Abstract: A collapsible panel structure consisting of at least one rod member, restraint elements secured to the rod member and a removable stress device acting to exert a continuous force between the rod member and the restraint elements. In one modification, two rod members have attached thereto a sheet of flexible material or fabric which acts as the restraint elements. Additional cable restraints can be employed joining the outer ends of adjacent rod members. The rod members are slightly bowed, and a bar member is secured centrally thereto in substantially chordal relationship. The stressing member rolls or slides on one bar member and pivots on the other. The stressing member is a slightly precambered one-piece rod or tube of spring material, carrying bifurcations at both of its ends to partially encompass the chord members, one bifurcation acting as a pivot and the other as a slide.

Abstract: A collapsible watertight structure has a pair of essentially rigid opposite end members linked together by a flexible skin or sheet so that the structure may be repeatedly extended and collapsed. Longitudinal beams which are laterally rigid but longitudinally compressible extend between and are secured at their ends to the end members and hold the structure in distended position. Each beam is secured to one of the end members by a universal joint, such as a ball and socket, and is secured to the other end member by a joint which is slidable transversely thereof whereby the end members are placed under chordal distension urging them apart and causing the flexible skin to be distended and stressed between the end members to attain its shape. Flexible cable members embedded or otherwise secured to the flexible sheet and secured to the end members limit the distension and stress imposed by the end members on the flexible sheet.