Rib grain orientation

[Delwin D Fandrich]

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Re: Rib grain orientation
  ----- Original Message -----=20
  From: Ron Overs=20
  To: Pianotech=20
  Sent: December 07, 2002 5:57 AM
  Subject: Re: Rib grain orientation


  Hi all,


  I have been wondering about the merit (one which seems to be a long =
standing tradition) in orienting the rib grain such that the growth =
rings run vertically, to set the medullary rays parallel to the sound =
board panel.


  Now I can understand the logic behind this with the CC guys, since =
they are likely to achieve a higher crown when the panel re-hydrates. =
However, in the case of rib crowned construction, wouldn't it be =
advantageous to set the grain in the rib such that the growth rings are =
horizontal and the medullary rays perpendicular to the sound board =
panel? I am contemplating setting the rib grain this way for piano no. =
004 (both 004 and 005 are now sold before completion, which is quite a =
relief).


  Dale, Del and Ron N., and any others who may be using RC construction. =
What are your thoughts on this matter?
Since we're using nothing by laminated ribs these days it hardly =
matters. But ... I did some experiments much like those Ron N wrote =
about with similar results. At least in the sizes and using the =
cross-sectional areas typical to soundboard ribs it really doesn't seem =
to matter which way you align the grain.



  By the way, we decided to build the cut-off as a laminated curve (I =
can't remember if I've mentioned this previously on the list, since I =
had originally planned to make it from scarfed material). We increased =
the cut-off rail section size to 50 mm wide by 35 mm deep, using 17 =
laminates of 2.9 mm thickness. I will try bending it with 4 mm laminates =
for piano 006. When cutting and drum sanding the laminates at 3 mm it is =
quite wasteful of wood. I'll get some photos of the buck and cut-off =
scanned and onto the website soon.
Within reason it doesn't matter how thick you make the laminates. =
Thicker laminates are physically harder to bend but, unless you try to =
vacuum-bag the things, any press you come up with will undoubtedly be =
able to handle whatever you throw in there. You will also get more =
spring-back with thicker veneers but if you were to use, say, 5 =
laminates each 10 mm thick I doubt you'd have enough spring back to =
worry about. Thinner laminates are easier to bend and will give less =
springback but are more awkward to work with, require more adhesive and =
will require a much longer period of time to completely dry and =
stabilize.=20

As with most everything else in the piano it's a compromise.

Del


  Ron O.
--=20

  _______________________

  OVERS PIANOS - SYDNEY
  Grand Piano Manufacturers


  Web: http://overspianos.com.au
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