O-class battlecruiser

Template:Infobox ship imageTemplate:Infobox ship class overviewTemplate:Infobox ship characteristics

The O class was a planned class of three battlecruisers for the (German navy) before World War II. Prompted by a perceived lack in ship numbers when compared with the British Royal Navy, the O class' design was born with the suggestion of modifying the Template:Sclass2 design with Template:Convert guns instead of Template:Convert.

The ships were incorporated into the 1939 Plan Z for the re-equipment and expansion of the ; while an aircraft carrier, H-class battleships and smaller ships engaged convoy escorts, one or more O-class ships would attack the merchant ships.

The O class' design reflected their intended role; a heavy main armament (six 380 mm guns in three dual turrets) for possible encounters with escorting Template:Convert-armed heavy cruisers, enough armor to defend against the same and nothing more, and a high top speed so that they could get away from slower but much better armored capital ships.

Although planned and ordered, construction did not progress due to lack of materials and higher priorities for ship construction.

Development

Genesis: P-class cruisers

Even with the completion of the two Template:Sclasss and the construction of two Template:Sclasss, the German Navy had fewer ships than other European navies. This led to a decision in 1937 to build ships to an improved Template:Sclass design. After more than twenty designs were considered to meet the navy's specifications,Template:Efn one was chosen; it was designated as cruiser "P" (the "P" for  — German: "armor"). Under the original plan, twelve P-class ships were to be built. The ships were designed as cruiser killers that would have heavy enough armament and armor to take on light and heavy cruisers but enough speed to outrun battleships and battlecruisers.Template:Sfn

Many problems were encountered with designing the ships, the most prevalent being armor. The required maximum speed of Template:Convert meant that the minimum length had to grow from the original Template:Convert. It also meant that the beam could be a minimum of Template:Convert—unless diesel engines, like those used in the Template:'s, were desired; they would increase the beam by Template:Convert. Unfortunately for the designers, the widened beam meant that an even longer hull was needed to maintain hydrodynamic efficiency. All of this complicated the armor arrangements, as more armor was needed to cover the longer length and widened beam. Eventually it was deemed that it was impossible to include diesel power on a Template:Convert displacement.Template:Sfn

The switch to battlecruisers was the result of a proposal to up the main armament from Template:Convert 55 caliber-long guns to Template:Convert/47-caliber guns. Various reasons were behind this. Among other reasons, experiments showed that the smaller gun was "far less effective"Template:Sfn than the larger gun, a class of twelve ships would have overtaxed the shipyards already heavily burdened with other ships, and the smallest guns on any foreign capital ship in service or under construction were more than Template:Convert larger in caliber than the 283 mm guns.Template:Efn The most persuasive argument for increasing the armament came in 1939, when Adolf Hitler denounced the 1935 Anglo-German Naval Agreement.Template:Sfn

Battlecruisers

File:OclassCruiser1-24ShipRearAngleA1hullMid.blend.jpg

The stern and amidships portion of the O class

Although interest in the P-class ships and the battlecruiser proposal waned for a time in late 1937 and early 1938, it was quickly revived on 28 April 1938 with Hitler's public airing of his views on the 1935 Anglo-German Treaty and the consequent increased possibility of war with the United Kingdom. Calling the Naval Staff and Admiral Erich Raeder to him, Hitler laid out his thoughts of a strong navy that could pose enough danger to the British such that they would enter into an alliance with Germany rather than go to war. As decided here, Plan Z entailed two task forces each centered on three H-class battleships and one aircraft carrier, with cruisers and destroyers as escorts. In war, these forces would collaborate with the three battlecruisers by occupying convoy screens while U-boats and one or more of the O class destroyed the cargo-carrying merchant ships.Template:Sfn The presence of the battlecruisers operating at large would have the secondary effect of forcing the Royal Navy to deploy battleships as convoy escorts, thus weakening any fleet that could engage the Plan Z task forces.Template:Sfn

