Aegir-class Battleship
 Gotland class battleship in 1940
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| Class overview | |
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| Name: | Aegir class |
| Builders: | Isenstadt Naval Works |
| Operators: | Arcaenian Königsmarine |
| Built: | 1918–1924 |
| Planned: | 4 |
| Completed: | 4 |
| General characteristics (as built) | |
| Type: | Fast battleship |
| Displacement: |
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| Length: | 270 m |
| Beam: | 33.5 m |
| Draft: |
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| Installed power: |
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| Propulsion: | 4 shafts, 4 geared steam turbines |
| Speed: | 31 knots |
| Range: | 16,000 nautical miles (30,000 km) at 14 knots (26 km/h) |
| Complement: | 1,300 |
| Armor: |
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Design
General characteristics
The Aegir-class battleships had an overall length of 270 meters, a beam of 33.5 meters, and a draft of 10.6 meters at full load. They displaced 43,800 tonnes at normal load and 53,600 tonnes at deep load. Externally the ships were similar to the Königsmarine's preceding Heimdall-class Battlecruisers and were built with a single tripod foremast mounted atop the large forward superstructure and a lighter pole main mast aft of the funnel. The hull was consructed from longitudinal steel frames with riveted on outer hull plates and was divided longitudinally into 21 watertight compartments and featured a double bottom running got 92 percent of the length of the hull. The ships featured a flush upper deck with a high freeboard and were fitted with a bulbous to reduce drag on the hull.
Propulsion
The Aegir-class ships driven by four screws, two diesel powered and two steam powered. The inner two shafts were each powered by two AMG 6L 85/105 double-acting two-stroke in-line six cylinder diesel engines through a pair of mechanical/hydraulic gear reduction units. Each AMG 6L 85/105 engine had an 85 cm stroke, 105 cm bore, a total displacement of 6,850 L, and a maximum continuous power output of 20,000 hp at 145 RPM.
The Aegir-class ships were equipped with four sets of steam turbines each of which drove a three-bladed propeller that was 5.4 meters in diameter through Föttinger type fluid transmission. Steam for the turbines was provided by 24 oil-fired marine-type boilers working at a pressure of 1,620 kPa(17 kgf/cm2) with exhausts trunked into a pair of large funnels. The powerplant was rated at *160,000 shp (120,000 kW) at 295 revolutions per minute with a maximum speed of 31 knots. Standard bunkerage was 5,000 tons of marine fuel oil which gave the ships a range of 16,000 nautical miles (30,000 km) at 14 knots (26 km/h). . Electrical power on the ships was provided by six DC diesel generators that provided a combined 4,500 kilowatts at 220 volts.
Armament
Main battery
he primary armament of the Aegir-class battleships consisted of four 42 cm SK L/45 guns mounted in four two-gun turrets in two superfiring pairs along the centerline, one pair forward and one pair aft with the aft turrets separated by the ship's engine rooms. The turrets were trained and loaded with electric motors with elevation and shell hoists being hydraulically powered. Each turret was capable of traversing +150 / -150 degrees at 3 degrees per second and elevating from -5 to +30 degrees at 5 degrees per second. The turrets each had a machinery room below the turret with a handling room for shells and fore charges beneath it. Magazines for the rear and additional fore propellant charges were located underneath the handing rooms. Projectiles were transferred from the handling room to the turrets using hydraulically powered hoists. Once in the turret the shells and cartridges were electrically rammed to the rear of the turret onto pairs of electrically powered loading cars running on a set of rails which transferred the shells and cartridges to each gun. The shells and cartridges were then rammed into the guns using an electrically powered chain and telescoping rammer, the shells and fore charges rammed first followed by the cartridge case with the main propellant charge. Loading the guns required them to be returned to 2.5 degrees elevation. The guns were designed to fire 1,030 kg (2,270 lb) kg projectiles at a muzzle velocity of 810 meters per second (2,700 ft/s) out to a maximum range of 36,400 m (39,800 yd) at an elevation of 30 degrees. Total ammunition stowage was 720 rounds or 90 rounds per gun with the typical shell allotment being 60 AP rounds and 30 HE rounds per gun. Rate of fire was around 2-2.5 rounds per minute per gun. The guns used a horizontal sliding wedge breech block with the propellant charge consisted of a 135 kg (298 lb) fore charge contained in a silk bag and a 128 kg (282 lb) main charge contained in a 90 kg (200 lb) brass case which acted to seal the breech.
Secondary battery
The secondary battery of the ships consisted of eight 15 cm (5.9 in) SK L/45 guns mounted in armored casemates mounted along the sides main deck grouped around the fore and aft main battery turrets and were intended for defense against destroyers and torpedo boats. The guns fired 45.3 kg (100 lb) shells at a muzzle velocity of 835 meters per second (2,740 ft/s) and were loaded with a 13.7 kg (30 lb) RPC propellant charge contained in a brass case. Each casemate had its own magazines and ammunition hoists which could supply up to 7 complete rounds per gun per minute. Each gun could depress to −7 degrees and elevate to 30 degrees with a maximum range of 17,600 m (19,200 yd) at 30 degrees elevation. Each ship was supplied with 1,280 rounds of 15 cm ammunition with 160 rounds per gun.
