A friend of mine tried to make his own curving machine, using
a length of steel pipe and a propane torch. We had great fun
watching as he burned his fingers and leaped about yelling
"Ouch ! Ouch !" and made all manner of wavy plastic, but it did
get a bit scary when he almost set his shop afire. After that he
ordered new pre-curved mylar from Germany.

See ya, Dave

PS: I'm sure Bumper could do better ! But not as entertaining.

PPS: Pipe is the wrong idea; as you pass the myler through
it heats the edges and not the area needing the curve...

PPPS: Bumper already knew that.

bumper wrote:
The Mylar is originally curved by passing the strip through a set of curved,
heated rollers. Complicated enough, all by itself (g) . . .