Ersatz Yorck-class battlecruiser

The Ersatz Yorck class was a group of three battlecruisers ordered for the Imperial German Navy in April 1915. The name derived from the fact that the lead ship was intended as a replacement (German: ersatz) for the armored cruiser SMS Yorck lost to mines in 1914. They were a slightly enlarged version of the, armed with 38 cm guns as opposed to the 35 cm weapons on the preceding design. The boilers would have been trunked into a single massive funnel. The three ships were originally ordered as part of the Mackensen class but the design was changed when details of the British s became known to German intelligence. The vessels were ordered under the provisional names Ersatz Yorck, Ersatz Gneisenau, and Ersatz Scharnhorst. They were considered to be replacements for the armored cruisers SMS Yorck, which had been sunk by German mines in 1914, and SMS Gneisenau and SMS Scharnhorst, both of which had been sunk at the Battle of the Falkland Islands also in 1914.

As with the Mackensens, the three ships of the Ersatz Yorck class were never completed. This was primarily due to shifting wartime construction priorities; U-boats were deemed more important to Germany's war effort, and so work on other types of ships was slowed or halted outright. The lead ship, Ersatz Yorck, was the only vessel of the three to have construction begin, though she was over two years from completion by the time work was abandoned. With the hull incomplete, the ship could not be launched and towed to ship-breakers; as a result, Ersatz Yorck was broken up in situ.

General characteristics
The Ersatz Yorck-class ships were an enlargement of the previous Mackensen-class ships. They were 227.8 m long, compared to 223 m on the earlier vessels. Ersatz Yorck had the same beam as the earlier vessels, at 30.4 m, and the same draft of 9.3 m. The ships were planned to displace 33500 MT at standard weight, and up to 38000 MT fully laden. This was approximately 2500 MT heavier than the Mackensens. The Ersatz Yorck-class ships' hulls were to have been constructed with longitudinal steel frames with the outer plating riveted on.

Machinery
As with all German battlecruisers that had been built, the Ersatz Yorck-class ships would have been equipped with four sets of Parsons turbine engines, each of which drove a 3-bladed screw that was 4.2 m in diameter. The turbines were supplied with steam by 24 coal-fired Schulz-Thornycroft single ended boilers and 8 oil-fired Schulz-Thornycroft double ended boilers. Ersatz Yorck and Ersatz Gneisenau were intended to use Föttinger fluid transmission for their turbines, while Ersatz Scharnhorst's turbines retained direct coupled geared transmissions. The ships were to have electrical power provided by diesel generators. The Ersatz Yorcks were intended to mount a pair of twin rudders alongside each other for steering.

The power plant was rated 90,000 shaft horsepower and 295 revolutions per minute, the same as the preceding Mackensen-class ships. Their slightly greater size reduced their speed somewhat, from 28 kn in the Mackensen-class ships to 27.3 kn for the new vessels. The ships were designed to store 850 MT of coal and 250 MT of oil in purpose-designed fuel bunkers. However, the areas of the hull between the torpedo bulkhead and the outer wall of the ship were also used for fuel storage. This additional space provided an increased total of 4000 MT of coal and 2000 MT of oil. With fuel stores topped off, the ships were estimated to have been able to steam for 5500 nmi at a cruising speed of 14 kn.

Armament
The ships' main battery was to have consisted of eight 38 cm SK L/45 guns in four Drh LC/1913 twin gun turrets, placed in superfiring pairs fore and aft of the superstructure. These were the same "Langer Max" guns as those mounted on the s. The guns could initially depress to −8 degrees and elevate to 16 degrees; this provided maximum range of 20,400 m. The gun mountings were modified to allow elevation up to 20 degrees; the range was correspondingly increased to 23,200 m. The turrets could train 150 degrees to either side of the centerline. The main battery was supplied with a total of 720 shells or 90 rounds per gun. The guns had a rate of fire of around 2.5 shells per minute. Post-war tests conducted by the British Royal Navy showed that the guns on the battleship SMS Baden could be ready to fire again 23 seconds after firing; this was significantly faster than their British contemporaries, the 38 cm guns on the, which took 36 seconds between salvos. The guns fired 750 kg armor-piercing shells with a 277 kg RPC/12 propellant charge in a brass cartridge. The shells were fired at a muzzle velocity of 800 meters per second (2,625 fps). Each gun was expected to fire 300 shells before replacement was required.

