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Vacuum forming lessons

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  • Member since
    January 2015
Vacuum forming lessons
Posted by TheMongoose on Friday, March 16, 2018 9:45 PM

Thought I would post this up for those who may find themselves in need of a custom or replacement part some day. I’m kinda kit-bashing a T-38A Talon together - some resin, two different F-5E kits and this custom canopy.

I’m working on a canopy for a 1/32 T-38A Talon. A little experimenting has proven that I cannot make it from 2 canopies alone. Looks like I will have to cut a 3rd to go betwen them to get everything to line up. If I make the blank for a mold, could someone form the finished canopy for me? I’d of course cover all materials and whatever you'd like for your efforts. 

I built a mold from the canopies I cut up. Don’t let those warnings on the perfect cast bags fool you, it doesn’t get hot enough to hurt the clear parts even though they say it will burn your skin.

tonight I learned to vacuum form. It’s to late for me to do anything with them tonight but I’ll post the pics of the process here and in the tips forum for all to see now. This wouldn’t be so easy without the great help I got. Isaac from Cincinnati Scale Modelers looked over my form and gave me advice on improvements before we did our forming. He does this alot for his paper models (wonderful work btw). Kudos to him because we got good parts the first time!

Started out with the basic mold on his vacuum box. Hooked up to a small shop vac. I tapered the sides of the balsa wood base to match the flare at the bottom of the canopy. I drilled holes in the balsa wood for additional vacuum due to that flare just to make sure the plastic pulled in there.


We’re using the kitchen oven here. Gas stove set at 350F. Firebrick on each side to support the frame.


The frame is metal picture frame style held together with aligator clips. Yep that’s me doing my best Vanna, the correct letter was T...-38A


It took 1min 20 sec for the 0.020” petg to sag and be ready to form. The first canopy was really good we thought. A little later we found it didn’t quite form completely in one corner so it will be my test fit piece and the one I use when i try to cut my first canopy out of the plastic form!



We did 3 good ones out of 0.020” petg and 2 out of 0.030” petg. The 030 petg was really really hard to get off the mold. We stopped after the 2nd one. I was worried we’d break the mold trying to get it out. We had to do a lot of cutting where the plastic pulled in around the edges and then pry it up with a stick between the plastic and the balsa wood.

In the pattern: Scale Shipyard's 1/48 Balao Class Sub! leaning out the list, we're down to a Monogram 1/72 SR-71 and that Tamiya P-38F/G to use the other nose art Exito Decal (in-flight for this one), & in keeping with MC's hydra theory I bought another F-5E to do in FROG camo! And I just got a Trumpeter 1/32 F/A-18F!

  • Member since
    January 2015
Posted by PFJN on Saturday, March 17, 2018 6:22 PM


Thanks for the post.  I have some things that I want to try vacuforming on, so its nice to see lessons learned from others. Smile


1st Group BuildSP

  • Member since
    May 2009
  • From: Poland
Posted by Pawel on Saturday, March 17, 2018 7:22 PM


I have built my own vacuum forming machine, works pretty well. It is decribed here:

What could help you is one trich that I have found out accidentally. Ihave made my master out of wood, that has been varnished with lacquer to make it smooth. I also had problems with sticking of the clear sheet to the master so I have wiped the master with liquid soap. After that no sticking anymore, even after many weeks, so I recommend you try it!

Another thing would be to fill your plastic master with plaster of Paris or something like that, to make it more stable and more heat resistant, too!

Hope it helps, have a nice day


All comments and critique welcomed. Thanks for your honest opinions!


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