CV-9 ESSEX Class - Original Design
The Essex class was a modified (enlarged) Yorktown (CV-5) class which provided better underwater protection. The Essex class of carriers was a half-way design. Carriers of that class were developed after the end of the Washington Naval Treaty and were thus considerably larger than comparable ships designed earlier. However, the outbreak of the war and the need to rush ships into action meant that they would be developed from earlier treaty-bound designs. The Essex class was essentially an enlarged improved version of the previous Yorktown class featuring added antiaircraft armament, new high pressure boilers, new en echelon machinery arrangement, better underwater protection, more powerful catapults, and a second armoured deck on the hanger level.
The Essex class had much increased AA capability, ammunition stowage, and could accommodate more aircraft than the Yorktown class; two of which were lost during action. The Essexes as authorized in the early phases of World War II underwent upgrades and modifications throughout the course of the conflict as combat experience was gained and wartime technologies advanced. One of the major wartime modifications affecting the external design of the Essexes resulted from the need to increase the number of anti-aircraft guns carried by the ships. In 1943, this lead to a redesign of the bow, making it longer and wider and shortening the flight deck by 11 feet forward and 7 feet aft in order to accommodate the additional anti-aircraft batteries. In March 1943 the Secretary of the Navy approved these alterations. With several carriers currently under construction, not all could receive this modification without significantly delaying delivery of the class. The “Short Hull” group (CVs 9-13, 16-18, 21, and 31) were completed without the modification; the remaining authorized carriers were altered and became known as the "long hull Essex" or Ticonderoga (CV-14) class. However, most sources acknowledge that the differences are not significant enough to warrant a new class designation.
The Essex class carriers had welded, steel hulls with an overall length of 872 feet and a length along the waterline of 820 feet. The flight deck ran 862 feet with an additional 4 foot 9 inch ramp curving down at each end. The flight deck width was 108 feet. The vessel's beam at the waterline was 93 feet and the depth of hull was 54 feet 8 inches with a draft of 28 feet 7 inches. Their original design displacement was 33,440 tons, standard displacement was 27,100 and the full load displacement was 36,380 tons. The eight Babcock and Wilcox boilers drove four Westinghouse geared steam turbines that delivered a speed of 32.7 knots. They carried a crew of 2,486.
Early ships were completed with 1.1-inch/75 Mk1 AA guns and .50-cal machine guns but these were replaced with 20/40mm AA during 1943. In 1945-46 the 20mm armament was removed [the 40mm AA battery was replaced by dual 3-inch/50 Mk27 DP guns during the 1950s on active units]. Armament included twelve five-inch 38 caliber dual-purpose guns mounted in four MK 32 DP twin mounts and four MK 40 MOD 33 single mounts. These mounts were directed by two MK 37 fire control directors, one mounted forward on the island, the other aft, and eight MK 51 directors. The MK 37 directors were served by two MK 4 fire control radars. When launched she had a total of eight MK 2 quadruple 40-mm Bofors anti-aircraft platforms. Four quad 40-mm mounts were located on the island, two forward of the flag bridge and two aft of the funnel. They also had a single quad 40-mm mount on the stem, a single quad 40-mm on the fantail and one each on the port and starboard catwalks. When refitted latter in the war, some had seven outboard quad 40-mm mounts added, five on the starboard hull and two on the port hull. These tubs were attached directly to the hull rather than on the catwalk and could be removed to allow passage through the Panama Canal. Lexington also carried sixty-two 20-mm anti-aircraft guns.
The Essex class carriers had hangar deck capacity for 103 aircraft. For instance, Lexington's first air group (AG-16), consisted of 89 aircraft that included thirty-two F6F-3 Hellcat fighters, thirty-five SBD-5 Dauntless dive-bombers and eighteen TBF-1 Avenger torpedo bombers. It was the practice early in the war to carry spare aircraft suspended above the hangar deck, thus the discrepancy between 103 standard complement versus the active squadron number of 89. The Air Group numbers are from the Action report 22 September 1943, describing the 18 September 1943 raid on Tarawa, Lexington's first mission. By the end of the war the fighter squadron had been increased to seventy-eight aircraft to meet the Kamikaze threat, while the torpedo and bomber units were comprised of fifteen aircraft each.
