Hydra-class battleship
 Line drawing of the Hydra class battleship
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| Class overview | |
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| Name: | Hydra class |
| Builders: | Isenstadt Naval Works |
| Operators: | Arcaenian Navy |
| Built: | 1939–1944 |
| Planned: | 4 |
| Completed: | 4 |
| General characteristics (as built) | |
| Type: | battleship |
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| Length: |
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| Beam: | 39 m |
| Draft: |
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| Installed power: | 192,000 shp (143,000 kW) |
| Propulsion: | 12 diesel engines, 4 shafts |
| Speed: | 30.5 knots |
| Range: | 19,000 nautical miles (35,000 km) at 19 knots (35 km/h) |
| Complement: |
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| Armament: |
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| Armor: |
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| Aviation facilities: | 1 Aircraft catapult |
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Design
General characteristics
Propulsion
The Hydra class ships were powered by twelve 24-cylinder V-configuration double acting two-stroke diesel engines that provided a total of 192,000 shaft horsepower at 450 rpm. Each 136.5-tonne (150.5-ton) engine had 24 cylinders with a 45 degree bank angle and had a 420 mm (16.5 in ) bore, a 580 mm (22.8 in) stroke, and displaced 3,686 L(224,957 cu in). The engines were grouped into four sets of three, each group of three engines connected to a hydraulic transmission which drove one of the ship's four 4.8 m (15 ft 9 in) diameter screws. The center two propellers featured a controllable pitch and could be feathered when not in use to improve cruising efficiency. At their rated power of 192,000 shaft horsepower (143,000 kW) the ship's engines provided for a top speed of 30 knots (56 km/h; 35 mph). Steering was controlled by two rudders which could each be jettisoned with an explosive charge in the event they became jammed. Each ship was designed to carry up to 10,000 t (9,800 long tons; 11,000 short tons) of diesel oil which provided a cruising range of {convert|19000|nmi|abbr=on}} at a speed of 19 kn (35 km/h; 22 mph) or 7,000 nmi (13,000 km; 8,100 mi) at a speed of 30 kn (56 km/h; 35 mph). Two oil fired boilers and two exhaust gas boilers where located between the transmissions supplied the ship's with hot steam for various functions. Electrical power for the ships was provided by eight 920 kW DC diesel generators at 230 volts and four 460 kW AC diesel generators at 110 volts for a total of 9,200 kW of electrical power.
Armament
Main battery
The primary armament of the Hydra class battleships consisted of four 42 cm SK L/50 guns mounted in four two-gun turrets, two forward and two aft. The 42 cm SK L/50 gun is 50 calibers long and fired both APC and HE shells weighing 1,220 kg (2,690 lb) at a muzzle velocity of 830 meters per second (2,700 ft/s). The turrets could each rotate 150° to either side of the ship's center-line at 4° per second and could be elevated from -8°(0° for the super-firing guns) up to +40° at up to 12° per second. At maximum elevation the maximum firing range of the guns was 45,000 m (49,000 yd). Training of the turrets was electric while elevation, loading, and all other functions was hydraulic. Traverse and elevation were both controlled remotely using Remote power control (RPC) gear. The loading angle of each gun was fixed at an angle of 2.5° and rate of fire was 2-2.5 rounds per minute per gun, depending on elevation. As was common with all Arcaenian naval guns of the era the guns used a horizontally sliding wedge breech block. The breech was fully sealed with a 127 kg (280 lb) brass (later mild steel) cartridge case that contained a 180 kg (400 lb) smokeless RPC main propellant charge which was supplemented with a bagged fore charge containing an additional 187 kg (412 lb) of RPC propellant. The guns featured a removable loose liner that was expected to last 200 rounds before replacement. The main battery was supplied with 960 rounds, or 120 rounds per gun with the usual division being 90 APC round and 30 HE rounds.
Secondary battery
The secondary armament of the Hydra class was twenty 12.0 cm (4.7") SK L/50 dual-purpose guns housed in ten twin turrets, five located along each side of the superstructure. Originally designed a destroyer weapon these guns were added to the Hydra class to give them a dual-purpose secondary armament capable of effectively engaging both air and surface targets. Each turret could be depressed to -10° degrees and elevated to +80°. The guns used single piece ammunition weighing 41 kg (90 lb) and fired HE shells weighing 24 kg (53 lb) at a muzzle velocity of 900 meters per second (3,000 ft/s). At 45° degree elevation the maximum surface ranges of the guns was 20,600 m (22,500 yd). Maximum anti-aircraft ceiling of the guns was 14,000 m (15,000 yd) at an elevation of 80°. The guns featured a loose-liner and a semi-automatic horizontally sliding breech block which opened automatically under the force of recoil. Integral electro-hydraulic shell hoists with automatic fuze setters and electro-hydrauli power rammers for each gun were fitted to each turret which allowed for loading at any elevation. Like the main battery turrets each of the secondary battery turrets was fitted with Remote power control (RPC) gear with each twin turret was trained using a 4 PS hydraulic motor which could train the entire turret at 25° per second and the twin guns were elevated by a 10 PS hydraulic motor which could elevate both guns at a range of 15° per second. The guns were designed to fired nose fuzed HE rounds which could be fitted point detonating (PD), mechanical Time (MT), and later proximity (VT) nose fuzes. Rate of fire was 15-20 rounds per minute for each gun and ammunition storage was 50 ready rounds per gun in the turret with an additional 500 rounds per gun located in each turret magazine.