Halloween has been a pirate theme around here for a while. I had the sword, I had the treasure chest, I needed a cannon. More than just a prop, this cannon will fire a potato slug a couple of hundred yards. For Halloween we dialed back the psi and shot harmless "cannonballs" made from tissue paper filled with baby powder. The result was a VERY popular addition to the pirate party we had.
Step 1: Build the Jig
The jig is made from 2X4 and MDF. First I determined the diameter of the front and rear of the finished cannon and the overall length I wanted. I then drew the profile out on a sheet of MDF and cut the profile out with a jigsaw.
Then I split the profile in half to attatch to the sides of the jig. This profile would provide the template I would use to carve out the material.
A piece of 1.5 inch Schedule 40 PVC is used to lay up the layers of foam and will also act as the barrel.
Step 2: Cut the Material
I used two inch ridgid foam for the main material of the cannon. One 4 X 8 sheet of two inch runs about $20.00. I marked out 12 inch by 12 inch squares and cut down the foam.
I marked the center point and cut a hole with a two inch hole saw for the barrel.
Step 3: Load The Jig
I cut two circles of MDF the diameter of the two ends. I placed a piece of 1.5 inch schedule 40 pipe into the jig then slid on the large MDF circle. I held it in place with a screw.
I stacked the squares of foam onto the pipe until the length I requried was achieved. The smaller circle of MDF went on. Then I got some help to compress the material to mark the pipe and drill a small pilot hole. I'ts important to compress the material a bit to hold it in place. The foam will not be glued until after it is shaped.