Captain Arthur David Linklater (1870-1951)


SAIL VERSUS STEAM

The whole purpose of using steam rather than sail was to escape the limitations imposed by the direction of wind. With favourable winds sail could and often did cover considerable distances and faster than steam. But with contrary winds or no wind at all steam naturally had an advantage. Over all it was eventually apparent that steam would consistently out perform sail in terms of speed and reliability. There were economic advantages to sail at first but with increasing engine efficiency steam was able to win that argument as well by the smaller number of men required to operate a steamer of comparable size to a sailer.

The ability of square rigged ships to sail to windward was very limited, whereas a steamship can progress more-or-less unimpeded. Consider; a square rigged ship needs to go due north. However, the wind is from due north. What progress could be made? The answer was about 30-35 miles in any one day north of the ship's starting point. An average square rigged vessel could steer no closer than about 65° to the wind. With the yards braced sharp up and laying no more than six points off the wind was considered very fine for a square-rigged ship. A point = 11° 15’ However, leeway, the effective sideways thrust of the wind exerted on the ships hull and rigging, would have pushed her another 5° off her intended course. An average modern yacht should be able to sail about 40° off the wind. While 30-35 miles beating to windward was not much, it was forward progress, but required sea-room to get the tacks in. Constricted space, such as a lee shore [nearby coast with wind blowing onto it] with a headland or other outlying obstructions often resulted in another little cross being placed on a chart signifying 'wreck'.

A steam ship can more-or-less ignore adverse weather conditions by steaming directly into the wind. A square-rigged sailing ship cannot do that. In very bad conditions a sailing ship had two options; to run before the storm i.e. sail with the wind coming directly from astern or to heave-to. The latter, by balancing rig and rudder effectively put the ship broadside on to the weather while keeping her roughly stationary. Heaving to was in itself a tricky manoeuvre requiring timely action; if the weather got too sever the manoeuvre could not be safely carried out. The only alternative then was to continue to run before the wind. If there was insufficient sea room that meant another small cross on the charts.

Speed of all ships, including modern super-tankers, is proportional to the length of hull. In sailing ships, given two vessels identical in every respect save for hull length, the longer hull will sail faster than the shorter. Brute force gets you nowhere as any hull has a maximum speed of travel beyond which it will become unstable and, in extreme conditions - such as having too large an engine or being towed too fast - will capsize. There is a complex relationship between a hull and its wake and wave pattern such that the closer a ship approaches its maximum hull speed, the greater the drag exerted by the water limiting its speed. The two principal sources of hull friction are the wave-making resistance generated by the hull and the frictional resistance or drag of the water passing over the hull, rudder, shaft [if any] etc. Frictional resistance increases steadily and proportionally with speed, but wave-making resistance increases exponentially with speed. At low speeds, frictional resistance is proportionally greater than wave-making resistance; as speed increases wave-making resistance becomes very much the greater force.

The bigger the ship, the more difficult she is to steer as a general rule. A square rigged sailing ship of say 2000 tons running before the wind in the Southern Ocean, where 60 ft high waves are common, gravity could propel 2000 tons of steel ship ‘down-hill’ at speeds greater than the maximum hull speed making her unstable and tricky to steer. A real danger then was a broach, i.e. where the ship's direction sheers suddenly across the wind which could lead to capsize, dismasting or being sunk outright by the following wave, generally foundering stern first. Such conditions were almost commonplace in the Southern Ocean and so unnerving that helmsmen were forbidden to look behind lest they desert the wheel in sheer terror. If broaching to did not sink the vessel outright she was often left on her beam ends at the mercy of the elements owing to the cargo shifting. According to Lubbock, ships on their beam-ends rarely sank, being held up by the compressed air below decks, a fact, if known, doubtless kept fervently in mind by the crew of any such boat.

Development of large, commercial sailing vessels is not over yet, nor indeed the debate as to the merits of wind versus other means of propulsion. With increasing awareness of the damage done to the earth's atmosphere by carbon emissions, to which modern shipping contributes disproportionately by burning particularly filthy and damaging fuels, it is hardly surprising that even now [2009] sail is once again being considered as a viable alternative. Were the argument merely about pollution it would be going nowhere but luckily petrochemical fuels have increased greatly in price thus compelling shipping companies and ship designers to cut the expense of fuelling and running massive container ships. Wind presents itself as a natural alternative.

Big container ships are taking it very slow these days, cruising at 10 knots instead of their usual 26 knots, to save fuel. This is actually slower than sailing freighters travelled a hundred years ago. The 1902 German Preussen, the largest sailing ship ever built, travelled between Hamburg (Germany) and Iquique (Chile): the best average speed over a one-way trip was 13.7 knots. Sailing boats need a large and costly crew, but they can also be controlled by computers. Automated sail handling was introduced already one century ago. In 2006 it was taken to the extreme by the Maltese Falcon, which can be operated by one man at the touch of a button. We have computer-controlled windmills, why not computer-controlled sailing cargo vessels?


 
 


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× Capt. Arthur David Linklater INTRODUCTION to the Journals JOURNAL Preface &
JOURNALS' LOGIN
BRITISH PRINCESS BIOGRAPHY Biography Contents page by page CAPE HORN The HOOGHLY River SAIL v. STEAM SAIL - unfinished; ran out of steam. NAUTICAL GLOSSARY SLIDE SHOWS