Inspired by Francois's recent tip, about using a kiddie pool for a mold to make a KIB moat, I decided to try building one in a similar fashion. Instead of an inflatable pool, however, I build my reverse mold using a pair of foam pool noodles, taped together at both ends, to create a circle, which I then wrapped in cellophane (for easy release) and then covered with three layers of drywall tape. I set the wrapped noodles on top of a 38x38" piece of compressed 1/8" hardboard from Home Depot and used liquid fiberglass resin (applied with a 2" paint brush) to cover the noodles. I used three layers, allowing each one several hours to fully dry before applying the next. Once i felt satisfied that the fiberglass was sturdy enough, I used a dremel, fitted with a cut off wheel, to carefully cut around the entire outter edge, as well as the inside edge of the fiberglass encased noodles and pried off the top half of my circle, discarding the noodles and hardboard. The inside was then coated with another layer of liquid fiberglass resin, to eliminate any remaining air pockets in the drywall tape and seal the moat well.
I still have some minor sanding to do around the lip of the moat but, the final product is a nice, light weight, yet sturdy moat that accomodates a hula hoop wand quite nicely. Can't wait to test it out!