Alma-class ironclad

The ''Alma''-class ironclads were a group of seven wooden-hulled, armored corvettes built for the French Navy in the mid to late 1860s. Three of the ships attempted to blockade Prussian ports in the Baltic Sea in 1870 during the Franco-Prussian War. Three others patrolled the North Sea and the Atlantic, while the last ship was en route to Japan when the war began and blockaded two small Prussian ships in a Japanese harbor. Afterwards they alternated periods of reserve and active commissions, many of them abroad. Three of the ships participated in the French occupation of Tunisia in 1881 while another helped to intimidate the Vietnamese Government into accepting status as a French protectorate and played a small role in the Sino-French War of 1884–85.

Design and description

The ''Alma''-class ironcladsIronclad is the all-encompassing term for armored warships of this period. Armored corvettes were originally designed for the same role as traditional wooden corvettes, but this rapidly changed as the size and expense of these ships caused them to be used as second-class armored ships. were designed by Henri Dupuy de Lôme as improved versions of the armored corvette suitable for foreign deployments. Unlike their predecessor the ships were true central battery ironclads as they were fitted with armored transverse bulkheads.de Balincourt and Vincent-Bréchignac 1976, p. 26 The original plan for these ships was to have a two-deck battery with four guns on the battery deck and four guns mounted above them on the upper deck, one gun at each corner of the battery. This design was changed to substitute four barbettes for the upper battery, but the addition of armored bulkheads proved to be very heavy and the rear pair of barbettes had to be deleted to save weight. In partial compensation the 164-millimeter guns in the remaining forward barbettes were replaced by an additional pair of 194-millimeter guns. Like most ironclads of their era they were equipped with a metal-reinforced ram.Gardiner, p. 302

The ships were built from the same general plan, but differed amongst themselves. They measured between perpendiculars, with a beam of . The ships had a mean draft of and displaced . Their crew numbered 316 officers and men.

Propulsion

The ''Alma''-class ships had a single horizontal return connecting-rod steam engine driving a single propeller. Their engine was powered by four oval boilers. On sea trials the engine produced between and the ships reached . Unlike the single funnels of the others, and had two funnels, mounted side by side. The ships carried of coal which allowed the ship to steam for at a speed of . They were barque-rigged with three masts and had a sail area between .

Armament

The ships mounted four of their 194-millimeter Modèle 1864 breech-loading guns in the central battery on the battery deck. The other two 194-millimeter guns were mounted in barbettes on the upper deck, sponsoned out over the sides of the ship. The four guns were also mounted on the upper deck. is the only ship positively known to have exchanged her 194 mm guns for newer Modèle 1870 guns.de Balincourt and Vincent-Bréchignac, p. 28 The armor-piercing shell of the 20- caliber Mle 1870 gun weighed while the gun itself weighed . The gun fired its shell at a muzzle velocity of and was credited with the ability to penetrate a nominal of wrought iron armour at the muzzle. The guns could fire both solid shot and explosive shells.

Armor

The ''Alma''-class ships had a complete wrought iron waterline belt, approximately high. The sides of the battery itself were armored with of wrought iron and the ends of the battery were closed by bulkheads of the same thickness. The barbette armor was thick, backed by of wood.de Balincourt and Vincent-Bréchignac 1976, p. 27 The unarmored portions of their sides were protected by iron plates.

Ships

Service

During the Franco-Prussian War of 1870–71 ''Thétis'', ''Jeanne d'Arc'' and ''Armide'' were assigned to the Northern Squadron that attempted to blockade Prussian ports on the Baltic until ordered to return to Cherbourg on 16 September 1870. ''Montcalm'', ''Atalante'', and ''Reine Blanche'' cruised the North Sea and ''Montcalm'' later watched a Prussian corvette in Portuguese waters.de Balincourt and Vincent-Bréchignac 1976, p. 30 ''Alma'' was en route to the Far East when the war began and she blockaded a pair of Prussian corvettes in Yokohama harbor once she arrived at Japan.

After the end of the war many of the ships were placed in reserve or sent to foreign stations, often as the flagship. During the Third Carlist War of 1872–76 ''Thétis'', ''Reine Blanche'' and ''Jeanne d'Arc'' spent time in Spanish waters where they could protect French citizens and interests. In 1875, the latter ship rammed and sank the dispatch vessel ''Forfait''. On 3 July 1877 ''Thétis'' rammed ''Reine Blanche'' who had to be run ashore to prevent her from sinking.

Further abroad ''Reine Blanche'' and ''Alma'' bombarded the Tunisian port of Sfax in July 1881 as part of the French occupation of Tunisia. ''Atalante'' participated in the Battle of Thuận An in August 1883. This was an attack by the French on the forts defending the mouth of the Perfume River, leading to the Vietnamese capital of Huế in an attempt to intimidate the Vietnamese government.de Balincourt and Vincent-Bréchignac 1976, p. 29 During the Sino-French War of 1884–85 the ship was in Huế in early September 1884, but she carried Admiral Amédée Courbet to Keelung, Taiwan on 23 September.

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Ships built in France

Corvettes of France