ribs and stuff (was alternatives.)

[A440A@AOL.COM]

Greetings, 
   Stephen writes:
 
 > The deflection of a centre-loaded
>beam is directly proportional to the loading force until the region of
>plastic deformation is reached. The proportionality constant - stiffness
>parameter - depends on the material properties and the geometry of the
>beam, span length, width and depth, but it *is* constant (unlike a
>hardening spring which is non-linear *below* the plastic deformation
>region). 
>A crowned soundboard is essentially a pre-stressed beam, the amount of
>crown being a measure of the pre-stressing.

OK,  so I got some questions> (?:}}

   I would like to ask, is that rib correctly regarded as only  a "beam"?  Is
there no "arch" aspect to the manner in which downward force is vectored
outward?  What is the centripedal resonator actually doing in those Masons? 
    If a board rises up when being destrung, is it because the soundboard is
losing compression across its grain and expanding?  Or are the edges coming in
with the case in the absence of downbearing pressure? 
Wondering on the weekend
Ed Foote
(also puzzling over the strangest stringing scale I have ever seen, can't wait
to try it!)











 The purpose of the
>pre-stressing is simply so that the net of vertical forces will maintain
>the final deflection within functionally acceptable limits for the desired
>down-bearing. The physical means to produce the crown - whether through
>curved ribs, or compression, or a pre-stressed case while gluing in the
>soundboard, or some other technique - is really irrelevant to the beam
>mechanics. It will matter if the desired crown, produced say by
>compression crowning, exceeds the fibre stress limit of the soundboard
>panel. But that is bad design and could be corrected by using a different
>crowning technique; or reduced down-bearing and/or or stiffer ribs to
>reduce the required crowning. It is the ribs that are the beams that
>balance the down-bearing forces. The panel itself is of no consequence in
>that mechanics, except insofar as it is used as a means to pre-stress the
>ribs, and the thickness of the panel itself adds to the overall height of
>the "beams" somewhat.