The Minotaur-class ironclads consisted of three armoured frigates built for the Royal Navy during the 1860s. They were enlarged versions of with heavier armament, thicker armour, and more powerful engines. The ships of this class were unique among ironclad warships in possessing on completion five masts, named fore-, second-, main-, fourth- and mizzen-.
Design
The Minotaur-class ironclads were the final class of the first generation of British ironclads that had begun with in 1860. The new ships were in many respects an enlarged version of , which was in turn an improvement upon the Warrior design.
They were originally intended to mount forty Armstrong 110-pounder breech-loading guns on the main deck, with ten more on pivot mountings on the upper deck. The failure of these guns in service led to a complete re-evaluation of their armament, with a concomitant delay in the arming of the whole class. The ships were armed with a combination of 9-inch muzzle-loading rifles (MLR) on metal carriages and 7-inch MLRs on rope-worked carriages. In a moderate swell these 7-inch guns were virtually unworkable, making the Minotaurs both the heaviest and the worst armed of the Victorian battleships.
Characteristics The ships of the Minotaur class were long between perpendiculars and long overall, and they were fitted with a ram bow. They had a beam of and a draught of . Their displacement varied from , the lightest being and the heaviest being . Their hulls were subdivided into sixteen watertight compartments, and they had a double bottom underneath the engine and boiler rooms. The ships had a crew of 800 officers and ratings.
Each ship's propulsion system consisted of a 2-cylinder marine steam engines with steam provided by ten coal-fired fire-tube boilers, which were vented through a pair of funnels. Their engines provided a top speed from from ; of the three, Northumberland was the slowest and Agincourt was the fastest. The ships carried of coal, enough to steam for at . The Minotaur-class ships were the largest warships to rely on a single screw for propulsion.
To supplement the steam engines, the ships were fitted with a five-masted full-ship rig. Minotaur was completed with a square rig on the first four masts and a spanker on the fifth. During sea trials, this arrangement was found to be unsatisfactory, so the yards were removed from the fourth mast. The other two ships were completed with the modified rig. The total sail area was . In service, the ships proved to be fairly poor sailers, making around under sail alone. This was primarily the result of the ships' screws, which could be disconnected from the engines to rotate freely, but they could not be retracted, so they still imparted drag on the hull. The funnels could be partially withdrawn into the hull to reduce wind resistance, however. The ships also handled poorly, though they had good seakeeping qualities.
The first two ships—Minotaur and Agincourt—were armed with a battery that consisted of four RML rifled guns, twenty-four RML rifled guns, and eight 24-pounder smoothbore guns. Northumberland received a slightly different armament that included four RML 9-inch guns, twenty-two RML rifled guns, and two RML 7-inch guns. Most of the ships' guns were carried on the broadside, but four were carried as chase guns in the bow and stern.
Armour protection consisted of of iron plate on the belt and above along the length of the battery. On either end of the ships, the side armour was reduced to thickness. The side armour extended from upper-deck level down to below the waterline. Transverse bulkheads that were 5.5 in thick connected the forward end of the battery sides, which extended far enough to protect the forward chase guns. All of the side armour was backed by of timber. Because Northumberlands battery had fewer guns, its armoured battery could be shortened. Unlike her sisters, she also received an armoured conning tower that had 4.5 in of iron plate on the sides.
Ships + Construction dataShipOriginal NameBuilder Laid down Launched Completed Elephant Thames Ironworks and Shipbuilding Company 12 September 1861 12 December 1863 19 December 1868Captain Laird, Son & Co. 30 October 1861 27 March 1865 1 June 1867 — Millwall Iron Works 10 October 1861 17 April 1866 8 October 1868
History
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