Nevada-class battleship

The Nevada-class battleship is a type of American battleship.

General characteristics and machinery
The ships of the Nevada class were 575 ft (175 m) long at the waterline and 583 ft (178 m) long overall. They had a beam of 95 ft 2.5 in (29 m) and a draft of 27 ft 7.6 in (8 m) at normal displacement and 29 ft 6 in (8.99 m) at full load. They displaced 27,500 long tons (27,900 t) as designed and 28,400 long tons (28,900 t) fully laden. The ships had a ram bow and a forecastle deck that extended half of the length of the ship. As built, the ships had a minimal superstructure, consisting of a heavily-armored conning tower directly aft of the forward main battery turrets. They were completed with two lattice masts fitted with spotting tops to assist in directing the main battery, a common feature of American capital ships of the period. They had a crew of 55 officers and 809 enlisted men.

Since the Board expected turbines to achieve greater efficiency, Nevada was equipped with a pair of direct-drive Curtis steam turbines, with steam provided by twelve oil-fired Yarrow water-tube boilers. Nevada was the first US capital ship to use reduction geared cruising turbines, which could be clutched into the high-pressure turbines to improve fuel economy at low speeds. Geared turbines were fitted in most subsequent US battleships, except those with turbo-electric propulsion. Oklahoma, meanwhile, received two vertical triple-expansion engines and twelve oil-fired Babcock & Wilcox boilers. Oklahoma's reciprocating engines were prone to excessive vibration, prompting the Navy to consider converting her to double-acting, two-stroke diesel engines in 1925, but the great weight of diesels at the time led to the idea being abandoned. Both ships' boilers were ducted into a single funnel located amidships.

Nevada's engines were rated at 26,500 shaft horsepower (19,800 kW), while those of Oklahoma were projected to produce 24,800 indicated horsepower (18,500 kW). Both ships had a designed top speed of 20.5 knots, though Nevada reached 20.9 knots (38.7 km/h; 24.1 mph) from 26,291 shp (19,605 kW) on speed trials upon completion. Their designed endurance was 8,000 nautical miles (15,000 km; 9,200 mi) at a speed of 10 knots (19 km/h; 12 mph). Under service conditions, Nevada was found to have an endurance of 5,195 nmi (9,621 km; 5,978 mi) at a speed of 12 knots (22 km/h; 14 mph), which fell considerably at 20 knots (37 km/h; 23 mph) to 1,980 nmi (3,670 km; 2,280 mi). With a freshly-cleaned hull, these figures improved slightly, to 6,494 nmi (12,027 km; 7,473 mi) and 2,475 nmi (4,584 km; 2,848 mi), respectively. Nevada had a tactical diameter—the distance it took to turn the ship 180 degrees—of 825 yards (754 m) at 15 knots (28 km/h; 17 mph) and 580 yards (530 m) at 19 knots (35 km/h; 22 mph). The only figure available for Oklahoma is her high-speed turning circle: 625 yards (572 m) at 20 knots (37 km/h; 23 mph).

Armament
The Nevadas were equipped a main battery of ten 14-inch /45 caliber Mark III guns mounted in two twin and two triple turrets. To save weight and keep the mounts as compact as possible, the triple turrets had all three barrels supported by two trunnions, which required all three guns to be elevated as a unit. Both of the twin turrets had armored rangefinders installed atop their roofs, with a centralized fire control room in the conning tower.

The guns fired a 1,400-pound (635 kg) armor-piercing (AP) shell at a muzzle velocity of 2,600 feet per second (790 m/s). Trials with the triple turret revealed excessive dispersion caused by interference between the projectiles while in flight, so a system was adopted to fire each gun individually, separated by a tenth of a second apiece. The turrets allowed elevation to 15 degrees and depression to −5 degrees. At maximum elevation, the guns had a range of about 21,140 yd (19,330 m). Two shell hoists serviced all three guns, which were electrically loaded and operated.

For defense against destroyers and torpedo boats, the ships carried a secondary battery of twenty-one 5-inch /51 caliber Mark VIII guns in individual mounts. Twelve of the guns were in casemates in the forecastle deck, six on either side, and another six were in casemates toward the stern at main deck level, with another weapon directly in the stern. These guns proved to be excessively wet in heavy seas and thus were frequently unusable, as experience with earlier vessels had already demonstrated. The last two guns were in open mounts on either side of the conning tower. The guns had a muzzle velocity of 3,150 ft/s (960 m/s) firing a 50-pound (23 kg) shell.

As was customary for capital ships of the period, both vessels were armed with a pair of 21 in (533 mm) torpedo tubes submerged below the waterline, one on each broadside. They were supplied with Bliss-Leavitt torpedoes of the Mark VII type; these carried a 321 lb (146 kg) warhead and had a range of 12,500 yd (11,400 m) at a speed of 27 kn (50 km/h; 31 mph). Nevada and Oklahoma were the first battleships to carry the Mark 7 torpedoes.

Armor
The Nevada class was protected by side armor that was 13.5 in thick in the central portion where it protected the ship's vitals, the magazines and propulsion machinery spaces. It was 17 ft 4.6 in (5 m) wide, of which 8 ft 6 in (2.59 m) was below the waterline. At the bottom edge, the belt was reduced to 8 in (203 mm) to save weight, relying on the assumption that shells that fell short and passed through the water, they would be slowed significantly, thus reducing their ability to penetrate heavy armor. On either end of the belt, both sides were connected by a transverse bulkhead that was 8 to 13 in (330 mm) thick. The bow and stern were left unarmored. The ships had a 3 in (76 mm) armored deck that consisted of special treatment steel (STS) in three layers over the central armored raft; further aft, the deck was increased in thickness to 6.25 in (159 mm), where it covered the propeller shafts. The armor deck was connected to the top of the belt. One deck below, another layer of armor 1.5 in (38 mm) thick was intended to contain splinters from shells and bombs that were detonated by the upper deck. The sides of the deck sloped down and were increased slightly to 2 in (51 mm) thick, and they were connected to the bottom edge of the belt. The lower deck consisted of nickel steel.

