A Treatise On The Principles And Practice Of Dock Engineering

466 DOCK ENGINEERING. unfortunate feature of graving dock construction that an extra foot in depth adds most disproportionately to the cost. The largest floating dock at présent in existence has a lifting power of 18,000 tons, or about one-half of maximum requirements. The increase in size of late years has, however, been so rapid that there is every proba- bility of the disparity being cancelled in a very short time. It has, moreover, been justifiably pointed out that, whereas a graving dock is unable to accommodate a vessel any one of whose dimensions exceeds a certain limit, a floating dock, on the other hand, is quite capable of partially raising a heavier vessel than she has been designed to lift entirely above water. A floating dock at Barrow, with a lifting power of little more than 3,000 tons and a length of 242 feet, raised the s.s. “ Empress of China,” 485 feet long and 4,500 tons displacement, sufficiently high to allow her propellers to be removed and replaced. Any excessive overhang, however, is liable to cause severe strain both in the ship and the dock, and it is inadvisable to risk carrying such an experiment too far. The following table affords some particulars of the largest existing ships :— TABLE XXXV.—Particulars of Some of the Largest Modern Vessels. Vessel. Line. Date of Con- struction. Extreme Length. Breadth. Moulded Depth. Draught. Gross Tonnage. Displace- ment. Feet. Feet. Feet. Feet. Tons. Tons. Baltic, . . . . White Star, 1903 725-7 75 49 23,000 40,000 Cedric, . . . . Nortli German Lloyd, 1902 700 75 49-3 36-5 21,000 38,200 Kaiser Wilhelm II., 1902 706-6 72 52-6 29 20,000 26,000 Kronprinz Wilhelm, White Star, 1901 663 66 43 29 15,000 21,300 Celtic, . . . . 1901 700 75 49 36 20,880 37,700 Deutschland, . Hamburg American, 1900 684 67 44 29 16,502 23,620 La Lorraine, La Savoie, . French Transatlantic, 1900 582-4 60-6 39-4 25-6 11,869 15,400 Oceanic, . . . . White Star, 1899 704 68-3 49 32-5 17,274 28,500 Kaiser Wilhelm der Grosse, North German Lloyd, 1898 648-7 66 43 28 14,349 20,880 St. Paul, St. Louis, American, 1895 554-2 63 42 26 11.629 in non Campania, Lucania, Cunard, . 1893 622 65-3 41-6 25 12,500 i 18,000 5. Initial Cost.—The factor of locality enters so largely into the question of cost of construction of slipways, that it is impossible to fix any absolute standard of comparison. For example, a slipway at Penarth, built in 1879, and capable of accommodating a vessel of 2,500 tons deadweight, cost £25,000 or £10 per ton. On the same basis, a slipway at Belfast, constructed in 1847, for vessels of 1,000 tons, should only have cost £10,000, whereas it cost £17,000 or nearly double that amount, of which £12,000 was spent on foundations alone. Mr. Walter Beer * estimates the cost of slipways for small boats of 600 tons at £9,000 or £15 per ton—an intermediate value to the previous cases. Not much reliance, therefore, * Beer on “ Ship Slipways,” Min. Proc. Inst. G.E., vol. oxviii.