Several years before the appearance of Mr Harvey’s kite or towed torpedo, the CSS Hunley was originally intended to tow behind her a 90lb (41kg) explosive charge. Diving under the hull of the target, she was to tow the charge into contact with the ship on the side from which she had commenced her run, when it would be detonated. The target’s hull was intended to cushion the little submersible from the blast.
Because of difficulties with towing a large charge by a slow-moving submersible, with the ever-constant danger of their own charge coming into contact with Hunley and sinking her, the plan was changed to the definitive spar torpedo design which she used with success against the Housatonic.
In 1871 Captain John Harvey, Royal Navy (retired), wrote in a letter that he had been working on the idea of a towed torpedo for some ‘quarter of a century’, which would mean that he had begun in or around 1846, but that his nephew Commander Frederick Harvey had brought it to the stage where it could be deployed operationally. The idea took up from where Fulton left off. The explosive charge was contained in an otter board, of the type used by fishermen to keep open the mouth of their trawl net. It was towed beneath the surface suspended from a cork float. The towing cable was kept at an angle of 45 degrees to the course of the attacking vessel by a second line controlled by brakemen.
The principle was simple but daring. The attacking vessel streamed its Harvey torpedo, and at a safe distance the firing key was activated, to avoid the risk of the tow cable becoming entangled in the ship’s propeller, pulling the device into one’s own ship. The attacker passed to one side of the target vessel, so as to bring the Harvey into contact with the victim’s hull. A pair of firing levers was then depressed, exploding the charge. It was simple, it worked, and it was much less expensive than a Whitehead torpedo, of which the Harvey was a contemporary, all factors designed to ensure its popularity with the Admiralty and the Treasury. And it must be said that although there were certain risks, faced with the slow-firing big guns of the day, it was much safer than the even cheaper alternative, the spar torpedo.
Just as with fishermen’s otter boards, those of the Harvey were shaped so as to be handed port and starboard. This meant that their firing levers also had to be handed, those for the port torpedo being fitted on the right and vice versa for the starboard torpedo, as can be seen in the drawings. These and all others in this description are taken from Frederick Harvey’s Instructions for the Management of Harvey’s Sea Torpedo, which he wrote in 1871. The torpedoes themselves were constructed of seasoned elm 11/2in (38mm) thick, reinforced by external iron strapping. An internal case containing the explosive bolt was made of thick copper sheet. The torpedoes in the illustration are the ‘large’ model.
Even the large model was of modest size, being 5ft long × 6⅛ in wide × 1ft 8¾ in deep (1.524m × 155.6mm × 527mm). The exploding bolt could contain, among other explosives, either 60lbs (27.2kg) of compressed gun-cotton, 76lbs (34.5kg) of black powder, or 100lbs (45.4kg) of dynamite. For the more impecunious, Harvey also offered a ‘small’ model, the dimensions being 3ft 8in × 5in × 1ft 6in (1012m × 127mm × 457mm). It could carry up to 22lbs (10kg) of compressed gun-cotton, 27lbs (12.25kg) of black powder, or 35lbs (15.9kg) of dynamite.
The Harvey was tested against the turret ironclad HMS Royal Sovereign, and the results were excellent. For the first trials the target was anchored, and blank-fired her turret guns to verify how many shots she could loose off before the torpedo hit. With a towline of 300ft (91.4m), the steam paddle-wheel tug Camel scored ten hits out of ten, all below the waterline. With Royal Sovereign manoeuvring at between 8 and 9 knots, and Camel towing at 10–11 knots, again all six torpedoes streamed scored hits.
Despite these excellent results, the British Admiralty were reluctant to purchase large numbers of Harvey torpedoes, despite the vigorous support of Fisher. The reason was clear: the Whitehead was proving its effectiveness, and the fish torpedo was in a different class altogether. Nonetheless, the Royal Navy did purchase Harvey torpedoes and kept them on the establishment for over forty years. They could be fitted with electrical firing primers invented by Captain McEvoy in 1871.
The Russians tried a copy of the Harvey in action against the Turks, also with an electric primer, invented by Captain Menzing, a German. It appears that their towed torpedoes made contact with their targets, but that the electrical firing key failed every time.
The French adopted the Harvey, but considerably modified it at Boyardville after 1872, presumably in order to avoid paying royalties to Harvey. According to instructions first issued in 1875, practice in the French navy was to stream the torpedo closely behind the towing ship, then extend the control spar and draw the torpedo out on the beam when the enemy was in range, a curious arrangement which risked fouling the ship’s propeller. It was the favourite weapon for squadron action, and every large ironclad was equipped with a towed torpedo on each beam. It was felt that if an enemy vessel avoided an attempt to ram her, then one or other of the towed torpedoes would strike. The French discovered that the towed torpedo worked even better if the target vessel was under way, rather than moored, as her own motion drew the torpedo into contact with her hull.
By 1877 the French torpedo tactics had been brought to such a high level of efficiency that the commander-in-chief of the French navy commented that the ram and the towed torpedo ‘tended to neutralize each other; [the towed torpedo] is destined effectively to hold at bay any enemy who desires to use his ram.’ They kept them in front-line service longer than most navies. The Americans experimented with the Harvey, but did not retain them for long.
The Harvey was useful if employed as a complement to the ram when fighting heavily armoured ships. If you missed with the ram, which was more than likely, then one or other Harvey had a good chance of striking a mortal blow to the target. A stealthy attack at night, on an anchored or slow-moving blockading ship, also had a good chance of success.
Of course, in daylight, unless your own vessel was heavily armoured, to close to ramming distance or towed torpedo range was suicidal. And in a daylight fleet action, with numerous vessels manoeuvring to bring guns to bear or effect a ramming, to stream two volatile explosive devices, ready armed and primed, on each beam of your own vessel was highly hazardous. If your vessel was disabled, or lost steering, then it was just possible that a Harvey might be drawn against your own hull, with the exploder levers towards your ship.