Soundboards/stress

[Delwin D Fandrich]

Jim wrote:
Jim wrote
> There is an almost right angle caul to which the Bass and front edge of
> soundboard is fitted to on the glue-up press. A curved fitted caul is
> placed around the curves side of the board. This caul is squeezed about
> 1/8 inch to put pressure across grain while the board is being held down
> by 2 or 3 unglued ribs while the others are being glued and set with the
> go-bars. Mind you, this was the system use back in the early 70's. I
> think they may have done away with go-bars by now. This system was
> used on all of the small grands. You are right that the ribs were flat
> and the table was flat. The 7' and 9' grands were pressed in curved
> cauls using pneumatic pressure on each curved rib in a controlled
> environment. I can't remember if these had cross grain pressure applied
> while gluing up.
> 
> Jim Coleman, Sr.
> 
Jim, (and Bob, and Ron, et al)

Baldwin no longer uses go-bars. Does anyone? 
(Actually, to answer my own question, yes. I just read through the
assembly process found on the Welmar Piano Page and one of the photos
shows the use of a go-bar deck. I fail to see why. I happly discarded
mine a couple of decades ago and switched to air bags. The benifits are
numerous.)

As may be, while I wase there all of Baldwin's rib presses used airbags
to apply pressure to the rib--in my opinion, a much better system. 

They also did not make any attempt to "pre-compress" the soundboard
panel. I question the value of doing this. Perhaps if the soundboard and
ribs were glued up in a flat press using flat ribs, but then, that isn't
good practice either.

The rib cauls were curved, as were the ribs.

The SF-10 and SD-10 were both bellied in a climate controlled room.

ddf