'', 1888 By late 1863, the Russian
Admiralty Board had begun planning for the second generation of ironclads to succeed those ships then under construction. They ordered eight ships, two fully rigged seagoing types and six
coastal defense ships, in March 1864. The British shipbuilder
Charles Mitchell submitted four different designs for the coastal defense vessels, two
broadside ironclads and two
turret ships. The Shipbuilding Technical Committee decided in August that the broadside designs would be based on the hull shape of the earlier for better seaworthiness, but they would be armed with fewer, but more powerful guns, than the numerous
smoothbore guns of the older ships. Two variants were worked out that differed in the fineness of the hull and
draft. In November the committee decided to revise the designs to use three
gun turrets, each armed with a pair of massive American-designed
Rodman guns, although the armament was changed to
rifled muzzle-loading guns two months later. On 4 June 1865,
Admiral Spiridov and
Admiral Chichagov were ordered to the shallower-draft version of the two designs. Construction of the ships was repeatedly delayed by design changes and delayed deliveries of components. Both of the most significant design changes were related to the armor protection. Shortly after they were ordered the Admiralty Board realized that the specified armor would be outclassed by the latest rifled gun and decided that the existing armor would be reinforced by an additional armor plate and additional wooden backing inside the existing armor. The additional weight was offset by increasing the height of the hull by which also deepened the ships' draft. The second change occurred after new rifled guns were able to penetrate a replica of the armor scheme in June 1866. The Admiralty Board decided to significantly thicken the armor of the two ships and removed one gun turret to compensate for the weight of the extra armor in November. Numerous other changes flowed from this decision as the engine and boilers had to be moved forward about to maintain the ships' trim and two transverse
bulkheads also had to be moved. This major change added over 270,000
rubles to the cost of the ships and added more delays as Russian ironworks had problems rolling the thicker armor plates. The
Admiral Spiridov-class monitors were significantly larger than their predecessors, the , and were long at the
waterline. They had a
beam of and a maximum draft of . The ships were designed to
displace , but turned out to be overweight and actually displaced . They were fitted with a plough-shaped
ram. The
Admiral Spiridovs had a
double bottom and their hulls were subdivided by six main
watertight bulkheads. Their crew consisted of 280 officers and crewmen.
Propulsion The
Admiral Spiridov class had a single two-cylinder horizontal
direct-acting steam engine. It had a
bore of and a
stroke of and drove a single three-bladed propeller. Steam was provided by four rectangular
fire-tube boilers at a pressure of . The engine was designed to produce a total of which gave the ships speeds between when they ran their initial
sea trials in 1869. The monitors also had a
donkey boiler for the small steam engine that powered the ventilation fans and pumps. The
Admiral Spiridov class carried of coal which gave them a range of about at a speed of 10 knots. They were fitted with a light
fore-and-aft sailing rig with three pole
masts and a
bowsprit. It had an area of and its primary purpose was to steady the ships and assist in turning.
Armament The monitors were ultimately designed to be armed with four
Obukhov 9-inch rifled guns, a pair in each
Coles-type turret. An armored bulkhead separated the guns inside each turret. In 1874–75 the guns were replaced by a single gun in each turret, based on a
Krupp design. During the
Russo-Turkish War of 1877–78 a 9-inch
mortar was fitted to attack the thin deck armor of enemy ships, but accuracy was poor and they were later removed, probably in the early 1880s. An improved, more powerful, 11-inch gun was installed aboard
Admiral Chichagov during the 1880s, although
Admiral Spiridov retained her original guns until 1902, if not for the rest of her career. Light guns for use against
torpedo boats were added to the
Admiral Spiridov-class ships during the Russo-Turkish War when a pair of 4-pounder guns were mounted on the roofs of each gun turret. Other guns known have been fitted included Baranov
quick-firing (QF) guns, QF
Hotchkiss guns, and QF Hotchkiss five-barreled revolving cannon. The ships could also carry 12-15
mines intended to be used to create a secure
anchorage.
Armor The hull of the
Admiral Spiridov-class monitors was completely covered by three
strakes of
wrought iron armor, the upper two were about high and the lower one, below the waterline, was high. The middle strake was thick for a length of amidships and the other strakes were generally thick (the upper strake was thick abreast the turrets). The armor thinned to aft and forward of the main belt. This outermost layer of armor was backed by 9 inches of
teak reinforced with
angle irons and then came the 1-inch inner armor plates, backed in its turn by another 9 inches of teak. The turrets had 6 inches of armor, except around the
gun ports, where it thickened to 6.5 inches, reinforced by 12 inches of teak. The
conning tower was thick. The
deck armor was in two layers with a total thickness of 1 inch that were separated by a layer of cloth or
felt to better deflect the glancing hits expected. The upper layer was thick and the lower was . ==Ships==