Tankers - An oil tanker under construction. The centre ˉbulkheads are being erected on the button of the ship. Oil tankers are a highly specialized type of vessel and require a very high standard of workmanship. Longitudinal bulkheads run the full length of the cargo space and are crossed by transverse bulkheads, thus dividing the ship into a series of tanks. This system greatly strengthens the ship, and breaks up the movement of oil from side to side, which otherwise would cause dangerous instability in bad weather. September 13, 1951.