Brazilian ironclad Rio de Janeiro

The Brazilian ironclad Rio de Janeiro was an armored gunboat (Canhoneira Couraçada Nr. 3) built for the Brazilian Navy during the Paraguayan War in the mid-1860s. Like the other two gunboats she was built in Brazil and was designed as a casemate ironclad. Commissioned in April 1866, the ship did not enter combat until September, when she bombarded Paraguayan fortifications at Curuzu. Rio de Janeiro hit two mines on 2 September and rapidly sank, taking 53 of her crew with her.

Design and description
Rio de Janeiro was designed to meet the need of the Brazilian Navy for a small, simple, shallow-draft armored gunboat capable of withstanding heavy fire. A casemate ironclad design was chosen for ease of construction and a bronze ram, 1.8 m long, was fitted. The hull was sheathed with Muntz metal to reduce biofouling. For sea passages the ship's freeboard could be increased to 1.7 m by use of removable bulwarks 1.1 m high. On riverine operations, the bulkwarks and the ship's masts, were usually removed.

The ship measured 56.69 m long overall, with a beam of 9.19 m and had a mean draft of 2.62 m. Rio de Janeiro normally displaced 871 t and 1001 t at deep load. Her crew numbered 148 officers and men.

Propulsion
Rio de Janeiro had a single John Penn & Sons 2-cylinder steam engine driving a single 2-bladed propeller. Her engine was powered by two tubular boilers. The engine produced a total of 420 ihp which gave the ship a maximum speed of 9 kn. The ship's funnel was mounted directly in front of her casemate. Rio de Janeiro carried enough coal for six days' steaming.

Armament
Rio de Janeiro mounted two 70-pounder Whitworth rifled muzzle loaders and two 68-pounder smoothbore guns in her casemate. To minimize the possibility of shells or splinters entering the casemate through the gunports they were as small as possible, allowing only a 24°-arc of fire for each gun. The rectangular, 9.8 m casemate had two gun ports on each side as well as the front and rear.

The 70-pounder gun weighed 8582 lb and fired a 5.5 in shell that weighed 81 lb. The gun had a maximum range of 5540 m. The 7.9 in solid shot of the 68-pounder gun weighed approximately 68 lb while the gun itself weighed 10640 lb. The gun had a range of 3200 yd at an elevation of 12°. All of the guns could fire both solid shot and explosive shells.

Armor
The hull of Rio de Janeiro was made from three layers of wood, each 203 mm thick. The ship had a complete wrought iron waterline belt, 1.52 m high. It had a maximum thickness of 102 mm covering the machinery and magazines, 51 mm elsewhere. The curved deck, as well as the roof of the casemate, was armored with 12.7 mm of wrought iron. The casemate was protected by 102 millimeters of armor on all four sides, backed by 609 mm of wood capped with a 102 mm layer of peroba hardwood.

Service
Rio de Janeiro was laid down at the Arsenal de Marinha da Côrte in Rio de Janeiro on 28 June 1865, during the Paraguayan War, which saw Argentina and Brazil allied against Paraguay. She was launched on 18 February 1866 and completed on 1 March 1866. Commissioned in April she reached the combat zone on 4 May. The ship reached Corrientes, with the ironclad BRAZILIAN IRONCLAD Lima Barros, in July 1866. On 1 September Rio de Janeiro bombarded the Paraguayan fortifications at Curuzú in company with the other Brazilian ironclads. A 68-pounder shell entered one of her gunports during the bombardment, killing four men and wounding five. The next day, after her damage was repaired, the ship struck two mines in the Apa River while trying to rendezvous with the other Brazilian ironclads bombarding Curupaity. Rio de Janeiro sank instantly with the loss of 53 of her crew. She remains there, entombed under some 15 m of sand.