I’ve used the high grade 3M blue or green tape for shades in buildings. They been outside for years.
The shades look great. If the tape eventually fails and you’d like to try thin styrene, paper, or envelope material but are still worried about messy glue ruining your windows, try a product called Zuper Z RC 56 Canopy Glue. It’s for model/RC airplane canopies and it works really well. Not as quick drying as CA, but it dries perfectly clear and is ideal for anything in and around windows. It’s also pretty flexible so you don’t have to worry about bumping things glued with it like you do with CA. How well it works outdoors is a good question. But if you don’t leave your cars submerged in water, it should do fine. I used this glue for window shades on my HO scale Santa Fe Hi-Level cars:
(http://img11.imageshack.us/img11/6101/holights1.jpg)
excellent tip–thank you. And thanks to all who replied!
A good adhesive for anything near clear plastic is RC56. Go to a hobby shop that caters to RC flyers. They should sell this glue, sometimes known generically as canopy glue. Its water based, so no solvents to fog the clear plastic. It comes out white and dries clear and sticks to smooth plastic. You can glue plastic to plastic, wood or metal, or other materials (i.e: paper, cardstock, etc) to each other and plastic. Just don’t count on it to add structure.
Hope this helps,
Dave