Soundboard stiffening

[Richard Brekne]

gordon stelter wrote:

>If the ribs are firmly suported on the ends they will
>not be trying to straighten the board out, as they
>will be kept in an upward arch independent of board
>crowning or gluing.
>     Thump
>
>  
>
The more I hear this "the ribs are doing nothing but trying to 
straighten out the panel" the less it makes sense.  Ok so the ribs are 
bent as part of the crowning process... so is the panel.. but nobody 
talks about the panel trying to staighten out ribs... yet you could just 
as well turn the whole "lets blame the panels expansion" argumentation 
on the ribs.

I would suggest that the ribs are not bent simply because the panel is 
taking on moisture... but because they are made to  resist any panel 
expansion at the interface between ribs and panel.  It seems only half a 
truth and one that easily leads to less then half truths to simply say 
the ribs are bent by the panel, and do nothing more then resist crown.

No doubt the bend in both panel and rib seen as isolated component 
forces will exert a force that works against crown. Funny how tho the 
net effect is plenty of crown and plenty strength.

Also.... this thread has hinted at a difference between the CC panel and 
RC panel yet to be brought to light... one that has quite probably 
significant performance ramifications.  This matter of increased 
stiffness when downbearing is applied to the one, vs constant stiffness 
for the other.

Curious indeed :)

Cheers
RicB