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CENTRE LINE OF
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CENTRE See also:LINE OF SH`FT See also:INN 0 See also:Elevation. Transverse See also:Section bars extending to the upper See also:deck; each tier of beams is securely riveted to them, and their See also:lower ends are connected to the margin See also:plate by strong brackets. At intervals the channel-See also:bar frames are replaced by deep built-up frames, the frequency of which depends on See also:local requirements. Heavy See also:side stringers of the same See also:depth as the deep frames run fore arid aft, to stiffen the side between the bilges and the first plated deck. Where the deep frames are cut by these 980 local support to the bottom as well as See also:general strength to the See also:vessel. There are in a warship so many structural features, such as See also:water-tight bulkheads and flats or platforms, required for the necessary subdivision, See also:armour decks, plating and framing behind armour, &c., which are made to contribute to the strength of the structure as a whole, that the strength of the See also:shell-plating and the transverse framing can be proportionately reduced. In a See also:merchant See also:ship there are many considerations which require the structure to be stronger and heavier than would be necessary'COURSE OF CONSTRUCTION See also:door or from a deck above water, or from both. Below the protective deck are the See also:engine and See also:boiler spaces, magazines, shell-rooms, submerged See also:torpedo rooms, and steering-See also:gear. A passage is provided on each side of the ship just below the protective deck, for the See also:supply of See also:ammunition to the secondary armament. Fig. 118 shows the " Idzumo " partially in See also:frame, looking forward from the after extremity: the frames below the armour deck over a considerable length of the ship are See also:complete, and a number of the beams which carry the armour deck are in See also:place. Fig. 119 shows the See also:ram See also:stem, which has just been placed in position. The collision bulkhead and the framing below the armour deck are for the most See also:part in place. Fig. 120 gives the See also:top of the armour deck, which is nearly completed, as seen from the fore end, with the forward citadel on a 9 g. t ~ 'e' 6 4', M ' 'e' 6' 65 in See also:perspective. to withstand the See also:wind and waves which she may encounter. The continual See also:change of See also:cargo and of disposition of cargo necessitates See also:special local strength throughout. The See also:custom, often pursued, of grounding vessels to See also:discharge cargo, and their liability to See also:touch the ground in the ports they frequent, make the See also:provision of See also:great strength in the floors and the shell-plating essential. Other considerations affect the decks, and See also:call for local strength in them with corresponding increase of See also:weight. Most warships, except gunboat, torpedo and other small See also:craft, have See also:double bottoms, chiefly for See also:protection against damage in See also:action, but also against accidental grounding. The space between the bottoms is divided into a large number of compartments by making some of the frames and longitudinals water-tight. The inner bottom extends on each side to the turn of the See also:bilge, and from that point is carried up vertically as a wing bulkhead, as shown in fig. 122, the wing spaces thus formed being occasionally utilized for See also:coal-bunkers. The framing, consisting of frame bars, See also:reverse frame bars and frame plates or brackets, is usually carried up in a See also:fair See also:curve to the armour shelf, supposing the vessel to be an armour-clad, as in fig. 122. From the edge of the armour, which is generally about 5 ft. below the load water-line, a change in structure is made, and the framing behind the armour is set back from the outside of the ship sufficiently to admit of an See also:internal skin of See also:steel plating (often worked in two thicknesses), See also:teak backing, upon which the armour is embedded, and the armour itself, to be carried with the See also:surface of the armour flush with the shell-plating. The See also:vertical frames behind armour are spaced 2 ft. apart, and the longitudinals are made intercostal, the whole having exceptional strength, to support the armour. Above the armour another change is made, the frames being brought again to the outside of the ship, and the topside plating directly attached to them becoming flush with the outside of the armour. There is generally a strong deck, called the protective deck, extending from stem to stern in the See also:form of a turtle-back, the lower edges being at the armour shelf on each side of the ship, and the top of the See also:arch forming the first deck above water, as indicated in fig. 120. With a view to maintaining its defensive See also:power where it has to be perforated for funnels and See also:air shafts, armour gratings, or armour bars as they are called, are fitted in the openings. As much water-tight subdivision as possible is introduced throughout the ship, but for communication between the various compartments openings are provided in the bulkheads, having water-tight doors which can be closed either from a position See also:close to the evation. Fin. 123.