One alternative was to fit the canoe with outriggers so that it could be rowed in the conventional manner with oars. This method was favoured in some quarters, especially in the Far East, where a simple design that could be fitted easily to a canoe was developed and tested at the Force 136 base at Trincomalee in Ceylon. It was claimed that a greater speed could be attained with less effort than with paddles.
A further possibility was to achieve propulsion using electric motors. A silent, electrically propelled canoe with a flexible drive was developed and put into production. This was the forerunner of the Sleeping Beauty to be described later. In remote areas it was possible to make the final approach by canoe fitted with an outboard petrol motor, but it was essential that the approach be made as silently as possible and the Engineering Section devoted considerable effort to the silencing of outboard motors but without great success.
The Budig Apparatus
An altogether novel method of propulsion was also investigated. Some time before the war, Ogston had seen in action on the Isis at Oxford a canoe being propelled by a most unusual and somewhat ‘Heath Robinson’ apparatus. The canoeist appeared to be rowing with the conventional to and fro strokes but no oars appeared above the water. It turned out that the canoe had been fitted out with a device invented by the German aeronautical engineer Friedrich Budig in the 1930s. This made use of the force generated by plunging an aerofoilshaped wing up and down in the water in a flapping motion. Indeed it relied on the same principle as bird flight, but underwater. Outline details had been published in the journal The Aeroplane in December 1935 and illustrated the basic principle and its practical application.2 The Engineering Section at Station IX was given the task of reproducing this device based on the limited information available. The mechanical problem was that of devising a linkage which converted a to-and-fro rowing action into an up-and-down motion. After a good deal of experimentation, a ‘Budig Apparatus’ was constructed and subjected to functional trials which were promising. Since the ‘wings’ did not break water the movement was nearly silent. But it turned out that the design imposed severe stress on some of the components which, during the user trial (see later) at Fishguard, failed. Assessment indicated that although redesign might overcome these shortcomings, this would take some time and the project was shelved and later abandoned.
Attack by Underwater Swimmers
Another procedure, developed and exploited originally by the Italians, for the final stages of approach and attack, was the use of underwater swimmers wearing wet suits and breathing apparatus and carrying explosive charges. They were often dropped from surface craft or a submarine some distance from the target and were usually expected to make their way ashore after the operation, where they were taken care of by local agents. They were called ‘Gamma assault frogmen’ and often participated in operations with Maiale (or SLCs), piloted torpedoes, whose two drivers were also frogmen. The Maiale were brought to the area of operations on the casing of a conventional submarine. When launched, the two drivers, sitting astride the torpedo, piloted it to the target to which they attached explosive charges with time delays. They then swam to a support vessel or to the shore. This technique was hazardous and casualties among the crew were high. But they carried out a number of attacks around Gibraltar in 1940– 41: their greatest success was in severely damaging HMS Queen Elizabeth and Valiant in Alexandria harbour in December 1941.
The idea of using frogmen for SOE operations (they were already in use by the SBS of the Commandos) was considered and the possibility of dropping swimmers by parachute was assessed. Preliminary experiments carried out by Blount showed that it was a feasible although highly hazardous operation; it is not thought that it was ever used in anger.
The Welbum
In certain circumstances, especially in warmer waters, it was envisaged that explosive charges might be carried by swimmers over considerable distances. The need was foreseen for some auxiliary source of power to enable the limit imposed by human endurance to be exceeded. In 1943 this led the enterprising engineers at Station IX to design and develop a bizarre invention, farcically named the Welbum. This was an electrically driven attachment for swimmers.
The device was intended primarily for use by a parachutist dropped into water, but it could also be used from a Folboat or other small surface craft. It consisted of a streamlined metal container housing an electric motor and batteries and fitted with a propeller. The device, which weighed 60 lb (27 kg) in air and was neutrally buoyant, was fastened by a suitable harness to the swimmer’s back.
