Why do we need crown?

[David Love]

Reverse crown doesn't have to mean negative bearing.  

David Love
davidlovepianos at comcast.net 

-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Ric Brekne
Sent: Sunday, April 23, 2006 4:55 AM
To: pianotech at ptg.org
Subject: Why do we need crown?

Hi Calin

I dont think one actually does need crown.  Del seems to think that crown
was an accident to begin with, and tho I am not sure I would go that far...
it seems to me that all you need is adequate downbearing support  and a good
combination of mass and stiffness.

Crown perhaps facilitates these needs to some degree tho.  We know we can
get a <<free>> increase in stiffness for same amount of mass with crown and
subsequent downbearing for example.

All this is one of the trains going through my mind with regard to grain
direction and laminate boards.  There is lots of stiffness/strength along
the grain.  Laminating a curve along the grain and orienting this
perpendicular to the bridge for the needed support  against downbearing
would perhaps allow more degrees of freedom in ribbing dimmensions needed to
aquire the desired combination of mass/stiffness.

Reverse crown would probably mean  using some other bridge termination
device then bridge pins... at least in the grand.  I would also think that
downbearing in such a situation would be a negative.  

Cheers
RicB

..........
Hello!

All the discussion about crowned ribs, panels and such led me to a question:
Why is there a need for crown in a soundboard?
If one would use a flat panel with adequately proportioned ribs, such as to
provide the necessary stiffness of the panel and resistance to the down
bearing of the strings, wouldn't the soundboard work just as well?
Yes, it would probably be bent in a reversed crown, but I really don't see a
problem with that for now.

Regards,

Calin Tantareanu