The Hemlington Nautical History Society

THE WELFREIGHTER 37ft SUBMERSIBLE.

From Dustcarts to Mini Subs.

While looking into the mini submersibles I thought it might be interesting to look at some of the British ones as well.  We are deeply indebted for the kind co-operation and help of Tom Colville who has meticulously researched the Welfreighter, and is the webmaster of the excellent site sited at the bottom of this page. And also Brian Carpenter as without their help this article would not have been possible. It is therefore recommended that anyone who has an interest in this topic contact Tom directly and visits his site.

There were many types of mini subs manufactured, most under the scrutiny of the RN and Admiralty.

And while the mini submersible I am going to explain here was tested under the Admiralty the design originated within the Inter Service Research Bureau (ISRB), which was a cover name for the Special Operations Executive (SOE). SOE had identified a requirement for a covert submersible craft suitable for the insertion of agents, and landing of stores, into occupied countries by sea. Known as the Welfreighter it was just 37ft in length, and had a cargo deck similar to a truck. Another use, for which the Welfreighter was considered suitable, was to lay mines in shipping channels near enemy ports and so block the port to shipping. (Later this idea proved unworkable...   it was found that if a heavy mine was released underwater the Welfreighter would rise to the surface fast.)

Because ISRB did not operate facilities suitable for volume production, the production of the Welfreighter was subcontracted to Shelvoke & Drewry, who were more famous for constructing dustcarts. The Company was employed to construct the hulls and assemble the submarines. Because S&D Ltd was already making various items for the War department, they were acknowledged by the War Office as being capable, reliable and secure. In the late summer of 1944 the Admiralty approached S&D with the contract to produce the Welfreighter. The work was highly classified. Even though S&D had no experience in ship construction, and the factory at Letchworth was 75 miles from the nearest coastal town, this location was almost perfect for security reasons. The ISRB headquarters (Station IX) near Welwyn was not far away.

Shelvoke & Drewry Ltd., of Icknield Way, Letchworth, Hertfordshire had been founded in 1922 by Harry Shelvoke and James Drewry to manufacture their innovative design for a small lorry which they named the SD Freighter.

This vehicle was very economical and highly manoeuvrable; the unusual tiller controls for gearbox and steering made the process of learning to drive extremely simple. The small diameter wheels produced a low loading height which very soon made the Freighter appeal to local authorities for refuse collection. Indeed by the 1930’s this had become the principal market for the SD Freighter. At their Letchworth factory S&D produced the engines, gearboxes, axles, chassis, bodies and cabs for the Freighters. Thus the Company had a wide range of skilled engineers and craftsmen.

Around fifty Freighter chassis were used as Public Service Vehicles, and a number of these had a conventional steering wheel to replace the tiller control. S&D also produced the French designed Latil KTL heavy duty road tractor for sale in Britain from 1932 to 1937. Power brooms were another product, as was the Aero Trolley for ground handling the RAF’s Vickers Virginia bomber.

At the outbreak of World War II the entire factory was turned over to war production. A Company brochure carries a list of items produced which included:-

30-ton Tank Recovery Trailers.

40-ton Multi-wheel Tank Transporters.

Radar Equipment Carriers.

Engine Room Gear for Landing Craft (including 2,800 cylinder blocks, 2,480 governors, 45,000 welded exhaust pipes.)

Driving Mechanism for Churchill Tanks, including more than 56,000 tank sprockets and wheels.

Bodies for 17-pounder Anti-Tank Guns.

Bomb Hoists for Bomber Planes.

Undercarriages and Landing Gear for more than 8,000 Aircraft.

Despite the fact that they weren’t ship builders S&D had the necessary expertise to manufacture the Welfreighter.

S&D created a small division in a special building within the factory to manufacture the first batch of 6 Welfreighters. The necessary jigs and fixtures were rapidly designed and produced and very soon the first hull was being welded in the West Works. Highly skilled staff were selected from within the works, and placed under the Official Secrets Act. Under constant supervision by Naval Staff from ISRB, total secrecy was enforced. Few non vetted employees of S&D were ever aware of what was going on. The full truth about what the factory was producing did not become public till some weeks after the end of the War.

Although one area of the factory had been declared ‘off limits’ due to the Official Secrets act, this would not have attracted much comment in the atmosphere of the war. But the Welfreighter building area was small. It was vital that production be as fast as possible. To achieve this many components were built and tested in less secure parts of the factory. Once complete these components were moved into the submarine building area, and incorporated into the sub under construction.  Welfreighter hulls were constructed from welded steel plates. The use of all welded steel in small boat construction was unusual at this time. Each plate had to be rolled to create the rounded shapes required. When completed the integrity of the hull welding was checked by pressurising the whole vessel. The outside of the hull was coated with liquid soap. Should any bubbles appear then that weld was ground out and reworked. The finished product was a testament to the highly skilled staff of S&D.

Once complete, each submarine was removed by road from the works at Letchworth under close supervision of a specialist naval officer. The sub was lifted onto a special trailer, and camouflaged under heavy tarpaulin covers. The movement to the ISRB station IX at Welwyn occurred at night. Here there was a huge engineering workshop in a giant hanger which also housed a deep water tank. This was where initial testing and trials was carried out. With the Welfreighter now almost complete it was left to the staff of the ISRB to assemble special secret equipment to the craft: things that S&D were not allowed to know about.

