USS Dunderberg (1865)

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Career (USA) United States Navy Jack
Name: USS Dunderberg
Namesake: Swedish "thunder(ing) mountain"
Ordered: 3 July 1862 (contract)
Builder: William Henry Webb
Laid down: October 1862
Launched: 10 May 1862
Out of service: 7 April 1865
Career (France) French Navy Ensign
Name: Rochambeau
Namesake: Comte de Rochambeau
Acquired: 1867
Commissioned: 1867
Struck: 1874
General characteristics
Class and type: Ironclad frigate
Tons burthen:

7,060 tons

7,800 tons full load
Length: 115 metres (377 ft)
Beam: 22.2 metres (72 ft 10 in)
Draught: 6.52 metres (21 ft 5 in)
Propulsion: 6 "return flame" boilers, 1-shaft return connecting rod steam engine, 4,500 ihp (3308 kW)
Speed: 15 knots

4 × 15 inch smoothbore cannons

2 × 11 inch smoothbore cannons

Iron Belt: 8.9-6.4 cm (3½-2½ inch)

Casemate: 11.4 cm (4½ inch) with 90cm (3 ft) timber backing

Dunderberg, which is a Swedish word meaning "thunder(ing) mountain," was an ocean-going ironclad screw frigate of 16 guns. She was designed by Lenthall as a reproduction of CSS Virginia, with two 21-foot screws, sloping armored casemate sides, and a 50-foot ram. She had a double bottom and collision bulkheads, and was the longest wooden ship ever built. Her keel was laid down in October 1862 by W.H. Webb of New York City. Her construction was initially spurred by the threat of war with the United Kingdom. After that impetus abated, construction lagged, and she was not launched until 2 March 1865. The American Civil War ended before she could be completed, and was formally rejected by the U.S. Navy in September 1866.

Webb began seeking buyers for the warship, the design of which was already beginning to influence naval architecture worldwide. Otto von Bismarck expressed some interest, and the thought of Prussia armed with such a vessel prompted France to hurriedly buy her and commission her in 1867 as Rochambeau. The French scrapped her in 1874.