Curve on Bridge Bottom

[Ron Nossaman]

>Yes, of course, absolutely. But the essence of my original question is: Is 
>there not an advantage to preserving this rib-induced 
>pre-bridge-installation soundboard crown with a bridge bottom machined to 
>match the board crown (or perhaps you want to machine the curve you think 
>you will have after board loading - whatever). It seems to me it's like 
>installing 16 of 17 machine-crowned ribs, but putting the last one in flat - 
>you know it will bend because there are already 16 on the board with a bend 
>in them - probably won't make much difference.

And the essence of my answer was that whether the bridge is crowned or not,
it is curved. Clamp a ribbed board in a piano so that long grain crown will
form. Lay a flat bridge in place on top and the bridge will fit quite
closely to the soundboard, just like a crowned bridge will. The bridge
doesn't support or depress this long crown. It merely rotates as necessary
to accommodate it. Grab a tenor/treble bridge with one hand at the low
tenor end, laying the treble end on the bench (which has about the same
flexibility of the soundboard treble). With pins up, and the other hand
placed in the middle of the bridge, try to bend it. Observe.  


>Again, I think I am really asking two questions here: First, from a 
>practical standpoint - you have already said there doesn't seem to be much 
>difference - I'll take you at your word. Second, from a theoretical 
>standpoint - I should think there would be at least a theoretical advantage 
>(and if so, perhaps a small, barely perceptible practical advantage - 
>perhaps the practical advantage might only show up after thirty years, as 
>maintaining original crown better?).
>
>Terry Farrell

Since the bridge isn't supporting the crown in the first place, I can't
imagine how it will help support it in the long run. You measure reverse
crown in a Steinway board, which you know has a crowned bridge. You tear
the board out and find the bridge still nicely crowned and as stiff as it
ever was - yet the board was reverse crowned. Where was the crown support
from the long bridge? There never was any to my thinking - the bridge
merely rotated and followed the board down as it went flat. I've read and
heard from day one that the crown formed by the bridge was the most
important crown in the soundboard. I just don't see anything either
logically or demonstrably that supports the idea.

Some folks say they like the treble better with a crowned bridge, some say
they detect no difference attributable to bridge crown. Each of these
people builds a soundboard a little differently from the other. I say bless
them all. They're doing what they perceive as working for them. If you feel
that a crowned bridge will provide long term crown support, then crown your
bridges. It may be beneficial, or it may not, but it won't do any harm that
I'm aware of.

Ron N