The Essex class carriers armor was designed to meet the requirements of resistance to fire from 6-inch guns at a distance of 11,250 to 18,700 yards. The hull was protected by steel armor, although unlike British aircraft carriers of the time and the future Midway class, the flight deck was not armored. The hangar deck had an armored deck of 2.5 inches of Special Treatment Steel (STS) steel. The fourth deck was armored with 1.5 inch STS to further protect the engine and fire room spaces. Side belt armor varied from 2.5 to 4 inches. The steering spaces were enclosed with 4 inches of class B armor on the sides and 2.5 inches of STS on top. Lexington was the only Essex-class carrier to serve throughout the war without the "dazzle pattern" camouflage measure. Instead she wore the solid "Measure 21" paint scheme of Navy Blue until 1945 when she was repainted in “Measure 12” a two-tone system of Ocean Gray and Navy Blue.
The flight deck arrangements included three aircraft elevators and three bomb lifts. The elevator layout included two hydraulic actuated "centerline" lifts measuring 48.3' x 44.3' each capable of lifting 28,000 pounds. These elevators were situated fore and aft of the island just off the centerline. The third elevator, on the port deck edge across from the island, measured 60' x 34' and had an 18,000 pound lift capacity. The hangar deck included large openings along the port and starboard side that could be closed with roller doors. These side openings provided ventilation which allowed starting aircraft on the hangar deck to warm up prior to their positioning on the flight deck. The hangar deck could be internally divided laterally into three isolated bays. Division was accomplished with asbestos curtains which could be closed from control stations in each bay. Aircraft maintenance was also divided by bay. Bay 3, in the stern was for heavy maintenance, Bay 2 was for flight operations and Bay 1, in the bow, was for storage and light maintenance.
While other Essex class carriers were equipped with a 1H 4A catapult on the forward hangar deck with hinged extensions on each side through the side ports, Lexington's hangar catapults were not ready by the time she was launched and were never installed. Lexington did have a 1H 4B catapult on the flight deck. Aircraft recovery was accomplished with a sixteen wire MK 4 arresting gear cable system later modified so that the wires were spaced from the stern to just aft of the island. The arresting wire system was augmented by a set of four wire cable barriers. Each barrier wire was suspended several feet above the deck to snag aircraft that missed the arresting system cables.
The ship's island is on the starboard side of the flight deck, halfway between the bow and stern. Island arrangements were placed on five decks comprised of a communications platform, flag bridge, navigation bridge, gun deck atop the pilothouse and an anti-aircraft platform. The island spaces provided the areas for control of ship operations. The Essex-class of aircraft carriers were not designed with radar fixtures in mind, thus each ship had a distinctive antenna array at different points in its career. Lexington as CV-16 carried a "bedspring" shaped SK long-range air search radar on a frame mounted to the starboard side of the funnel. An SC-2 air search antenna was mounted on the opposite side and a prototype height finder SM (CXBL) mounted in March 1943 sat atop the tripod mast. SG surface search antenna was also mounted on the mast. In 1945 Lexington was equipped with a SO-11 zenith search, prototype air search antenna designed to fill the blind spot directly above the carrier. This system proved unusable, however. Lexington also had five hinged radio antenna masts arranged along the starboard edge of her flight deck, three forward of the island and two aft.
Combat experience also drove a need for advances in the radar and radio technology that was used to locate enemy forces, coordinate carrier movements, and to direct offensive and defensive tactics. As such, more specialized radars were developed to fine-tune their detection and identification function. Ship-to-air and ship-to-ship long-range and short-range communications were also upgraded to increase the number of frequencies for transmission and reception. These improvements meant more radio channels, radio sets, radar sets, as well as antennas all of which had to be arranged and rearranged within the upper levels of the carrier superstructure in a manner that would ensure their effectiveness and minimize interference between the different signals.
Wartime modifications helped to improve the carrier’s ability to withstand enemy assault and inflict damage upon enemy forces. With speeds that allowed them to outrun most enemy combatants and keep pace with the Navy’s fast fleets of cruisers and destroyers, the Essex-class carriers were most vulnerable to other carrier air attack. Advanced communication, coordinated through the carrier’s central location for synthesizing tactical data –the combat information center (CIC), became the key to successful fast multi-carrier task force operations.
With radar and radio used to track ships and aircraft and to coordinate air group operations and anti-aircraft fire, carrier groups could conduct long-range air offensives while being assured of mutual anti-aircraft protection against enemy air and surface attacks. No longer considered just a reconnaissance platform, the Essexes elevated carriers to the status of major surface combatant. With aircraft that extended the fleet’s firepower beyond that of battleship guns, the Essex-class carriers were to become the primary strike weapon for World War II operations in the Pacific Theater.
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