The ships' secondary battery consisted of twelve 15 cm SK L/45 quick-firing guns mounted in armored casemates along the central superstructure. Each gun was supplied with 160 rounds, and had a maximum range of 13,500 m, though this was later extended to 16,800 m. The guns had a sustained rate of fire of 5 to 7 rounds per minute. The shells were 45.3 kg, and were loaded with a 13.7 kg RPC/12 propellant charge in a brass cartridge. The guns fired at a muzzle velocity of 835 meters per second (2,740 ft/s). The guns were expected to fire around 1,400 shells before they needed to be replaced.

The ships were also armed with eight 8.8 cm (3.45 in) L/45 Flak guns in single pedestal mounts. Four were arranged around the rear superfiring main battery turret and the other four around the forward conning tower. The Flak guns were emplaced in MPL C/13 mountings, which allowed depression to −10 degrees and elevation to 70 degrees. These guns fired 9 kg shells, and had an effective ceiling of 9,150 m at 70 degrees.

As was standard for warships of the period, the Ersatz Yorcks were equipped with submerged torpedo tubes. There were three 60 cm tubes: one in the bow, and one on each flank of the ship. The torpedoes were the H8 type, which were 8 m long and carried a 210 kg Hexanite warhead. The torpedoes had a range of 6000 m when set at a speed of 36 knots; at a reduced speed of 30 knots, the range increased significantly to 14000 m.

Armor
The Ersatz Yorck-class ships were protected with Krupp cemented steel armor, as was the standard for German warships of the period. The armor layout was identical to the preceding Mackensen class, which was itself very similar to the armor scheme on the preceding Derfflinger-class ships. They had an armor belt that was 300 mm thick in the central citadel of the ship, where the most important parts of the ship were located. This included the ammunition magazines and the machinery spaces. The belt was reduced in less critical areas, to 120 mm forward and 100 mm aft. The belt tapered down to 30 mm at the bow, though the stern was not protected by armor at all. A 45 mm thick torpedo bulkhead ran the length of the hull, several meters behind the main belt. The main armored deck ranged in thickness from 30 mm thick in less important areas, to 80 mm in the sections that covered the more critical areas of the ship.

The forward conning tower was protected with heavy armor: the sides were 300 mm thick and the roof was 130 mm thick. The rear conning tower was less well armored; its sides were only 200 mm thick and the roof was covered with 50 mm of armor plate. The main battery gun turrets were also heavily armored: the turret sides were 270 mm thick and the roofs were 110 mm thick. The 15 cm guns had 150 mm worth of armor plating in the casemates; the guns themselves had 70 mm thick shields to protect their crews from shell splinters.

Construction and cancellation
Three ships were ordered for the new design. Ersatz Yorck, a replacement for the armored cruiser SMS Yorck, was ordered from AG Vulcan in Hamburg, laid down in July 1916 under construction number 63. After 1917, work on the ship only took place in order to keep dockyard workers occupied. Construction was suspended to concentrate on the U-boat program, and the hull frames that had been assembled were subsequently scrapped on the slip. Ersatz Gneisenau, a replacement for the armored cruiser SMS Gneisenau, was ordered from Germaniawerft in Kiel under construction number 250. Work was not started due to shifting priorities, though some material had been constructed. The diesel engines that had been built were subsequently installed on the first four Type U 151 U-boats SMU U-151, SMU U-152, SMU U-153, and SMU U-154. Ersatz Scharnhorst, a replacement for the armored cruiser SMS Scharnhorst, was ordered from Blohm + Voss in Hamburg under construction number 246. Construction never began on her as well, due to shifting priorities. However, the design formed the basis for the s built by the Kriegsmarine in the mid-1930s.