Plywood shrinkage??? Laminated soundboards???

[Farrell]

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I wonder if there is any chance a glue might have been used that allowed =
some level of "creep" to the joint - although you said antique furniture =
- is it not the case that all that furniture would have been put =
together with hot hide glue, and is it not true that hide glue is =
considered to be non-creeping?

Will a panel laminated with Tightbond potentially allow some creep? =
Better to use a urea resin formaldehyde two part adhesive glue that =
cures glass-hard?

Terry Farrell
  ----- Original Message -----=20
  From: Sarah Fox=20
  To: Pianotech=20
  Sent: Friday, February 13, 2004 6:31 PM
  Subject: Plywood shrinkage??? Laminated soundboards???


  Hi all,

  My friend and I were examining some antique furniture, figuring out =
how we are going to restore it.  I noticed that many drawer bottoms in =
several pieces were made of thin plywood and, further, that the plywood =
panels were almost universally shrunken by perhaps 1% of their original =
size (e.g. 1/4" over a 25" span).  Moreover, the greater shrinkage =
seemed to be in width, rather than in length, with regard to the =
direction of the grain of the outer veneer.  The drawers weren't made =
this way, as the side pieces of the drawers still fit properly, and the =
bottoms have shrunken out of their channels.  Either that, or the =
original measurements were pretty sloppy, which I doubt.

  How does this happen?

  Perhaps repeated fluctuation in MC causes the panel to expand, =
compress against the drawer sides, and then receed, whereupon dirt and =
debris fills the void in the channel?  With each cycle, the panel is =
compressed smaller and smaller?

  Or perhaps repeated MC fluctuations cause the different laminates to =
play off of each other, somehow causing longitudinal fiber =
compression???

  How???

  And if I'm not imagining that this is happening, what are the =
implications for laminated soundboards?  Perhaps they don't crack, but =
do they shrink?  If so, does that not present the same problem as with a =
conventional soundboard?

  Just curious.  I don't have any laminated soundboard type pianos, but =
I think it's an interesting question.

  Peace,
  Sarah

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