The 1930s was the period of extensive growth of military aviation throughout the world, including carrier-based aviation. The world’s greatest navies began extensive effort of aircraft carrier procurement.
The German Navy, rebuilding its potential after the First World War also had the ambition to possess carriers. The first of them was the Graf Zeppelin, but it was never to enter service.
As early as during the First World War studies on a new type of warship – the aircraft carrier – were conducted in Germany. In the country isolated by the conflict the work progressed independently from other countries. The result was the plan to convert the ship Ausonia to the first German carrier. The construction was never completed, but the design had many features of later successful carriers of world’s leading fleets.
The stoppage in works on aircraft carriers in Germany lasted until as late as 1933. Only then, due to Hitler’s and his party NSDAP’s rise to power quick growth of all military service branches took place. In March 1934 a conference took place, during which the main features and technical specifications of the future ship were discussed. Following it the design work began, although at that time there were no prospects for construction of the ship. Proper conditions appeared in June 1935, when Germany signed a naval treaty with Great Britain, by force of which Kriegsmarine received the official approval for growth to 35% of Royal Navy’s tonnage.
The task assigned to the design team led by Ing. Wilhelm Halder was breakneck. They had to design from scratch an entirely new type of warship, without having any experience in construction or operation of such vessels. An additional impediment was the fact that in Germany, like elsewhere in the world at that time, little attention was paid to aircraft carriers and the design work was not a priority for Kriegsmarine command. The only pattern to base on was the British class Courageous, but naturally the information about it was scarce. More information was obtained from allied Japan. The German delegation managed even to visit the carrier Akagi (in autumn of 1935) and receive copies of a part of her documentation. The design work on the German carrier ended soon.
The main features of Graf Zeppelin’s silhouette were similar to those of aircraft carriers built contemporarily in other countries. The flight deck situated high above the waterline ran along the entire length of the hull (although in earlier variants several shorter decks at various levels were envisaged). Amidships at the starboard side a massive “island” superstructure, housing fire and air traffic control devices, command rooms and part of armament. Initially the ship featured conventional straight and relatively broad bow stem. Early experience with heavy German ships revealed that such hull has poor seakeeping at rough sea. Therefore it was decided to rebuild the bow section with slanted and much narrower stem, like in battleships (early 1939). The unique feature of the Graf Zeppelin was her hull height. The hangars were its integral part up to the flight deck level, which gave the total height of 22.5 m.
The design requirements for the carrier included unprecedentedly high maximum speed – as much as 35 knots. Such performance could be provided only by very powerful propulsion system – total power of four Brown, Boveri & Cie geared turbines amounted to 200 000 shp. Steam was provided by 16 La Mont high pressure boilers located in four boiler rooms. An untypical feature was the installation of two Voith-Schneider thrusters in the bow section. They were deployed from ship’s bottom and each one could move the ship in any direction. It was particularly useful during maneuvers in confined basins, taking into consideration large lateral area of the ship.
For her size, Graf Zeppelin was a lightly armored ship. The weight of the entire armor amounted to ca. 5,000 tons. The thickness of the main armor belt did not exceed 100 mm, the main armored deck – 60 mm and the flight deck – 40 mm. The protection of such elements like the superstructures, hangars or communication lines was poor (not exceeding 25 mm), which was equivalent to standards of light cruisers of that time. In the later version of the carrier’s design of 1942 additional protection against torpedoes was provided by two bulges mounted on the hull near the waterline. They gave also better stability to the hull of an increased displacement in the new variant.
Initially 20,3 cm guns were chosen for the main armament. However, installation of such heavy artillery on a carrier posed many technical problems and it was decided to use 15 cm guns. There were eight of them in the original design, but this number was doubled by accident. One of the officers suggested to use twin mounts instead of single ones to conserve space. It was misunderstood and as result Graf Zeppelin was fitted with eight twin 15 cm SK C/28 gun mounts in casemates, 16 guns in total.
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