Engineering Wonders of the World
Volume I

352 ENGINEERING WONDERS OF THE WORLD. are termed “full.” To Form of the Ship. in weight of material ; and she must have a form which can be driven easily at the re- quired speed. As regards form, vessels with sharp ends “ fine,” and with blunt ends indicate the degree of “ fine- ness ” or “ fullness,” naval architects commonly use a ratio known as the “ block ” coefficient, which represents the relationship of the actual volume of dis- Fig. 3.—DIAGRAM TO SHOW THE MEANING OF THE TERM “ BLOCK COEFFICIENT.” The coefficient is obtained by dividing the displacement of a vessel by the displacement of a rectangular box having the same length, breadth, and depth of the below-water part of the hull. placement to the displacement of a rect- angular box, having the same dimensions as the length, breadth, and draught of the ship to indicate how the displacement is utilized in typical vessels, as given in the following table :— Battleship. Armoured Cruiser. Hull 37 pep cent. 40 per cent. Armour 27 20 Armament 11-5 6 Machinery 12 20 Coal 6’5 9 General equipment. 6 . „ . ■ 5 High-speed Low-speed Atlantic Liner. Cargo Steamer. Hull and equipment 53 per cent. 25 per cent. Machinery 27 4 Coal 16 5 Cargo Stores, fresh water, 2-5 „ 65 etc 1-5 „ 1 „ The terms “ gross ” and “ net ” tonnage, largely used for statistical purposes, represent the internal capacity of the ship as measured legally by the Board of Trade for payment of harbour dues, etc. Gross tonnage includes the capacity in cubic feet, Gross and Net Tonnage. divided by 100, of all enclosed spaces ; while to obtain the net tonnage, deduction of the space occupied by the propelling machinery, fuel, and crew is made from the gross, so that the net tonnage may approximately be pro- DIAGRAMS TO EXPLAIN THE TERMS “ METACENTRE ” AND “ METACENTRIC HEIGHT.” (Fig. 3). High-speed cruisers or passenger liners may be as fine as *5 block coefficient, while low-speed cargo vessels may be as full as '8. It will perhaps be of interest at this stage portional to the earning power of the ship. It will be seen from the foregoing explanation that these terms do not show the weight of cargo carried. The problem of stability will be better