This was my daughter's costume for Halloween. I wanted something that would last. That she can used for cosplay and when the family goes to conventions. I refuse to use cardboard, but in saying that, foam takes longer.
You will need.
1: Blue insulation Foam (I used 1/2")
2: Razor, box cutter, or hot knife
3: Hot glue
4: Dow rod
5: Ruler, yard stick
Step 1: Research
Look around the internet for exactly what you want. I went square for mine but most of hers are round.
Step 2: Cut the Foam
Really any measurement depend on what you want, and the size of the person. I made this one for the long haul.
Make sure you make and oversize rectangle and make a hole on either side of the top and bottom.
I don't have a lot of pics so bare with me.
Take the dow rod, I used a 2" diameter full rod
Step 3: Make Sure
Make sure you have a 2" hole in top and bottom for the rod
Step 4: Cut Angles
Take the razor and angle it at a 45 degree angle as best you can, we want to hid the seems in the mallet.
Its ok if it's not perfect. We can sand it to spec.
Once you get them all cut and angled make sure they fit. if not sand the angles until it does.
Hot glue them into a box.
Step 5: Insert the Pole
Make sure it goes all the way through. It needs to go through both sides. Cap with a 2" plumbing cap from a hardware store if you want. Glue into place.
Step 6: Add the Outside Frame
I went 2 ' strips for this. I angled these again to make it look seemless.
TIP: You don't have to be perfect, if you have some holes, use some spackle to fill and let dry. Then sand the ruff edges
Step 7: Painting and Finish
This is the most time consuming part. With foam, you can't use spray paint, it will eat it.
I used water based acrylic paint and hand painted. I painted the main parts red, and the secondary parts black.
After you finish I suggest mod podge to seal it. It will make it more resistant and sturdy. Its puzzle glue. It will go on white in some places, don't worry it will turn clear