Soundboard Installation & MC

[Delwin D Fandrich]

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  ----- Original Message -----=20
  From: Erwinspiano@AOL.COM=20
  To: pianotech@ptg.org=20
  Sent: April 26, 2002 1:28 PM
  Subject: Re: Soundboard Installation & MC



      You're still talking about something like 0.003" rim spread from =
full crown to flat.
       Dale wrote
  >>>>I'm not sure I agree with that. I'm about to press up an Stwy L =
board and  after it's pressed and crowned I'll measure across the bottom =
from each end of the longest rib and then I personally will sit or stand =
on  the board on the floor and see how far the rib dimesion expands. Hmm =
this might be hard to measure but I'm going to try anyway. Maybe I'l =
just make a mark on the floor at each rib end and visually observe. Ever =
done this? It seems to me that .003 figure would have to be greater for =
the crown to completely col.lapse
  Actually I see your point thought that even if the board/ribs were =
pressing significantly into the rim like a buttress the wood creep in =
the rim over time would still eventually be the crowns undoing. Still it =
seems like it would have to spread at least .050.=20
   =20
          Ron wrote

    You bend a rim more than that just leaning against it, so there's no =
way it
    will support board crown as a buttressed arch under the bearing =
loads the board
    is subject to. The PSI pressures involved are well beyond the yield =
point of
    the spruce even if you did have an absolutely rigid rim - which you =
don't.

    -=3D-=3D-=3D-=3D--=3D=3D-
    >
    >    >>>>>>>> This is the false crown measured by piano techs that =
is mistaken
    > for real crown values. 1/8" crown on the logest ribs isn't really =
crown. As
    > you know  this false crown disappears as soon as the board is =
released from
    > the rim bevel.


    Exactly the point.


      >>>>>>>>Hey I catch on quick after a long time.
               >>>>>>>>>Dale>>>>>>>>



    .



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