Sometimes a kit canopy is useless. Luckily some companies produce vacuform canopies, but you may manufacture on yourself. You don't even need a vacuform machine. But this technique had it's
limitations. If there is a blisters or very complex shapes, you cannot do canopies with this technique. On the other hand blister could be produced in separate parts.
Master.
First you'll need a master. There is couple of ways to make it.
If original injected canopy is otherwise ok, but that is too thick or there is scratches, it could be used as master. If canopy is in several pieces, clue them together. Just
fill it inside with putty or resin and add a screw for handle. If frames are too heavy or totally wrong, sand them off. You could make frames into new canopy for example from tape, but there is
better ways.
a) add the frames to master. Clue a thin styrene strip or stretched spruse into master. It should repeat
nicely in new canopy.
b) make a separate frame part. When you have made one a "vacu" canopy, leave it to the master and make another part to the top of first
part. You should get two canopies which fits perfectly together. Then cut carefully all "clear" parts off from second canopy, leaving just a frames. And look mom, no masking required!!
If original part is useless, it must be made from scratch. Wood is easy to work with, but wood grains are problematic. Usually they will show in the
result. If you make a master from wood, paint it several times with heat resistant paint.
I have successful used two compound putty,intend to car use. It dries fast and is quite easy to work with.
Third option is resin, but that is quite hard and it could crack easily. It could be useful if you copy original canopy. First brush silicone oil into canopy and
then fill it with resin.
Whatever material you choose, fitting is important. Fit and trim, fit and trim..... And remember to make it little bit smaller than coming canopy. How much smaller, it depends how thick plastic
you use.
Tool
Then you'll need a "vacu" forming tool. I have used 5mm plywood, but other material can be used too.
First you have to cut a hole, which must be slightly bigger than master. Edges must be smooth, so some sanding is required. Then screw it to another plywood plate or to
the board, just like in the picture below.
Making the canopy
The process is very simple. Attach the clear plastic sheet in to of the tool with wooden clothespins or metal clamps. Add
one in each side of the tool.
Then put the it to oven. Temperature depends what kind of plastic you use.
When the plastic is soft take it out of oven and quickly push the master through the hole.
Do not push it too deep. When the master is below the holed plate, its deep enough.
Let it cool and remove the master. And there you go, a new canopy.
Tips
Don't except at first try is perfect. Usually you'll need a couple of "practice pieces" until result is acceptable.
If your better behalf ( wife, girlfriend etc.. ) doesn't allow you to use a oven, use a hotair-gun. It's not as good as oven, but it works fine.
Very small parts, like landing lights or blisters could be made without the tool.
DO NOT USE plastic clothespins!! They will melt in the oven.
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