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Old 05-08-2010, 03:13 AM   #1
copeab's Avatar
Join Date: Mar 2005
Location: near Houston
Default [WWII] Welfreighter covert operations midget sub (UK)

Although the technical data on this boat is a bit sparse, it's perfect size and role for a typical group of PCs just screams for a write-up ;)
Welfreighter covert operations midget submarine
Copyright 2010 by Brandon Cope

The Welfreighter was a midget submarine design initiated by the British Special Operations Executive (SOE) as a way to covertly insert agents and equipment by water. After some changes during development in 1942-43 (increasing in size and capability) the Wefreighter entered production in 1944. Few (perhaps 25) were built and even less saw service. By that time in the war, there was little need for such a boat.

Apart from it's small size, the Welfreighter was unusual in that it was constructed to resemble a coastal boat while surfaced. The crew and passenger area was slightly raised to provide more headroom, while the “bridge” section, which seated the two crewmen, was raised even higher. A folding table was located in the passenger cabin, where the periscope was also accessed. It had portholes for vision like any other surface boat. Cargo was 1.5 to 2 tons, carried in six or seven containers recessed into the stern (a tailgate was lowered to allow the canisters to slide out). Properly loading the containers was a delicate balancing act: if containers were too light the extra buoyancy might prevent the craft from submerging while an overloaded container would sink as soon as it was rolled off the sub. Another recognition feature were the compressed air tanks located amidships (between the raised bridge and cargo area) which were used to blow water out of the two main (side) ballast tanks.

While the Welfreighter did not play any useful part in WWII, there is no technical reason in an alternate-history it couldn't have been built a year or two earlier, when they were uses for it. Also, a craft of similar capabilities might come in handy in a Cliffhanger's or Atomic Horror campaign. This craft should not be confused with the one-man Welman submarine (also for SOE use), a much smaller sub used to emplace a demolition charge.

The Welfreighter Mk III has a crew of two. The engines burn 1.8 gallons of diesel fuel per hour of routine usage. The Welfreighter can travel 1,000 miles at 5.5 mph surfaced and 40 miles at 2 mph submerged.

Subassemblies: Large Boat chassis with Sub option +4.
Powertrain: 44-kW marine diesel engines with 44-kW water screws and 330-gallon standard tanks; 22-kW electric motors with 22-kW water screws; 50,000-kWs batteries†.
Occupancy: 2 CS, 4 PS Cargo: 17

Body: 4/22

Body: Autopilot; bilge pump; 17-VSP open cargo hold; fire extinguisher†; 10-man-days life support†; navigation instruments; precision navigation instruments; 20-man/days of provisions; 10’ 5 periscope; large radio receiver and transmitter; searchlight.
† Limited access.

Size: 37’8’15’
Payload: 2.7 tons
Lwt: 13.5 tons
Volume: 120
Maint.: 103 hours
Price: $3,800
HT: 11
HP: 750 [Body]

wSpeed: 7
wAccel: 0.1
wDecel: 0.5(0.6)
wMR: 0.1
wSR: 2
Draft: 3'
Flotation Rating 13.7 tons.

uSpeed: 3
uAccel: 0.05
uDecel: 0.3(0.4)
uMR: 0.1
uSR: 2
uDraft: 105
Crush Depth 44 yards.

Design Notes
Design wSpeed was 13 mph and uSpeed was 4 mph; the historical figures were used instead.

For long missions, only three passengers were carried, with two seats being combined as a cot. The Welfreighter could carry extra fuel, up to 1,000 miles worth in disposable tanks (preventing it from submerging) and up to 600 miles worth in place of cargo.

No armament was carried; the crew would have to rely on small arms such as pistols and SMGs on the surface. A collapsible dingy was often carried on the rear deck, over the high pressure air tanks.

For design simplicity, no extra subassemblies were added to represent the raised crew and passenger section. The cargo area is protected from all sides but the top.

The original prototype carried two passengers and 2 tons of cargo, with a range of 600 miles.
A generous and sadistic GM,
Brandon Cope

GURPS 3e stuff:

Last edited by copeab; 09-02-2010 at 03:56 AM.
copeab is offline   Reply With Quote

british, covert ops, soe, submarine, wwii

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