soundboardinstal again

[David Love]

I see, so there is a large "by feel" component in prestresssing the board. 
I can accept that.  So then you pound on the board while inserting the
wedges until it feels right and then set the bearing.  What relevance,
then, is the amount of deflection.  For example, David Hughes writes that
he aims for about 3mm at the centermost strut.  Is this, then, just a check
to be sure that the board, when stressed to your satisfaction by feel,
hasn't moved farther than you anticipated serving as a general indication
of stiffness?

David Love
davidlovepianos@earthlink.net


> [Original Message]
> From: Ron Nossaman <RNossaman@cox.net>
> To: Pianotech <pianotech@ptg.org>
> Date: 7/25/2003 4:29:07 PM
> Subject: Re: soundboardinstal again
>
>
> >I was basing my assumption on an article I read some years back by Bob
Hohf
> >(I think) about bridge recapping.  He used a go bar method for
prestressing
> >the bridge prior to setting bearing.  In wedging the board, you are
aiming
> >for a certain amount of deflection at each strut, right?
>
> You're going more for a certain amount of stiffness than deflection.
>
>
> >Wouldn't the
> >amount of pressure on the board based on the amount of deflection vary
> >quite a bit based on the location of the struts and flex in the struts,
> >among other things.
>
> Yes, to some degree, though I don't think strut flex will have much - uh
- 
> bearing (sorry) on the process. Actual soundboard deflection will vary 
> depending on the board stiffness. Some boards will be stiff enough at a 
> relatively small deflection, some will require more. Many an old board
has 
> been restrung that wasn't stiff enough to support the bearing put on it
and 
> still have positive crown.
>
>
> >Why would this be a more reliable method (though, you
> >are right, I have not experimented with the go bar method).
>
> Because with wedges you can feel what you've got in board stiffness. and 
> can compare stiffness with remaining crown.
>
> Ron N
>
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