My son wanted to be an alien with a flying saucer this Halloween, and as usual, I'm getting a late start on this.
I needed something lightweight, so I picked foam insulation board. The closed cell stuff is easier to cut, but the material that home depot had came in narrow sheets, and I wanted a 4 ft circle. If I tried to piece it together I thought it wouldn't be strong enough, so I bought a 4x8 sheet of foil backed Styrofoam.
Styrofoam is a pain, as the little blobs peel off when you try to cut it unless you have a hot knife or wire foam cutter.
I don't so I used a rotozip spiral cutter. Lots of static-y dust particles and cleanup later, I have an OK circle/donut. I sealed the edges with a butane lighter. It's a little irregular, and I wish I had taken more time then I could have cut identical panels for the hull, but now I have to piece them together.
Here's the circle as I'm starting to attach some fuselage/framework made from the pink foam (I had lying around):
I made a lot of identical framework triangles and as the edges were a little rough I sanded them. They weren't perfect either so I attached them with construction adhesive and hot glue fillets.
I also attached a string of led battery powered christmas lights along the edge with hot glue and staples (to hold them in place while the hot glue hardened.)
I'm covering the "hull" with a bubblewrap type of insulation (I had left over from some ductwork insulation)
I plan to seal the seams with foil tape. I still have to figure out how to hang it from him, I assume some sort of straps over the shoulders.
I'll post completed pictures here, and with the rest of his costume in the "completed costume" thread.