J3 battlecruiser

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Class overview
Name	J3
Builders	Vickers
Operators	Royal Navy
Preceded by	Template:Sclass-
Succeeded by	Template:Sclass-
Planned	5
Cancelled	5
General characteristics
Type	Battlecruiser
Displacement	about 43,100 long tons (43,800 t)
Length	860 ft (262.1 m)
Beam	106 ft (32.3 m)
Draught	32 ft (9.8 m) (at deep load)
Installed power	151,000 shp (113,000 kW)
Propulsion	4 shafts, 4 geared steam turbine sets
Speed	33 knots (61 km/h; 38 mph)
Armament	3 × triple 15-inch (381 mm) guns 6 × twin 6-inch (152 mm) guns 6 × single 4.7-inch (120 mm) AA guns 4 × quadruple-barrel 2-pdr pom-pom mountings 4 × 21-inch (533 mm) torpedo tubes
Armour	Belt: 13 in (330 mm) Deck: 6 in (152 mm) Barbettes: 13 in (330 mm) Turrets: 8–15 in (203–381 mm) Conning tower: 13 in (330 mm) Bulkheads: 9–14 in (229–356 mm)

The J3 class battlecruiser was a design study conducted during the Royal Navy's 1921 Fleet modernization program. As a follow on to the Template:Sclass2- the J3 class incorporated all the lessons learned from that conflict, specifically the battle of Jutland. The design was seen as an improvement to the Admiral class by virtue of its heavier and improved armoring scheme, specifically the deck armor, although the offensive armament remained roughly the same. The design was superceded by the G3 battlecruisers, as the G3 mounted a heavier main armament, and further improved the protection scheme, on roughly the same tonnage. The 1921 fleet program was cancelled due to signing of the Washington Naval Treaty in 1922, which limited the size and armament of battleships to 35,000 long tons (36,000 t) and no gun bigger than 16 inches (406 mm).

Background

In 1916 the US had declared its intention to create a Navy "second to none"; Congress had authorized the building of a large number of battleships and battlecruisers. In response, the Japanese government also began a large programme of warship building (the 8-8 fleet). Two improved Template:Sclass- hulls were rebuilt into the two Template:Sclass-s by the Royal Navy during the war. The only new capital ships laid down during the war were the Template:Sclass2-s. Their design had been called into question after the Battle of Jutland in 1916 and three ships of this class were cancelled, leaving only Hood to be completed to a modified design.

The US plan had been delayed by the wartime need to build smaller vessels. Nevertheless, estimates by the Admiralty were that by the early 1920s the Royal Navy would be behind in ships. By the beginning of 1920, the Americans had completed one battleship since the end of World War I and had five more building. Seven more were intended to be laid down in 1920–21, six of these were the very large and powerful Template:Sclass-, armed with twelve 16-inch guns. The Japanese had finished one battleship since the end of the war and had three more under construction. To correct this state of affairs, the Admiralty initially planned to build three battleships and one battlecruiser in Fiscal Year (FY) 1921–22 and again in FY 1922–23, but this was changed to four battlecruisers to be built first, presumably to be followed by the same number of battleships the following year.

The British did have access to German technology through ships such as the battleship Baden which had been saved from the scuttling of the interned German High Seas Fleet in Scapa Flow and the experiences of the war. A committee concluded that any new ship should be able to match the speed of the new US Template:Sclass-s, expected to make 32 knots. Consequently, a series of designs was prepared of ships with displacements ranging from 53,100 to 44,500 long tons (54,000 to 45,200 t), the only limitations being the ability to use British dockyards and passage through the Suez Canal. These designs were given letters of the alphabet running backwards from K to G. The related battleship designs under consideration at the same time had design letters from L upwards.

The first two design proposals, 'K2' and 'K3', had a general layout similar to Hood, but were armed with either eight or nine 18-inch guns, in four twin or three triple gun turrets, respectively. The numeral in the designation came from the number of guns in each turret. These ships were very large, displacing 52,000 to 53,100 long tons (52,800 to 54,000 t), could only reach 30 knots (56 km/h; 35 mph), and could only be docked in a single ex-German floating dock and one dock, Gladstone Dock, in Liverpool. The 'J3', the next proposal, saved nearly 10,000 long tons (10,000 t) by reducing the main armament to nine 50-calibre 15-inch (381 mm) guns and the main deck armour to 4 inches (102 mm). This reduction in size allowed the ship to dock anywhere that Hood could dock and to pass through the Suez and Panama Canals.

General characteristics

The J3 battlecruisers were very similar to the Admiral class in terms of size. They had an overall length of 860 feet (262.1 m), a beam of 104 feet (31.7 m), and a draught of 32 feet (9.8 m) at deep load. They would have displaced 43,100 long tons (43,800 t) normally and 48,000 long tons (49,000 t) at deep load, over 2,500 long tons (2,500 t) more than the older ships. The main benefit of the design was a reduction in the weight of the main armament but increase in firepower by converting from twin to triple mount turrets, with the additional weight savings being used to improve protection and armouring.

