Formatube (250mm ID) was used as a mold for the tube. Here you can see it wrapped in a layer of peel-ply with some e-glass cloth loosely draped on it. The formatube first had some release wax rubbed onto it. It has some internal support rings of plywood (cut with my circle cutting jig) that help retain a circular shape and also allows horizontal support using steel water pipe. The wooden rings that are secured to the outside provide mold ends for the fibreglass. Note that this is to be a 2-part tube that will be bolted together for ease of transport.