-Steering Gear of Merchant Ship. bulkhead in course of construction. Fig. 121 shows the after part of the vessel, which is not so far advanced as the forward portion shown in fig. 120. In fig. 121 the framing has been carried to a bulk-See also:head near the after extremity, the See also:rudder See also:post is in place, and the bearing for the rudder head can be seen in the foreground. The construction of the armour deck is proceeding, and the after citadel bulkhead is also well advanced, though no backing is yet upon it, as in the See also:case of the forward bulkhead, but the See also:base of the See also:redoubt which carries the after See also:turret is erected. The fittings in a ship cannot be fully described in the See also:present See also:article, but we shall conclude with some See also:account of the See also:auxiliary machinery. Two See also:ordinary arrangements of steering-gear Auxiliary fitted in merchant steamers are shown in fig. 123. In the machinery. first example a three-See also:quarter circular grooved rim, keyed to the rudder head, carries the steering-chains, which are led forward one on each side of the hatches to the See also:steam engine, placed in this case in the engine-See also:room casing, and controlled by shafting from the See also:bridge. The usual steering-See also:wheel is fitted on the bridge, and actuates the controlling See also:valve of the steam engine by means of the shafting. The second example is very similar to the first: a quadrant is keyed Elevation. [FIG. 124.-Steering Gear of Warship. on the rudder head, and worked by chains led over pulleys one on each side of the ship to the steam gear, which in this case is placed on the bridge, close to the wheel. In all such cases gear is also provided by which in an emergency the ship can be steered by See also:hand, by steering-wheels placed close to the rudder head, as indicated in the figures. In a warship the arrangement is different, as it is necessary to keep the steering gear below the water-line for protection. The breadth available at the rudder head is as a See also:rule not sufficient for a tiller or quadrant to be fitted. Fig. 124 illustrates an arrangement frequently adopted. A crosshead of sufficient See also:size is keyed on to the rudder head, and is worked by connecting rods from a similar crosshead placed a little farther forward, where the breadth of the ship is sufficient to allow a tiller to be worked. The tiller is worked by a See also:block or See also:carriage, which is See also:drawn across the ship on a See also:guide, at the same See also:time sliding upon the tiller, which is machined for the purpose. The block-and-guide arrangement is known as Rapson's slide. The block is hauled to and fro across the ship by a See also:chain which passes See also:round a sprocket wheel upon a See also:shaft, which is driven in either direction, as required, by the steering-engine. In fig. 125 the arrangement is shown which has been for a considerable See also:period adopted in large merchant See also:ships and has in See also:recent years been adopted in ships of the See also:British See also:navy. It is known as See also:screw steering gear. On the same central shaft there are right- and See also:left-handed screws as indicated on the See also:plan, by which blocks A and B are made to travel always in the opposite direction when the shaft is rotated. These actuate the crosshead on the rudder E by means of the rods C and D, one of which will communicate a thrust and the other a pull, and See also:vice versa according to which way the shaft is made to rotate. The shaft may be actuated either by hand-gear or by steam by means of the clutch F. In many cases the steam steering-engine is placed in the engine-room, to avoid See also:heating the after-compartments by the steam pipes, and for the See also:sake of easier See also:control by the See also:engineers. Amongst the auxiliary machinery usually fitted in passenger and other well-found vessels may be mentioned the windlass for working the cables and weighing the anchors; a warping See also:capstan forward in connexion with the windlass, and another aft with its own engine; steam winches for handling the cargo and baggage, and for hoisting coals on See also:board; and occasionally steam See also:cranes, fitted either in addition to or in place of the winches. Then there are the electric See also:light, pumping, ventilating and See also:refrigerating installations. See also:Hydraulic power is employed in many cases, especially for cranes, but here the source of the power is necessarily a steam engine, which is usually placed in the See also:main engine-room. Electric power sometimes replaces steam for operating some of the See also:machines enumerated above; for instance, ventilating fans are now generally driven by electric See also:motors in passenger and See also:war ships. A large number of comparatively small fans are used, each supplying air to a particular part of the ship. In warships the amount of auxiliary machinery has been very greatly increased in recent years. On each side of the deck amidships there is generally a steam winch for raising and lowering the boats, one of the See also:principal functions of the See also:mast in the See also:modern warship being to carry the See also:derrick used for this purpose. Electric motors are fitted for working the after-capstans, ash hoists, sometimes the winches, and the workshop machinery; also to See also:traverse, elevate and See also:work the guns, and bring the See also:powder and projectiles up from the magazines to the guns. But for the heavier guns, the steering-gear, and certain other purposes, hydraulic power or steam is still preferred. The writer is indebted to Mr H. G. See also:Williams, Mr See also:Lloyd See also:Wool-See also:lard and Mr A. W. A. Cluett for valuable assistance in preparing this article. (P. Additional information and CommentsThere are no comments yet for this article.
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