Soundboard drydown for installation

[Richard Brekne]

One thing I found interesting about that experiment was that the thing 
did exactly the opposite of what is popularly thrown around.  We all... 
(at least I) have heard  countless times that the rim will support and 
enhance crown as the panel takes on humidity.  But Rons experiment shows 
that on initial glue in the opposite happens.  I.e.  crown is 
prevented.  The thing is tho... the panel still is taking on all that 
humidity...and it still is trying to grow.... so maybe what is REALLY 
the goal here is to put even more compression into the entire panel.  I 
keep remembering that CC believers are real fanatic about getting as 
much <<Tension>> (read stress) into the board as possible over here.  
There IS some grounds for consideration that goes to how one creates 
stiffness in an assembly.

One can not deny that CC boards with wide and short ribs do end up with 
sufficient and more stiffness degrees as any RC board does from the get 
go.  Since that stiffness is not coming from the ribs in the same 
sense... then it must be coming at least somewhat from a compressed 
panel.  Such stiffness would be more uniform over the entire panel.... 
for whatever that is worth.  So if a dried assembly achieves even that 
much more compression by also setting the top half of the panel under 
more compression stress then otherwise... then even more panel stiffness 
would be achieved.... as long as the panel holds its compression 
strength anyways.

Just more thoughts.

Cheers
RicB



         > 'Course, none of this actually works - the ribs won't shrink
        much, the
         > panel top edge will just crush when it expands the 1/10 mm
        that it might
         > move and the rim has enough flex to negate any "arch" support.


    In fact, as my experiment written up for the Journal shows, if
    the panel is constrained from expanding by a nice firm
    buttress, the crown won't form at all if it isn't already
    there in the form of crowned ribs. It ain't an arch. That's
    pretty much a no-brainer by now.


         > But I think the first paragraph above is pretty much the
        reason the
         > practice persists. And in any case, even if it doesn't have any
         > significant effect, some minimal drying prior to installation
        is likely
         > to make most any rebuilder sleep better at night because s/he
        hasn't
         > offended the Goddess of the piano soul.


    I've seen (or think I have) what seems to be an amount of
    "squirm" in soundboard assemblies. Things *move* with MC
    changes. In anticipation and accommodation of such, I tend to
    want to fit the panel, rib it, locate and install the bridges,
    and glue the assembly in at as nearly the same MC as I can
    manage. When I do this, surprises seem to minimize, and
    predictability (and peace of mind) increases.

    A view from the trenches.
    Ron N