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Unadilla-class gunboat

USS Kanawha
Lithograph of a Unadilla-class gunboat, ca. 1861
Class overview
Name: Unadilla or "90-day" class
Builders: See table
Operators: U.S. Navy
Cost: $90,000–$103,500
Built: 1861–62
In service: 1861–1885?
In commission: 30 Sep 1861–18 Sep 1869
Completed: 23
Active: None
General characteristics
Class and type: Unadilla-class gunboat
Displacement: 691 tons
Tons burthen: 507
Length: 158 ft (48 m) (waterline)
Beam: 28 ft (8.5 m)
Draft: 9 ft 6 in (2.90 m) (max.)
Depth of hold: 12 ft (3.7 m)
Propulsion: 2 × 200 IHP 30-in bore by 18 in stroke horizontal back-acting engines; single screw
Sail plan: Two-masted schooner
Speed: 10 kn (11.5 mph)
Complement: 114
Armament:

The Unadilla class was a class of gunboat built for the Union Navy at the outbreak of the American Civil War. Ships of the class were also known as "90-day gunboats" due to their rapid construction. The class was designed to be fully oceangoing while having a light enough draft to be able to operate close inshore, for blockade duty or other operations in shallow waters.

Unadilla-class gunboats took part in many coastal and river operations, most notably as the bulk of the fleet which captured the vital Confederate port of New Orleans in April 1862. As blockade ships, the 23 vessels of the class captured or destroyed no fewer than 146 enemy blockade runners during the war— about 10 percent of the total number of Confederate blockade runners so neutralized.

The Unadilla class was sold off quickly by the Navy at the end of the war, most of them going into merchant service. Little is known about their subsequent careers.

With the outbreak of the American Civil War in April 1861, the U.S. Navy was faced with an urgent need for light-draft gunboats able to operate both at sea and close inshore to help enforce the Union blockade of Confederate ports. Since the Navy's Chief Engineer, Benjamin F. Isherwood, had recently designed and overseen construction at the Novelty Iron Works in New York City of the engines for two similar gunboats, built for the Imperial Russian Navy, he had to hand a ready-made design suitable for the new U.S. Navy gunboats, which was accepted by Secretary of the Navy Gideon Welles.


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