[CAUT] pre-stretching new string Wet vs Dry Soundboard

[Andrew Anderson]

I think Mike may be on to something here.

Has anyone looked into the relative "stiffness" of wood assemblies 
under different MCs?

Andrew Anderson

At 02:38 PM 6/8/2007, you wrote:
>REVELATION:
>   We tune by listening only to the OUTPUT pitches of the soundboard
>resulting from the INPUT forces of the strings.  If the INPUT of the strings
>stays constant, but the board changed in stiffness due to humidity, the
>OUTPUT pitches would be different with the same INPUT.  SO WE CHANGE THE
>TENSION ON THE STRINGS OR THE INPUT TO GET WHAT WE WANT.  This would explain
>how giant pitch swings can occur without any corresponding major change in
>string length, tension, bridge position, or changes in crown.
>   I doubt one could tune a piano by adjusting wire tensions to
>pre-calculated theoretical amounts without listening to the pitches and
>achieve any reasonable result.
>
>-Mike Jorgensen----I'm outa here for a week now.
>
>
>
>On 6/7/07 7:13 PM, "Ron Nossaman" <rnossaman at cox.net> wrote:
>
> >
> >> Where the bridge pin ends up relative to the front
> >> termination is an open question, not one easily measured.
> >
> > Hi Fred,
> > No, not easily measured.
> >
> >> One of the
> >> Fandrich's (I forget which, but think Darrell) wrote about pitch change
> >> due to elongation of the bridge toward the tenor end about ten years
> >> ago, citing speaking length change as a major factor.
> >
> > That was Darrell, and his premise was based on strings not
> > rendering through the bridge. An interesting thought though.
> >
> >
> >> Soundboard movement in response to humidity change isn't just up/down.
> >> The position of the bridge relative to the front termination may change
> >> due to whatever is happening to the board. A bit sideways, a bit back or
> >> forth, a bit of change in cant. It certainly isn't as simple as up and
> >> down, increasing/decreasing bearing (and, hence, distance from a to b,
> >> and, hence, tension).
> >
> > Nothing is simple or isolated, and this isn't a discussion on
> > every potential detail of why and how pianos go out of tune,
> > is it? My initial intention was to illustrate that string
> > stretch wasn't the likely primary reason for long term pitch
> > drop. I don't have authoritative details on everything that
> > happens in soundboards with moisture changes, and most likely
> > never will. I've picked up what I think are a few clues, and
> > reported why I think so. That's the best I can do.
> >
> >
> >> You really think the moisture transfer from the bottom of the soundboard
> >> into (and from) the bridges of a grand is enough to stabilize the
> >> bridges to a significant degree?
> >
> > When it rains outside, the humidity level in my house
> > increases even though the doors and windows are closed.
> > Dampp-Chasers are least effective when the lid is always wide
> > open, with no bottom cover, and most effective with a top and
> > bottom cover.
> >
> > Ron N