Piano Construction Origins, was: Butt-Jointed Ribs

[Delwin D Fandrich]

----- Original Message -----
From: "Roger Jolly" <roger.j@sasktel.net>
To: "Pianotech" <pianotech@ptg.org>
Sent: November 23, 2002 10:28 AM
Subject: Re: Piano Construction Origins, was: Butt-Jointed Ribs


> Hi Terry,
>                Baldwin pin blocks was originally developed to make mine
> sweeper hull ribs, in WW11.
>
> Roger
---------------------------------------------


Close, Roger, but I think you'll have to give back that Cuban cigar.

The Compreg -- COMpressed, imPREGnated, wood fiber -- process was developed
to replace brass and aluminum (both non-magnetic materials but prone to
cracking and other catastrophic work related stresses) engine stringers for
mine sweepers.

The process involved coating maple veneers with a (then recently developed)
resorcinol resin adhesive and allowing it to dry. Resorcinol resins will dry
without curing. The veneers were then placed in a heated press and taken up
to (if memory serves) somewhere between 600 and 900 psi and something over
500º to 600º F. (Details are sketchy. It's been a 20 years since I read the
research paper which might still be available from the USFPL-Madison.) The
combination of pressure and heat would liquefy the resorcinol resin and
force it into the wood fibers. (All of this was kept from burning by a
nearly complete lack of oxygen.) It would also force a rapid cure to the
resorcinol resin. The resulting fiber-reinforced plastic was both more dense
that brass and much, much tougher.

The Baldwin pinblock making process is closely related to the Compreg
process with somewhat lower pressures and temperatures resulting in a
slightly less dense fiber-reinforced plastic.

Regards,

Del