Propulsion

The J3 battlecruisers would have had four geared steam turbine sets, each of which drove one propeller shaft. They were arranged in two engine rooms. The forward engine room held the two turbines for the wing shafts, while the aft engine room contained the turbine for the port and starboard inner shafts. The turbines were powered by 18 Yarrow small-tube boilers divided between nine boiler rooms. They were designed to produce a total of 151,000 shaft horsepower (113,000 kW) at a working pressure of 200 psi (1,379 kPa) and temperature of 200 °C (392 °F) with superheat. Maximum speed would have been 34 knots (63 km/h; 39 mph).

Armament

Housing the main armament in triple turrets was new to the Royal Navy though British companies had been involved in the production of triple gun turret designs for other navies. The choice of a high muzzle velocity with a relatively lighter shell was taken from the German practice; it ran counter to previous British guns such as the BL 15-inch Mark I gun of 42-calibre length which were lower-muzzle-velocity weapons firing heavy shells.

The G3 design mounted nine 15 inch 50-calibre guns in three triple hydraulically powered Mark I gun turrets, designated 'A', 'B', and 'Z' from front to rear. The guns could be depressed to −3° and elevated to 40°. The ships' maximum stowage was 116 shells per gun. They fired 2,048-pound (929 kg) projectiles at a muzzle velocity of 2,670 ft/s (810 m/s). Their maximum range was about 38,000 yards (35,000 m) at maximum elevation. These weapons would have been very similar to the BL 16-inch Mark I produced for the Nelson class battleships. The J3s carried a secondary armament of 12 BL 6-inch Mark XXII guns in twin turrets instead of casemates. the six turrets were sited amidships behind the main bridge structure and ahead of the Z turret. The guns could elevate between –5° and +60°.

An anti-aircraft battery of six QF 4.7-inch Mark VIII guns was included. They had a maximum depression of -5° and a maximum elevation of 90°. They fired a 50-pound (23 kg) high explosive shell at a muzzle velocity of 2,457 ft/s (749 m/s) at a rate of eight to twelve rounds per minute. The guns had a maximum ceiling of 32,000 ft (9,800 m), but an effective range of much less. A maximum of 256 rounds per gun could be carried. The ships were intended to carry four 8-barreled mountings for the 40-millimetre (1.6 in) QF 2-pounder Mark VIII gun (commonly known as a pom-pom), two abaft the funnels and two at the stern. Each barrel was provided with 1300 rounds of ammunition. The gun fired a 40-millimetre (1.6 in) 2-pound (0.91 kg) shell at a muzzle velocity of 1,920 ft/s (590 m/s) to a distance of 3,800 yards (3,500 m). The gun's rate of fire was approximately 96–98 rounds per minute.

Fire-control

The main guns of the J3 battlecruisers could be controlled from any of the three director-control towers (DCT). The primary DCT was mounted at the top of the forward superstructure. Another was mounted on the roof of the conning tower in an armoured hood and the third was aft. Each main gun turret was provided with a 41-foot (12.5 m) coincidence rangefinder in an armoured housing on the turret roof. The secondary armament was primarily controlled by three DCTs. Two mounted on each side of the bridge and the third was located aft of the secondary armament. The anti-aircraft guns were controlled by a high-angle control system mounted on the very top of the forward superstructure. Each pom-pom mount had its own director and there was also a height-finder aft. Two 15-foot (4.6 m) torpedo rangefinders were located on the sides of the funnels.

Armour

The J3 was armoured simlar to the Hood, with bands of varying thickness. The armour was angled to up to 25 degrees on the belt, to increase relative thickness. One of the considerations that led to the cancellation of the J3 design was the protection scheme did not use an 'all or nothing' layout as later designs, such as the G3. This led to the J3 wasting tonnage on armour that would not have withstood incoming fire, a situation that the admiralty found unacceptable.

References

• Brown, David K. (2003). The Grand Fleet: Warship Design and Development 1906–1922 (reprint of the 1999 ed.). London: Caxton Editions. ISBN 1-84067-531-4.
• Campbell, N. J. M. (1977). "Washington's Cherry Trees, Part 1". Warship. I (1). London: Conway Maritime Press: 2–12. ISBN 0-87021-975-8.
• Campbell, N. J. M. (1977). "Washington's Cherry Trees, Part 2". Warship. I (2). London: Conway Maritime Press: 12–19. ISBN 0-87021-975-8.
• Campbell, N. J. M. (1977). "Washington's Cherry Trees, Part 4". Warship. I (4). London: Conway Maritime Press: 37–41. ISBN 0-87021-975-8.
• Friedman, Norman (1985). U.S. Battleships: An Illustrated Design History. Annapolis, MD: Naval Institute Press. ISBN 0-87021-715-1.
• Raven, Alan; Roberts, John (1976). British Battleships of World War Two: The Development and Technical History of the Royal Navy's Battleship and Battlecruisers from 1911 to 1946. Annapolis, Maryland: Naval Institute Press. ISBN 0-87021-817-4. {{cite book}}: Unknown parameter |lastauthoramp= ignored (|name-list-style= suggested) (help)