The ships' main battery turrets received very heavy armor protection; the triple turret faces were 18 in (457 mm) thick, with 10 in (254 mm) sides and 5 in roofs. The twin-gun turrets had slightly thinner protection, consisting of 16 in (406 mm) faces and 9 in (229 mm) sides. Both turret types had 9 in rears and they rested atop barbettes that were 13 in thick. The conning tower had 16 in sides and a 8 in roof, the latter consisting of STS. The uptakes from the boilers to the funnel were protected by a conical mantlet that was 13 in thick.

Modifications
The ships underwent a series of changes over the course of their careers, particularly with regards to their secondary batteries, along with the addition of a tertiary anti-aircraft battery. The first such alteration, the addition of a pair of 3 in (76 mm) /50 cal. anti-aircraft guns, was made at the time the ships were completed. In 1918, Nevada had her seven aft-most 5-inch guns removed along with the two guns in open mounts; Oklahoma had the same reduction in her secondary battery, though she retained the centerline gun in the stern. These were used to arm merchant ships that would have a greater likelihood of encountering a German U-boat on the voyage to Europe. In 1919, both ships received flying-off platforms for aircraft on their superfiring turrets, but these proved to be problematic in service, as they prevented the guns from being fired without destroying the ramps and they severely limited the ability of the guns to be elevated and depressed.

In the late 1920s, both ships were substantially modernized. Both were re-boilered with six Bureau Express boilers that were significantly more efficient than the original twelve boilers. In addition, Nevada was re-engined using the turbines that had been installed in North Dakota in 1917 and removed before the latter was scrapped under the terms of the Washington Naval Treaty. Design speed remained the same, but designed horsepower fell slightly to 25,000 shp (19,000 kW) for Nevada. She nevertheless achieved 31,214 shp (23,276 kW) on trials, for a top speed of 20.22 kn (37.45 km/h; 23.27 mph). Fuel capacity was also substantially increased, to 3,148 long tons (3,199 t) normally and 6,274 long tons (6,375 t) for wartime conditions. This increased the ships' range to 15,700 nmi (29,100 km; 18,100 mi) at 10 knots and 6,090 nmi (11,280 km; 7,010 mi) at 15 kn (28 km/h; 17 mph). The re-boilering saved a considerable amount of weight that was used to increase the deck armor and add torpedo bulges that increased their beam to 107 ft 11 in (32.89 m). Both vessels' main armor deck was increased in thickness by 2 in (51 mm), bringing the total to 5 inches, though because it consisted of layers, it was not as effective as a single plate of the same thickness.

Both vessels' armament was significantly improved. The main battery turrets were modified to allow elevation to thirty degrees, which increased their maximum range to 34,300 yd (31,400 m). The remaining 5-inch casemates were plated over and the guns were moved a deck higher in an attempt to improve their ability to be used in heavy seas. The eight 3-inch anti-aircraft guns were replaced with an equal number of 5-inch /25 cal. guns, also in individual mounts. In addition, they received eight 0.5 in (13 mm) Browning machine guns. Both vessels had their torpedo tubes removed at this time. Their lattice masts were replaced with more robust tripod masts, and they had a pair of aircraft catapults installed, one of which was placed on the fantail, the other being mounted atop her rear superfiring turret. The alterations increased the ships' displacement to 30,500 long tons (31,000 t) as designed and a maximum of 33,901 long tons (34,445 t) at full load. The ships' crews increased to 1,374. At some point in 1941, Nevada was fitted with an SC air search radar.

In 1942, during repairs for the damage sustained in the Japanese attack on Pearl Harbor, Nevada was again heavily reconstructed. Her tripod mainmast was removed, along with her heavily-armored conning tower, the former to clear up firing arcs for the anti-aircraft weaponry and the latter to save weight for further additions to the anti-aircraft battery. In place of the conning tower and mast, a large bridge structure was installed She had both her 51-cal. and 25-cal. guns removed. They were replaced with battery of sixteen 5-inch /38 cal. Mark 12 dual purpose guns in eight twin gun mounts. Four were mounted on either side of the vessel amidships. The guns fired a 55.18-pound (25.03 kg) shell to a maximum range of 17,392 yards (15,903 m) or a maximum altitude of 37,200 feet (11,300 m) at an elevation of 45 degrees. Her light anti-aircraft battery was completely replaced as well; she now carried thirty-six Bofors 40 mm (1.6 in) guns in nine quadruple mounts and thirty-eight Oerlikon 20 mm (0.79 in) autocannon in individual mounts. By the end of the war, she had received an additional quadruple 40 mm mount, while her 20 mm guns were reorganized into five single and twenty twin mounts, for a total of forty-five barrels. Unlike many of the other battleships rebuilt after the attack, Nevada did not receive fire-control radar for her main battery, but she was fitted with Mark 37 directors for her new secondary battery.

History
While both known Nevada-ships were present in Pearl Harbor during the attack, only Oklahoma is confirmed onscreen, where it flipped upside-down after being swamped and damaged, trapping a few men inside. In the aftermath, rescuers tried ripping off the underside plates to free the trapped men, but this backfired when the attempt only helped swamp the inside more and killing the men.