Anti-aircraft battery
The anti-aircraft armament of the ships consisted of four 15 cm (5.9) in FlaK L/45 guns mounted in enclosed pedestal mounts grouped around the rear superfiring main battery turret. These guns were the same as the 15 cm (5.9 in) SK L/45 guns but mounted in high angle mountings which allowed depression to −10 degrees and elevation to 70 degrees. The guns had a maximum range against surface targets of 18,400 m (20,100 yd) at 45 degrees elevation and a maximum AA ceiling of 10,400 m (11,400 yd) at 70 degrees elevation. The guns could also fire 41.0 kg (90.4 lb) illumination rounds. Each gun was supplied with its own magazine and ammunition hoistsas and rate of fire was around 5-7 rounds per minute with each gun being supplied with 200 rounds of ammunition.
Torpedo armament
As was typical for capital ships of the era the ships were armed with submerged torpedo tubes with two 70 cm (27.6") tubes on either beam to the rear of the engine rooms supplied with a total of 10 torpedoes. The torpedoes were the J9a type which were 9 m (30 ft) long and carried a 315 kg (694 lb) Hexanite warhead. The torpedoes used a decahydronaphthalene (decalin) wet-heater propulsion system and had a range of 18,000 m (20,000 yd) at a speed of 30 knots or 10,000 m (11,000 yd) at a speed of 36 knots.
Armor
The main armor belt of the ships was 350 mm (13.8 in) thick and ran from slightly forward of the forward main battery barbette to slightly aft of the rear main battery barbette which protected the central citadel of the ship containing the ammunition magazines and the machinery spaces. The main strake extended from 195 cm (76.8 in) above above the waterline to 35 cm (13.8 in) below the waterline where it tapered to a thickness of 170 mm (6.7 in) along its lower edge. Directly above the main belt armor was a 250 mm (9.8 in) thick strake of armor plating extending up to the main deck which covered the sides of the hull above the main belt. Forward of the forward turret the belt armor was stepped down to 200 mm (7.9 in) and then to 150 mm (5.9 in) tapering down to 130 mm (5.1 in) at its lower edge with a 30 mm (1.2 in) thick splinter bulkhead extending from the forward edge of the belt all the way to the bow. Aft of the rear gun turret the belt stepped down to 200 mm (7.9 in) tapering down to 150 mm (5.9 in) at its lower edge which extended all the way back to the stern and protected the ships steering gear.
The main armor deck was 60 mm (2.4 in) thick over the central citadel with 100 mm (3.9 in) thick sloped sections on either side of the main armor deck extending down at a 30 degree angle to meet the lower edge of the belt armor. This formed a classic "turtle deck" armor scheme where shells fired by enemy warships would have to penetrate both the 350 mm (13.8 in) thick main belt and the 100 mm (3.9 in) thick sloping deck armor to penetrate into the ships vitals and was designed to provide immunity against 1,020 kg (2,250 lb) 16 in (406 mm) shells fired at any range over 11,000 m (12,000 yd). Aft of the central citadel the thickness of the armor deck increased to 100 mm (3.9 in) with 120 mm (4.7 in) slopes with along with the aft extension of the main belt armor formed an armored raft designed to protect the steering gear of the ships. Above the main armor deck was the forecastle deck which was 20 mm (0.8 in) thick aft, increased to 40 mm (1.6 in) in the central part of the ship, and decreased down to 20 mm (0.8 in) thick over the bow. An additional a 30 mm (1.2 in) thick longitudinal splinter bulkhead extended from inboard edges of the sloped part of the armor deck up to the forecastle deck.
The main battery turrets had 350 mm (13.8 in) thick faces, 250 mm (9.8 in) thick sides, and 290 mm (11.4 in) thick rears to balance them while the turret roofs were 150 mm (5.9 in) thick. The main battery turret barbettes were 350 mm (13.8 in thick on the front and sides and 250 mm 250 mm (9.8 in) on the rear. Below the upper belt armor the barbette thickness was reduced to 150 mm (5.9 in) and then to 100 mm (3.9 in) below the main belt armor. The 15 cm casemate guns had 170 mm (6.7 in) thick armor plating for the casemates while the guns themselves had 80 mm (3.1 in) thick shields to protect the crews from shell splinters. The 15 cm (5.9) in FlaK guns were enclosed with 20 mm (0.8 in) thick gun shields to protect their crews from splinters. The forward conning tower had 350 mm (13.8 in) thick sides and a 170 mm (6.7 in) thick roof while the aft conning tower had 250 mm (9.8 in) thick sides and an 80 mm (3.1 in) thick roof.
The underwater protection of the ships was designed to withstand a 300 kg (660 pound) hexanite charge and consisted of an outer air space, 8 mm (0.31 in) thick bulkhead, inner fuel bunker, and a 60 mm (2.4 in) thick torpedo bulkhead located 3-5 meters inboard from the side of the ship which ran the length of the hull and extended from where the inboard edges of the sloped part of the armor deck down to the ship's double bottom. The inner fuel bunkers were filled with water as fuel oil was burned and were fitted with compressed air systems which could rapidly blow the liquid out of the buoyancy spaces and restore the ships buoyancy in the event of a torpedo hit.