page_title: RMS Lusitania
section_title: Design
hierarchical_section_title: RMS Lusitania / Development and construction / Design
caption_attribution_description: English: Drawings of deck layout on RMS Lusitania as designed. Laid down 1904, sunk by torpedo 1915 off Queenstown, Ireland. Note that some alterations were made to the layout during construction. lifeboat arrangement was changed later so that in 1915 there were 11 boats either side plus collapsible boats stored under each lifeboat and on the after deck rather than the 16 shown.
context_page_description: RMS Lusitania was a British ocean liner that was sunk on 7 May 1915 by a German U-boat 11 miles off the southern coast of Ireland, killing 1,198 passengers and crew. The sinking presaged the United States declaration of war on Germany. Although the Lusitania sinking was a major factor in building support for a war, a declaration of war did not take place until nearly two years later, after repeated attacks and German use of unrestricted warfare against American shipping.
  Lusitania held the Blue Riband appellation for the fastest Atlantic crossing and was briefly the world's largest passenger ship until the completion of her sister ship Mauretania three months later. The Cunard Line launched her in 1906 at a time of fierce competition for the North Atlantic trade. She was sunk on her 202nd trans-Atlantic crossing.
  German shipping lines were aggressive competitors for the custom of transatlantic passengers in the early 20th century, and Cunard responded by trying to outdo them in speed, capacity, and luxury. Cunard used assistance from the British Admiralty to build Lusitania, on the understanding that the ship would be available as a light merchant cruiser in time of war.
context_section_description: Cunard established a committee to decide upon the design for the new ships, of which James Bain, Cunard's Marine Superintendent was the chairman. Other members included Rear Admiral H. J. Oram, who had been involved in designs for steam turbine-powered ships for the Royal Navy, and Charles Parsons, whose company Parsons Marine was now producing revolutionary turbine engines.
  Parsons maintained that he could design engines capable of maintaining a speed of 25 knots (46 km/h; 29 mph), which would require 68,000 shaft horsepower (51,000 kW). The largest turbine sets built thus far had been of 23,000 shp (17,000 kW) for the Dreadnought-class battleships, and 41,000 shp (31,000 kW) for Invincible-class battlecruisers, which meant the engines would be of a new, untested design. Turbines offered the advantages of generating less vibration than the reciprocating engines and greater reliability in operation at high speeds, combined with lower fuel consumption. It was agreed that a trial would be made by fitting turbines to Carmania, which was already under construction. The result was a ship 1.5 knots (2.8 km/h; 1.7 mph) faster than her conventionally powered sister Caronia with the expected improvements in passenger comfort and operating economy.
  The ship was designed by Leonard Peskett and built by John Brown and Company of Clydebank, Scotland. The ship's name was taken from Lusitania, an ancient Roman province on the west of the Iberian Peninsula—the region that is now southern Portugal and Extremadura (Spain). The name had also been used by a previous ship built in 1871 and wrecked in 1901, making the name available from Lloyds for Cunard's giant.
  Peskett had built a large model of the proposed ship in 1902 showing a three-funnel design. A fourth funnel was implemented into the design in 1904 as it was necessary to vent the exhaust from additional boilers fitted after steam turbines had been settled on as the power plant. The original plan called for three propellers, but this was altered to four because it was felt the necessary power could not be transmitted through just three. Four turbines would drive four separate propellers, with additional reversing turbines to drive the two inboard shafts only. To improve efficiency, the two inboard propellers rotated inward, while those outboard rotated outward. The outboard turbines operated at high pressure; the exhaust steam then passing to those inboard at relatively low pressure.
  The propellers were driven directly by the turbines, for sufficiently robust gearboxes had not yet been developed, and became available in only 1916. Instead, the turbines had to be designed to run at a much lower speed than those normally accepted as being optimum. Thus, the efficiency of the turbines installed was less at low speeds than a conventional reciprocating (piston-in-cylinder) steam engine, but significantly better when the engines were run at high speed, as was usually the case for an express liner. The ship was fitted with 23 double-ended and two single-ended boilers (which fitted the forward space where the ship narrowed), operating at a maximum 195 psi and containing 192 individual furnaces.
  Work to refine the hull shape was conducted in the Admiralty experimental tank at Haslar, Gosport. As a result of experiments, the beam of the ship was increased by 10 feet (3.0 m) over that initially intended to improve stability. The hull immediately in front of the rudder and the balanced rudder itself followed naval design practice to improve the vessel's turning response. The Admiralty contract required that all machinery be below the waterline, where it was considered to be better protected from gunfire, and the aft third of the ship below water was used to house the turbines, the steering motors and four 375-kilowatt (503 hp) steam driven turbo-generators. The central half contained four boiler rooms, with the remaining space at the forward end of the ship being reserved for cargo and other storage.
  Coal bunkers were placed along the length of the ship outboard of the boiler rooms, with a larg
caption: Deck plans of Lusitania. Modifications were made both during, and after the ship's construction. By 1915 the lifeboat arrangement had been changed to 11 fixed boats either side, plus collapsible boats stored under each lifeboat and on the poop deck.
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