Soundboard crown

[Delwin D Fandrich]

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Re: Soundboard crown
  ----- Original Message -----=20
  From: Phillip Ford=20
  To: Pianotech=20
  Sent: August 17, 2003 10:23 PM
  Subject: Re: Soundboard crown



      I was also speculating about what would happen to this board if it =
was subjected to a drier or more humid environment.  My thought was that =
in a drier environment the board would want to move up.  My thought was =
that the board is describing an arc.  As it dried this arc would have to =
get shorter, so the board would want to flatten out, which in this case =
would mean moving up.  You seem to think it would move down.  Why do you =
think that?

    Good question. You'll have two forces fighting each other, but =
they'll not be equal forces. I think the stress interface will win. At =
least until the panel self-destructs.

  Do you think this panel will be any more likely to self destruct than =
a rib crowned soundboard with positive crown?

I've no idea. It depends on the MC of the panel when the ribs were glued =
on, I should think.

    ....I was making the assumption that any board (whether RC or CC) =
with positive crown and having downbearing would have compression in the =
panel.  But I can see that this gets back into the arch behavior =
territory again.  I presume your position would be that with positive =
crown and downbearing on a RC soundboard there would be no compression =
in the panel because the panel can't support it and all the load is =
being resisted by rib bending.
There might be some. Or there might not be any. It would depend on what =
the MC was at any given moment. If it is above 6.5% there will be some =
nominal amont of compression. If below 6.5% there will be some nominal =
amount of tension.


    Perhaps I can explore that in my experiment as well.

But I suppose we shouldn't hold our collective breaths....

Del
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