Editing Formidable-class battleship (section)

===Armament and armour===
[[File:Formidable class 12 inch gun turret right elevation.jpg|thumb|upright|left|Right elevation of 12 inch gun turret & ammunition hoists]]

''Formidable'' and her sisters had four {{convert|12|in|mm|adj=on|0}} 40-calibre Mk IX guns mounted in twin-[[gun turret]]s fore and aft; these guns were mounted in circular barbettes that allowed all-around loading or elevation. Shell allowance was 80&nbsp;rounds per gun. The ''Formidable'' class were the first to carry these guns, which featured several improvements over the earlier Mk VIII guns used in older battleships, including a stronger barrel design and higher [[muzzle velocity]]. ''Formidable'' and ''Implacable'' had BVI type mountings for their guns, while ''Irresistible'' received newer BVII mounts, the primary difference between the two types being the arrangement of the shell hoists and other equipment.{{sfn|Burt|pp=190–192}} Both types of mountings had a range of elevation from -5&nbsp;degrees to of 13.5&nbsp;degrees. The BVI mounts required the guns to return to 4.5&nbsp;degrees to be loaded, while the BVII mounts allowed for loading at any angle. The guns had a muzzle velocity of {{convert|2562|to|2573|ft/s}}, and they were capable of penetrating 12 inches of Krupp armour at a range of {{convert|4800|yd}}. At their maximum elevation, the guns had a range of {{convert|15300|yd}}.{{sfn|Friedman|pp=57–58}} The guns had a [[rate of fire]] of one shot every eighty seconds.{{sfn|Fraser|p=44}}

The ships also mounted a [[secondary armament|secondary battery]] of twelve [[BL 6 inch Mk VII naval gun|{{convert|6|in|mm|adj=on|0}} 45-calibre guns]] mounted in [[casemate]]s, which were supplied with 200&nbsp;rounds per gun. The guns had a muzzle velocity of {{convert|2536|ft/s|abbr=on}}. These guns could penetrate 6&nbsp;inches of Krupp armour at {{convert|2500|yd}}. Maximum elevation was 14&nbsp;degrees, which allowed the guns to engage targets out to {{convert|12000|yd}}.{{sfn|Friedman|pp=79–81}} For close-range defence against [[torpedo boat]]s, they carried ten [[QF 12 pounder 12 cwt naval gun|12-pounder guns]] with 300&nbsp;rounds per gun and six [[QF 3 pounder Hotchkiss|3-pounder guns]] with 500&nbsp;shells per gun. As was customary for battleships of the period, they were also equipped with four [[British 18 inch torpedo|{{convert|18|in|0|adj=on}} torpedo]] tubes submerged in the hull.{{sfn|Lyon & Roberts|p=36}}{{sfn|Burt|p=191}}

The ''Formidable''-class ships made more extensive use of Krupp steel than the preceding ''Canopus'' class, with most of their side armour consisting of the stronger steel. They had an armoured belt that was {{convert|9|in|0}} thick and extended from the forward main battery barbette to the aft barbette; the transverse bulkheads on either end of the belt were 9&nbsp;in thick forward and {{convert|9|to|10|in|abbr=on|0}} thick aft. The belt extended from main deck level ({{convert|9|ft|6|in|0|abbr=on}} above the [[waterline]]) to {{convert|5|ft|6|in|abbr=on|0}} below the waterline. The ships' side plating forward of the belt was {{convert|3|in|abbr=on|0}} thick, while it was only {{convert|1.5|in|abbr=on|0}} aft of the belt. The ships were fitted with two armoured decks; the first was a flat deck that was {{convert|1|in|abbr=on|0}} thick, above the main deck, which was 2&nbsp;in on the flat portion and increased slightly to 3&nbsp;in on the sloped sides, where it connected to the belt armour.{{sfn|Lyon & Roberts|p=36}}{{sfn|Burt|p=191, 193–195}}

The ships' main battery turrets sides and faces were {{convert|8|in|0|abbr=on}} thick—reduced slightly compared to earlier ships to account for the heavier belt armour—with {{convert|10|in|abbr=on|0}} thick rears. The turret roofs were 3&nbsp;in thick. The turrets sat atop 12&nbsp;in thick [[barbette]]s, though ''Irresistible''{{'}}s barbette armour was reduced in thickness to 10&nbsp;in behind the belt. Above the main belt was a [[strake]] of armour that protected the casemate guns, which was 6&nbsp;inches thick; behind the casemates, an interior bulkhead that was {{convert|2|in|abbr=on}} thick protected the interior of the ship. Their forward [[conning tower]] had {{convert|10|to|14|in|0|abbr=on}} thick sides, with a communication tube below the tower that had armour protection that was {{convert|8|in|abbr=on|0}} thick. The aft conning tower had 3&nbsp;in thick sides with a 3&nbsp;in tube below.{{sfn|Lyon & Roberts|p=36}}{{sfn|Burt|p=191, 194–195}}