Polyphemus-class Torpedo Ram, HMS Polyphemus (1881)

nathanclawfish · July 20, 2023, 12:30am

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Polyphemus-class Torpedo Ram, HMS Polyphemus (1881)

Vehicle design and history:

In 1872, the admiralty set up the “Torpedo Committee”, to examine ways in which the newly invented Whitehead torpedo could be launched at sea. The first ship built for this testing was HMS Vesuvius, which was the first purpose built torpedo launching ship in royal navy service. The ship was designed to have a maximum speed of less then 10 knots, and it was intended to stealthily approach to a couple of hundred yards of an enemy ship at night and launch her torpedoes. As a follow up to this design, Barnaby and his assistant J Dunn proposed a fast, well armoured cigar-shaped vessel, carrying 5 submerged torpedo tubes. This design was then further modified into an even larger vessel with a ram, with the final design being a 240ft (73) torpedo ram with a top speed of 17 knots. Interestingly the ship was equipt with a 250 ton, cast iron keel, that could be detatched in an emergency to increase the buoyancy of the hull, which was controlled by the turning of two spindles. This vessel would be powered by a pair of boiler and engine rooms, protected by a low turtle-back hull, that meant that almost the entire hull was submerged when the vessel was travelling at speed.

In terms of weaponry, the ship posessed 5 submerged 14-inch-diameter torpedo tubes, which could fire the 18 MK ii torpedoes carried on board. These torpedeos possessed a limited range of just 600 yards, and travelled at 18 knots, which was only slightly faster than Polyphemus herself. The centre torpedo tube was fitted under the combined cast steel bow cap and ram, which hinged upwards to open, meaning much experimentation was required to establish the best hydrodynamic design, since this would cause a major impact of ships performance. This testing with models resulted in Polyphemus possessing a bulbous bow very similar to those fitted on modern cargo ships. The bow was also fitted with a two-bladed rudder, that could be retracted into the hull, allowing the ship to be more manouverable in turns as through testing the ship was found to have a 12% smaller turning circle with the retractable rudder deployed. In addition to the torpedos, the ship was also fitted with 6 twin barreled Nordenfelt 25mm automatic guns, though later these were replaced by single Hotchkiss 3-pounder (47mm) quick-firing guns. In terms of armour, HMS Polyphemus possessed an armoured deck of 3 inches (76.2mm) of armour plate.

Two other interesting footnotes are the fact that HMS Polyphemus was the first Royal Navy vessel to be fitted with 80-volt electric lighting, following a fatal electrocution aboard HMS Inflexible, which had an 800-volt circuit. And that the ships flying deck which housed the bridge and machine guns was designed to detatch if the vessel sank, giving it two additional sea worthy rafts.

Service history:

Hms Polyphemus was ordered on the 5th of February 1878 and was laid down on the 21st of September 1878 at Chatham Naval Dockyard. She would ultimately be launched on the 15th of june 1881, and would be complted in september of 1882. Initially there were plans to have a second ship to the same design, under the working name HMS Adventure, but this was ultimately cancelled. Eager to test the new design, the ship undertook a simulated attack on the fleet at anchor at Berehaven in 1885. The principle of the attack was to test if the tactics would be viable for an attack on Kronstadt harbour, in the event of a war with russia. Boons and nets designed to catch propellers were laid across the channel, along with observation mines, and coverage by machineguns and torpedo boats. Polyphemus launched her attack on the 30th of jne, evading ten torpedoes fired by 6 torpedo boats, and managed to complete her two mile run in and easily smash through the boons and the 5 inch steel hawser holding them in place. Despite this success, the ship was an evolutionary dead end, as the development of quick traversing and quick firing guns had rendered the concept of a torpedo ram redundant, as previously the only guns that would have been able to track her were not capable of penetrating her armour. Becuase of this Polyphemus was assigned to the mediterranean fleet, before ultimately being paid off in january of 1900, after which she was employed as a tender for HMS Defiance, before shortly afterwards being scrapped.

Specifications: