I have been asked to make a styrofoam propeller for a VBS. They want to paint it themselves so I just have to make it.
I started by drawing off a pattern on paper mill paper. It is about 4 feet long from tip to tip. I cut it out a little big with the heat knife. The heat knife tends to melt a little farther than you really want it. (In the past I have used an electric knife. That's right just like the one that is used only at Thanksgiving to carve the turkey. It works well for cutting styrofoam.) I want a very clean edge because I am going to shape it.
I also cut out 3 circles. (I know only there are only two here. I can count ok? I just didn't take a picture of the third circle.)
I cut out the shape on the band saw. I took my time because one small bump can make a huge cut in the wrong spot.
I stacked the circles, one on the bottom, and two on the top. It has to be away from the wall a little. These two on top will be shaped into a cone.
I glued the circles with gorilla glue. This glue does not eat foam and it bonds extremely well. Just be careful not to put too much glue. The glue doesn't sand as well or as fast as the styro so learn from my mistakes and don't use too much.
I put glue on all the pieces not realizing that I didn't need it on the top one. So the top circle got twice the glue that it needed.
One thing about Gorilla Glue is that it needs moisture to work, so I sprinkled some water on it before I put them together. I was going to use my spray water bottle but I couldn't find it.
I clamped it together and waited.
Then I used my sander to shape it. Yes you can sand styrofoam.
I did the same for the other side and formed the nose into a cone.
I am going to ask them to take a picture of the final product so I can post it here.