I have also successfully free blown canopies using a method similar to that
described by Bill D.

I blew the canopy using compressed air and used a deflector plate to make
sure that the cold air did not directly blow on the canopy.

I started with the plexiglas clamped between two sheets of plywood .... the
lower one with a plan view of the canopy cut out of the middle. The
plexiglas and plywood were calmped together by a hundred or so screws around
the edge of the profile. The whole thing was then sat on top of the oven
(really an insulated plywood box with approx 5 kw of electric heaters in the
bottom (make sure you shield the plexiglas from direct radiant heat !!) .
The temperature in the box was monitored with thermocouples. When the
desired temp is reached open the valve on the compressed air and slowly blow
the canopy down into the box. The rest is as per Bill's description.

Actually the hardest bit was getting the plexiglas hot enough (we had to
insulate the box). Also you need a fan in the box to circulate the air and
keep the temperature constant or you WILL get a funny looking canopy !! I
know - I learnt the hardway.

The above process was developed after seen how one manufacture of
certificated aircraft was producing their canopies and by reference to an
article in the old Homebuilt Aircraft magazine.





"c hinds" wrote in message
om...
I know this has been beat to death over the years, but, I am ready to
proceed with canopy fabrication. I am fortunate enough to have a
canopy tool (female mold) but am unsure how to proceed. Use the
female to make a male plug and try stretch forming over the plug? If I
use this method, how do I compensate for the thickness of the plexi
when making the plug? Or I could use the female and attempt to vaccum
it down?
I have an oven started, a huge plywood shipping crate about 6'x4'x4'.
My plan is to heat the plexi and plug together in the crate and upon
reaching proper temp, slide it out and stretch it down.
I have already sent photos of the tool to a canopy house and they
estimate $3k to make one. I figure I can burn up a lot of plexi for
that.
Words of wisdom appreciated.
Thanks,
Clark