Making Vac or Stretch-formed Canopies

Discussion in 'Tips, Tutorials & Tools' started by cdavenport, Jul 24, 2008.

  1. cdavenport

    cdavenport Member

  2. Millenniumfalsehood

    Millenniumfalsehood Active Member

    Awesome! I always wanted to know a good way of thermoforming! :thumb:

    I've used a similar technique for my plastic models to get an ultra-thin but rock-solid canopy for realistic glass thickness on large models(be warned, it takes for-freaking-ever to make canopies this way, but you don't need any special equipment such as a vacuform table):

    Make the mold exactly like you do, only I usually use sculpting putty.

    Pour some Future floor polish into the cavity.

    Rotate and move the mold around until the surface is evenly coated, and keep rotating it until the polish dries.

    Repeat several times, until the canopy is at the desired thickness.

    Remove the canopy from the mold carefully as it will be slightly malleable and set it aside a few days to cure.

    When the canopy it fully cured, sand it down using something like 220-400 grit sandpaper, moving on to progressively finer grits until it's smooth.

    Use a polishing compound to bring back the glassy surface, or alternatively brush on a thin layer of Future(be careful if you do this, as Future will self-dissolve in order that more layers can be added, and you don't want to leave brush-strokes. An airbrush would be useful here, as it distributes an even coat and Future will flow through an airbrush without needing to be thinned).
  3. cdavenport

    cdavenport Member

    Millenium, that looks like an incredible technique. I have an idea that may obviate the need to sand the Future canopy (was that your idea?):

    1. On your Sculpey mold, treat it just like the professional steel mold makers do. Polish the mold and get it glass smooth.

    2. Once your Future canopy is extracted, it should be near perfect. Instead of polishing it, mist on several coats of clear gloss lacquer to hide any blemishes. The Future and Lacquer are incompatible. The Future should be fine.
  4. Millenniumfalsehood

    Millenniumfalsehood Active Member

    I find that Future actually produces a better finish than high-gloss coats myself.

    I actually use Aves epoxy sculpting putty to make molds with, as it is *so* easy to use(1:1 mixing ratio and it doesn't have to be precise at all) and I can thin it and smooth it with denatured alcohol or even water! :mrgreen: It's also %100 non-toxic. I guy I know at Wonderfest demonstrates this property by eating it :eek: (he says it tastes like Fritos, and judging by the smell he's probably right, but I'm not game for it :wink: ).

    The reason I sand the canopy after I demold it instead of making the mold glass-smooth is that I normally just cover the stock paper kit canopy in Aves(after smoothing it down with Future and greasing it up) and then after I cast a canopy I have to sand it to get rid of the fold lines of the paper canopy. I supposed I could just sculpt a canopy from Aves before I make the mold, but this is easier for me. Of course, YMMV. I sort of geared the above tutorial toward paper kits, because I actually mold the plastic kit parts in Aves when I do plastic kits. I have to sand them down usually though, because something about clear plastic makes it deform in most kits and I have to sand down the deformations to restore the original high-gloss sheen.
  5. cdavenport

    cdavenport Member

    I had to reread your post to fully digest what you described. As I understand this, you use the plastic canopy part as the male buck and form the Aves around it to make a female cavity.

    What I do not understand is if the male buck is perfectly smooth why would not the interior of the female mold be equally smooth? Am asking this because I would like to try your technique out on a model I have.

    Also, how to you adhere the Future canopy to the plastic model? I can think of several ways to do this; I want to learn your technique as a baseline.

    Thanks for sharing this with me. Wish we were in a modeling club together.
  6. Millenniumfalsehood

    Millenniumfalsehood Active Member

    Wish there was a modeling club within a fifty mile radius of me, but hey, that's life. :wink: Hey, maybe if you ever make it to Wonderfest sometime we could meet and discuss techniques, models, etc.

    (I hope I understood your question, asking about whether the mold would be smooth because the buck is): The thing is, with all injection-molded plastic parts there will always be a little bit of shrinkage when the parts cool down after being in a molten state, which produces distortions, differing thicknesses, etc. When this happens with opaque parts, it's not noticeable, but in clear parts it's extremely noticeable because the parts act like a lens, distorting the light waves and making the parts into, basically, fun-house windows. I use this method to produce a canopy that is both at scale thickness and is smooth. High-quality kits usually have distortion-free clear parts, but cheaper kits will have distorted clear parts, so it's necessary to sand them down anyway to make them the correct shape. And after they are sanded as smooth as sandpaper and polishing compounds will get them, a dip in Future is usually enough to get that specularity that is unique to glass. I actually had a guy comment that I was crazy to cut glass for my model when plastic would suffice. :roll: Apparently he'd read about how film crews would use glass slide covers to get scale windows and thought it was a model builder's technique.

    If you're molding a paper canopy, then of course you'll need to sand the end product down because of the fold lines and the texture of the paper.

    To attach the canopy, I use either white glue(if I feel like I may want to modify the cockpit later) or, again, Future. Future, since it is extremely sticky and is somewhat self-dissolving actually makes the perfect glue to use for Future canopies, as it both bonds to the plastic and the canopy, the latter at the molecular level. As you may know, never, under any circumstances, use superglue. It crazes clear plastic of all kinds, including Future canopies(learned that one the hard way. Stupid, stupid, stupid. . . ).
  7. cdavenport

    cdavenport Member

    Thanks for the explanation Millenium. That sounds so interesting I can hardly wait.

    BTW, kudos on the mugshot thread. I have been wondering what everyone looks like.

    Finally, you are on for WFest next year assuming the date does not conflict with school. I live in Athens, GA about 6 hours away.

    If you subscribe to Amazing Figure Modeler or Modeler's Resource (now defunct I believe), check your back issues from about 10-12 years ago. I penned columns for both mags.

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