At ISRB a special compass system and periscope were fitted, along with radio equipment, depth sounding and other classified equipment. It was only after this was done that the sub was placed into the giant water tank and adjustments to its balance and trim could be made. Submerged tests lasting many hours were conducted to confirm that all the systems would work.  Once the Welfreighter was complete it was stripped down and again loaded on the heavy transporters. Under supervision of the same Naval officer who had transported it to the hanger, the craft was moved to the ISRB trials base at Fishguard in the west of Wales, -a two day journey.  Once there, commissioning tests and sea trials would be completed.  

Trials would have tested all the instruments and systems aboard the mini submarine. Trim and stability trials would be performed, loaded and empty, in operational trim etc., engine, fuel consumption and battery endurance tests. Complete procedures were established at Fishguard for maintenance, operational use, and methods to be employed while under tow in a wide variety of sea conditions. Endurance while submerged was always an issue, plus, of course, essential navigational tests, instrument and compass adjustment. Finally speed trials would be conducted to assess the range and capability of each craft.

During early trials of the prototype Welfreighter, a stability problem had become apparent. While being delivered to the Royal Navy for trials on the Clyde one craft had actually capsized while under tow.  Later at Fishguard development work was done to improve this problem. Extra compartments containing wood blocks were added either side of the hull, and a keel shoe was fabricated.

While at Fishguard experimental exercises under operational conditions were also carried out. Each Welfreighter was equipped with a collapsible dory boat strapped to the rear deck. This would have been a safety feature on trials, but would also have been an important operational asset, to get agents and stores ashore. It is also possible that an inflatable boat or collapsible canoe (folbot) might be carried for this purpose. Once trials were satisfactorily concluded each Welfreighter would be degaussed, this cancelled the magnetic signature of the craft, useful for any naval vessel, but vital for a submarine to avoid detection and be safe from Magnetic mines.

 By October 1944 the Welfreighter order placed with S&D had grown to a total of 48 craft. The craft were to be constructed in batches of 6, as modifications were approved. However it was clear that the war in Europe was now going in the Allies favour. The use of the Welfreighter was no longer required in European waters. Consideration turned instead to use of the Welfreighter in the war against Japan.

 In early November 1944 two craft were shipped to Australia to enable trials in tropical waters to be conducted. Training, trials and evaluation of new craft continued meanwhile at Fishguard.

 The Tropical trials team assembled at the Services Reconnaissance Department (SRD) base on Garden Island, off Fremantle, West Australia in January 1945. Here a training base for clandestine submersible craft was established. Trials using WF 4 were conducted in March 1945 between Broome and Darwin. Later the craft was delivered under tow to the SRD advanced base in Darwin. But there were many engineering issues that needed to be resolved, mainly due to the heat and humidity of the tropics.

 So was the craft ever used? It is not confirmed in any archive that the Welfreighter was ever used operationally. The work to perfect the idea came too late in the war. But plans were certainly in place for deployment in the intended landings that would have been made in November 1945, and March 1946 on the Japanese mainland. But before then the atomic bomb brought the war to an end.

 In July and August 1945 SRD moved its clandestine fleet north to Morotai. (In the Halmaheras islands, south of the Phillipines).  Reports indicate that a further 10 Welfreighters were to have been shipped from the UK. 6 to Morotai, 4 to Australia. The two craft already in Australia were to have been used as a source of spares. In the same months the original order with S&D for Welfreighters was withdrawn. Although by now S&D were producing one Welfreighter a week, the contract was reduced to a total of 32 craft from the 48 at first required.

The end of the war in the Far East did not immediately end Welfreighter production. During 1944/5 ISRB had taken over the premises of the United Dairies Co. Ltd at 487 Western Avenue, Park Royal in London W3 as a store for the submersible craft. In an inventory dated 13th September 1945 it is recorded that 19 Welfreighters, along with quantities of spares, were stored there. In a further inventory dated 6th October they were all gone. No detail concerning the disposal of these craft has yet been located. It has not been discovered what became of them.

Later four craft in various stages of construction, along with components for others not yet built, were returned by Shelvoke and Drewry Ltd to Station IX at the Frythe. The factory then reverted to its civilian business. At the time of the Victory celebrations in Letchworth, in early November 1945, one of the completed craft was placed on display outside the factory gates...much to the amazement of local people who had no idea that the factory had been doing this type of work. For many years S&D displayed a model of the Welfreighter at their headquarters. This model is now on display at the National Maritime Museum at Greenwich. Further information on the Company is to be found at www.bcarpent.webspace.fish.co.uk

 By the time that it was wound up in October 1945 Station IX of ISRB had created a whole new approach to war at sea. SOE had been responsible for the construction of over 160 SB canoes, over 100 Welman one man craft, and, of course, the Welfreighter. There were also several other classified ideas for prototype submersible craft, some of which were still being worked on.

An exact number for the quantity of serviceable Welfreighters produced has not yet been located. But it appears that the total may not exceed 25 altogether.

 There is an excellent website which sets out in great detail the whole of the Welfreighter story (so far as is now known)

http://www.welfreighter.info/WPages.html

Sources used in this document:

http://www.welfreighter.info/WPages.html

http://www.bcarpent.webspace.fish.co.uk/History.htm

Various documents held by the Public Records Office, Kew, and the National Maritime Museum at Greenwich

Tom Colville

Brian Carpenter