Abbildungen der Seite

by means of a yoke, A B C fig. 6 (I K, fig. 6 a), on the main deck, and by a similar yoke EF, on the lower deck, by either of which the ship may be steered. Each yoke consists of two arms, straight or curved, which are worked by tackles made fast to, and rove through a stern-beam, and can be moved through an angle of 36 degrees in either direction. When additional power on the helm is required, it is obtained by means of relieving-tackles, consisting of double blocks, one of which is attached to each arm of the yoke, and the other to the side of the ship. The lower yoke EF works underneath and close to the beams of the main deck P Q (fig. 6 a), and the upper yoke I K close under the beams of the quarter-deck M N.

The arms of the yoke being short, compared with the length of an ordinary tiller, it has been found necessary, in order to obtain sufficient power to turn the rudder, to have a multiplying purchase, consisting of a system of pulleys near the end of each arm of the yoke, and also in a main beam in its rear; the rope, or rather the chain (for a rope, though made of prepared hide, is soon worn through), is made fast to the yoke, and passes round a sheave in the beam behind ; then round one in the arm of the yoke; and, after passing about a second sheave in the beam, it is carried to the barrel of the steering-wheel on the quarter-deck. In consequence of the complexity of this apparatus, a considerable revolving motion of the steering-wheel is necessary in order to produce even a small movement of the rudder; and there is, therefore, a want of promptitude in the corrective power of the helm, when moved by the yoke, which is not experienced when a ship is steered by a simple tiller in the ordinary way.

Various other modes of steering have been tried with the yoke and with a short tiller, as I K, fig. 6 a, fixed in front, or in the rear of the Norman head, but no satisfactory result has yet been obtained from them. Experiments are now being made at Portsmouth with

* In three-decked ships, the lower yoke is under the beams of the middle deck, and the upper yoke below the beams of the upper deck.

a tiller shipped to a cross-head on the stem of the rudder, and leading towards the quarters of the ship; and this is worked by tackles in either direction. But these complicated expedients to compensate, by the multiplicity of gearing, for the defects occasioned by the absence of the long tiller, do but increase the evils complained of, and are evidences of the necessity of reverting to the use of that simple agent.

The great force of torsion exerted on the stem of the rudder by the yoke on the lower deck, by the short tiller in the Norman head, and sometimes by both acting together, wrings the stem to such a degree that many rudders have been entirely destroyed by it, and it has been found necessary to provide against this evil by giving additional strength to the rudder-heads in all screw line-of-battle ships recently constructed.

Besides this injury to the rudder arising from the employment of the yoke, the great force which it is necessary to apply to the wheel in order to give motion to the rudder, particularly when the latter is acted upon by sudden and violent impulses from the striking of waves against it, is also the cause that the steering of screw-steamers, having trunks, is far less steady than that of ships whose helms are managed by the ordinary tiller.

The author has no personal experience in the art of steering a steam-ship by the yoke, but he is enabled to judge accurately on the subject by information obtained from flag-officers who have inspected, captains who have commanded, and officers who have served on board screw-steamers, as well as from experienced quartermasters who have performed the mechanical operation of steering such ships : all these admit that the trunk, from the space it occupies—not less than 243 cubic feet on each deck-has rendered it necessary to resort to that disadvantageous means of giving motion to the rudder ; but, believing it to be unavoidable, they accept it as a necessary evil. But is it necessary ? Why should a structure so detrimental to the steering power of the ship, and so obstructive to the general service of the decks, be suffered permanently to remain, since its use is only occasionally required ? Apertures must be made in all the decks to admit of the screw being hoisted up for the purpose of repairing it, or of replacing it by another. In the latter case, the spare propeller (screw) is brought out of the stowagebed in the hold, and transported aft on a suitable sledge. The tackle by which the screw is hoisted consists of a double system of pulleys suspended from a strong timber (chock) spanning the aperture in the upper deck : each fall is made fast at one end to an immoveable object; passing then over a friction-pulley in the chock, it is led under a pulley fixed to the metal frame which carries the screw, and is passed from thence over another friction-pulley in the chock to the barrel of the capstan :- by heaving on this the metal frame, with the screw, is raised through the trunk to the upper deck. When the screw is damaged and requires to be replaced or repaired, shears are erected of sufficient altitude to hoist the screw entirely clear of the aperture; the frame with the screw is then lowered to the deck, when what is amiss may be repaired, or the screw may be replaced by a spare one. While this operation is being performed, which is accomplished in ten or twelve minutes after the gearing is prepared, the long tiller cannot, of course, be used; this must, therefore, be unshipped and triced up to the beams, and the yoke or short tiller must be applied for the purpose of steering the ship till the screw is refixed; . but it must be unnecessary to enclose the apertures by permanent bulkheads. Might it not suffice to carry the trunk up from the top of the aperture in which the screw works, as high as the lower-deck, and no higher ? To prevent the surge of the sea, up the permanent trunk, from getting into the lower deck, a strong cap of timber should be made to close the aperture, the chain attached to the screw being passed through a hole perforated in the centre of the cover, and kept ready to be passed through the apertures in the decks above, when the operation of hoisting the screw is required. When the screw is to be hoisted up, temporary stanchions might be fixed in mortices at the four corners of the rectangular

