Bridge design

[Delwin D Fandrich]

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  ----- Original Message -----=20
  From: Erwinspiano@AOL.COM=20
  To: pianotech@ptg.org=20
  Sent: July 11, 2002 11:01 PM
  Subject: Re: Bridge design


  .
  Our own experience bears this out. We've been using laminated Sitka =
spruce ribs for many years and our direct comparative tests have not =
indicated that they are any stiffer than comparable solid Sitka spruce =
ribs. They do have many characteristics we find to be desirable, but =
greater stiffness is not one of them.         Del




   =20
  Del
        Then why go thru the trouble of laminating ribs except it's a =
good use of otherwise unusable spruce or the design characteristics are =
vastly superior. It's a good deal more work

        Since no one asked the obvious question earlier there must be =
some very desireable attributes to laminated ribs to compel one to do =
this routinely. For me the jury still's still out.

         So far all I can determine with my limited experience with Glue =
Lam. ribs is that, when I've done this I've laminated three or four =
pieces of quartered sitka in my soundboard press. Instant 60ft crown =
glued in, but the process is a bit messy. I thought that the ribs seem =
to be more uniformly stiff though.
    Also the rib is uniformly thick like old  flat ribs only nicely bent =
into an arch/arc negating the cutting of the ribs radius unless a =
different one is desired.

               Laminated ribs aren't thicker in the middle than on the =
ends as are crown/radius cut ribs. Desirable or not? Dunno yet.
    I didn't find the ones that I did too have any better tone than the =
no laminated boards. I've also Found that white spruce to be far stiffer =
and more uniformly stiff than Sitka (which seems to vary greatly). Hmm =
another reason to laminate.
         Any secrets left. Don't feel obligated
  .                                Dale Erwin


Consistency. Uniformity. Stability. And a pre-determined and predictable =
crown radius -- we mold the various radii into the rib as it is being =
laminated.

Del



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