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pillar supports the skid beams, and is thus not fitted to assist the structural strength of the ship.

In many cases where pillars are necessary, the obstruction caused is very inconvenient, as in way of capstan gear, torpedotubes, etc. In such cases the pillars are made portable. The head is fitted with a pin (Fig. 37), so that the pillar can be hinged up clear, or, if desired, removed altogether for the time. Figs. 38 and 38A show two forms of heel fitting; in the first case there is an inconvenient obstruction left, in the second this heel fitting is also made portable.

Deck Plating.-Plating is worked on decks and flats for various reasons, (a) for the purpose of contributing to the structural strength, as on the upper deck; (b) for the purpose of protection, as on the main and middle decks in Fig. 12; (c) to divide the ship into watertight compartments, as in the hold forward and aft; (d) to distribute the strains on the deck, as under bollards, boathoists, etc.

The Upper Deck is a most important part of the structure, especially in a vessel of large proportion of length to depth as a cruiser. It forms the upper flange of the girder, and so contributes materially to the ship's structural strength. Fig. 39 gives the arrangement of the upper deck plating amidships in such a ship The side stringer has a total breadth of 10 ft., worked in two strakes of 20-lb. (in.) high tensile steel. There is also a funnel stringer 5 ft. wide, also of 20-lb. high tensile steel. This runs fore and aft along the funnel and engine hatches as shown. The remainder of the plating is 10-lb. (4 in.) mild steel. The plating of this deck is laid direct on to the beams, with single riveted edge strips on the upper side connecting the edges together. The butts are all double riveted; those of the 20-lb. plating being double, i.e. on both sides of the plate. Holes that are necessary in the deck for coal shoots, hand-ups, etc., are carefully compensated for by pieces of plate on either side of the hole to make up the sectional area cut away. The butts of the various strakes of plating are carefully shifted clear of one another, and clear of the butts of the sheer strake (see Chapter V.).

The above instance has been taken to show the care taken to render the upper deck specially strong when such strength is required, but in many cases, where the proportion of length to depth is not so great, this exceptional strength is not necessary. In such ships, as in Majestic, the plating does not completely cover

the deck, the most important part being the stringer next the side. We also find that only such a stringer is worked at the ends of many ships.

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In the most recent ships, however, decks are nearly always

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completely plated; when wood is worked above as for the upper deck, there is less likelihood of the wood catching fire with the For other decks we have corticine, and this

steel underneath. necessitates a complete steel deck to receive it.

In the most recent large ships an armoured battery is worked between the main and upper decks, and this is covered in by a protective deck, about 1 in. thick. This deck is very advantageously situated to assist in the ship's structural strength.

Protective Decks. -In decks fitted for the purpose of protection the plating is usually worked in two or more thicknesses. Thus in the Duncan the main deck is 2 in., worked in two thicknesses of 40 lbs. The middle deck is 1 in., and here two 20-lb. plates are worked. In this way no edge strips or butt-straps are necessary, as each thickness acts as security for the edges and butts

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of the other thickness. The lower thickness only is riveted to the beams; the general arrangement of the riveting is shown in Fig. 40.

Platforms, etc.-The plating of platforms and flats is usually of 10-lb. (in.) plating, with both edges and butts lapped and single riveted. For compartments where a good foothold is desirable, and where there is a lot of heavy wear and tear, the

flat is formed of 15-lb. galvanized ribbed plating. In a large ship the flats of the submerged torpedo-rooms, auxiliary machinery compartment, etc., are fitted in this way.

Watertightness of Flats, etc.-In watertight platforms, etc., the connection of the plating with the ship's side must be made watertight. Fig. 41 shows two methods of doing this, one when the zed bar frame passes through, and the other when a simple angle bar passes through. In either case angle bars are smithed round to cover the holes completely; the riveting is closely spaced and the whole carefully caulked and made watertight. The pressure such a flat, 20 ft. below water, would have to stand if the compartment below were bilged amounts to about 60 tons per

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100 square ft., so that substantial work is seen to be very necessary. There is no difficulty in securing a watertight connection with the side at the main or middle decks of an armoured ship, because the transverse framing is not continuous through the deck, and a foreand-aft angle can be run along and caulked (Fig. 34).

Wood Decks.-The use of wood decks has been very much reduced in recent years in vessels of the Royal Navy, on account of the probability of the wood catching fire in action. Wood is now only used for weather decks, in the Admiral's apartments and the ward room, in casemates and ammunition passages, and for magazine flats. In the Admiral's apartments and ward room

the flat is of Dantzic fir, 2 in. thick. In the other cases the flat is of teak, on account of the suitability of this timber to stand heavy wear and tear. For the weather decks the thickness is generally 3 in., with thicker planks called waterways round the edges of the decks, forward and aft, and round barbettes, etc. Thicker planks are worked in way of the rub of chain cables. In casemates the teak is 2 in., and in ammunition passages 1 in.

When a steel deck is laid, the wood deck is fastened by

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through bolts to the plating between the beams. To decks which have to stand severe compressive strains, the connection of the wood deck to the steel deck is made a very efficient one, so that the wood and the steel may act together in resisting the buckling (see Fig. 42A).

When, however, as is sometimes the case, the wood deck has

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to be laid direct on to the beams, the bolts must be taken through the upper flange of the beam. For this reason, when a wood deck is thus worked, it is desirable to make the beam of tee bulb, so

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