A method of manufacturing a cylindrical cargo container includes: providing a plurality of rigid panels together formable into a cylindrical shell; forming a first semi-cylindrical shell from a first set of the panels; forming a second semi-cylindrical shell from a second set of the panels; forming the cylindrical shell from the first semi-cylindrical shell and the second semi-cylindrical shell; forming a collar conformably encircling the cylindrical shell; constricting the collar to compress joints formed at abutting edges of pairs of adjacent panels; rolling the cylindrical shell and collar to bring respective joints of pairs of panels to a lower position, and welding an inside seam of the joint when at the lower position; removing the collar from the cylindrical shell; and rolling the cylindrical shell to bring respective joints of pairs of panels to an upper position, and welding an outside of the joint when at the upper position.