Under the more prosaic name ‘Motorisation of Swimmer’, a preliminary model was tested and demonstrated at Station IX in March 1943. Within the limited test facilities available at The Frythe the swimmer was reported to be comfortable and to have acceptable control of the device. It propelled a man silently at 1½ knots but a new model was to raise this to 2½ knots. It was reported that the drag of the waterproof suit was greater than anticipated.
The new model was tested at Staines reservoir where it took an hour and a quarter to cover two miles in fairly rough water and it was estimated that the batteries would have propelled it another quarter of a mile. A lighter case was made to compensate for heavier batteries and future models were forecast to complete an hour’s run at 2– 3 knots.
Although it had been relatively easy to control in the still water of the Welwyn test tank, in the open water of Staines reservoir the Welbum was much more difficult to handle. George Brown, who conducted the user trial, reported that it was almost impossible to maintain a straight course and to prevent the swimmer from going round in a series of circles, especially when kitted out in the shallow water diving suit. It was, he said, an unpleasant experience made worse by the thick algae and mangy fish in the reservoir.
In June it was reported that tests conducted with the Welbum fastened to a simple paddleboard considerably improved its performance, increasing its range to 5 miles and its speed to 2½ knots. Furthermore, the board used in these trials supported not only a man weighing 184 lb (83 kg) dressed in a waterproof suit, but also eight limpets, a Sten gun and its magazine. The man, it is claimed, suffered no inconvenience from the cold. Station IX was still enthusiastic and plans were afoot to conduct parachute jumps with the Welbum.
At the end of June it was announced that the Welbum could be put into production if there was a demand for it, but then SOE Council decided to hand over the design to the War Office as it was seen to be of more use to the Airborne Forces.3 Nothing further was heard of this device: a bright idea but perhaps ahead of its time?
It is interesting that the same basic concept resurfaced in December 2001 with an advertisement in a Sunday newspaper for the ‘Personal Propeller’ for use by snorkellers and scuba divers. Weighing 66 lb (30 kg) it is powered by a battery giving a speed of 2 knots and a duration of 50 minutes after a charging period of 10– 12 hours. Whether its handling is an improvement over the Welbum is not known.
Chariots
The German battleship Tirpitz, which was lurking in the safety of Trondheim Fjord, remained a serious threat to Allied shipping in the critical period 1941– 42. It had to be prevented from breaking out into the Atlantic as had the Bismarck in February 1941. This blockade tied up a considerable proportion of the Allied naval forces. A major proposal was to use underwater attack by frogmen, and this led to the development of the Chariot series of piloted torpedoes. They resembled the Italian SLC in that they depended on the use of frogmen carried on the outside of a conventional submarine to within swimming range of the target. The craft were then launched, charges laid and the frogmen withdrew to safety.
The first Chariot operation against the Tirpitz, Operation Title, was planned and commanded jointly by Admiral Sir Max Horton, Flag Officer (Submarines) (FO(S)) and Lt Col J.S. Wilson, Head of the Norwegian Section of SOE. Horton had been associated with submarine development since the First World War. As Captain of the 2nd Submarine Flotilla in 1923 he was involved with th
e ‘Devastator’ project – a proposal somewhat like the Chariot.4 Two Chariots were shipped across the Norwegian Sea on board a Norwegian trawler, the Arthur, in October 1942. They were then hoisted out and secured beneath the hull of the trawler for the passage up the fjord to the Tirpitz. German security checks were passed, thanks to the forged papers provided by SOE, and the Arthur was given a permit to enter the security zone around the battleship. Unfortunately, a severe storm caused the Chariots to break loose and sink. The crews, with one exception, made their several ways through SOE-organised escape routes to Sweden.
Subsequently, several operations in the warmer waters of the Mediterranean yielded partially successful results. The failure of some of these operations could be attributed to the exhaustion of the charioteers and the effects of breathing pure oxygen for too long. In the end, the main use of Chariots was for beach reconnaissance. Undoubtedly the lessons learned from experience with Chariots influenced the design of the next generation of underwater equipment.
