Neptune Class battleship - HMS Neptune

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The name Neptune[edit]

There have been nine ships in the Royal navy with the name Neptune, named after Neptunus ; the Roman god of the sea. The Dreadnought battleship Neptune being the eighth ship to carry the name

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Circa 1909 image of HMS Neptune, the flying bridge decks ( Marble Arches) over the two midship turrets ( P & Q) can be clearly seen. Picture courtesy of Wikipediea

Class information[edit]

A follow on design to the St Vincent class there was originally meant to be three ships of the Neptune class but a change to the armour scheme on the last two ships resulted in them being quite different from the Neptune , hence the single ship Neptune class and the two ship Colossus class ( Colossus and Hercules ). Neptune was the first capital ship in the Royal Navy to use super-firing where one main turret is placed on the centre-line above another turret, this produces a compact pair of turrets taking up less length in the ship needing less weight of armour for protection, an added gain is that both turrets can also fire on either beam. One of the great concerns was that muzzle blast from the upper turret could adversely affect the lower turret, a great concern in days when the guns were fitted with open sighting hoods, to prevent damage to the lower turret ‘Y’ by ‘X’ turret firing astern by ‘X’ turret was limited to no closer than 30 degrees from right astern. Another feature of the Neptune was the midships turrets P and Q, on all previous British Dreadnoughts these were placed one abeam of the other and they could then only fire on their own side of the ship, on the Neptune they were staggered ( En Echelon) along the length of the ship allowing limited cross-deck firing and in theory a ten gun broadside. Although some length was saved by having x and Y turrets arranged for super-firing the en echelon arrangement of the two midships turrets, p and Q took up a lot more space than the old abreast layout. To combat this a a novel way of fitting the ships boats was devised, this consisted of a flying bridge type deck between the forward and aft deck houses, nicknamed the ‘Marble Arches’ after the RN offices of that name due to their arched appearance, they were not a good idea, the fear was than in battle they could be damaged and drop onto the gun turrets below disabling them.

Building data[edit]

Built by the Portsmouth Royal Dockyard she was ordered under the 1908 Naval estimates and was laid down on the 19th January of 1909 and was launched on the 30th September 1909. She commissioned in January 1911, her building costs were £1,668,916

Basic Details[edit]

L 546’ B 85’ Draft 27’ to 31’ Displacement 19,900 tons Standard to approx 23,100 tons full load, Crew 810 to 820 men.


Machinery : Quadruple propellers driven by Parsons direct drive steam turbines in a more or less identical layout to the Dreadnought with the exception that no cruising turbine was fitted, instead an extra stage was fitted to the High pressure turbines, this was separated from the main turbine by a by-pass valve. As in the Dreadnought, Bellerophon and St Vincent classes the high pressure turbines drove the outboard propeller shafts and the low pressure turbines the inner shafts developing just under 26,000 SHP on trials at about 345 Rpm giving a maximum speed of 21.5 knots , normal power was 25,000 HP for 21 knots, slight more power than previous classes to compensate for the slightly larger hull and higher displacement. Steam was provided by eighteen Yarrow boilers arranged in three groups essentially coal fired they were however fitted with oil sprayers to permit faster raising of steam. Steam pressure was 235 psi with a heating surface of 63,414 square feet Bunker capacity was 2,800 tons of coal and 940 tons of oil, consumption at full speed being in the order of 360 tons per day, range was about 4,000 miles at 18 knots rising to 6,300 miles at 10 knots


Main battery Ten 12” C50 Mk11 guns in five twin turrets The New weapon was not a success, now fifty calibres in length the longer barrel was designed to give higher muzzle velocities and thus greater range and hitting power, it used a larger propellant charge of 307 lbs against the earlier 12” guns 258 lbs of MD size 45 cordite. The larger charge did not always burn correctly within the barrel length resulting in a very poor shell spread pattern, also the higher pressures within the gun barrel , something akin to 20-22 tons per square inch, caused serious wear and thus the guns only had a working life of around 220 rounds. Shell weights were the same for the earlier 12 “ guns at 850 to 859 lbs the range was around 21,000 yards at 15 degrees elevation against 19,000 yards for the C45 guns of the earlier classes. From new Neptune was designed for, and fitted with, a main battery gun director, still in it's infancy this was more an experimental design and used for trials purposes.

Secondary battery At last the Idea of mounting the secondary battery on top of the main turrets had died a death and all the secondary armament was mounted in the deck houses, sadly 16 of rather useless 4” guns were fitted largely in case mates. A further four 3 pounder guns were fitted Torpedo armament Three 18 inch submerged torpedo tubes were fitted, one on either beam and one firing astern.

