[CAUT] question

[Richard Brekne]

Hi folks


    "The riblets just add some extra stiffness to the overall
    assembly--or the section where they are installed.  The design of
    them is such that the center of the riblet needs to be pulled up by
    the screw to contact the board in the center.  That insures that the
    outer feet also make contact."

This is the other bit that bothers me about these. As the things are to 
be screwed into the bottom area around the bridge, the net effect of  
forcing the middle of the riblet upwards is to engage a reverse crown  
force (over a very short breadth) on the underside of the panel. I 
understand the idea is that one <<bends>> the riblet by screwing it 
in.... but in doing so one has to remember the reasoning used time and 
time again here as one of the main objections some have to CC boards in 
general... the ribs resist bending. In essence then one is exerting a 
downward force on the area of the panel that the screw goes in and 
pushing up on the feet. Even tho this pressure is slight... its there 
and the idea doesn't appeal to me.

As far as gluing any part of the riblet to the soundboard at all is 
concerned... it still strikes me that any along the grain length of rib 
however short that is glued cross grain to the soundboard will exert (on 
the glued breadth of the soundboard/riblet contact) the same kind of 
stresses that any length of rib will.  As such, a short segment glued 
cross grain at high RH seems like a recipe for SB tension cracks later 
on at the area of the glue joint.  I dont see how you can get around 
this myself.

Cheers
RicB

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