The USS Dunderberg was an imposing ocean-going casemate ironclad built for the Union Navy during the American Civil War. Designed as an enlarged, two-masted vessel resembling an extended version of the Confederate CSS Virginia, she was intended to be heavily armed and armored. Her construction began in 1862 at William H. Webb’s shipyard in New York City, but progress was slow due to material shortages, labor issues, and wartime economic challenges. Webb’s design initially included both gun turrets and a casemate, but the turrets were later eliminated during construction, leading to extensive redesigns that delayed her completion. Dunderberg measured approximately 358 feet 8 inches in length between perpendiculars, with an overall length of about 377 feet 4 inches, making her the longest wooden ship ever built. She had a beam of roughly 72 feet 10 inches and displaced about 6,948 long tons at her nominal draft of 18 to 21 feet. Her hull was constructed with a strong, reinforced frame filled with timber, and protected by a combination of armor and external zinc and copper layers to prevent biofouling. The ship's armor scheme included 4.5-inch thick plates above the main deck, tapering below, with additional armored decks and a double bottom for enhanced durability. Propelled by two back-acting steam engines driving a single 21-foot propeller, Dunderberg was powered by six tubular boilers generating steam at 25 psi. During her first sea trials in 1867, she reached about 12.5 knots, with demonstrations later reaching nearly 14 knots. She was rigged with two masts and a modest sail area, allowing auxiliary propulsion. Armament was initially planned to include four massive 15-inch Dahlgren guns in turrets and eight 11-inch Dahlgren guns in a casemate, but the turret arrangement was canceled during her construction. Trials with her casemate-mounted guns revealed issues with recoil and gun port design. Her hull featured a ram bow sheathed in cast iron, emphasizing her role as a formidable combat vessel. Although never commissioned into active service by the Union, she was sold to France in 1867, renamed Rochambeau, and served briefly during the Franco-Prussian War. Her operational history included modifications to her armament and rigging under French control. She was eventually scrapped in 1874, marking her as a significant, if ultimately unrealized, example of Civil War-era ironclad design and construction.

This description has been generated using GPT-4.1-NANO based on the Vessel's wikidata information and then modified by ShipIndex.org staff.