But all this was intended to cover her real function, as a fast, armoured torpedo ship, intended to be able to break into a defended harbour such as Cherbourg or Kronstadt, and then spin round inside, firing and reloading her five underwater tubes, creating mayhem among the unprepared enemy ironclads. The ram, once its cast-steel rotating bow cap was closed, would be useful in finishing off any vessel which had not immediately sunk. Taking advantage of the general chaos her action had caused, she would then attempt to escape at high speed. In any case, as with all torpedo boats of the era, even the Polyphemus was considered expendable, and her designers had built in lifesaving features to succour her crew. Risking a 2600-ton ship in the hope of crippling the enemy battle fleet was a good trade-off. For Polyphemus in action at Berehaven, see Part III.
The sectioned profile shows her retractable twin bow rudders, the shaft for opening the bow torpedo tube cap, the torpedo storage and her broadside submerged torpedo flat. The piping to drain all five torpedo tubes for reloading is included. In addition to the swivelling cast steel cap, the bow torpedo tube was also protected by a sluice gate, in case of damage to the cap during a ramming attack. The bow rudder layout pioneered by Polyphemus was to reappear some thirty years later on German torpedo boats and destroyers, although the retracting feature was not copied.
In the plan view it is clear that the broadside tubes split horizontally to open, as there is insufficient space behind the tubes for a rear door, as was fitted on the bow tube. The broadside tubes are sealed against the outside seawater by horizontal sluice gates, while the bow tube is protected by an internal vertical sluice gate. The torpedo warheads are stored in a separate torpedo magazine. Note how, as the beam reduces, the forward torpedo tubes are angled. On the original plan was written the torpedo magazine capacity:
Torpedo Heads War allowance 24 Torpedo Heads Peace allowance 18 Cases for Torpedo Gun Cotton Charges 5 Cases for Damp Gun Cotton 15 Cases for Dry Gun Cotton 9 Cases for 20 Empty Primer Tins 1
Interestingly, although the ship’s plan has been amended to show the modifications to Polyphemus, and in particular her new 3pdr (47mm) QF guns, the part of the plan detailing the contents of the small arms magazine lists the following:
Nordenfelt Ammunition Boxes 110 Nordenfelt Hopper Boxes Double 4 Nordenfelt Hopper Boxes Single 6 Gardiner Ammunition Boxes 12
In other words, when she originally went to sea, she carried Gardiner machine guns, probably in .45-cal, as well as the 1in Nordenfelts in their pillbow turrets.
As a footnote, it is generally held that HMS Polyphemus was the inspiration for H G Wells’ HMS Thunderchild in his science fiction novel War of the Worlds.
Hood had completed with two underwater 21in torpedo tubes, forward of A’ turret, despite the director of naval construction noting on 10 December 1918 that it would be difficult to envisage launching the underwater torpedoes at the high speed of which the Hood was capable. Nevertheless, the underwater tubes were not removed until 1927, leaving her with the four above-water tubes and mounting points for four more in time of war.
The plan view shows the fine lines of these battleships up forward, presumably to try to offset their modest engine power imposed by the tonnage limitations of the Washington Treaty.
The torpedo areas were certainly an exposed battle station — the armour belt and the torpedo defence system ended abreast ‘A’ turret. Between ‘A’ turret magazines and the torpedo body room with its highly explosive contents, the designers had wisely placed the cold room and its supplies of meat and other perishables.
At least the torpedo-men on Nelson enjoyed overhead protection after 3in (76mm) armour plates were worked in above the torpedo body room and the torpedo tube compartment during a refit in 1937–38. Rodney never received this extra protection. The torpedo body room where the tubes were loaded was separated by a watertight bulkhead from the actual torpedo tube compartment with the horizontal sluice gate and the launch controls. This was an attempt to limit the possibility of major flooding to a single torpedo flat, as had occurred during the Great War.
From the plan it does not appear the tubes were provided with a spoon (or ‘bar’ in RN terminology), as they were practically bow tubes requiring very little gyro angling for straight ahead launches. The torpedo warheads were stored below the torpedo body room.
When HMS Nelson was mined on 4 December 1939, the torpedo spaces were flooded, but were otherwise undamaged. However, when she was in action against Italian aircraft on 27 September 1941 she was hit on the port side forward by an 18in torpedo, and the torpedo body room and ten of the twelve torpedoes she carried were wrecked. Luckily, the captain had ordered the torpedo-men to evacuate the spaces before the torpedo hit.
Obviously, since the crews loading submerged torpedo tubes were out of sight of the enemy they were fighting, some means of directing torpedo launches had to be devised. Just before the start of the Great War, but for different reasons, the old system of individual firing and spotting of the big guns of a battleship’s main armament gave way to director-control firing, feeding data from rangefinders and observers into a mechanical computer in the transmitting station.
The same system was applied to controlling torpedo launch. The Iron Duke, Jellicoe’s flagship at Jutland, had the latest and most elaborate system to control her underwater torpedo tubes. A torpedo control tower with its own 15ft (4.5m) rangefinder in the rotating hood was situated in front of ‘X’ turret. A repeater indicator from the Forbes log gave the ship’s speed. Other instruments in the control tower were used to estimate the enemy’s range, course and speed, and the torpedo deflection necessary to hit the enemy where he was likely to be when the torpedo arrived.