space (a a fig. 6) to which the boss must be confined in moving the screw up and down; and by these stanchions the edges of the metal frame in which the screw is set may, in lowering it, be conducted into the metal guides fixed vertically in the permanent trunk below the lower deck, so as to bring it, as before, to the proper place for connecting the screw with the propelling shaft. By suppressing the trunk, the decks would be free for the movements of a tiller of the ordinary length and description, which, like the yokes, might be placed immediately under the beams of the quarter-deck and main deck respectively : the apertures being covered by shutters, on which guns might be placed, the stern batteries on each deck would be strengthened by the two guns which the trunk had rendered useless; and thus spaces of about 700 and 1000 cubic feet, in two and three deck ships respectively, would be restored to the gun and ward room accommodation, and to the apartments appropriated to the captain and the admiral.

* The great advantage of applying screw-propulsion to ships of war consists in these being enabled to execute, with the utmost precision and certainty, the tactical movements which the new system of naval warfare will introduce. But that precision in execution depends entirely upon the accuracy with which the new moving power is directed by the helm; and so indispensable is correct steering in the evolutions of steam-fleets, that the full benefit which steam propulsion is capable of affording cannot be obtained without it. The reader will see, in the sequel of this work, the immense importance of steady and correct steering in the evolutions of steam-fleets; and naval officers, in practising the new and delicate manoeuvres of which the author is about to treat, will find that the most serious consequences will result from any defect in the apparatus by which steam-ships are steered.

The steering of a screw steam-ship of the line, with all sails furled, should be as if instinct with life, intuitive, and quick as volition. The more simple and direct the regulating power of the helm is, the more it will conform with the above attributes.



80. THE tactics of naval warfare under the power of steam cannot be advantageously studied except in comparison with those in which the movements of the ships depend on the action of the wind ; and it, therefore, will be necessary to begin by a short description of the elementary principles which have governed the operations of hostile fleets in past times, when the manoeuvring powers of the sail alone could be employed to effect the requisite evolutions. The nature of these evolutions being explained, it is proposed to enter upon a description of the means of executing them, and of the modifications which must be made in the tactics of naval warfare when ships are moved by the power of steam.

81. The science of naval warfare may be classed under two principal divisions :—the order of movement in advance or retreat, and the order of battle.

In 1697 Paul Hoste a published his treatise of Naval Evolutions; and this work, which was reprinted in 1727, is, by all writers on the art, pronounced to be the ground on which succeeding theories have been based.

82. With respect to the first of these divisions,

a Father Paul l’Hoste, a Jesuit, was born at Bresse in 1652, and died Professor of Mathematics in the Royal College of Marine, at Toulon, in 1700, aged 48. He was present in many of the battles he describes, having served for many years with some of the most distinguished admirals of France. He was on board the Count de Tourville's ship at the battle of La Hogue in 1692, and served in some of the sanguinary battles fought between the English and Dutch fleets in the 17th century.

b The principal writers on naval tactics since the time of Paul Hoste are : M. Bourde de Villehuit, 1769; M. de Moroques and M. du Pavillon, 1780; Clarke of Eldon, 1790; Viscomte de Grenier, 1788; Steel, 1794; Admiral Sir Charles Ekins' Naval Battles.

« ZurückWeiter »