As part of the plan, design work on the P class was halted in mid-1939 in favor of the O class. Displacement was limited to Template:Cvt in the new designs so that the length of construction would be shortened from the normal four or more years that a battleship required, to an estimated threeTemplate:Sfn to three and a half years.Template:Sfn Required characteristics for the battlecruisers was a displacement of Template:Cvt, a main battery of six Template:Convert guns, a secondary battery of dual purpose guns, a top speed of Template:Convert, a range of Template:Convert at Template:Convert, and enough armor to counter the Template:Cvt guns of heavy cruisers.Template:Sfn

Like the P class, there were problems with fitting an all-diesel drive into the hull of the ships. It was enough that the design team decided that it would not be prudent to use an all-diesel arrangement; instead, a hybrid diesel-steam turbine propulsion plant was to be used. The change allowed the central armored citadel to be reduced by Template:Convert and the aft beam to be lowered by Template:Convert.Template:Sfn

Although plans were not finalized, the third battlecruiser, "Q", was ordered from in Kiel on 8 August 1939. One month after, the contract design was refined. The displacement was increased to Template:Cvt (design) and Template:Convert (full-load), while the draft at those two figures was Template:Convert, respectively. At the waterline, the length was set at Template:Convert and beam at Template:Convert. The main battery was the same as previously (six Template:Cvt/47-caliber guns in dual turrets), while the secondary battery was split between six paired Template:Convert/48-caliber anti-surface guns and paired Template:Convert/65-caliber anti-aircraft guns because German designers had not been able to develop a satisfactory dual-purpose gun. Light anti-aircraft guns were eight 37 mm in four dual mounts and twenty 20 mm autocannon in single mounts. Twelve Template:Cvt torpedo tubes finished out the armament aboard the ships. Four floatplanes for scouting were planned. At the design displacement, the maximum speed was reduced by half a knot, to Template:Convert; this required a top shaft horsepower of 173,600.Template:Sfn

By 1940, project drawings for the three battlecruisers were complete. They were reviewed by both Hitler and Raeder, both of whom approved. However, outside "initial procurement of materials and the issuance of some procurement orders",Template:Sfn the ships' keels were never laid down.Template:Sfn In large part, this was due to severe material shortages, especially of high-grade steel, since there were more pressing needs for these materials for the war effort. In addition, the dockyard personnel necessary for the ships' construction were by now occupied with more important work, primarily on new U-boats.Template:Sfn

Specifications

General characteristics

The final design, which was completed by 1940, called for a ship that was Template:Cvt long at the waterline and Template:Cvt long overall. The planned ships had a beam of Template:Cvt and a designed draft of Template:Cvt. The ships' designed displacement was Template:Convert, but displaced Template:Convert standard and Template:Convert at full displacement. The ships were to be of welded steel construction, with twenty watertight compartments and a double bottom that extended for 78% of the length of the hull. The ships were to have had a crew of 65 officers and 1,900 men.Template:Sfn

They were intended to carry a number of boats aboard, including two picket boats, two barges, two launches, two pinnaces, two yawls, and two dinghies. The ships were also to be equipped with a double catapult mounted between the two funnels, and four Arado Ar 196 seaplanes for maritime reconnaissance. The aircraft were stored in a main hangar just aft of the forward funnel, along with two smaller hangars, one on each side of the rear funnel.Template:Sfn

Propulsion

The O-class ships were to be driven by three screws, two diesel powered and one steam. Eight MAN 24-cylinder V-configuration two-stroke diesel engines powered two Vulcan gearboxes, both of which drove the outer pair of Template:Convert diameter three-bladed screws. Aft of the diesel engines was a single boiler room with four Wagner high-pressure boilers that provided up to 55 atmospheres of pressure. These supplied steam for one set of Brown, Boveri & Cie turbines, which provided power for the center Template:Convert three-bladed screw. The O-class ships were designed to store 1,000 tons of fuel oil for the high pressure boilers, and up to 4,610 tons of diesel oil for the diesel engines. This enabled a maximum range of 14,000 nautical miles at a cruising speed of 19 knots. They were designed to steam at a maximum of 33.5 knots, but were capable of up to 35 knots. The ships had two rudders each. Eight 920 kW diesel generators supplied electrical power for the ships, for a total of 7360 kW, at 220 V.Template:Sfn

