Mainz

History

Design

The Kriegsmarine in 1936 intended to follow up two further heavy cruisers after the three that were under construction. However, in order to not provoke the British it was decided to disguise these ships as light cruisers, by equipping them with an armament of twelve 150mm guns instead of eight 203mm guns, similar to how the Japanese disguised the Mogami class as light cruisers.

At a length of 212.5m and a width of 21.9m, with a draft ranging between 6.9 and 7.9m, these ships were to displace more than the earlier classes. The standard displacement was 13,581 tons, however at full load this would raise up to 19,533 tons. Crew complement was intended to be 1,409 men.

The main armament was to consist of four turrets, each housing three 150mm L/55 C/28 guns. With a maximum rate of fire of eight rounds per minute these guns would fire a 44.7-45.5kg heavy shell at ranges up to 23km. The secondary armament was copied from the Admiral-Hipper class with twelve 105mm L/65 C/33 guns, distributed equally into six triaxially stabilized mountings. However, unlike the preceding classes, these were to be the more modern C/37 mountings. The initial AA outfit saw twelve 37mm C/30 guns in six twin mounts as well as eight 20mm automatic guns for close range defense. Twelve torpedo tubes in four mountings would provide the torpedo armament.

The machinery differed from the earlier cruisers. The number of boilers was reduced from twelve to nine, with three in each boiler room. Three Wagner-Deschimag turbine sets were to generate up to 132,000shp for a maximum speed of 32kn. Furthermore, the propulsion was redesigned in the hopes of extending the cruising range. The intended cruising range was to be 6,100nm at a speed of 15kn.

The armor was not changed compared to the Admiral-Hipper class. The main belt, inclined by 12.5°, had a thickness of 80mm and covered the entire length between the barbettes of A- and D-turret. Behind it followed a 30mm turtleback, with the thickness of the main armored deck being identical except for a few spaces above the magazines which were reinforced to 40mm thickness. The main belt was extended towards the bow, however it was thinner with 40mm which eventually was reduced further to 20mm at the bow. Likewise the belt extended towards the aft end of the ship, covering the steering gears with a thickness of 70mm. The barbettes for the main armament were protected by 80mm of armor. The protection of the turrets can only be estimated but they would most likely enjoy relatively heavy protection as the 150mm triple turrets were designed to match the 203mm twin turrets in both weight and barbette diameter. The conning tower had up to 150mm armor.

Aviation facilities included two catapults and a hangar for a total aircraft capacity of three floatplanes.

Service

While two ships of this class, cruiser K and cruiser L, Seydlitz and Lützow respectively, were laid down, in both cases it was decided to arm them with 203mm guns before the 150mm armament had a chance to be installed. Thus both received the heavy cruiser armament from the get-go, although four 150mm triple turrets would remain under construction until 1941, however at low priority.

Historical inaccuracies

• The in-game ship carries the same turrets and guns from the light cruiser Nürnberg. However, the Kriegsmarine intended to develop new turrets that were to match the weight and barbette diameter of the larger 203mm twin, using the newer 150mm L/55 C/28 gun, not the older 150mm L/60 C/25 one. Nürnberg’s turrets as they are are more than 100 tons too light.
• The turtleback was identical in thickness to the Admiral-Hipper class, with a thickness of 30mm. In-game Mainz has a 40mm turtleback. Furthermore, the 40mm belt extension thins down at the bow to half its thickness. This is absent on the in-game model.
• Mainz carries the 105mm dp guns in the older C/31 mountings, when the design saw them to be mounted in the newer C/37 mountings.
• The design called for 12 torpedo tubes in four triple launchers, not 16 torpedo tubes in four quadruple launchers.
• Mainz carries seven target selectors for the heavy AA armament, while at the same time only having four AA fire directors which could receive the orders from these selectors.
• The Admiral-Hipper class carried eight sub-caliber 88mm guns which could be inserted into the main guns in order to prevent barrel wear during gunnery exercises. When not in use these would be stored on deck in long cylindrical boxes. Mainz also carries these eight boxes, yet has twelve main guns.