Best way to make a mold for vacuform canopy?

[billn53]

I am building Special Hobby’s Lockheed Electra, which is a 20+ year old kit. The kit includes a vacuform canopy, which has become yellow and brittle with age. 
I wish to use the existing canopy to create a male mold, which I will then use to vacuform a new canopy. 
A few questions:
 

1. Does this sound like a viable plan?
2. What material is best for creating the mold? I’m looking for something that can be poured or pressed inside the existing canopy, then extracted after hardening. 
3. What (if anything) should I use as mold release?
 

Thanks,

Bill

[Stu_davros]

I have replicated numerous vacformed 43rd car windshields by filling the existing vac with plaster of paris. I rig something up to keep the vac level when upside down and pour the plaster mix in, a screw pushed into the setting plaster will make it easier to remove the cast from the vac when the plaster is set.

I've never used anything as a release agent as I've never found it necessary with vacforming.

 

Hope this helps.

 

Stuart

[tomprobert]

In  addition to Stuart’s suggestion above, Millipit is also a very good medium for making masters for vacforming. 
 

Tom

[billn53]

Thanks, Tom & Stuart. I have plenty of both Milliput and PoC, so it seems I’m good to go. And, the screw idea is a great one!

- Bill