Protection, machinery, and endurance in the Formidable design

Formidable had a forward armoured bulkhead, while the London class extended its belt to the stem. The change is significant enough to justify a distinct class in this interpretation, although combining both forms of protection might have been preferable. Formidable displaced about 14,700 metric tons normally and 16,100 metric tons fully loaded. She was 431 feet 9 inches long, 75 feet in beam, drew a mean 25 feet 11 inches, and carried a crew of roughly 780. Twenty water-tube boilers fed two triple-expansion engines driving twin screws for 18 knots and a range of 5,500 nautical miles at 10 knots. Her weapons included four 12-inch Mark IX guns, twelve 6-inch Mark VII guns, ten 12-pounders, six 3-pounders, and four 18-inch torpedo tubes. A 9-inch belt, heavy bulkheads, armoured barbettes and casemates, a 14-inch conning tower, and one to three inches of deck armour made her a solidly protected ship. The strong forward protection followed a post-Trafalgar expectation that British ships might break an enemy line or receive fire while an opponent tried to cross the British T.