Unusual rib structure?

[Sarah Fox]

Hi Ron,

OK, thanks for the explanation (and the photo)!

> Hi Sarah,
> This is done where there should be a cutoff bar, but isn't, like the
> Steinway B shown here
[link redacted at request of site owner - Jul 25, 2015]
> I understand it, when the soundboard gets too big (as they most all are),
> and the ribs too long, the board breaks up into too many competing
> vibrational modes and resonances and fights itself. The small bar
> connecting rib bottoms stiffens critical areas and helps minimize the
> formation of these counterproductive modes. It also stifles some necessary
> soundboard movement, so the ribs are thinned where the bar attaches to try
> to get back some, but not all of what the bar eliminated. It's a fix of
the
> fix. The second step level is the regular feathering. Putting in a real
> cutoff bar instead would have been a better approach, but would have
> lowered the number of square inches of active soundboard area, which
> wouldn't have looked good in the brochure. I don't know why they did it in
> the tail too.

Hmmmm...  I doubt it was for reasons of boasting more square inches.  I
actually have one of the old Wissner catalogs (from 1914, I think), and
there's very little in the way of specs (Style H / Wissner Concert Grand /
The concert pianist's choice / length 8 feet 11 inches', width 5 feet / Made
in ebony, mahogany, and oak" .  Of course most things back then were sold
with quite a paucity of specifications.  Were cutoff bars consistent with
the technology of the day (1933)?

> >Was it a way of bracing the crown, which is quite a lovely one.
>
> Measured where?

As I recall, roughly the tail-most 2/3 of the soundboard, measured parallel
to the ribs.  I didn't really have adequate access to the remainder of the
soundboard to stretch a line.  It has about a 1/4" crown in these areas.

Peace,
Sarah