"Morgans" wrote in message
...

"Alan Baker" wrote

Is everyone forgetting the deHavilland Mosquito? Constructed almost
entirely of cold-moulded plywood.

Isn't cold molding done using layers of wood, with glue applied as the
wood
is bent in the mold, with the glue setting up in the new shape?
--
Jim in NC


Exactly. Plywood is nothing but thin veneers of wood glued together face to
face with the grain running at different angles, generally ninety degrees,
but sometimes other angles for special applications. Plywood is normally
laminated on a flat plate making a flat sheet of wood that is very hard to
bend into anything other than a conical curve because the laminated layers
are glued together so they can't slide.

Cold Moulding is merely a low temperature process using ordinary waterproof
glues, for makeing you own plywood from thin veneers that is formed over
something other than a flat plate, so that it comes out with the shape of
the mould it was laminated in or on, as the case may be.

No reason in the world you can't make compound curved plywood by laminating
it up over a male plug and useing a vacuum bagging process to apply the
requisite clamping pressure. Ideally pick a good waterproof glue that gives
you a rather long working time and bonds well with a fairly low clamping
pressure. Say 5 to 10 pounds per square inch clamping pressure that you can
easily obtain with simple vacuum equipment. Working time of fifteen or
twenty minutes should allow time to build up thin laminations and get
clamping pressure onto them. This can be stretched a lot by using staples
with a pull pad under them to apply temporary clamping pressure as you build
up the lamination.

I have only done this using older glues like resorcinol and aerolite and
urea resin. I would think it would work very well with some of the more
modern epoxy based wood glues like T-88, etc. If it works for canoes, it
oughtta work for a Bowlus. :-)

Highflyer
Highflight Aviation Services
Pinckneyville Airport ( PJY )