[CAUT] question

[David Love]

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.
Remember that the ribs are undercut between the center where the screw goes
and the outer edges where the riblet contacts the board.  It's not a
continuous contact along the entire rib.  Pulling them up with the screw
doesn't impact the crown when they are being installed and drying the panel
down to flatten it before you install the riblets might even be
counterproductive as it may restrict the board (slightly) from reforming the
original crown.  You might even be better off installing them when the board
has high moisture content.  However, since the ribs don't expand or contract
much with change in MC (along the grain) it's probably best to glue them on
when the MC is in the most neutral.  Either way it's probably not that
important.  You are not really trying to rebuild crown with them or
influence crown at all, just introduce some added stiffness. 
 
David Love
www.davidlovepianos.com

-----Original Message-----
From: caut-bounces at ptg.org [mailto:caut-bounces at ptg.org] On Behalf Of
Richard Brekne
Sent: Thursday, April 02, 2009 8:11 AM
To: caut at ptg.org
Subject: Re: [CAUT] question

Hi David.

I suppose crown formation itself is more or less out of the question... 
but then again even a 10 cm long riblet will constrain that breadth of 
panel just as much as any other rib will constrain the same width... yes 
??  If thats so then at the very least it would seem wise to me to make 
some attempt at equalizing the degree of panel compression each new 
riblet will have on the panel with the existing rib structure.  What am 
I missing here ?

Cheers
RicB


        The riblets are too short to have any impact on crown formation
        so drying down the panel is probably meaningless.
        David Love
        www.davidlovepianos.com
        ---

    My concern with these has been why there is not advised to dry down
    the panel somewhat prior to installation... or take regard at all to
    panel  MC. Given all the discussion about the effects of rib
    constriction on  climate induced panel change you'd think this would
    be advisable. These  are relatively new devices. It will be
    interesting to see what happens  to the various installations done
    at random climate conditions in the next few years.
    RicB