Restoring crown in old soundboard

[gordon stelter]

Some people have routed a bunch of grooves, with
Spurlock's set-up, and installed a  bunch of shims
with the board in "flexed-out" state, and claim to
have successfully re-introduced enough measurable
crown to make the piano sound good. ( D.L. Bullock
wrote an article on this, that I have. ) Others say
it's all "hogwash".  Personally, I don't see why it
wouldn't work, although I might also try laminating
thin "piggybacks" to the rib spines, with the ribs
also "bowed out" and impregnating the board with
something that gives it more body, to compensate for
compression of the wood fibers, over the years. Let it
dry before removing your shims from behindthe bioard,
athat are keeping it bowed. Del Fandrich wrote some
articles about epoxy soundboard coating/impregnating,
in which he claims, or so I've heard, that the epoxy
adds more "mass and stiffness"  , helping it extract
the vibrations from the strings better. I also
suspect, though, that the epoxy, being denser than the
wood, may help vibrations pass across the panel, and
add some of the aforementioned reinforcement.
    That's all I know, and it ain't very much. And
it'll win no friends with the "gotta build a new
board" crowd. So I'm not really recommending it, just
passing on info. Wear adequate carbon-filter gas
masks, and gloves, if you fool around with epoxy, or
any other toxic materiual.
     Thump


--- David Ilvedson <ilvey at sbcglobal.net> wrote:

> Ah...new soundboard, that is...
> 
> David Ilvedson, RPT
> Pacifica, California
> 
> 
> 
> 
> 
> 
> Original message
> From: Hotwheelsp at aol.com
> To: pianotech at ptg.org
> Received: 6/18/2006 4:42:39 PM
> Subject: Restoring crown in old soundboard
> 
> 
> As I have progressed through my first restoration, I
> have now come to repairing the soundboard. After
> inspecting it for cracks (there was only one which
> traversed the upper left corner), I turned my
> attention to the crown of the board. My question now
> is: How do I restore crown to this old board. Is
> this possible? The board has negative downbearing,
> which I guess could be corrected through the
> soon-to-be recapped bridges, but I figured this was
> not the long term solution. Any advice would be
> greatly appreciated
> 
> Phillip Pardue
> 


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