X-Craft
At the same time, the British X-Craft was being developed. They were essentially midget submarines carrying, in place of torpedoes, two large explosive charges, one on either side of the hull. It was envisaged that they would carry divers who could fix additional charges or cut holes in the protective nets and clear obstacles around a target. For this purpose they were fitted with ‘wet and dry’ compartments through which a diver could leave and re-enter after completing his task. Since they had a range of 1,300 miles on the surface using a diesel engine, or 85 miles underwater using electrical propulsion, the mother ship did not need to remain in the vicinity but could withdraw to a rendezvous at a safer distance. The X-craft were towed to within reach of the target by a conventional submarine. When close to the target the passage crew of three exchanged places with an operational crew to which was now added a diver.
The first X-Craft were ready for initial trials in March 1942 and they were in production by January 1943. But it was not until September 1943 that, using six X-Craft to mount Operation Source, two were successful in seriously damaging the Tirpitz, which put it out of action until the RAF could finish the job. However, the casualties were high and success was only achieved by the courage of the crews. Full accounts of this operation which are available elsewhere emphasise the hazardous nature of underwater warfare.5
X-Craft were also used in an attack on Japanese warships at Singapore in July 1945 using one large side-charge and a series of limpet mines fixed by divers. The net cutters were used by the divers to sever the Saigon– Hong Kong and Saigon– Singapore communications cables. Again, the severe stress of working underwater for many hours breathing oxygen left the crews in a state of near-collapse and led to the deaths of two crew members during an operational trial.
The Welman One-man Submarine
The serious threat imposed by the Tirpitz had led to widespread concern in the highest military circles, and it is not surprising that SOE, which had provided some back-up for the failed Operation Title, should have given serious thought to its own possible involvement.
Some months earlier, consideration had been given to the use of submarines for the infiltration of agents and stores. The improvement in the availability of aircraft in 1941 led to this idea being left in abeyance. The possible use of submarines was reconsidered later in 1942 in response to the Tirpitz problem. Information from the Naval Intelligence Department (NID) and (NDC) was passed to the SOE Technical Planning Section who put forward a proposal to Lt Col Wilson of the Norwegian Section for the use of one-man submarines for an attack on the Tirpitz. This proposal was later to form part of the operational plan code-named ‘Frodesley’.
Financial sanction for the princely sum of £3,000 enabled work on the first Welman (as the one-man submarine was called) to go ahead in March 1942. The project was taken over by Lt Col Dolphin, the assertive Head of the Engineering Section, who despite his name was more used to designing coal-cutting equipment than submersibles.
The Welman was the largest project to be undertaken by SOE’s research and development team. It also happens to be the best documented and yet the least understandable. For an essentially land-based clandestine sabotage organisation to have become involved with midget submarines may seem on the face of it highly unusual until one considers the wide-ranging originality of thought exhibited by the engineers and scientists at Station IX.
The initial suggestion by two Norwegian members of SOE was for a super-silent underwater vessel to be propelled by pedal-power and towing a magnetic 600 lb (272 kg) delayed-action charge. It is interesting to recall that the concept of a pedal-driven underwater craft was not by any means new. In 1776 the American States in revolt used such a craft (the Turtle) in an unsuccessful attempt to attack Lord Howe’s flagship HMS Eagle in New York harbour with a 150 lb (68 kg) charge of gunpowder.
Although the general shape of the hull proposed by the Norwegians was sound and, in fact, was retained in the initial models, the idea of pedal-power was considered impractical and dropped. The towing of the explosive charge presented directional and depth control problems so alternative ways of carrying it were under consideration while the initial craft was being constructed. The hull was made in two parts, an upper and a lower, with a longitudinal weld holding them together. The conning tower was only just wide enough for a man to move through and had a series of portholes intended to give sufficient visibility when surfaced. Inside the hull, the single seat was from an Austin 7 motor car, one of the cheapest popular vehicles of the prewar era, while the novel single rudder and hydroplane control was by means of a joystick, reputedly salvaged from a crashed Spitfire. The do-it-yourself theme was continued with the 2.5 hp electric motor, which was said to have come from a London trolley bus – a double-decked vehicle running on normal tyres but with a spring-loaded electrical pick-up boom contacting overhead wires.
