The Duilio class was a pair of ironclad turret ships built for the Royal Italian Navy (Regia Marina) in the 1870s and 1880s. The two ships, and , were fitted with the largest guns available, rifled muzzle-loading guns, and were the largest, fastest and most powerful ships of their day. To save weight on such large vessels, the ship's designer, Benedetto Brin adopted a radical solution for the time: he reserved armor only for the central portion of the ship where it protected the ships' engines and ammunition magazines, while the rest of the hull were extensively sub-divided with watertight compartments.
Both ships had uneventful careers. They spent the majority of their time in service with the Active and Reserve Squadrons of the main Italian fleet. There, they were primarily occupied with conducting training exercises. In 1895–1898, Enrico Dandolo was heavily reconstructed, but the excessive cost of the modernization prevented Duilio from being similarly rebuilt. Both ships were reassigned as training ships in the early to mid-1900s. Duilio was stricken from the naval register in 1909 and converted into a floating oil tank, while Enrico Dandolo remained in service as a guard ship during World War I. She was sent to the breaker's yard in 1920. Duilios ultimate fate is unknown.
Design
Starting in the early 1870s, following the Italian fleet's defeat at the Battle of Lissa, the Italians began a large naval expansion program, initially aimed at countering the Austro-Hungarian Navy. In addition, the opening of the Suez Canal in 1869 promised to restore the strategic significance of the Mediterranean; Italy would need a powerful fleet to assert its will and protect its merchant shipping in the region. The program began with the Duilio class, which was designed by the naval architect Benedetto Brin. Originally intended to carry Armstrong muzzle-loading guns, they were modified several times during their lengthy construction time to accommodate the largest guns that Armstrong produced, next to guns and ultimately to the 450 mm gun.
Brin had originally wanted to build three ships, but their great cost forced him to settle for two. At the time, Italy's industrial capacity was insufficient to build the ships out of domestic material. Everything from the iron used to build the hulls to the ships' machinery and guns had to be imported. The Duilio class formed the basis for the following two ironclad designs, the , also designed by Brin and laid down in 1876, and the , designed by Giuseppe Micheli and laid down in 1881–1882.
General characteristics and machinery
The ships of the Duilio class were long between perpendiculars and long overall. Duilio had a beam of , while Enrico Dandolo had a slightly narrower beam of . The ships had a draft of . Duilio displaced normally and up to at full load; Enrico Dandolo was slightly heavier, at and , respectively.
The ships had a small superstructure forward that included the conning tower and one funnel; this was connected via a hurricane deck to a central military mast and the aft superstructure, with included a second funnel. They were the first ironclads in any navy to dispense with sails, rigged only with the military mast. The ships had a crew of 420 officers and men, which later increased to 515. Both ships carried a number of smaller boats, but Duilio was built with a compartment in her stern to house a small torpedo boat, the .
The ships' propulsion system consisted of two vertical compound steam engines each driving a single screw propeller, with steam supplied by eight coal-fired, rectangular boilers. The boilers were in two groups, one forward and one aft, and each group was trunked into a single large funnel. Duilios engines produced a top speed of at . Specific figures for Enrico Dandolos original engines have not survived. The new engines installed in her 1895–1898 refit were slightly more powerful, producing a speed of from . The ships could steam for at a speed of ; the range fell to at .
Armament and armor
Duilio and Enrico Dandolo were armed with a main battery of four 100-ton guns of 20-caliber, mounted in two turrets placed en echelon amidships. These guns fired a shell at a muzzle velocity of depending on the propellant charge. They had a rate of fire of one shot per fifteen minutes; the guns fired so slowly primarily as a result of their great size. As was customary for capital ships of the period, they carried three torpedo tubes. The torpedoes carried a warhead and had a range of .