Armament

File:OclassCruiser1-23BigGuns1A1hullMid.blend.jpg

The rear main battery turret, with the superfiring secondary turret. Also visible is a twin 10.5 cm FlaK 38 anti-aircraft gun

The ships' main armament batteries were to have consisted of six [[38 cm SK C/34 naval gun|Template:Cvt L/47 SK C/34]] quick-firing guns mounted in three twin turrets, the same Drh LC/38 gun turrets as were used on the Bismarck-class battleships.Template:Sfn Two of the turrets were mounted in a superfiring pair forward, with the third turret placed aft of the main superstructure. The guns could depress to −8 degrees and elevate to 35 degrees. At maximum elevation, the guns could hit targets Template:Convert away. The guns had a designed supply of 630 shells, for a total of 105 rounds per gun.Template:Sfn There were three types of shells: capped armor-penetrating, and two different high-explosive shells; all three shells weighed Template:Convert. The guns used a Template:Convert fore charge and a Template:Convert main charge in a brass case. This provided a muzzle velocity of 820 meters per second (2,690 feet per second).Template:Sfn

The secondary battery consisted of six [[15 cm TbtsK C/36 naval gun|Template:Convert L/48]] quick-firing guns, also mounted in three twin turrets; two were placed on either side of the forward superstructure, the third was placed aft of the main superstructure, superfiring over the rear main battery turret. These guns were supplied with 900 rounds, for 150 shells per gun, and had a maximum range of Template:Convert. The ships were also armed with six Template:Cvt above-water torpedo tubes, with a total of 18 torpedoes.Template:Sfn

The ships had an anti-aircraft battery consisting of eight [[10.5 cm FlaK 38|Template:Convert L/65 SK C/33]] heavy anti-aircraft guns, eight [[3.7 cm SK C/30|Template:Convert L/83 SK C/30]] anti-aircraft guns, and twenty Template:Convert. The 10.5 cm guns were emplaced in twin mounts, two on either side of the superstructure, as were the 3.7 cm guns. The 2 cm SK C/30 guns were placed in single mounts, dispersed on the superstructure amidships.Template:Sfn

Armor

The O-class ships were to be protected by Krupp steel armor. The main armored belt was Template:Convert thick in the most critical areas of the ship, including the machinery spaces and ammunition magazines, and Template:Convert in other less important areas; the armor tapered to zero at the stern and bow of the ship. A torpedo bulkhead ran the length of the hull; the bulkhead was Template:Convert thick for the majority of its length. A second bulkhead was placed in the central portion of the ship. The bulkhead was Template:Convert thick but increased to Template:Convert in the more important portions of the ship. Critical areas were further protected by 80 mm-thick shields set back from the torpedo bulkhead. All of the lateral armor protection was steel, with the exception of the torpedo bulkhead, which was .Template:SfnTemplate:Efn

The ships had several layers of horizontal deck armor. The upper deck was Template:Cvt thick, and the armored deck ranged in thickness from Template:Convert; important areas were also protected by Template:Convert thick overhead shields. The armored belt connected to 110 mm-thick sloping armor. The forward conning tower had a roof 60 mm thick and Template:Convert armored sides; the aft conning tower was significantly less well protected. The roof was decreased to Template:Convert and the sides were 50 mm thick. The rangefinders were protected against shell splinters by Template:Convert roofs and 30 mm sides. All of this armor was .Template:Sfn

The main battery turrets had 50 mm thick roofs and sides that were Template:Convert thick. The inner shields were Template:Convert thick. The 15 cm gun turrets had Template:Convert thick protection against shell fragments. All of the anti-aircraft weaponry were also protected with 14 mm-thick gun shields. The aircraft hangars also had 14 mm-thick splinter protection.Template:Sfn The relatively thin armor protection given to the ships of the O class led to their derisive nickname "" (Without armor nonsense), a play on their provisional names.Template:Sfn

Ships of the class

Construction data

Ship	BuilderTemplate:Sfn	OrderedTemplate:Sfn
		Projected
	Wilhelmshaven	Projected
		8 August 1939