HSwMS Thordön (1865)
HSwMS Thordön was the second ship of the monitors, built for the Royal Swedish Navy in the mid-1860s. She was designed under the supervision of the Swedish-born inventor, John Ericsson, and built in Sweden. Thordön made one foreign visit to Russia in 1867, but remained in Swedish or Norwegian waters (at the time, Sweden and Norway were united in personal union) for the rest of her career. The ship was reconstructed between 1903 and 1905, but generally remained in reserve. She was mobilized during World War I, and sold in 1922 for conversion to a barge. Design and description The John Ericsson-class ironclads were designed to meet the need of the Swedish and Norwegian navies for small, shallow-draft armored ships capable of defending their coastal waters. The standoff between and the much larger during the Battle of Hampton Roads in early 1862 roused much interest in Sweden in this new type of warship, as it seemed ideal for coastal defense duties. John Ericsson, designer and builder of the Monitor, had been born in Sweden, although he had become an American citizen in 1848, and offered to share his design with the Swedes. In response they sent Lieutenant John Christian d'Ailly to the United States to study monitor design and construction under Ericsson. D'Ailly arrived in July 1862 and toured rolling mills, gun foundries, and visited several different ironclads under construction. He returned to Sweden in 1863 having completed the drawings of a Monitor-type ship under Ericsson's supervision. The ship measured long overall, with a beam of . She had a draft of and displaced . John Ericsson was divided into nine main compartments by eight watertight bulkheads. Over time a flying bridge and, later, a full superstructure, was added to each ship between the gun turret and the funnel. Initially her crew numbered 80 officers and men, but this increased to 104 as she was modified with additional weapons. Propulsion The John Ericsson-class ships had one twin-cylinder vibrating lever steam engines, designed by Ericsson himself, driving a single four-bladed, propeller. Their engines were powered by four fire-tube boilers at a working pressure of . The engines produced a total of which gave the monitors a maximum speed of in calm waters. The ships carried of coal, enough for six day's steaming. Armament Thordön, and her sister ship Tirfing, were briefly armed with a pair of M/66 smoothbore guns before being rearmed in 1873 with two M/69 rifled breech loaders, derived from a French design. They weighed and fired projectiles at a muzzle velocity of . At their maximum elevation of 7.5° they had a range of . An improved version was developed in the 1870s; the guns were heavier, , but had a higher muzzle velocity of . Coupled with the increased elevation of 11.29°, this gave them a range of . Thordön received her guns in 1882. In 1877 each monitor received a pair of 10-barreled M/75 machine guns designed by Helge Palmcrantz. Each machine gun weighed and had