Defence-Class

The Defence-class ships were powered by the same engine as fitted in the preceding vessels, a single two-cylinder trunk steam engine built by John Penn and Sons, except this time steam was generated by only four rectangular boilers, as compared to the previous ships’ ten. This meant the engines only produced between 2,428-2,537 indicated horsepower, which was about half that of the Warrior-class. They were also equipped with a barque sailing rig with a sail area of 2,276m2. The lower masts and bowsprit were made of iron to withstand the impact of a ramming attack. During sea trials, the engines allowed them to travel at between 11.62 – 11.83 knots, exceeding their contractual obligation of 11.0 knots but noticeably slower than the Warrior class. They were able to make around 10.50 knots under sail power alone, which slightly brings into question the value of their steam powerplant. They carried about half the coal supplies of the Warrior class, at 460 tonnes, which allowed them to steam 1,670 nautical miles at a speed of 10.0 knots.

Like their predecessors, the propeller could be hoisted to reduce drag when under sail power alone. The funnel was also semi-retractable. Their speed, however, remained one of the primary drawbacks of their design, being considerably slower than the Warrior class, with a greatly reduced steaming range. However, manpower commitments were also reduced, with these ships requiring a crew of 460 including officers for full operation.

The armament of the Defence-class ships was again reduced from the Warrior-class, although the guns themselves were largely of the same type. The original design called for eighteen 206mm/15 68pdr 95cwt Smoothbore Muzzleloading Guns in a traditional broadside arrangement, with two acting as chase guns. However, this requirement was changed during construction to replace eight of these with Defence instead receiving eight 183mm/17 110pdr 82cwt Breechloading Guns and Resistance receiving six such guns. Notably, Defence carried the same number of 121mm/21 40pdr 35cwt Breechloading Guns as the Warrior class, meanwhile, Resistance was instead equipped with two 161mm/15 32pdr 42cwt Smoothbore Muzzleloading Guns. The 183mm/17 110pdr 82cwt Breechloading Guns were in short supply at the time and highly sought after, but poor results in armour-penetration tests precluded plans to fully equip these ships with this weapon. They were also problematic in service, being labour-intensive to load and fire and some even exploded when used in action. This meant that future use required them to operate with a reduced propellant charge, which rendered them largely useless.

The 206mm/15 68pdr 95cwt Smoothbore Muzzleloading Rifles weighed 4,826.2KG, with the solid shot that it fired weighing in at 30.8KG. The gun had a muzzle velocity of 481 M/S and a maximum firing range of 2.9 km at an elevation of 12.0 degrees. The 183mm/17 110pdr 82cwt Breechloading Guns weighed 4,165.79KG and fired a shot weighing 48.5-49.9KG. It had a muzzle velocity of 350 M/S and could fire out to a maximum range of 3.7 km at an elevation of 11.25 degrees. The 121mm/21 40pdr 35cwt Breechloading Guns weighed 1,778.0KG and fired a shot weighing 18.1KG. The muzzle velocity was 350 M/S, and its maximum firing range was 3.5 km. Between 1863 and 1864, the 121mm guns were replaced with a heavier version with the same ballistics. All the guns fitted to the ships could fire both solid shot and explosive shells. The 161mm/15 32pdr 42cwt Smoothbore Muzzleloading Guns fitted to Resistance were old weapons previously used on the Caledonia-class first-rate ships-of-the-line. They were only briefly equipped by Resistance, being replaced along with the rest of her armament during a refit in the late 1860s. Not much is known about the weapon’s ballistic qualities, although it should be noted that it was not intended to be used as a form of primary armament, but rather as saluting guns.