Derfflinger Class Battlecruiser (1913)

Armament

Main Battery

Eight 30.5cm (12-in) guns in four double turrets arranged on the centerline.

Secondary Battery

Fourteen 5.9-in guns (twelve in Derfflinger).

Other Guns

Twelve 8.8cm guns, reduced greatly in number in 1916 to two in Derfflinger and four in Hinderburg.

Torpedoes

Four 50cm (19.7-in) submerged torpedo tubes in Derfflinger, four 60cm (23.6-in) submerged torpedo tubes in others.

Fire Control

This page is sourced from a post-war American intelligence report based on interviews with the ordnance officers of Lutzow and Derfflinger. The O.N.I. considered the information "absolutely reliable".

Rangefinders

Seven "large" Zeiss stereoscopic rangefinders good to 20,000m.

Each employed two men: one to take the range cut and the second to transmit the data by a telegraph.

Target Bearing Indicators

The German director system was very similar to a target bearing indicator.

Gunnery Control

Control Positions

The main, forward control position was a tower with 350mm nickel steel armour located in the rear of the conning tower. This station contained:

• fire control officer
• third gunnery officer (commanding the secondary battery)
• one ensign
• two rangetakers
• three men to operate the "Direction Indicator"
• five men to transmit orders

Below this, a receiving station contained

• six more order transmitting men
• a petty officer
• two talkers
• an ordnance mechanician

The forward position contained a Mittlungsapparat to average range cuts being received, with the mean rangefinder range of the moment used for ranging shots, and a periscopic target bearing transmitter — the German training-only director.

An alternate control position manned by the second gunnery officer was located aft.

The forward spotting top had a spotter for the main battery and another for the secondary battery, each in telephone contact with the fire control officers in both control positions.

Both control positions and the spotting positions had time-of-flight clocks to ring bells when a salvo was due to fall.

Directors

Main Battery

The training-only director was driven by a periscopic sight in the forward control position. Convergence in training was effected automatically as the angles went to each turret, where [[F.T.P.] systems permitted men to move the guns to match the indicated, convergence-corrected bearings.

Usually the fire control officer would use the director, and a petty officer would use a second eye-piece on the lower end of the periscope to check that the crosshairs were on the target. The working of two men on the Mittlungsapparat would provide the range used to complete the convergence angle computations.

The layers would generally aim at the waterline of their target, but late in the war the standard was to aim for the top of the funnel or a mast to increase range a little. After Jutland, there may have been a gyroscope-based system of automatic firing introduced, similar to the Royal Navy's Henderson Firing Gear. Like Henderson gear, this also had a means of factoring in delay time from trigger-press to shells leaving the barrels.

Transmitting Station

A "central station", in the US telling, was comprised of two rooms below the waterline forward, protected by heavy armour and by coal bunkers. As in British ships, all communications to the guns emanated from the transmitting station, with telephones being the primary medium and voicepipes as a fallback.

The T.S. contained two transmitting range clocks, one for main and one for secondary batteries. The ranges transmitted were received at the guns via F.T.P. receivers on the sight bars.

See Also

• Wikipedia

Bibliography

• Template:BibKoopSchmolkeGrossenKreuzer
• US Office of Naval Intelligence. Fire Control Systems, German Navy 1918-20, File R-3-C, Register 13826, dated Nov 9, 1920. Electronic copy courtesy of Keith Allen.

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