The Prince Consort class of ironclad battleship were four Royal Navy wooden-hulled broadside ironclads: HMS Royal Oak, HMS Prince Consort, HMS Ocean, and HMS Caledonia. They were originally laid down as s, but were converted to ironclads while under construction. Royal Oak was Britain's fifth ironclad battleship completed.
Prince Consort, Ocean, and Caledonia were built to a common design and are today known as the Prince Consort class,Roberts, p. 10 though contemporaries knew them as the Caledonia class.For example: Reed, "Our Iron-Clad Ships". Robinson, "Remarks on Admiral Yelverton's Report on the Cruise of the Channel Fleet". Parkes writing in the 1950s also called them the Caledonias, Parkes, p. 55 Royal Oak was their half-sister.
Genesis
The of nine 91-gun two-decker steam line-of-battle ships were laid down between March 1859 and October 1860 (a further three were ordered, but never laid down, and eventually cancelled in 1863). Their dimensions were the same as (101 guns), but had a new timbering plan to suit the smaller armament. The reduction in armament was intended to improve the efficiency of the guns. Bulwark and Robust were suspended in March 1861 in an advanced state of construction and were eventually broken up in March 1873 and August 1872 respectively.Lambert, "Battleships in Transition", p. 126 The remaining seven ships of the Bulwark class were less complete state and were converted into 'ironclad frigates'. Of these Triumph (later renamed Prince Consort), Ocean, and Caledonia were converted to 'broadside ironclads' with 1,000 nhp engines. Royal Oak had a similar conversion but with the original 800 nhp engine. Royal Alfred, Zealous and Repulse were later converted into 'central battery ships'.Roberts, pp. 10–13
Reasons for the conversion programme
When the first British ironclads were conceived, the Surveyor (Rear Admiral Sir Baldwin Wake Walker) said, "They must be regarded as an addition to our force, as a balance to those of France, and not as calculated to supersede any existing class of ship; indeed no prudent man would, at present, consider it safe to risk up the performance of ships of this novel character, the naval Supremacy of Great Britain."Submission to Board of 27 July 1858, quoted in Lambert, "Warrior", p. 16 For this reason, the Royal Navy continued to lay down and complete steam two-deckers and three-deckers.Lambert, "Battleships in Transition", pp. 122-140 However, in 1861, it was clear that Britain was falling behind in ironclads laid down (see table below).The data in the table refer to sea-going ironclads. It excludes coast defence ships. The ten French ironclads laid down in 1861 were the start of the French programme of 1860, which was intended over a number of years to produce: 20 sea-going ironclads for the active fleet, 10 sea-going ironclads for the reserve fleet, and 11 floating batteries.Parkes, p. 30
YearCumulative Sea-Going Ironclads Laid Down or Commenced ConversionData compiled from Roberts and Lambert, "Battleships in Transition"Cumulative Sea-Going Ironclads CompletedData compiled from RobertsFranceBritainFranceBritain 1858 3 0 0 01859 6 4 0 01860 6 4 1 01861 16 15 1 21862 16 18 6 41863 17 22 6 51864 17 23 6 101865 27 24 11 11
The British response to the French programme was taken in a number of steps.
On 28 September 1860, the Board of Admiralty decided to order three new iron-hulled ironclads: one large - Achilles, and two medium-size - Hector and Valiant. Though there was still great uncertainty as to the value of ironclads, and the ControllerIn 1859, the post of Surveyor of the Navy was changed to Controller of the Navy. was directed to report as to their "fitness for use as transports or other duties in case it should be deemed advisable at any time to strip off their armour plates."Quoted in Parkes, p. 30
On 7 February 1861 Rear Admiral Sir Baldwin Wake Walker resigned as Controller. He was replaced by Rear Admiral Sir Robert Spencer Robinson.Lambert, "Battleships in Transition", pp. 79–82
Following a report from the British naval attaché in Paris regarding the progress of the French 1860 programme, the Naval members of the Board asked for the provision of ten new sea-going ironclads and the adaptation of ten or more existing steam line of battleships for armour protection with a total outlay of £3,000,000.Parkes, p. 49
The Prime Minister, Lord Palmerston, advocated cutting down and armouring the last sailing battleships rather than reducing the number of steam line of battleships.Lambert, "Battleships in Transition", p. 82 (In 1861, the fleet of steam line of battleships were extremely modern, and comprised the main battle strength of the Royal Navy.)
The Chancellor of the Exchequer, William Ewart Gladstone, had decided in November 1859 that ironclads must be the vessels of the future.Gladstone to Palmerston, 25 November 1859, in Guedalla, P Gladstone and Palmerston, pub London, 1928, p113, referenced by Lambert, Battleships in Transition, p 78. In early 1861, he was willing to accept a bigger appropriation for armoured ships if it could be offset by reduction in expenditure on wooden line of battleships. Gladstone suggested that the navy build wooden-hulled ironclads like the French.
