Christchurch and District Model Flying Club
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Making replacement canopy with hot air gun and pop bottle

by Frank Bayes

I have had a go at making a new canopy from a plaster cast from the  inside of my original Dynam Vampire canopy, and shrinking a Tesco Juice bottle over it using a Hot Air Gun.

When choosing a donor bottle make sure that the labels are not glued on. The Tesco Juice bottle  labels are lightly glued in one place only and the plastic is crystal  clear.

Making a plaster cast was easy, just upturning the canopy  and levelling it up with blutak underneath, although I recommend  reinforcing fragile areas, such as the front of the Vampire casting  where it is very thin, by laying in either small pieces of cloth as you fill with plaster, I had some offcuts of thin fibreglass cloth so I  used that.

The plaster cast needs to be strengthened by glueing a piece of wood or card to the underside, as some considerable pressure  is exerted during the shrinking process and plaster obviously is  brittle. The best glue for plaster is PVA White glue. The water based  glue soaks into the plaster. Allow the first coats to dry on both  surfaces before reapplying and allow to dry.

The plaster needs to be placed inside the bottle as near to the top as possible, after the  end is cut off, by placing wood spacers underneath.

I used the  low setting on the Heat Gun as I discovered on the first attempt that  the shrinkage can be very sudden and uncontrollable, as you can see in  one of the photos and causes severe creasing.

There is a need for an undercut under the plaster mould to allow the plastic to curl under.

The first end of the canopy will be fairly simple, but when attempting the  other end, you need to grasp the plastic with pliers as it goes soft and pull it down. It is quite tricky and needs practice.

The plastic is much harder as it shrinks down and cools, as the material is  obviously thicker, and it can be a struggle cutting the plastic to  remove it.

Make sure you don't remove the plaster cast before it  comes out easily after removing the packing, as you can scratct the  plaster which is fragile.

The Vampire canopy is just a bit too  long to use the small bottle I had, so I did two and I have two good  ends which I will attach together.

I think the result is good and costs nothing and was a load of fun to do.

I now have the tricky task of lining in the silver canopy surrounds.

I saw a video on Youtube where the chap attaches a vacuum cleaner directly to the bottle cap end and adjusts the vacuum with his hand over the open end of the bottle. That's the next experiment I think, however I will need to grow a third hand.

The windows have real aluminium frames, well, aluminium foil actually, and look OK.

Vampire aficionados will point out that the rear transverse frame is not in the correct position, this is because the canopy had to be made with two  pop bottles due to the small size and the frame hides the join.........

I have just found a long plastic paint brush container from Hobbycraft,  that is twice as long as a pop bottle so maybe I will try for perfection using that.

Frank

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