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steam propulsion


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The aphorism ‘steam gives way to sail’ came out of the marine steam revolution of the 19th century, for steam-powered vessels had a range of speeds and manoeuvrability denied to sailing ships. The International Regulations for Preventing Collisions at Sea, ratified in the 1890s, recognized this new technology and steamships were nearly always required to keep clear of sailing ships. But in all other respects sail gave way to steam, in terms of economies of scale, reliability, speed, and profitability. Coastal and riverine traffic adapted to steam propulsion, but on the high seas the transition was an extended one, with, ironically, sailing ships hastening their demise by carrying coal, and later fuel oil, to bunkering stations throughout the world.

Coal Burners.

Early steamships fuelled by coal were all paddle steamers and they had to carry large amounts of coal, which meant less space for cargo or passengers. The engines were unreliable and had a short steaming range, and this, combined with the innate conservatism of shipowners and navy boards, resulted in ocean-going ships being also rigged for sailing for many decades after they became powered by steam. It was an unsatisfactory combination, and even when steam engines became reliable, ships continued to be built with masts, though, eventually, not the rigging and sails that went with them.

Steam is vaporized water. Its production requires high temperatures and pressures in efficient boilers using fossil or nuclear fuel. Before the last quarter of the 18th century steam machinery had no practical uses afloat, but in the 1780s James Watt did make it more efficient by means of the separate condenser and other improvements. However, it was in France in 1776 that the practical application of steam technology on water was initiated by the French engineer the Marquis de Jouffroy d'Abbans (1751–1832). The American John Fitch (1743–98) was another pioneer and their experiments were followed in the early 1800s with the Clermont and the Charlotte Dundas.

The first transatlantic voyage by a steamship, the Savannah, took place in 1819, but she had to sail most of the way with her collapsible paddle wheels stowed on deck. The voyage was not commercially successful, nor was the one undertaken to India by the Enterprize in 1825, and it was not until 1838 that the Sirius proved a steamship could cross the Atlantic under power. Even so, the inefficiency of the double-acting single cylinder engine was not overcome, by John Elder on the Clyde, until the 1850s. He patented a system of compounding where high-pressure steam at high temperature was expanded in two stages—this was the compound engine. Initially a two-stage expansion, it developed into the ubiquitous triple and quadruple expansion reciprocating engines which dominated the world's fleets for the rest of the 19th century. Compounding, combined with better, higher-pressure boilers, such as the cylindrical Scotch and Yarrow water tube boilers, reduced fuel consumption by at least 60%, allowing profitable passages to be made as far afield as the Far East and Australasia.

With the introduction of the screw propeller, and iron and steel into shipbuilding—large wooden ships were too flexible in a seaway and had difficulty coping with the increased stresses in power transmission—steam propulsion slowly gained the upper hand over sail. However, despite the success of Brunel's Great Britain, both iron construction and propellers were initially treated with some scepticism. To see if the propeller was superior to the paddle wheel, the British Admiralty even arranged a tug-of-war between two same-sized frigates, HMS Rattler (screw) and HMS Alecto (paddle). It took place in 1845 and the former won. Although the relative power of their engines is debatable, it did show the inherent caution with which shipbuilders treated anything new. It was not until the late 1880s, when ocean liners adapted the twin screw, that they ‘at last dared to rely on their engines alone’ (C. Gibbs, Passenger Liners of the Western World (1952), 101), and began to discard the heavy masts and spars that were needed to raise sails in an emergency.

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Subjects: Maritime History.


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