In March 1861, construction of the Bulwark-class two-decker steam line of battleships was suspended. Then in May 1861 it was decided to convert the five least complete ships of the Bulwark class into ironclads.Parkes, pp. 49–50 It was also decided to lay down three new very large iron-hulled ironclads, which became the Minotaur, Agincourt, and Northumberland.
Writing in December 1866, the Controller wrote: "The Caledonia and Ocean were ships of the line, of the largest class of two-deckers, in a certain state of advancement when in the Spring of 1861 I was appointed to the Controller’s office. The proposals I made in May 1861, to the Board, to convert these ships and three others into what they are now, was accepted, and I beg leave to call their Lordships’ attention to the concluding paragraphs of those submissions which in substance were as follows - "'No doubt is entertained that the ship would be a sufficiently good sea boat to go to the Mediterranean, if required, and that her speed would be at least as great as that estimated (12.4 knots)' - 'but while proposing this mode of action I beg leave to observe that such ships will, in my opinion, be in every way inferior to ships of the Achilles class with those modifications which we propose to make in her Plating, but I have no hesitation in making these proposals, not as the wisest, and not as the safest way of meeting the exigencies of the case, but because I am led to believe that other considerations make this plan the only practicable one.' "I certainly appeal with confidence to the Admiral’s reports as a proof that my expectation and those I held out to their Lordships in proposing these ships have been realized."Robinson, "Remarks on Admiral Yelverton's Report on the Cruise of the Channel Fleet".
Conversion
"The two-decked wooden ship which were turned into armoured frigates had their sides cut down considerably, and the main deck and its battery removed; while the armour, although about equal in weight to the parts removed, is not as high above water. the iron-clad is, therefore, less top-heavy than the wooden ship was previously to be converted; in other words the conversion has the effect of bringing down the centre of gravity of the ship."Reed "Our Iron Clad Ships", p. 125
As part of the conversion they were lengthened by 21 feet. "The object of lengthening was to provide more space for an armament mounted entirely on one deck except for chase guns. Such extensions are carried out by a process well recognised in naval architecture; which is quote possible at any stage in the building of a ship [or afterwards], not by adding to the extremities, but in cutting her in two at the point of greatest beam and separating the halves sufficiently to insert a new section between them. This is usually done by erecting a launching cradle round the stern half, moving it down the slipways on the cradle as far as required and building up the gap. In such fashion the Prince Consort, Caledonia and Ocean (as well as the Royal Alfred and Royal Oak) were each drawn out 23 feet when already partially on the frame... But as the midship portion of a hull is always the part subjected to the greatest sagging and hogging strains in a head or following sea, special care is necessary to ensure the inserted section is sufficiently strongly built in; particularly if it has to bear the burden of the engines as it did in the Prince Consort class. Exceptionally stout timbering was therefore used for the purpose in those ships; even with that their central structure sometimes exhibit signs of stress giving rise to trouble in a minor degree." "Although the added central section had a full bilge throughout, their floors rose in the old fashion forward and aft, because their underwater lines had taken shape before conversion was ordered and could not be altered without an almost entire rebuilding of the ship. This reduced the carrying capacity of the hull compared with that of a full bodied vessel such as the Bellerophon; but retained a good model for easy movement and contributed to their excellent steering qualities alike under steam and sail."Ballard, p. 116
The bows of the Bulwark class were of the normal knee-shape for wooden warships. When they were converted to ironclads, the Prince Consorts and the Royal Oak were completed with stems approaching the upright above water, and this style, which was so much decried at first, had by the late-1860s won aesthetic approval. "The bow has been modified in order to dispense with overhanging weight, to increase its fitness to cleave and surmount waves, and to adapt it for ramming purposes."Reed "Our Iron Clad Ships", p. 3 Though they did not have underwater rams.
"The stern has been modified in order to give protection to the rudder-head, to deflect raking shot, and to render it more fit to receive easily the blows of following waves."" "Aft the overhang of the counter was narrowed to an oval termination foreshadowing what became the normal battleship type of stern thirty years later, except that the counter was above water instead of below. As these were the first vessels with that novel design of stern they were often called 'double-enders' until the design became so common as to suggest no peculiarity." "The upper parts of the wooden rudder... showed above water, and the rudder was of the old narrow unbalanced type with a bronze neck socket to receive an iron double-tillered norman head."
As wooden-hulled ships the Prince Consorts and the Royal Oak lacked the double bottom and water-tight bulkheads given to iron-hulled vessels. However, at the time people did not consider these things necessary for wooden ships, whose sides and bottoms were very thick, and for which there was much experience. With an iron-hulled ship the "bottom is without any doubt very thin and liable to penetration by a rock or any other hard substance; but the danger resulting from penetration is very greatly reduced by the adoption of a proper number of watertight divisions or bulkheads in the ship's hold, while it may be almost got rid of by the cellular bottom, now given to all our iron-clads, which prevents the entrance of water into the hold even when the outer plating is penetrated."Reed "Our Iron Clad Ships", p. 76 It should be added that before the introduction of the bracket-frame system with the Bellerophon, double-bottoms on British iron-hulled iron-clads were very partial.Reed "Our Iron Clad Ships", p. 81
Armour