The Principe di Carignano class was a group of three ironclad warships built for the Italian Regia Marina (Royal Navy) in the 1860s. The class comprised the ships,, and . Originally ordered as wooden frigates, they were the first ironclads to be built in Italy, but the inexperience of the Italian shipyards and the redesign process produced lengthy construction times, such that only the lead ship was completed in time to see action during the Third Italian War of Independence in 1866. The first two ships were protected by a complete belt of wrought iron plating that was thick, while Conte Verde only received a partial iron belt.
Principe di Carignano took part in the Battle of Lissa on 20 July 1866, where she led the Italian line of battle, but was not heavily engaged. Rendered obsolescent by the advent of central battery and turret ships in the 1870s, the three Principe di Carignano-class ships did not have particularly long or active service lives. In an effort to reduce the maintenance budget to offset the cost of newer ships under construction, Principe di Carignano was stricken from the naval register in 1875; Messina and Conte Verde followed in 1880, the latter just nine years after completion.
The first two vessels of the Principe di Carignano class were initially ordered as steam frigates by the Regia Marina Sarda (Royal Sardinian Navy) shortly before the unification of Italy. While they were on the stocks, the Regia Marina (Royal Navy) of the newly-formed Kingdom of Italy decided to convert the ships into ironclads. A third ship,, was too far advanced in her construction to allow for conversion, and so she was completed as a wooden vessel. These ships had been designed by Inps. Eng. Felice Mattei. A fourth ship, Conte Verde, was built to a modified design created by Inps. Eng. Giuseppe De Luca. These ships came as part of a major naval expansion program that was designed to prepare a fleet of ironclads capable of defeating the Austrian Navy. Italy considered the Austrian Empire to be its main rival, since it controlled predominantly Italian areas, including Venice, that the newly unified kingdom sought to incorporate into the country.
The ships of the Principe di Carignano class varied slightly in their dimensions. Principe de Carignano was 72.98m (239.44feet) long between perpendiculars, with a beam of 15.1m (49.5feet) and an average draft of 7.18m (23.56feet). She displaced 3446LT normally and up to 3912LT at full load. The second ship, Messina, was 72.8m (238.8feet) between perpendiculars; she had a beam of 15.1m (49.5feet) and an average draft of 7.27m (23.85feet). At normal loading, she displaced 3868LT, and she reached 4245LT with a full load. Conte Verde was 73.7m (241.8feet) long between perpendiculars and her beam was 15.3m (50.2feet). She had a draft of 6.5m (21.3feet), and displaced 3514LT normally and up to 3866LT at full load. The ships had a crew of 572.
Their propulsion system consisted of one single-expansion marine steam engine that drove a single screw propeller, with steam supplied by six coal-fired, cylindrical fire-tube boilers. The boilers were trunked into a single funnel. Their engines produced a top speed of 10.2kn11.4kn, with Conte Verde being the fastest member of the class, from 1968ihp. They could steam for about 1200nmi at a speed of . To supplement her steam engine, the ship was barquentine-rigged with three masts.
The Principe di Carignano-class ships were broadside ironclads; the lead ship was armed with a main battery of ten 72-pounder 80NaN0 guns and twelve 164mm rifled muzzle-loading guns Messina and Conte Verde instead carried four 8 in guns and eighteen 164 mm guns. The ships were equipped with a spur-shaped ram at the bow. In 1870, the ships' armament was revised; Principe di Carignano retained four of her 8 in guns, with the other four being replaced by 164 mm guns. Messina lost ten of her 164 mm guns and gained a pair of guns, while Conte Verde was reequipped with six 10 in guns and one 8 in gun.
The above-water portions of the first two ships' hulls were sheathed with wrought iron armor that was 4.750NaN0 thick. Unlike her two sisters, Conte Verde did not have complete iron armor on her sides. She instead had wrought iron armor that covered only parts of her bow and stern instead of the full armored belt fitted to her sisters. The rest of the ship received traditional timber armor.
| Builder | Laid down | Launched | Completed | ||
|---|---|---|---|---|---|
| Italian: [[Cantiere della Foce]] | January 1861 | 15 September 1863 | 11 June 1865 | ||
| Italian: [[Regio Cantiere di Castellammare di Stabia]] | 28 September 1861 | 20 December 1864 | February 1867 | ||
| Italian: [[Cantiere navale fratelli Orlando|San Rocco]] | 2 March 1863 | 29 July 1867 | December 1871 |
Though the Principe di Carignanos were the second class of Italian ironclads, the foreign shipyards that built the subsequent and es completed almost all of those vessels before the first member of the Principe di Carignano class entered service. Principe di Carignano was the only member of the class to enter service in time to take part in the Third Italian War of Independence against the Austrian Empire. The war broke out in June 1866, as Italy, which had allied with Prussia, sought to take advantage of the Austro-Prussian War to seize Austrian-controlled Venice. After initially remaining in port, the Italian fleet under Admiral Carlo Pellion di Persano launched an attack on the island of Lissa in mid-July; the Austrian fleet under Rear Admiral Wilhelm von Tegetthoff sortied to mount a counterattack, which resulted in the Battle of Lissa on 20 July. Principe di Carignano, the lead ship in the line of battle, was not heavily engaged, as Tegetthoff had attacked the Italian fleet at its center. Principe di Carignano tried to attack the wooden vessels of the Austrian fleet without success before Persano broke off the action; the Italian fleet had become disorganized and two ships, and had been sunk.
The three ships, which rapidly became obsolescent due to the development of central battery ironclads and later turret ships, saw very limited service in the 1870s. Principe di Carignano and Messina were modernized with new guns in 1870. Neither ship played a role in the attack on Civitavecchia that year—the last stage of the Italian wars of unification that resulted in the seizure of Rome—owing to the very poor state of the Regia Marina in the aftermath of Lissa. In 1875, Principe di Carignano was sold for scrap to reduce the maintenance budget in an attempt to offset part of the cost of the new and s then under construction; Messina and Conte Verde followed in 1880, though the latter remained laid up until she too went to the breakers' yard in 1898.