Derfflinger Class Battlecruiser - Design

Design

The Derfflinger class battlecruisers were a result of the fourth and final Naval Law, which was passed in 1912. Admiral Alfred von Tirpitz used public outcry over the British involvement in the Agadir Crisis of 1911 to pressure the Reichstag into appropriating additional funds to the Navy. The Fourth Naval Law secured funding for three new dreadnoughts, two light cruisers, and an increase of an additional 15,000 officers and men in the ranks of the Navy for 1912. The three dreadnoughts secured in the bill were to become Derfflinger, Lützow, and Hindenburg. Design work on the first two ships began in October 1910 and continued until June 1911; Hindenburg was built to a slightly modified design, which was created between May and October 1912.

When design work began, the navy department was asked to submit new requirements to fix deficiencies found in the preceding battlecruiser classes, which primarily covered propulsion systems and the main armament. Previous battlecruisers used a four shaft arrangement for their engines; reducing the number to three would allow the new ships to equip a diesel engine on the central shaft. This would substantially increase the cruising range, and would ease the transfer of fuel and reduce the amount of crew members needed to operate the ships' machinery. The navy department also argued for an increase in the main battery guns, from 28-centimeter (11 in) guns to more powerful 30.5 cm (12 in) weapons. This was due to the fact that the latest British battleships had thicker main belt armor, up to 300 millimetres (12 in). Since the German battlecruisers were intended to fight in the line of battle, their armament needed to be sufficiently powerful to penetrate the armor of their British opponents. Weight increases were managed by reducing the number of guns, from 10 to 8—the increase in gun caliber added only 36 tons to the ships' displacement. Admiral Alfred von Tirpitz argued against the increase in gun caliber, for he thought the 28 cm gun was powerful enough.

A new construction technique was employed to save weight. Previous battlecruisers were built with a combination of transverse and longitudinal steel frames; the Derfflinger class ships dispensed with the transverse frames and used only the longitudinal ones. This enabled the ship to retain structural strength and a lower weight. As with all preceding capital ships, the outer hull spaces between the hull wall and the torpedo bulkhead were to be used for coal storage.

On 1 September 1910, the design board chose the 30.5 cm, to be mounted in four twin turrets on the centerline of the ship. The armor layout was kept the same as in Seydlitz. In the meantime, pressure from the British public and media had forced the British Parliament to step up ship building. Kaiser Wilhelm II requested that the build time for the new battlecruisers be reduced to two years each, as opposed to three years. This proved unfeasible, because neither the armor or armament firms could supply the necessary materials according to an expedited schedule.