[4] 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.

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 Controller[11] 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.

[15] (In 1861, the fleet of steam line of battleships were extremely modern, and comprised the main battle strength of the Royal Navy.)

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.

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.

"[20] "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.

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.

"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.

"[20] As wooden-hulled ships the Prince Consorts and the Royal Oak lacked the double bottom and water-tight bulkheads given to iron-hulled vessels.

The principal advantages possessed by this disposition of the armour over that of the Warrior are that the extremities of the ship, especially on the parts near the water-line, are iron-cased, and that the protected guns can be ranged along the length of the broadside instead of being concentrated in a central battery.

For wood-built iron-clads this plan has the additional advantage of protecting the upper works throughout the length from the destructive effects of shells.

[25] "In 1861 many verbal discussions took place between myself [the Controller] and the constructors of the day, as to the cause of the excessive rolling of our ships, when compared with similar French constructions.

This record is, however, of great interest, on account of the comparison it renders possible between the behaviour of the iron-clads and the wooden two-decker, the latter proving the heaviest roller in the squadron.

In Admiral Yelverton's Report [on the Channel Squadron] for 1866, there are given examples of the comparative rolling of several of the iron-clads, obtained from three days' observations, of which the mean results are:- Achilles and Bellerophon, 6.6 degrees; Hector, 11.3; Ocean, 14.3; Lord Clyde, 16.1; Pallas, 17.3.

"[29] Parkes claims, "In the Service their construction was regarded as a retrograde movement, their very heavy wooden hulls having only 80 per cent of the carrying capacity of iron ones.

It is of course true, that when Reed's bracket-frame system was introduced with the Bellerophon (laid down December 1863), iron hulls became much lighter for the same strength.

[32] "The Prince Consorts were all three engined by Maudslay and Sons on an identical plan, … the arrangement of their machinery was very unusual, though not entirely without precedent in wooden-hulled steamers.

When horizontal reciprocating marine engines were being installed it was necessary as a first step to select a position for the cylinders with enough athwartship level to give a proper length for the stroke… As the Prince Consorts had been shaped with an underwater run of the old style before being ordered for conversion… their floors rose considerably abaft the midship point; which meant the only practicable position for the much larger engines they were to carry was in the added central body halfway between bow and stern.