The Screw

Pettit-Smith's won after scientific experiments

This is a continuation of Naval History carrying on from: "Propellent"

Captain John Ericsson, and Francis Pettit-Smith's, patients were taken out during 1836, and by 1840 the courageous decision was taken of the fitting with screw machinery to the latest Atlantic liner then on the stocks, the "S.S. Great Britain." She was a pronounced success.

Nor was the Admiralty far behind. It fitted a screw to its steam-sloop, "H.M.S. Rattler," and conducted a series of realy scientific experiments with various shapes, sizes and settings. The screw finally selected was Pettit-Smith's.

It was this ship, with this screw, which took part, one May evening in 1845. The Admiralty had produced a rival, choosing for the purpose a smaller sloop, as like as possible as the "Rattler" in shape, lines and power.

She was H.M.S. Alecto, a paddler, and what added immensely to the drama of the affair was the whole shipbuilding world, not to mention the whole Navy, was just about evenly divided in its allegiance to the Paddle and the Screw.

Propellent

Racing against the Wind

The first trials were ordinary races-exciting enough, yet not out of the ordinary. The Rattler won with comparative ease, beating her rival on an 80-mile course in a calm by 23.5 minutes; with sails in a moderate wind , on a course less than half as long, by 13 minutes; and finally on a 60-mile course, dead into wind and sea, by as much as 40-minutes.

But the Alecto-ites still claimed superiority in towage; whereupon the rivals were attached stern to stern by two stout cables, and as soon as they were taut, "full steam ahead" was rung in both ships. The tug-of-war was on.

The knotty problem of Paddle v Screw was to be decided there and then before the very eyes of their supporters. For a brief space, we are told, nothing happened, but then the "Rattler" was seen to be making headway, and her speed gradually increased until she was travelling at a rate of 2.5 knots. The old was now having to give way to the new.

The invention of the Screw is one of the peak-points in warship development. It solved a problem which had been exercising men's minds for centuries. The Galleass had failed to solve-how to combine the advantages of "free-movement," which Sail could never do, and give an uninterupted field of fire, which oar and paddle tended to obstruct.

The advantages were identified

The Screw combined the advantages of both, free-movement and permitted room for the guns to have their broadside. The "Rattler" v "Alecto" trial was convincing in so far as the choice lay between Screw and Paddle. The Battle of "Steam" v "Sail" was also won so far as the small ships was concerned.

With regard to these special treasures, the battleships, the Admiralty had not brought its courage to a sticking point. None the less events forced her hand, In the mid 1840s, France, and especially certain French ministers with advanced ideas on ship-construction, began to look menacing once more, and that, along with Louis Napoleon displaying his desires.

In 1852 was launched the "Agamemnon," the first "line" ship to be fitted with screw machinery. She was, in all other respects, an old Wooden Ship; her screw was to remain auxilliary to her full rig. Steam had been admitted into partnership, strictly on the understanding that it was to be the Junior Partner in the firm, the Senior was still far from sleeping.

Yet the "Sail's" end was fast approaching. In a hard competitive world, its efficiency was being challenged almost hourly by its rival. What at length revealed the victor was the acid test of Action.

The Crimean War found us with our main fleet still composed of full-rigged sailing ships. Of the British "line" ships, engaged in bombardment of Sevastopol on 17th October 1854, only two were fitted with screws. The action brought little credit to anyone.

The sailing ships, having taken a considerable amount of time in getting pushed and prodded into position by the exertions of small paddle and screw vessels, engaged the enemy batteries at too long a range, inflicting very little damage while receiving much.

The Screw displayed its benefits

The two screw-ships steamed into action more briskly, and opened fire at a shorter range, it was Sir Edward Lyons, flying his flag in the "Agamemnon" (screw).

Elsewhere the smaller ships fitted with steam did well. At Odessa five paddle-ships, steaming up as they fought, escaped any serious punnishment, but did a lot of damage to the port instalations.

None of our ships, achieved outstanding success, for War had reached one of those moments in history when Offence was temporarily forging ahead of Defence. Yet, it is safe to say, that by the end of the conflict, the Steam-engine had established its claims to be installed in all ships.

