Mag man, great contest!
Instead of a barrel shape I would go with a rectangle. Make it out of plywood and epoxy (West system is what I use). It will be light, strong, and if coated properly on the inside it will be food safe. Build the container around your frame needs to fit the number of frames your motor can handle.
Only down side is there will be increased wind resistance over the barrel shape design.
for example build your container 20 inches high (1 frame on end), 24 inches wide (to accomodate 4 frames wide) and 36 inches on the axis ( to accomodate 4 frames on either side of the bearing / center rod). THis would let you do up to 8 frames at a time.
This is a woodworkers answer