soundboardinstal again

[David Love]

John:

I don't know if you are rib crowning or compression crowning, but might
that difference be explained by changes that occur due to compression after
the board is installed?

David Love
davidlovepianos@earthlink.net


> [Original Message]
[link redacted at request of site owner - Jul 25, 2015]
> To: <davidlovepianos@earthlink.net>; Pianotech <pianotech@ptg.org>
> Date: 7/22/2003 5:18:04 AM
> Subject: Re: soundboardinstal again
>
> David Love wrote:
> > A point made earlier in this discussion about the tightness of fit
around
> > the perimeter brings up a question.  I know that some soundboard
installers
> > prefer to do the bridgework with the board out of the piano, i.e.
notching
> > and pinning.  So, they lay in the board, and put the plate in on top,
clamp
> > in a few key places, wedge the board down under the struts and set the
> > bearing, take everything out and notch and pin the bridge.  With a
certain
> > amount of gap around the perimeter of the board, you would think that
the
> > board would move outward slightly in the wedging process such that
setting
> > the bearing would give a different result than when the board was
actually
> > glued in.  Any comments on this method and whether it presents a
problem?
>
>
> David,
>
> I set DB with the bridge glued on and the SB dry fit in the case. The 
> plate is clamped in with wood spacers between the plate bosses and the 
> SB. Wedges are used to pre stress the board so that DB can be set with 
> the SB at its point of equilibrium. Later after all the bridge work is 
> done and the SB is glued in DB is checked before the bolts and screws 
> are installed. I am not sure about the sliding problem you mentioned (I 
> can't see this happening) but I always find that the plate needs to be a 
> little higher. It seems that the SB is a little stiffer (about 20% ?) 
> when it is glued in. I can tell this when I install the wedges. This 
> would indicate that the rim does contribute in some way to the stiffness 
> of the SB. Weather it does this by preventing the ribs from sliding or 
> by preventing them from rotating I am not sure.  I do not have the 
> information in front of me but as I recall that a beam that is clamped 
> at its ends is stiffer than one that is not. I am now building and 
> installing my 200th Soundboard (A guess based on dwindling shop supplies 
> and fatigue) and have found this increase in stiffness to be predictable.
>
> John Hartman RPT
>
> John Hartman Pianos
[link redacted at request of site owner - Jul 25, 2015]
> Rebuilding Steinway and Mason & Hamlin
> Grand Pianos Since 1979
>
> Piano Technicians Journal
> Journal Illustrator/Contributing Editor
[link redacted at request of site owner - Jul 25, 2015]
>