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The above image scanned from an elderly admiralty manual is of the Hercules but the gun layout of the Neptune was identical, the main turret ID is 'A' forwards, 'P' to port and 'Q' to starboard of midships the 'X' and 'Y' aft. P & Q could traverse inboard to fire across the deck to the opposite beam but this risked serious blast damage to the decks beneath the guns from muzzle blast, this was most marked at low elevations.

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Armour Protection[edit]

Essentially the armoured protection scheme remained very similar to the Dreadnought and apart from minor differences was essentially that of the preceding St Vincent class. The main belt was 10 inches tapering to 8 inches on the lower belt and although of Krupp cemented armour (KCA) this was rather inferior, it was also not carried high enough allowing plunging fire relatively easy access over the top of the belt to the weak deck armour. The armoured bulkheads closing off the citadel were of 8 inches KCA forwards and 5” KCA aft The fore and aft torpedo bulkheads were still set rather too far inboard and were really magazine screens rather than true torpedo bulkheads these ran from the forward end of the forward magazine to the aft end of the after magazine, thickness varied between 1 to 2 inches with 3 inches in way of the mid-ships p and Q turrets.. The decks were all of Krupp Non Cemented Armour ( KNCA), the upper-deck being ¾. “ The main deck 1 ¾. Inches Middle deck 1 ½. Inches increasing to 3 inches as special protective screens over the magazines , boiler and engine spaces. The gun houses ( turrets) had 11 inch faces and 4 inch roofs all KCA , the forward control tower had 8 inches of KCA and it’s communications tube 5 inches of KCA , whilst the figures for the aft tower were 4 inches also KCA.

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Scanned from an old admiralty manual this is the ouline of the Colossus and although the interior schemes were quite different the exterior belts were alike enough to give a good idea of the way the armour was provided.

Service History[edit]

Neptune ran her acceptance trials in November 1911 and failed to meet her designed speed, her maximum recorded speed being 21.129 knots. In may 1912, working up completed, she became the commander in Chief Home Fleet’s flagship joining the 01st Battle Squadron ( BS). Her first major refit was from December 1914 to March 1915, in april 1916 she suffered minor damage when involved in a collision with a merchant vessel. She was still with the 1st BS at Jutland on the 31sy May 1916 being in the 5th division led by Rear Admiral Gaunt in the Colossus, followed by Collingwood, Neptune and St Vincent. Neptune’s first action during the battle came at 1840 when the St Vincent which had been masking her view moved aside and a German battleship appeared very indistinctly in the mist, two salvo’s were fired but they fell well short. At 1903 (approx) she was forced to turn of line by torpedoes fired by the German 3rd. Destroyer flotilla (DF) around this time she briefly sighted the disabled German light cruiser Wiesbaden and fired a single salvo of 12” at her, Wiesbaden was under fire from a large number of the British battle-fleet and the numerous shell splashes round her made it difficult to tell the fall of shot or if she was hit. At 1910-11 Neptune sighted the Derfflinger and opened fire at a range of 11,000 yards this went over, range was reduced by 800 yards and a straddle was achieved with the following salvo, hits were claimed on the next two salvoes but she cannot be credited with any hits owing to the confusion of who was firing at who at the time, during this engagement she took further avoiding action when three torpedoes were seen. Sometime around 1914 she sighted a number of German destroyers and engaged these with both her 12” and 4” batteries, in all Neptune fired 48 rounds of 12” , 21 being Common Percussion capped at the Derfflinger and 27 HE at the destroyers and Wiesbaden , she also fired 48 rounds of 4” this being the highest number from these useless weapons apart from the Temeraire which fired 50 rounds. Neptune was undamaged and did not receive any casualties in the action. Post Jutland she remained with the 1st BS on routine patrols and manoeuvres , in June 1916 now superceded by the 13.5” gunned super-dreadnoughts of the Orion and Iron dukes classes she transferred to the 4th BS on largely inferior roles. Post war she went into reserve in February 1919 never re-commissioning she was sold and scrapped in September 1922

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This picture from the port quarter of Neptune shows another unique feature of the classes fitted with the flying bridges, the boats stowed on these structures needed perculiarly long boat davits, a pair of which can be clearly seen in this picture. In view alongside are a couple of pulling boats and two steam pinnaces Picture courtesy of Maritime Quest


Bibliography: IWM, Jutland – John Campbell, Jutland - Geoffrey Bennett, Wikipedea - Picture of neptune

Article completed by Steve Woodward 17th October 2007