Trans RINA, Vol 152, Part A2, Intl J Maritime Eng, Apr-Jun 2010


then became possible to evaluate the benefits of for example higher tensile steel, e.g. in destroyers and torpedo


boats, and of longitudinal 2. INTO THE TWENTIETH CENTURY framing, e.g.


Isherwood’s system of 1908. Simple beam theory applied to the midship section had been shown by experience to produce scantlings of adequate strength for seagoing ships in association with nominal stresses.


Froude’s towing tank first at Torquay (in 1872) and then at


Haslar near Portsmouth, based on his law of


comparison between model and ship resistance, provided the means to explore a great variety of hull forms as well as predict power with greater confidence. It was this latter advantage that persuaded shipbuilder Denny of Dumbarton to build the first commercial towing tank in 1883. The company built many high speed and shallow draft ships, so a more accurate prediction of power enabled them to determine dimensions and hull form and to size the machinery with greater confidence and lower margins when tendering.


By this time, the major Classification Societies had become well established, Lloyds Register starting in 1760 (100 years before RINA), Bureau Veritas in 1828, American Bureau of Shipping in 1862, Norske Veritas in 1864 and Germanischer Lloyd in 1867, to be followed by a British (or rather Scottish) rival to LR in 1890, the British Corporation, and Nippon Kaiji Kyokai in 1899. These societies also assigned freeboards, statutory in British registered ships from 1890, but not


agreed


internationally until 1930 – one of many steps towards the level playing field so necessary to an industry like shipping. Indeed such subjects were regularly discussed in the various technical forums such as (R)INA or North East Coast Institution of Engineers & Shipbuilders (1884)


or Society


The most significant enabling technology at the start of the 20th century was the introduction of the steam turbine. Although Charles Parsons is regarded as the pioneer, there were also designs prepared in the USA, Germany and Sweden. The turbine offered almost unlimited power compared with the steam reciprocator, and in a smaller engine room and with less vibration, although initially fuel consumption and cost were much the same. Following Parsons’ experiments with Turbinia in 1894-97 (now on display in Newcastle’s Discovery Museum) Royal Navy applications progressed rapidly from destroyers to cruisers, and then to the battleship Dreadnought ordered in 1905. In parallel, merchant ships moved from the 3000-shp Clyde ferry King Edward in 1901 to the momentous decision by Cunard in 1904 to order 70,000-shp turbines for their 25-knot transatlantic liners Mauretania and Lusitania. This sixfold increase in power from destroyer Viper’s 11000-shp in 1900 was just as bold as Brunel’s step from the 3000grt (gross registered ton, a measure of volume not weight) iron steamer in the mid 1850s to his 18915grt Great Eastern. But unlike the latter, the Cunard liners were a great commercial as well as technical success. What modern engineer would make a six fold jump in capability in only four years?


of Naval Architects & Marine


Engineers (1893). With its large merchant fleet, Britain often took the lead in establishing new safety legislation covering matters such as life saving appliances, tonnage rules, subdivision, crew qualifications and provision of navigational aids, enshrined in major legislation like the Merchant Shipping Act of 1894.


Other late 19th century technical developments which enabled bigger, better and faster ships to be built included forced draft for boilers (increasing power output and reducing fuel consumption) and electrical generators (including some early steam turbines) permitting electric lighting. This was particularly useful in larger ships with extensive accommodation like passenger ships and battleships and in engine rooms where guttering oil lamps or candles were the only alternatives if no natural light could be arranged. Electrically driven machinery began to make an appearance both on board ship and on docksides, simplifying power transmission. Manganese bronze propellers (usually then blades bolted to the boss) reduced erosion and corrosion as well as improving efficiency in high powered vessels, albeit at higher cost than cast iron.


Figure 7. The decision in 1904 to use steam turbines in Cunard’s express Atlantic liners Mauretania and Lusitania was a momentous one, coming only ten years after Parsons had installed his first experimental turbine in Turbinia. The 70000 shp developed on four screws enabled them to maintain 25 knots with ease; they were a great technical and commercial success. The photo shows Mauretania’s direct drive turbines in the erecting shop at Wallsend Slipway & Engineering company’s works in 1906.


The early steam turbines were coal fired, so boiler capacity and firing rate were limitations on sustained power. Many new designs of watertube boiler were developed offering greater steam raising capacity, but few survived more than a few years, Babcock & Wilcox being one the most successful. But experiments with oil fired boilers had started in the 1880s, so by the early


A - 54 ©2010: The Royal Institution of Naval Architects


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