HMS Polyphemus (1881)
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 HMS Polyphemus in dry dock |
|
| Career |  |
|---|---|
| Builder: | Chatham Dockyard |
| Laid down: | 1878 |
| Launched: | 15 June 1881 |
| Status: | Sold for breaking up 7 July 1903[1] |
| General Characteristics | |
| Displacement: | 2640 tons |
| Length: | 240 ft |
| Beam: | 37 ft |
| Draught: | 20ft 6 in |
| Speed: | 17.8 knots maximum |
| Endurance: | "capable of making a passage in any weather from Plymouth to Gibralter, or from Gibraltar to Malta at 10 knots without assistance"[2] |
| Complement: | 80 |
| Armament: | 5 x 14 inch torpedo tubes, 18 torpedos 6 x 1 inch calibre Nordenfelt machine guns, ram |
| Armour: | deck 3 inches compound armour, hatch coamings 4 inches, conning tower 8 inches |
HMS Polyphemus was a Victorian Royal Navy torpedo ram. A shallow-draft, fast, low-profile vessel, she was designed to penetrate enemy harbours at speed and sink ships anchored in it.[3] Designed by Nathaniel Barnaby as primarily as a protected torpedo boat, the ram was provided very much as secondary armament.[4] [2]
H. G. Wells’ fictional HMS Thunder Child from his novel The War of the Worlds may have been based on this ship.
Contents |
[edit] Design
The Admiralty set up the "Torpedo Committee" in 1872 to examine ways in which the newly invented Whitehead torpedo could be launched at sea. The Royal Navy's first purpose-built torpedo launching ship was HMS Vesuvius, which, with a maximum speed of less than 10 knots, was intended to stealthily approach within a few hundred yards of enemy ships at night to launch her torpedoes. Leading on from this, Barnaby and his assistant J Dunn, proposed in the mid-1870s a fast cigar-shaped vessel with five submerged torpedo tubes and protected by 2 in armour over the deck. The design was modified in late 1875 into a larger vessel equipped with a ram. Early in 1876 the design was modified again into a 240 ft long unarmoured torpedo ram with a top speed of 17 knots. Later the design was modified yet again to have armour added to the exposed steel deck. [5]
The ship was equipped with a 250 ton cast iron keel which could be released in an emergency to increase the buoyancy of the hull. It was held in place by two spindles which both had to be turned to release the keel and which were tested fortnightly.
The ship was equipped with twin boiler and engine rooms, and a low turtle-back hull which was almost submerged when the vessel was travelling at speed, and had a normal bunker capacity of 200 tons of coal, and 300 tons maximum.
[edit] Armament
[edit] Torpedo tubes
The ship had five submerged 14 inch diameter torpedo tubes, and carried 18 Mark II torpedoes. With a range of just 600 yards, these had a 26 pound guncotton charge and a speed of 18 knots; only marginally faster than Polyphemus.
[edit] Ram
The centre torpedo tube was fitted with a combined cast steel bow cap and ram. It hinged upwards to open, and considerable effort went into selecting the best hydrodynamic design through model testing since its size and location were found to have a major impact on the ship’s performance. It had the same effect on Polyphemus’ hull as the bulbous bow fitted to many modern ships. [5]
The bow also had a balanced two-bladed rudder fitted into it, which could be retracted into the hull, that allowed the ship to be maneuveable when going astern. It also slightly reduced the diameter of the turning circle (by 12 percent) when the ship was moving forwards. [5]
[edit] Other innovations
The ship was the first Royal Navy vessel to be fitted with 80 volt electric lighting. [5] This was adopted by the Royal Navy in 1882 following a fatal electrocution aboard HMS Inflexible, which had an 800 volt circuit.
The vessel was fitted with a flying deck which housed the bridge and machine guns. It was designed so that if the vessel sunk it would float off as two sea-worthy rafts.[2]
[edit] 1885 Berehaven trial
In 1885 the ship undertook a simulated attack on a fleet at anchor at Berehaven. The principle object of this was to test tactics for a possible attack on Kronstadt Harbour in the event of the threatened war with Russia. Booms and nets (to catch propellers) were laid across the channel behind Bereshaven, along with small observation mines and the area covered by machine guns and torpedo boats. Polyphemus launched a simulated attack on 30 June, evading around ten torpedoes fired by 6 torpedo boats during her 2 mile run-in and easily smashed through the booms and a 5 inch steel hawser holding them in place.
Despite this success, no similar vessels were ordered by the Royal Navy, possibly because the development of quick traversing and quick firing guns as she entered service had rendered the concept behind her design less practical. [4] When she was designed, the only guns capable of penetrating her armour were too slow to train and fire to have much chance of hitting such a fast moving ship, but by the time that she entered service a few years later this was no longer true.
[edit] Footnotes
- ^ J. J. Colledge, Ships of the Royal Navy, Greenhill Books, 1987.
- ^ a b c John Beeler. Birth of the Battleship, British capital ship design 1870-1881, 151-152. ISBN 1-86176-167-8.
- ^ Richard Hill. War at Sea in the Ironclad Age. Cassell and Co, 189. ISBN 0-304-35273-X.
- ^ a b David Lyon (1980). The Ship - Volume 8 - Steam, steel and torpedoes – The Warship of the 19th Century. Her Majesty’s Stationery Office, 49-50. ISBN 0-11-290318-5.
- ^ a b c d David K. Brown (2003). Warrior to Dreadnought, Warship Development 1860-1906. Caxton Editions, 84. ISBN 1-84067-529-2.
