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How to fit vacuum-formed clear parts to a model car

Learn the best practices for installing vacuum-formed plastic parts
Many older car kits, and some recent ones, too, use vacuum-formed plastic instead of injection-molded styrene for clear parts. Installing these parts usually means cutting them from thin, pre-molded stock or “pulls.”
It’s best to have the body cleaned up and prepped for paint before fitting the vacuum-formed pieces. You can fit them after painting, but I prefer to handle a painted car body as little as possible.
You’ll need a sharp hobby knife (a No. 11 blade or No. 16 work well), a good set of scissors (I prefer small ones for better precision), both 400- and 1000-grit sandpaper, and a fine Sharpie. Decal tweezers can be handy, too, because they are unlikely to mar the thin plastic.
As with many other kits, indented lines show where you should cut out the vacuum-formed headlight covers (left) and windshield and side windows (right). Those lines can be deceiving and can make the parts too large or, worse, too small.
For big, curved parts like the windshield, score a line around the part, being careful not to cut into other parts. After several light passes, the knife will cut through. Do not bend or twist the plastic more than needed because it can crack, tear, or kink — no scissors yet!
After separating the windshield from the rest of the pull, it has enough flex to safely use scissors to trim the bulk of excess material from the edge. Remember, you’re not cutting to the line but leaving extra to allow you to fit to the space on the body.
Rather than try to get all of the edges to fit well at the same time, pick one and shape it with 400-grit sandpaper. I worked the windshield’s rear edges to fit the body, using one as a reference for the other. With those in place, there was a consistent fit for shaping the rest.
With a large, curved edge, marking a line on the clear part with a fine Sharpie can eliminate some of the guesswork with sanding. Test-fit as you sand, even with the guide. You can always sand more off, but you can’t un-sand. You should be able buff the marker off the part.
The windshield has been sanded to fit, but the plastic often has fuzzy remnants from the 400-grit sandpaper. Lightly sand the edges with 1000-grit sandpaper to eliminate the fuzz. You can also use the backside of a hobby knife to scrape the edges on thicker parts.
Small curved parts have less chance of crimping, so you can cut them out with scissors. Place each over its opening and trim the top, rear, and bottom edges. Sand the rear and bottom edges to fit, and then the top. Use the Sharpie method above to fit the front edge.
For parts that have no curves, like the headlight covers, trim them with scissors and fine-tune them with sandpaper as before. I find fitting the front and back edges first works well to provide conistent alignment to trim the angles on the sides. You don’t want any gaps.
Trimmed and fitted! The tape on one headlight cover indicates which side it goes on. If in doubt about how tight the clear parts fit, err on the side of them being loose. With the fitting done before painting, the openings will shrink. You can always sand a little more afterward.
The parts install from the outside, so apply a tiny bead of Pacer Formula 560 Canopy Glue along one edge, set the part in place, and let the glue dry. Run a bead around the rest of the perimeter with a toothpick. Remove excess glue with a damp cotton swab.
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