Technical Sheet
ENGINEERING NEWS
September 27, 1906
THE CUNARD STEAMSHIP “MAURETANIA”, THE LARGEST VESSEL EVER BUILT.
The “Mauretania,” which was launched Sept. 20, is one of the two large steamships ordered by the Cunard Steamship Co. in fulfillment of its agreement with the British Government. She is of interest on account of her immense size and the fact that her steam turbine equipment is designed to give ten times the power of the largest marine turbine installation in use. Under the agreement whit the British Government the Cunard Steamship Co. undertook to build for the British mail service two liners, to run at not less than 24 ½ knots in moderate weather, on the Atlantic passage and to retain them at the call of the admiralty for service in time of war.
This agreement was not only acceptable to great Britain on account of the advantage, or prestige, accruing from the possession of the fastest ocean passenger steamships afloat, but was welcomed by the marine engineering profession, as it promised the solution of important problems and conduced to further advances in propelling machinery. One of the ships was ordered from Messrs. John Brown and Co., Ltd., Sheffield and Clydebank, and the other, which forms the subject of the present article, from Messrs. Swan, Hunter, & Wigham Richardson, Ltd., Wallsend-on-Tyne, with machinery from the Wallsend Slipway & Engineering Co., Ltd
The conditions of the contract are as follows:
The vessels shall attain a speed of 25 ¼ knots on trial, and that within a year of going upon their station they shall maintain in one complete voyage to New York and back a mean speed of 24 3/4 knots.
Except in a few minor details, the “Mauretania” is a duplicate of the “Lusitania,” which was launched some months ago; the turbines differ somewhat in construction, but their proportions are not dissimilar. The form of the propeller blades on the “Mauretania” is more elliptical, and the hull is of 6-in. greater depth, which increases her gross tonnage by 700 tons.
The dimensions of the “Mauretania” are:
Length over all…………………..............785 ft.
Length between perpendiculars…….........760 ft.
Beam, extreme……………………..…......88 ft.
Depth, molded………………..........60 ft. 6 ins.
Gross tonnage…………………....33,200 tons.
Maximum draft………………...…….........38 ft.
Displacement at maximum draft…....43,000 tons.
Figs. 1 and 2 illustrating the longitudinal section and plan of the ship, show the arrangement of the decks and bulkheads. Excluding the hold, there are nine decks. These are: the lower orlop, the orlop, the lower, the main, the upper, the shelter, the promenade, the boat and the sun decks. In the center of the ship, however, there are only six decks, the boiler, machinery and coal-bunkers occupying fully 420 ft. of the total length of the vessel, and the depth from the main deck to the hold. There is very little capacity for cargo, the vessel being exclusively intended for carrying passengers and mails.
Two electric passenger elevators in the center of the ship run to each of the six passenger decks. Instead of the steel decking of the ship being covered with wood, the floors are lined with corticine, a special cork cement extensively used in warships to minimize fire risk, and in this case largely to save weight.
The numbers of passengers and crew provided for are:
First class passengers……….……560
Second-class passengers……...…500
Third-class passengers……....…1.200
Crew……………………….........810
Total population…………..…....3,070
The decks with state-rooms are for the most part 9 ft. in height, but where there are saloons the height is from 10 to 11 ft. The top of the wheel-house is 100 ft. above the keel, and the funnels 152 ft.
There are 15 transverse bulkheads closely spaced forward and aft, where there is greater chance of injury owing to collision. Two of the largest of the compartments might easily be flooded without any difficulty arising. The coal-bunkers are also fitted with bulkheads, and as shown in Figs. 1 and 2 there is a well-arranged scheme for closing all the doors simultaneously on the Stone-Lloyd system. In the event of any contingency, every door can be closed by hydraulic power by the officer on the bridge, or at one of several positions throughout the ship. A door then can only be reopened from within the compartment to liberate any one imprisoned, and even in such case the door closes again automatically after the lapse of a sufficient period of time to allow any one to pass through.
The construction of the double-bottom of the ship is interesting. The flat keel is made up of three thicknesses of plating, varying according to the position in the ship, from 1 in. to 1 ¼ ins. Thick. The holes were, in all cases, formed by electric drills, with the plates superposed, so as to secure absolute alignment, and the riveting was done by hydraulic power. This, indeed, was used throughout the whole of the double bottom, and as the plates were for most part 1 in. to 1 1/16 ins. Thick, the conditions were more analogous to boiler making than ordinary ship riveting. The depth between the outer and inner bottom is, at the center, 5 ft.
On account of the high speed, the entry, as shown in Fig. 3, is exceptionally fine. As is indicated by this view, there is not in any part a hollow; rising from a sweet curve from the keel which extends almost to the vertical stem, the lines are straight until slightly above the water line, where they flare out. Wedge-shaped bars are fitted along the laps of the shell plating so as to obviate any possibility of the anchor catching in the projection formed by the laps. A peculiar form of anchor hawse-pipe is used; it is thought this form will enable the anchor to be more snugly housed, and thus reduce the disturbance due to waves when the vessel is running at high speed through a heavy sea.
The amidship framing is of channel bars with deep web frames at intervals, which vary according to their position in the ship. They are most frequent and heaviest, of course, at the machinery spaces. The channel bars extend from the margin plate of the double bottom, to which they are connected by heavy brackets, to the sheltered deck, 60 ft. 6 ins. above the level of the keel. The length of the bars is 55 ft. , and they weigh in most cases 15 cwt.
The rudder weighs 65 tons, and is of the balanced type, made up of a series of castings, bolted together with heavy ribs. The rudder-head is of forget ingot steel, of 25 ½ in. diameter.
There are four turbine shafts, each with one propeller. The two outer shafts are driven by high-pressure turbines; while on the two inner shafts are the low pressure turbines, with the astern turbines located at the after end. The condensers are placed to the rear of the engines, and outside of the inner shafts. The two inner shafts turn outward ad the two outer shafts inwards. As a result of experiment, it was considered that this arrangement would give better results than with all propellers working in the same direction. The total power will be 68,000 I. HP., equally divided through the four shafts, which will run at from 190 to 200 r. p. m.
Fig 4 shows one-half of the turbine installation. Thee group illustrated has a length of 150 ft., and the height from the floor is over 20 ft. The turbine bearings have been given a spherical form to afford greater freedom. In the seats there are adjusting pieces for taking up the wear at the sides and bottom, so that the bearings can be reset without the shaft being lifted for the renewing of the white metal.
The rotor disks differ from general practice. They are dished out, forming a triangle in elevation. This should add to their rigidity an important desideratum in view of the tendency toward a whipping action by a rotor of 130 tons, nearly 12 ft. in diameter, making 200 r. p. m.
The shafting, of Whitworth steel, is, in the case of the low-pressure turbines, about 33 ins. In diameter, and in the high-pressure turbines 27 ins.; in all cases the shafts are hollow.
The steam installation includes 23 double-ended and two single-ended boilers, the former having eight, and the latter four, furnaces, so that there are 192 furnaces in all. The larger boilers are 17 ft. 3 ins. in diameter and 21 ft. long. The boilers are to work under a forced draft system, and the fans will be driven by electric motors. There will be about 160,000 sq. ft. of heating surface and nearly 4,000 sq. ft. of grate area. The working pressure of the boilers will be 180 lbs., and at the turbines 160 lbs. The boilers will be arranged in four stokeholds, with seven boilers in the forward stokehold, and six in each of the others. For each of the four groups of boilers there will be a funnel which will rise to a height of 152 ft. above the keel of the ship. These funnels are elliptical in plan, and measure externally 23 ft. 6 ins. x 17 ft. 6 ins.
