Bridge design

[Greg Newell]

Del,
    I take it then that your ribs are horizontally crowned into the shape you 
    desire. Do you find the stability to be any different between horizontally vs. 
    vertically laminated ribs? I think we talked about this once but I'd like to firm 
    it up in my mind.

Greg Newell


On 11 Jul 2002 at 23:37, Delwin D Fandrich wrote:

> 
> 
>     ----- Original Message ----- 
> From: Erwinspiano@AOL.COM 
> To: pianotech@ptg.org 
> 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
> 
> 
> 
> 
> 
>     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
> 
>