HMS COLOSSUS
Int14200 Col2520
Protecting the Vitals (3)
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The Raft

Weight and displacement restrictions (and cost) prevent the whole of the side of the ship from being armoured. While the magazines and shell rooms are well below the waterline, they could be vulnerable to the effects of a shell exploding in a deck above (or from plunging fire from shore batteries). Protection is therefore provided by an armoured deck, 2 to 3 inches thick, built above the lower deck, but still about five feet below the waterline. The compartments below this armoured deck and within the citadel are considered to be watertight and proof against enemy damage. While these compartments remain undamaged, the ship will float, even if the superstructure and decks above are riddled.

Further protection is provided by subdividing the spaces within this raft into watertight compartments.

Int6600
Int6900

Note the torpedo body stowage compartment forward and the turning engines for the starboard turret, which are inset into the coal bunkers.

Now add the main armour belt, made up of a layer of compound armour 18 inches thick, backed by a further 20 inches of teak in two layers.

Int7130

Add the armoured decks forward. The wing compartments are filled with cork, or rope/oakum, to provide buoyancy if a shell penetrates. Centrally, and directly above the magazines and shell room are three coal bunkers. These provide the main coal storage for the ship, protection, since 2 foot of coal is equivalent to an inch of armour plate, and buoyancy - if the bunker is full of coal, there is little room for flooding.

Int7600

On the after armoured deck above the magazines and shell rooms there are three smaller coal bunkers flanked by wing compartments filled with cork.

A point to note with the aft coal bunkers is that all the coal in them must be manhandled through the starboard engine room and starboard aft boiler room. This implies that there were watertight doors connecting all the boiler rooms and engine rooms. In action, however, these doors would be shut and boilers would be fed from the coal bunkers adjacent to the boilers themselves.

Int8040
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(c) Rob.b1904 2008