I have plans to build a model that will require a special canopy. I have never attempted to form a canopy so I have a lot of questions. First off when I was at the airplane mfg surplus store I picked up a 2x4 ft piece of .040 acrylic plastic. This was the thinnest they had. I have heard that you could make a male mould and by using a heat gin, soften the plastic and pull it down over the mould. I have also heard you can make a female mould and use vacuum to form the heated plastic. I need any information that anyone can give on canopy construction.

From the sound of your description of "molding", I think you are describing the tchnique where youmake a mold and mount it firmly on a pedestal.  Take a pieceof th eclear and secure it to a frame somewhat larger than your projected square area of material needed to form.  Heat the plastic in either the oven (where it "sags" in the frame) or carefully with the heat gun.  You then "pull" it down over the mold. 

A vacuum forming fixture isn't terr)bly hard to make, but Bill Sawyer (Winddancer Models) can probably make you one very inexpensively from yor mold.

Bill <><

  I had a look at my canopy "stash" today, hoping I had a 5-6" bubble canopy for the new "ramrod" that I am building.

 Doh!, no such luck.  I read up on that ACLN article that Jim Thomerson posted the link for.

 It took about an hour to "knock up" a plug out of some (heavy) scrap block and I was away.

 The first couple of attempts worked ok around the middle (highest point) of the canopy but the front and rear ends wrinkled up and didn't shrink nicely around the plug. 

 After a re-think, I cut the bottle down enough so that there was enough plastic over each side to be clamped in the vice with the plug. This held it nice and firm so that I could pull the "over hang" down each end with pliers whilst carefully applying heat with the heatgun.

 It took 4 goes to get a feel for the technique and produce a useable result. More practice will certainly improve the odds.

 For best results use a nice "fresh" bottle that doesn't have any scratches on it and (if possible) use a bottle that has no lines or dimples, so that you get a nice flat, clean sheet of plastic when you cut the bottle up.

 The lines and dimples in coke/sprite bottles etc iron out fairly good but they don't totally disappear.
May not be as noticeable on a little 1/2 A canopy, but the larger the canopy is the more the lines stand out.

 The best thing is that they are free and nothing is lost in attempting to learn the technique.
 
I for one will definately be attempting to perfect the method as it will be quite handy to "Knock up" canopies at will.

Cheers, Rob.

P.S Thanks Jim for posting the link!