Olympic & Titanic : Evolution of the Design

THE evolution of the Atlantic liner of to-day has been one of the most remarkable achievements in the scientific progress and commercial activity of modern times. It is difficult to realize that only 73 years have elapsed since the Atlantic was first crossed by a vessel continuously under steam power. This pioneer steamer, the Sirius (Fig. 13), was a small wooden paddle steamer 208ft. long overall and 178ft. along the keel. Her breadth was 25ft. and depth of hold 18ft.

Upon her first Transatlantic voyage, in April, 1838, she carried 94 passengers and averaged about 7½ knots speed. What a contrast to the present-day Kronprinzessin Cecilie, La France, Lusitania, Mauretania, Olympic, and Titanic, to mention but the most celebrated of recent ships !

It is impossible in the short space of this article to trace all the stages of development from the Sirius to the two latest White Star liners, and only the most important facts can be mentioned. The increase in size and speed has been continuous, as will be seen from Table I. giving the particulars of notable Atlantic liners, and also from Fig. 2 showing the development of White Star ships. The use of wood as the material for construction of the hulls was followed by the introduction of iron, which in turn was superseded by steel. Paddle wheels as a means of propulsion were abandoned in favour of the screw propeller driven by reciprocating engines. The reciprocating engine developed from the compound to the triple, and later to the quadruple-expansion type, two sets of engines, driving twin screws, being adopted as larger powers were required. The highest perfection of this type of engine was reached in the German record breakers Kaiser Wilhelm II and Kronprinzessin Cecilie, which have twin screws and four sets of engines, two sets being mounted on each shaft.

Turbine propelling machinery in conjunction with triple screws appeared on the Atlantic in 1904, when the Allan liners Victorian and Virginian entered upon service, and was also adopted for the Cunard liner Carmania, completed in 1906. The greatest triumphs of the turbine have been won by the quadruple-screw express Cunarders Lusitania and Mauretania, which now hold all the Atlantic speed records. But although the turbine has been eminently successful for the high-speed ship, at more moderate speeds its economy is not so marked, a fact which has led to the introduction of the latest type of propelling machinery, the combination of reciprocating engines with a low-pressure turbine. When considering the type of machinery to be adopted for the Olympic and Titanic, the White Star Line and Messrs. Harland and Wolff, as already mentioned, agreed to test the merits of the combination system compared with reciprocating engines of the ordinary type by building two vessels exactly similar except in regard to propelling machinery. These two vessels, the Megantic, fitted with reciprocating engines, and the Laurentic, fitted with combination engines, were completed in 1909. Their relative performances in the White Star Line’s Canadian service completely justified the expectation regarding the superior economy of the combined type of machinery, and it was decided to adopt combined engines for the later and much larger vessels.

Factors of Design.

It may not be out of place at this stage to briefly indicate the many problems which beset the designer of an Atlantic liner and the main considerations determining the dimensions, form, and arrangement of ships like the Olympic and Titanic which are intended to eclipse earlier vessels. The two most important factors of design are the speed and passenger accommodation to be aimed at, and it has always been the endeavour of the competing steamship companies on the Atlantic to possess vessels which excel in one or both of these respects. Both factors are favoured by increase in size of ship ; hence the tendency to greater dimensions which has been so marked during the past few years. The maximum possible dimensions of a new vessel depend upon the dock and harbour accommodation available when the ship is completed ; and it is for this reason that Lord Pirrie, among others, has devoted so much time and energy to the question of increased dock and harbour facilities.

Reverting to the subject of speed, high speed is a very costly requirement, not only owing to the great initial cost of the propelling machinery and the heavy cost of fuel on service, but also on account of the necessary fineness of the ship, which limits the earning power as regards cargo-carrying and the extent of passenger accommodation. In a high-speed Atlantic liner, the difficulties of design are greatly increased, as the designer is handicapped by the limited draught of water available at the terminal ports, and very careful consideration has to be given to the question of weight, any saving which can be effected being of great value. If, on the other hand, a more moderate speed is aimed at, the problem of weight is much simplified, as the vessel can be built to a fuller model and. a greater displacement secured, without exceeding the draught available. It has been the custom of the White Star Line to strive for pre-eminence in passenger accommodation in conjunction with a speed which can be obtained without too great a sacrifice of cargo capacity, and the Olympic and Titanic have been designed in accordance with that policy. Although a passenger on one of these vessels will not have the honour of crossing in the fastest ship on the Atlantic, he will have many compensating advantages as regards increased comfort at sea and the greater extent and variety of the accommodation provided.

TABLE 1.—LARGE ATLANTIC LINERS

Other matters which require the careful consideration of the designer are the problems of strength, stability, and behaviour at sea. The subject of the strength of an Atlantic liner was ably dealt with by Professor J. Meuwissen in a former special number of The Shipbuilder (Mauretania Number, 1907) and those interested in the technical aspect of the question are referred to that article. As regards stability, while the metacentric height must be sufficient to prevent the vessel taking an unpleasant list when subjected to a beam wind, it should be kept within moderate limits to ensure easy rolling in a seaway. Metacentric heights of from 1ft. 6in. to 2ft. 6in. have been found satisfactory in this respect. Close attention must also be given to the problems connected with watertight subdivision, steering, ventilation, heating,, electrical equipment, and the hundred and one items which go to make the complete ship and the magnitude of which will be better realized by the general public from a perusal of the following pages. Enough has been said, however, to indicate that the task of the naval architect in the production of two such vessels as the Olympic and Titanic is no light one. Indeed the design and construction of these two magnificent ships, would have been beyond the range of possibility but for the cumulative experience available from earlier efforts during the past half-century.