But still the Admiralty hesitated. Marine steam-engines, though much improved since "Comet" days; it was believed, still might break down, and what then? So the Senior Partner, left more and more work to its Junior, yet remained firm-just incase. All through the 1850s the sail stayed, and all through the 1860s too.

Still the full rig persisted, and inspite of all the technical difficulties involved in retaining it. It was like a Victorian oven in a twentieth-century modern kitchenette.

The sail got in everyone's way; it upset everyone's calculations; it rendered necessary a drastic reduction in gun-power. But it stayed, the Admiralty wouldn't let the sail go.

Enter the Iron Ships

In 1869, there was launched an iron, armoured turret-ship called the "Captain." There was nothing else of the wooden ship about her, but she was fully rigged.

Her hull lay very low in the water-dangerously low. She was designed to have a freeboard of eight feet, as against the fourteen feet of her rival, the armoured turret-ship "Monarch." Worse, When she was loaded and commissioned, it was found that her freeboard had dwindled to six feet.

Above was the flying deck from which the sails were worked, and at which all of the rigging stopped short. She was also fitted as an afterthought, with poop-decks and forecastles-more weight placed high. The result was Disaster.

If her freeboard had been greater, or if she did not have her full spread of canvas she might have been safe. She could not sustain the double handicap, and, in her first commission, on the night of the 6th September 1870, she capsized in a gale off Cape Finisterre and she turned right over, drowning all her people except the gunner and 17 men.

So Steam won the day, which was inevitable. The lesson was learnt, but it cost the Navy and the Nation 472 good men. Yet, even then sail had a dying kick left in it.

The "Devastation," which succeeded the "Captain," was built in the heat of a fierce anti-sail reaction, she was given one sailing mast to be used for signalling purposes only. Nothing like a fully rigged battleship ever appeared again. Still, somewhere a hankering after sail-power remained; though, strictly as a supplement to steam-power.

Ten years after the "Captain's" end there appeared the "Infexible." She was certainly a "steamer," she carried forty-eight distinct and separate steam-engines, but she also carried two masts, with yardarms, and was at first rigged as a brig. Those masts were also fitted that in an instant they could be jettisoned.

But the "Inflexible" happened to be a good steamer, and never had occasion to use her sail-power either to steady her at sea or to remedy a mechanical breakdown. So in the end, Sail in big ships did not perish gloriously in battle, or tragically in disaster; it just faded out, and died quietly of old age.

Little remains to be told of the propulsion of the Screw story. The improvements in the engine, and the remarkable increases in horse-power and steam pressure, and the coming of the turbine, important as they are, are developments of technical character which are well outside the scope of this script.

The phenomenal growth of power

Yet a few figures, revealing the magnitude of transformation, will not be out of place here. They serve to show the nature of the phenomenal growth of power with which man has replaced Wind and Oar.

The little pleasure steamer "Comet" 0f 1812 had a 3 h.p. engine. The naval tug comet of 1822 developed 80 h.p.. Its successors up to about 1840 added but little to this, and worked with steam pressures of from 3 to 5 pounds per square inch.

The "Terrible," one of the first of the ill-starred paddle-frigates; a much larger ship, had advanced to 800 h.p. (Nominal: at least 2,000 i.h.p.). Compare this with the "Hannibal," a 90-gun Sail of the Line converted for screw, whose i.h.p. was only 1,070, and whose steam pressure of 12 pounds per square inch. The "Devastation"-the first without masts and yardarms-was of 6,650 i.h.p. and her steam pressure was 30.

The "Majestic's" 1893 figures were 12,000 and 155 respectively; the "Iron Duke's" 1911-Jellicoe's flagship, engined with turbines-31,000 and 225. H.M.S. King George V, laid down in 1936, developes 100,000 i.p.h. and had a steam pressure of 400 ponds per square inch.

One last fact, not perhaps very widely known, shows that hoping that things in this land should idealy move uniformly fast. An examination of the registers of all ships new-built in this country reveals that, in numbers, it was not until the year 1880 that new steamers exceeded new sailing ships for the first time. Perhaps the Naval Authorities were not really so sleepy after all.

The continuation of this Naval History will be: "Fuel"

The Screw Fuel

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