I use a couple different methods of constructing these forms. Here’s the process I’m currently using in making the mid-sized pieces.
First, I build a simple armature made out of medal piping parts assembled in such a way that will support the shape I’m making. Then I pile clay along the pipes, and build out to create the shape of the piece. Once this stage is completed, I allow it to dry until it’s hard enough so that when I cut into it to dis-assemble, the form will not distort too much. I end up with a puzzle of pieces that I will hollow out and then re-assemble.
Check out my blogspot on the construction of my car kiln. It was quite a project, and the kiln fires like a cadillac!