clear plastic for vacu forming

Squadron markets a clear material they call Thermaform in small sheets, plus any hobby store that serves the RC market will have acetate or butyrate sheets. Sometimes HobbyLobby carries these items as well.

Also try Evergreen Plastic Models for sheet plastic in various thicknesses, including clear sheets, as well as numerous shapes, e.g. "I" beam, "L" shape, Tubing, etc.

Micro-Mark also sells the plastic sheets in different thicknesses and colors for vacuforming.  They also have a vacuform machine that I'm thinking about.

Jim 

Does your vacuforming machine recommend a thickness? I would estimate the starting thickness your stock plastic to be reduced by half when the material is stretched around the form (assuming the surface area doubles) So 0.010" stock would be approximately 0.005" thick when formed.  So for this example in 1:32nd scale the stock 0.010" plastic is 0.32" thick in scale thick and being reduced to approximately 0.16" scale thickness after being stretched. According to their website Evergreen makes clear polystyrene in 0.005, 0.010, and 0.015" thicknesses.

Unless someone is aware of a reference with some 'non-standard' aircraft dimension specifications you're going have to take a guess at the canopy thickness. Based off engineering judgement I would make these generalizations: Windscreens and forward facing glass are probably thicker than side and rear facing windows, pressurized cabins are thicker than non-pressurized. I'd guess most folks do like me and make it thin (>0.010) so it doesn't look ridiculously thick like some of the older kit canopys.

Squadron Thermaform has not been available other than Ebay for years. It's good stuff with the advantages of not needing a vacuform machine all the waste of using an entire sheet for one small mold that comes from using a vacuform machine. Near as I can tell Squadron has gotten out of the 'stock' plastic business as it not even a category on their website. Spruebothers sells Evergreen.

I have pretty good luck with material from .015 to .030. A compromise has to be struck between being too thick to accept detail such as framing, and drawing down to .0toothin. About any vac-formed canopy is going to beat the socks off injection molded styrene as far as scale thickness goes. I don't know of any references that specify canopy "glass" thickness for any particular airplane, except you will sometimes see a value for a bullet-resistant flat panel. But, looking at some of the warbirds around today, it doesn't appear very thick, maybe 1/4" to 3/8". And yes, pressurized windows or canopies will be much thicker, windshields especially being several inches thick and laminated.

thanks Mij, I'm using an old Mattel Vacuforming machine and it works quite well- however the first canopy I made with the plastic from the Mattel stock was to thin and flimsy. I will try what Fox or Ashley have said and see how that works. Thanks to all who contributed.

ICIT

I have a Mattel Vac-u-form that I found in the basement that my older siblings used. Still heats up and seems like the pumping system doesn't leak. Don't have any plastic for it though. I still have most a package of Squadron Themaform that I use the "heat & smash' method so I haven't looked that hard for plastic sheets for the Vac-u-form.

Have you tried not letting the plastic sheets get as hot (reducing the cook time)? When I use Thermaform it's like stretching sprue, the hotter it gets the thinner it gets when pulled. Maybe your canopy will be slightly thicker (and firmer) if you reduce the cook time. Just a guess.

The Mattel machine works wonderfully, and .015 is just about optimum. You can use any thermal plastic cut to fit the machine, the spikes in the frame trap the sheet just fine even if the sheet is not perforated. I use mine for engine cowls and other panels like gear doors as well. If you need larger capacity than the Vac-U-Form, a custom machine is not hard to fabricate. It is just a box with a perf board top! I built one about 14" by 14", and use a shop vacuum for the vac source. The plastic sheet is trapped in a frame of two sheets of formica and heated with a standard household heat gun. This allows me to make larger pieces and/or use thicker material.

Gonna ask a silly question here.  The other day I was drinking a soda from a clear plastic bottle.  I don't have the equipment needed to do vacuforming but I was thinking that the plastic was impressively clear.  Can one use the plastic from a plastic bottle to form new canopies?

Eric