November 2026

X-Craft Midget Submarine

Kraken 3 Autonomous Vessel

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X-Craft Midget Submarine

12th Submarine Flotilla, HMS VARBEL, Port Bannatyne, Isle of Bute.

Operation Source (attack on Tirpitz), Kåfjord, Norway, September 1942.

3D Printed 1/72

The Royal Navy introduced the X-Craft mini submarines around 1942, with the purpose of entering enemy harbours and destroying ships whilst they sat alongside.

Just over 51 feet long and displacing about 35 tons, they were manned by a crew of 4, including a diver who could exit the submarine whilst submerged to cut boom defence nets and allow the submarine to enter. Armament consisted of 4 tons of Amatol explosive carried in 2 saddle tanks attached to the side of the vessel. These would be deposited beneath the target using a water-based time fuse to allow the attacking submarine to escape to a safe distance.

Maximum speed was around 7 knots surfaced and less than 5 submerged. Although they had a long theoretical range and could remain at sea for up to 14 days, it was normal for them to be towed to the operating area by a full size submarine. Propulsion was provided by a 40 hp Gardner diesel charging a large lead-acid battery and a 30hp electric motor. Degaussing coils reduced the risk of them being detected by harbour magnetic defence loops.

Based out of HMS VARBEL at Port Bannatyne on the Isle of Bute/Firth of Clyde they undertook several missions to disable German ships in Norwegian Fjords, the most famous if which was Operation Source, which disabled the Battleship Tirpitz in Kafjord. During this mission, 4 X-Craft penetrated the defences, with 2 successfully planting their charges.

Four X-craft were lost, with two crew being awarded the VC. Three crew were awarded the DSO, one made an MBE and another Mentioned In Despatches.

Later missions included beach surveys for Operation Neptune (the D-Day landings), dropping divers at night to gather beach samples and survey the landing grounds. On D-Day itself they acted as navigation beacons to direct British and Canadian landing craft to Sword and Juno beaches.

One complete X-Craft is displayed at the RN Submarine Museum in Gosport, whilst the wreckage of another is at the Imperial War Museum in London, with the remains of two XT Training Craft still visible on the Beach at Aberlady Bay near Edinburgh, where they were used as targets for aircraft training.

Building an X-Craft

I often find that it’s the casual purchase/side build that gives me most satisfaction, and this is no exception. This was a quick 3d print whilst my SAAB GlobalEye was being painted. It uses a free set of .stl files provide d ia Cults3d by “Bleblet”.

The print was very finely detailed, which did prove a little difficult when scaled down to 1/72, so some details had to be reinstated after printing , using plastic card and rod. As built, the submarine does not carry its two explosive packs, so I assumed it to be alongside and have provided a White Ensign and a Captain figure standing beside the voice pipe. I also added the smaller periscope.

Sitting it alongside the German WW2 Seehund mini-sub that I built back in 2013 provides an interesting comparison, although they were designed for very different tasks.

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Above: For comparison, a German Seehund mini-sub at the same scale.

Kraken 3 Autonomous Vessel

Royal Navy Coastal Forces Squadron & 47 Commando Royal Marines.

Portsmouth/Poole, September 2026.

3D Printed 1/72

The Kraken 3 is produced by racing powerboat manufacturer Kraken technologies in Fareham, near Portsmouth. Intended as a flexible technology demonstrator, the RN acquired 20 boats in March 2026 as part of Project “Beehive” and has used them to explore a number of tactical uses for small autonomous/remotely controlled boats. This has included remote control of the vessels over a satellite link from Australia as part of the AUSUKUS activities.

Kraken 3 can carry a payload of up to 600kg and has a maximum range of 650 nautical miles at a speed of 25 knots, with a maximum speed of 55 knots. Endurance is up to 30 days, depending on mission and payload.

The boats are built around a modular payload bay allowing different sensor and mission fits depending on the task. At this stage, the craft are unlikely to be armed (The armed model I have built is pure speculation; although it is within the payload weight, stabilisation might be an issue!), meaning their primary value would be as an ISTAR asset, extending the detection range of the wider force.

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Background - An XT training craft can be seen wrecked on the sands at Aberlady Bay, East Lothian

having been used as a aircraft target in the late 1940s (picture source unknown).