The definite adoption of the screw propeller, both for the Royal Navy and the Mercantile Marine, may be said to have taken place in 1840-41. For some years no bearings of brass or other metal could be got to stand the strain of the stern shaft, “and at one moment it seemed as if the screw must be abandoned and the paddle-wheel reverted to. Mr. Penn solved the problem by using lignum-vitæ wood bearings, which, lubricated by water, were found to act without any appreciable wear, and in this simple way the screw has already been able to reach a point of development from which we can now calmly look back upon the financial risks and terrors which beset the early days of steam navigation.”[85]
[85] The Times.
The difficulty of steering screw-propelled vessels was considerable, principally owing to the method of placing the screw in an aperture in the deadwood, while at the same time retaining the full underbody aft. The full power of the screw could not thus be exerted, and the attendant churning of the water interfered with the steering power of the rudder. A system of double rudders was brought out in an attempt to solve the difficulty, but the disadvantages it possessed were against its general adoption. These rudders were hung respectively one on each side of the forepart of a somewhat extended sternpost, against which they lay when amidships, moving out as required to steer the ship, or both could be moved outwards to help to stop her. The sternpost was really a vertical hollow box through which the screw framing passed, the screw working behind it and beyond the rudders. Later improvements in shipbuilding rendered this device unnecessary.
The difficulty was solved by the simple expedient of placing the sternpost farther aft so as to give room for a greater space in the deadwood in which the propeller was to act.
The superiority of the screw to paddles was now being gradually admitted, and the number of small vessels fitted with screws increased. But no one had as yet dared to launch a large screw steamer for ocean voyages.
The honour of being the first to do this was gained by the Great Western Steamship Company. The Great Western, which has been mentioned in [Chapter V], had been so successful that her owners felt justified not only in ordering another vessel but in determining that their new steamer should be the largest afloat and illustrate the latest theories of construction. There were already rumours of competition in the North Atlantic trade, and the Great Western directors did not intend to be forestalled. They decided to build an iron ship and it was accordingly announced that the Great Western was to be followed by the Great Britain, of iron. This project was roundly condemned by the public. The fact that iron steamers were already in existence on Irish waters did not count for much. These might be good enough for Irish lakes and rivers but would be unfit for the Atlantic Ocean. The Garry Owen was already forgotten.
The Great Western Company, however, persisted. The Great Britain was designed by the younger Brunel and launched in 1843. Her length of keel was 289 feet, and length from figure-head to taffrail 320 feet. Her beam was 51 feet. The total depth from the under side of the upper deck to the keel was 31 feet 4 inches. Her tonnage was 3500 tons and her displacement at 16 feet was 2000 tons. Her cargo capacity was 1200 tons measurement, and her coal bunkers held 1000 tons. Since no shipbuilder had the necessary data for the construction of such a vessel, and shipbuilders as a whole were by no means favourably disposed towards iron ships, possibly because they had not the plant necessary for their construction, and as there was also a very widespread belief that a vessel of the size and dimensions of the Great Britain could not be built of iron, the directors were unable to find a contractor who would undertake her construction. They were therefore obliged to instal the plant for building the ship and the engines also. She was built under the supervision of Paterson of Bristol, who was responsible for the Great Western. It was at first intended that the Great Britain should be a paddle-steamer and her lines followed in several respects those of the best paddle-steamers of the day; though the Great Britain herself contained so many novel features and was of so experimental a character that it could hardly be said that she followed anything.
Little had been done to demonstrate the power of the screw propeller, which for some unfathomable reason was considered to be suitable only for small vessels. However, after the construction of the Great Britain had been commenced, the steamer Archimedes, fitted with Smith’s screw propeller, arrived at Bristol during her tour of the ports and demonstrated once and for all that the screw propeller could be used in seagoing vessels, and that, provided engines of sufficient power were installed, the screw propeller was more suitable for large hulls built to make ocean voyages than the best paddle-wheels then designed. But many years were to elapse before the shipping industry generally accepted this view.
The advantages of the screw, as proved by the Archimedes, were not, however, lost upon the enterprising directors of the Great Western Steamship Company, and they did not hesitate to order the designs of the Great Britain to be altered so that she could be fitted with a screw instead of paddles. She was not built on a slip whence she might have been launched into the river, but in an excavated dock, and when she was afloat in the dock it was found that she was too big to be got out of it. That is to say, that having been fitted with her engines while still in dock, their weight immersed her to such an extent that she could not float out. This was owing to the dock officials’ delay in finishing alterations to the dock entrance, and not to any mistake or negligence on the part of the steamer officials. She was water-borne on July 19, 1843, and was christened by Prince Albert. The floating was attended by vexatious mishaps. The Great Britain was attached by a hawser to the tug Avon, which was outside the dock, but at the critical moment the hawser broke. The bottle of wine thrown at the ship by the Prince fell several feet short. He threw another bottle of champagne, which struck the bows, and the wine and broken glass fell upon the men below, who were pushing against her sides to keep her off the dock walls.
