Generally these designs are created to minimize waste when using standard 4-foot by 8-foot sheets of plywood. The scow hull is also the basis for the shantyboat or, on the Chesapeake, the ark, a cabin houseboat once common on American rivers. The ark was used as portable housing by Chesapeake watermen, who followed, for example, shad runs seasonally. The Thames sailing barge and the Norfolk wherry are two British equivalents to the scow schooner. The Thames sailing barges, while used for similar tasks, used significantly different hull shapes and rigging. The term scow is used in and around the west Solent for a traditional class of sailing dinghy. Various towns and villages claim their own variants (Lymington, Keyhaven, Yarmouth, West Wight, Chichester), they are all around in length and share a lug sail, pivoting centre board, small foredeck and a square transom with a transom-hung rudder. An American design that reached its zenith of size on the American Great Lakes, and was also used widely in New Zealand, the schooner-rigged scow was used for coastal and inland transport, from colonial days to the early 1900s. Scow schooners had a broad, shallow hull, and used centreboards, bilgeboards or leeboards rather than a deep keel. The broad hull gave them stability, and the retractable foils allowed them to move even heavy loads of cargo in waters far too shallow for keelboats to enter. The squared-off bow and stern accommodated a large cargo. The smallest sailing scows were sloop-rigged (making them technically a "scow sloop"), but were otherwise similar in design. The scow sloop eventually evolved into the "inland lake scow", a type of fast racing boat. Sailing scows were popular in the American South for economic reasons, because the pine planks found there were difficult to bend, and because inlets along the Gulf Coast and Florida were often shallow. The American scow design was copied and modified in New Zealand by early immigrant settlers to Auckland in the 1870s. In 1873, a sea captain named George Spencer, who had once lived and worked on the American Great Lakes and had gained a first-hand knowledge of the practical working capabilities of the sailing barges that plied their trade on the lakes, recognised the potential use of similar craft in the protected waters of the Hauraki Gulf, Auckland.