, cap or epoxy
> the bridges, install
> new bridge pins, re-surface the v-bar and agraffes. 
> Control your shop
> humidity at the lower end of the normal seasonal
> range.  Trying to put
> crown back into an old board by radically drying
> before shimming, or
> pushing up on the underside before shimming, only
> ensures that during next
> summer's high humidity the soundboard will compress
> and crush, and the
> following winter the cracks will come back.  Bottom
> line:  if you want more
> crown, install a new board and/or new ribs.  If you
> want to increase the
> stiffness of the existing board, try the epoxy
> surface treatment.  If you
> want noticeable improvement with low risk, do the
> basics with precise
> attention to detail.
> 
> JMHO
> 
> Mike
> 
> > [Original Message]
> > From: William R. Monroe <pianotech@a440piano.net>
> > To: Pianotech <pianotech@ptg.org>
> > Date: 3/13/2005 7:42:17 AM
> > Subject: Increasing Crown
> >
> > List,
> >
> > I am currently working on rebuilding my own little
> piano to gain some
> > experience, and have a question about improving
> the crown, function of the
> > soundboard.  I had heard of shimming up the SB
> from underneath, prior to
> > shimming, or doing anything else on top (Bridge
> repairs, etc.), in hope
> that
> > by doing these repairs while the board was shimmed
> up, they might act to
> > improve the crown, even a very little bit.
> >
> > My question is about flowing epoxy over the
> surface of the board, as was
> > discussed here a while back, and I'm wondering
> what you all think about
> > having the board wedged up & flowing on epoxy.  My
> concern is about what
> may
> > happen when the wedges are removed - cracked
> epoxy?!?!?
> >
> > What say you?
> >
> > William R. Monroe
> >
> >
> >
> > _______________________________________________
> > pianotech list info:
> https://www.moypiano.com/resources/#archives
> 
> 
> _______________________________________________
> pianotech list info:
> https://www.moypiano.com/resources/#archives
> 


		
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