Engineering Wonders of the World
Volume I

DESIGNING A SHIP. 355 ARRANGEMENT OF MACHINERY, HOLDS, BUNKERS, ETC. in the weight of material required. The arrangement recently adopted, known as the Isherwood system, is illustrated by Fig. 9, the Fig. 8.—SECTION OF A CANTILEVER FRAMED SHIP WITH SIDE WATER-BALLAST TANKS, W W. longitudinal framing being supported by deep transverse girders spaced about 12 feet apart. The general arrangement of a steamship will best be understood by studying the most simple example—the ordinary cargo steamer, as shown in Fig. 10. To avoid difficulties with regard to trim —that is, difference in draught at the ends of the vessel—the propelling machinery is usually placed amid- ships, being divided from the cargo spaces General Arrange- ment. by transverse water-tight partitions known as “ bulkheads.” Similar bulkheads divide the cargo spaces and shut off the end compart- ments, the function of the bulkheads being to limit the sinkage of the ship should the com- partments be holed and laid open to the sea. In the highest class of passenger vessels the Fig. 9.—LONGITUDINAL FRAMED SHIP : CLEAR HOLD. Board of Trade requires that they must re- main afloat with any two compartments flooded—a provision which renders these ships practically unsinkable. Another important question when design- ing a cargo steamer is the provision of ample water ballast capacity to give the vessel good immersion when making voyages without cargo. For this purpose a double bottom is usually fitted, which, offers the additional advantages of increased longitudinal strength