Description and Operation of Craft.

The Welfreighter resembled a 37ft motor boat. On the surface it was propelled by a Gardner 4LW 44 hp. omnibus engine driving a large 4 bladed screw. The deck arrangement was very functional. The sharp flared stem was equipped with towing eyes and fairleads for towing cables. Stretching aft long hand rails doubled as exhaust pipes for the Diesel engine when on the surface, and as venting pipes for the floatation tanks when submerging. The shape of these rails was intended also to deflect underwater cables, anti- submarines nets and other obstructions clear of the craft. The foredeck was raised to give some small headroom in the interior of the craft. This “deckhouse” was fitted with small square port lights.

Above and behind the deckhouse stood a domed structure, also fitted with square port lights and protected by a large breakwater. This structure was equipped with the only opening - the main hatch into the interior. It was here that the “pilot” sat and could monitor a complete instrument panel of controls for the craft. Within the breakwater rose two tubes. The taller of these was a Barr and Stroude periscope which served a double purpose. When submerged it was a navigational instrument. However, while on the surface a mast and sail could be attached to help disguise the boat as a fishing smack. The tube behind this was composed of cast brass and housed a magnetic compass. The reading from this compass was projected down the tube to be displayed via a prism onto a ground glass screen in front of the “pilot's” seat in the cockpit.

Aft of the main structure was a small slatted raised deck, beneath which were situated 6 high-pressure air cylinders. To the rear of this deck was the cargo well, which was fitted at the stern with a hinged drop-down tailgate, similar to a truck. It was here that the 7 special cylindrical drums of cargo would be stowed. Carefully loaded so as to provide a small positive buoyancy these drums would contain equipment for use by agents or saboteurs They could be floated out through the tailgate to be towed ashore by the agents, either swimming or using an inflatable craft. (There was a great skill involved in loading these containers for transport on a submersible craft . Trim was a constant problem. If they were too light they could prevent the Welfreighter from submerging. Too heavy and they would sink while being towed ashore.)

When submerged the craft was driven by two 2 hp electric motors, which turned small screws for underwater propulsion. The batteries( Exide) for the craft were deep within the hull.

Each Welfreighter was manned by a Sub Lieutenant RNVR as Commander, and an Naval Engine Room Artificer (ERA) or Army mechanic (REME) as second man. There could be up to four special agents…although two would be more normal. These would usually be Army personnel, who would assist with handling the craft when on the surface. The design of the craft meant that a minimum of two men were required to operate it while submerged.

The Welfreighter could travel at night on the surface towards an enemy held coast, submerging as necessary to avoid detection. The agents would go ashore along with the equipment they required from the deck containers. The Welfreighter would then go out to sea, and could be submerged in a suitable depth of water, to wait, sitting on the seabed, until the following night. At a pre-arranged time or on hearing a signal from the shore party made by a "bong stick" (a mechanical device where turning a handle caused a hammer to bang a metal rod) it would surface again. When the coded recognition signal flashed by torch from the shore had been received it could then to go back inshore to pick up the agents, before heading back out to sea.

'Mission accomplished' it might rendezvous - if necessary - with a larger surface vessel ( mother ship) or fleet submarine, or simply proceed back to base under its own power.