The initial craft was not capable of carrying an explosive charge on its bow as the hull came almost to a point both fore and aft. Later models were 20 ft long with a blunter bow designed to eventually carry a 495 lb (225 kg) warhead. Complete with explosive charge the craft weighed 5,240 lb (2382 kg). Its operating depth was 75 ft and its endurance was ten hrs at 2.5 knots. The electric motor, its sole means of propulsion, was powered by a 40-volt, 180 amp hr capacity battery of accumulators, but this was later increased to 220 amp hr. NiFe accumulators were used as these could be sealed to avoid acid spillage or chlorine poisoning as well as minimising the creation of hydrogen gas pockets with their explosion risk. Initially, the trim when submerged was achieved by the simple expedient of hand-moving a 300 lb (136 kg) sliding weight fore and aft but the difficulty of doing this in the highly confined space was soon apparent and later versions used compensating tanks with trimming by pump. Port and starboard ballast tanks were blown by compressed air but flooded by means of a hand lever.
The crewman, referred to as ‘the driver’, sat in the cramped cockpit amidships on his car seat wearing a face mask fed from an oxygen cylinder beneath the control panel, with a duration of 10– 14 hours. To improve the atmosphere within the very restricted space, there was a tray of Protosorb CO2 absorption crystals, sufficient to purify the air for ten hours.
The rudder and single hydroplane formed a common unit at the stern operated by a highly innovative single-column control. The pump for the bilges and the trim tanks was foot-operated. A compass, barometer, ammeter, voltmeter and depth gauge made up the control panel. There was no periscope, an omission which was later to be regretted, visual navigation being catered for by fitting the conning tower with six armoured glass ports. Dolphin was not, of course, experienced in the design of submersible craft. Neither was he amenable to even constructive comments about his ideas. When he insisted that the Welman should not have a periscope it might have been because of the severely restricted space beneath the conning tower; or the problem of leakage; or uncertainty as to whether control would be precise enough to maintain periscope depth for a
useful length of time; or even on grounds of cost saving. Or perhaps he saw the vessel as a very basic and expendable weapon which in many ways it was. The initial estimate from Davies to the Head of Operations Section, Brig Gubbins, was that it would take six weeks to construct a Welman. The astute Gubbins expressed his misgivings at this optimistic time-scale.
Word of the construction of Welman 1 reached the Admiralty and Flag Officer (Submarines), FO(S), Admiral Horton expressed an interest and visited Station IX to see things for himself. Horton, an experienced First World War submariner, was obviously impressed because he sent Submarine Officer Lt Cdr Hall on attachment to act as adviser. They were not convinced that it would be a practical vessel but thought it might well give useful experience for the design and construction of other offensive weapons. They were curious about the novel features of this craft, such as the stressed-skin construction and the joystick control for the hydroplanes and rudder, which both reflected aircraft design practice. However, there is a report that certain features were redesigned following the failure of a (fortunately unmanned) Welman at 100 feet during a depth test. It was now planned to carry the explosive charge on the bow of the submarine. This would be equipped with two arrays of powerful magnets to hold it against the steel hull of its target and an anti-handling device to dissuade the enemy from removing it before its time delay had run its course. Work on the tricky problem of exactly how to attach it and release it safely had not yet been resolved. As an alternative to a purely offensive role, consideration was given to converting the casing for the explosive charge into a container for 600 lb (272 kg) of stores to be released when submerged, but this idea was not pursued. Further Admiralty interest was shown by two visits to Station IX by Admiral Renouf, Professor Blackett of Admiralty Scientific Research, ‘D/Navy’, Commander Simms, and by engineering personnel from the Department of Miscellaneous Weapons and Devices (DMWD) to discuss navigation and fittings. What they thought of this vessel being designed by an Army mechanical engineer is not recorded.
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