So, since my last post, I've been trying to find something that could serve as the base to sculpt my column onto. After reading more about expanding foam, I realized that it would probably warp the posterboard shell, so I nixed that idea. My second thought was to find a large cardboard shipping tube, but you would not believe how much they want for a 9" diameter shipping tube! Most places I found wanted no less than $40-50 for one. O.o
Then, by happenstance, I came across the magical words "sonotube concrete form". These wonderful things are actually heavy duty cardboard tubes that are used for making concrete pillars, such as the bases for mailbox posts, soccer goals, etc. The best thing about them is that they are cheap, at around $7, and Home Depot and Lowes both carry them, under the name "Quik-tube building form", with HD being slightly cheaper. There are 6", 8", 10", and 12" inch diameters available, and come in either 4', 10', or 12' lengths.
Tomorrow, I'm going to start enlarging the design for the pillar and transferring it onto the quik-tube so I can start sculpting. I am really excited with how nicely things are moving along, let's just hope they stay this way!