Increasing Crown

[gordon stelter]

Thanks Terry, I certainly don't mind your considering
this idea  "beneath you", but if it could easily save
some glorious old pianos ( like Knabe uprights ) from
the dump because they would simply be economically
unfeasible to put new boards into, isn't that a nice
thought ? 
     I have put the whole procedure into a simple 
step-by step format, and will elaborate at length when
I have more time, but, basically: a brace is attached
to the piano back through which are threaded inserts
which allow bolts ( 3/8") to impinge upon the rib
spines at the point where the bridge crosses on the
other side of the board. By adjusting the bolts any
amount of pressure can be applied to bow the board out
at the bridge line, up to popping it right out of the
piano ( if not adequately secured at the margins. ) A
thin laminate ( designed by someone else, I guess, as
you seem not to be interested ) is glued to the ribs'
spines, with a another layer of laminate temporarily
on top as a caul. Then the whole shiboo is bent
outward by turning in the bolts, bellying out the
board, allowed to dry, and the brace and cauls
removed. 
    Specifically: I wonder what laminate would be
thin, strong and light enough ? It's kind of neat to
think of an old, shot CC board suddenly becoming a
rib-crowned board, IMHO. 
     I'll put up the whole procedure as it occured to
me ASAP> I invite anyone with more time than me
presently to put this idea to the test.
     Thump

P.S. I also thought that the elliptical rib laminate (
as in Ron Overs' I beam type, which are wider across
under the bridge line ) might be nifty, if he doesn't
hold patent rights on them. Also: one simple brad
could be placed through the added laminate at the
bridge line point, to keep it from sliding all over
once pressure is applied. And a 4 more hanging driven
through the caul-laminate sides, to keep the glued-up
laminate from sliding off sideways. The problem of
gluing a flat laminate to a  curved rib spine might
not be so bad, if the "squeeze-out" were trowelled
along the glue-line, to add a  bit of filler. I
imagine "West's" with some of the additive to give it
"body".

> 
> I didn't answer because I didn't know quite how to
> respond without sounding
> sarcastic.
> 
> Sooooo, not meaning to sound sarcastic.........
> 
> Yes, I suppose if you wedge up a flat board and glue
> on some auxillary
> laminations, you might be able to get the structure
> to retain a bit of
> crown - but will that do any good? You are
> increasing the mass of the ribs.
> What effect will that have? How much crown do you
> want? Will it get you
> enough crown?
> 
> I guess I just don't have any real interest in
> haphazardly applying
> band-aids to a soundboard that is shot.
> 
> Terry Farrell
> 
> > 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
> 
> 
> 
> 
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