Tonnerre-class ironclad
The Tonnerre class was a group of two coastal-defense ships built for the French Navy in the 1870s. A design based on the preceding but with similarities to the Royal Navy breastwork monitor, the class comprised and. Their main battery of two was mounted in a single turret powered by a hydraulic machinery, an early use of the technology, that was situated forward of a narrow superstructure and was. The ships could be distinguished by their different engines, the diameter of their single funnel and the slightly different calibre of their secondary armament. They were commissioned into the Armoured Division of the Northern Squadron in 1891. They participated in naval exercises. Changes in naval doctrine, alongside the introduction of more capable battleships and new technologies like submarines meant that the ships were obsolete. Tonnerre and Fulminant were struck in 1902 and 1905 respectively and, after serving as target ships, sold to the broken up.
Design and development
On 10 November 1871, the Minister of the Navy Louis Pierre Alexis Pothuau issued a specification for a new coastal defense ship. Of the three alternatives submitted on 9 August 1872, the French Navy accepted that developed by Louis de Bussy, which was signed on 29 July. The design was based on his existing second-class coastal defense ships, as epitomised by the, but with an armoured deck raised by, sitting above the waterline and all vertical dimensions increased by 25 percent. Having a superficial similarity to the Royal Navy monitor but with a shorter breastwork, the design was agreed and built as class of two vessels.Characteristics
Breastwork monitors that had hull of steel, the ships of the Tonnerre class had a single turret forward and a narrow superstructure, wide, aft. The vessels displaced, had an overall length of, at the waterline and between perpendiculars. The ships' beam was at the waterline and draught was mean and aft. The ships' complement numbered 190 sailors of all ranks.The powerplant for the two ships differed. Power for Tonnerre was provided by a single horizontal simple expansion steam engine while Fulminant was powered by a single horizontal Schneider compound engine. All drove one propeller shaft and vented through a single funnel, Tonnerre being distinguished by having a larger funnel. The engine on Tonnerre was rated at while that on Fulminant was rated at. Steam was provided by eight boilers. The ships had a light mast and no sails. In service, the ships were rated at.
The ships mounted a main battery of two 19.75-calibre Modèle 1875 guns in a single enclosed turret mounted forward. The guns were capable of firing every seven or eight minutes. They each weighed and fired a shell that weighed. They were hydraulically loaded using the Rendell system, which also powered the turret. This was the first use of hydraulics in the French Navy to power a turret and, despite the equipment being supplied by the British firm W. G. Armstrong & Company, ahead of the Royal Navy adopting it to use in its turrets. Defence from torpedo boats was provided by either four 17-calibre 12-pounder bronze guns or four guns mounted at the corners of the flying deck, raised above the hull. The ships were fitted with a ram.
The ships were fitted with wrought iron armour with a full-length waterline armour belt that tapered from a maximum thickness of amidships to forward and aft. The deck armor was thick amidships with ends had of wood mounted on plating. The belt stretched from below the waterline to above. The breastwork had armour that was amidships and 300 mm at the ends. The turret was also protected by armour that is 300 mm thick, although the gun ports themselves were thick. The turret was itself in diameter. A cylindrical conning tower was mounted on the turret, supported on a fixed shaft.
Modifications
During their lives, the ships had their armament modified. Six Hotchkiss revolving cannon were added early in the vessels' service, which were replaced, in 1900, by six Canon de Modèle 1885 Hotchkiss guns and two Hotchkiss revolving cannons. Four Mangin searchlights were also added.Service
Tonnerre and Fulminant were fully commissioned after undertaking trials on 1 April 1878 and 29 May 1885 respectively. Tonnerre was placed in reserve but was allocated to the Evolution Squadron in 1884. Both vessels joined the Armoured Division of the Northern Squadron in 1891. Although they saw little active service, the vessels participated in naval exercises. Fulminant joined the coastal defense ship, three cruisers and nine torpedo boats in a training exercise over 22 days from 22 June. Tonnerre operated with fellow ironclads and on another exercise between 26 July and 4 August 1893. Although nominally defending Cherbourg, the ship made a successful attack against a more powerful force on 3 August using dummy torpedoes. On 7 September 1894, it was announced that they were to be retired from active service and replaced by the newer s.French naval doctrine was changing and the focus on coastal defense was being replaced by one of larger sea-going warships. The size of ships was also increasing, and newer, more capable battleships entered service. Other technologies were also advancing that made the ships vulnerable to new forms of attack. In July 1902, Fulminant took part in a trial for the s, where the ship acted as the target for them to demonstrate their stealthy characteristics. Neither vessel lasted far beyond that point. Tonnerre and Fulminant were struck on 12 December 1905 and 14 August 1908 respectively. Both were allocated to be target ships before being sold to be broken up, the latter on 4 November 1912 and the former between 1920 and 1922.