The invention pertains generally to manufacturing and installing a semi-membrane tank for liquefied natural gas (LNG). Specifically, the invention relates to a method and apparatus for facilitating off-hull manufacturing of a completed semi-membrane LNG tank and installation of the tank in a permanent supporting structure, such as a ship's hull. Embodiments of the invention include attaching a support structure to the top and the sides of an LNG tank and attaching a support net to the support structure. The support net may be configured to support the bottom of the tank including any insulation that may be applied to the bottom. Once the support structure and support net are attached to the tank, the tank may then be moved from an assembly location to a permanent support structure where it may be permanently attached.