Abstract: A lightweight, inflatable structural member, having a substantially tubular shape and sealed at both ends, includes an inner lining to maintain internal pressure upon inflation. The inner lining is covered with a filament reinforced matrix structure comprising resin impregnated filaments of high tensile strength. The uninflated structural member is stowable in a collapsed condition. Curing of the resin matrix is inhibited by storing the collapsed member at a low temperature. Prior to use, the member is inflated with a fluid and heated to enable curing of the resin matrix.