X-CRAFT H.M MIDGET SUBMARINE X-24

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1 X-CRAFT H.M MIDGET SUBMARINE X-24 History This is a model of H M Midget Submarine X-24, which is now preserved at The Royal Navy Submarine Museum, Gosport. She was made famous by the attacks on the Laksvaag German Naval Harbour and floating dock in Bergen harbour, Norway. And also the sinking of the German freighter Barenfels during the first daring raid on that target. She returned some months later to finish the job and sank the dock. These submarines, known as X-Craft, carried a four-man crew and were usually towed to their target areas by a larger submarine. Probably the most famous of their targets was the German battleship Tirpitz. Five midgets attacked this ship when she was anchored in Kaafjord, Norway. All five boats were lost in the raid but the battleship sustained serious damage and never put to sea again. Lancaster bombers of 617 Squadron, RAF, eventually capsized her. Vickers at Barrow built the original five operational boats X5-10 and a training version the known as the XT boats (X -Training). These boats had no explosive side cargoes fitted and were therefore less complicated and easier to maintain. A member of the Broadbent group of private engineering company s, Marshalls of Gainsborough Lincs, built X-24 in 1943, she was from the X series, the second group of five operational boats built. Other boats from this series took part in

2 the marking of the D-Day beaches in Normandy in preparation for the allied landings in June The boats were originally developed for use by the Army who had a requirement for a vessel that could operate in shallow waters and river estuaries, but, because of their sophistication and being designed as true midget submarines, they were adopted by the Admiralty and integrated into the submarine service. X-24 was 51ft 7ins long and had a beam of 5ft 9ins. She was of welded construction and could dive to a depth of 300ft. Her armament consisted of two side cargo mines containing 4 tons of Amatex explosive. The crescent shape of these charges conformed to the contours of the submarine hull and when released they dropped from the hull to the seabed under a target. A timer set by the crew allowed the charge to explode when the submarine had cleared the area. X-24 is the only surviving wartime X Craft of this type. She was extensively rebuilt during the early 70s to allow her to be displayed at The Royal Navy Submarine Museum in Gosport Hampshire, where she is displayed with the rear section parted allowing the interior to be seen. Much of her original plating was replaced during this time and a dummy representative charge fitted to her starboard side. The Model My research started with a trip to Gosport where X-24 is preserved, to measure and photograph her, and whilst I pondered over the best way to build her, I made an appointment to look in the Submarine Museum records to see if there was any other information that would be of help. I discovered a great deal of useful material from this visit and I would like to acknowledge the help given me by the very enthusiastic staff there. Coincidentally, just after my decision to make the model, a new book, Midget Submarines of the Second World War written by Paul Kemp and containing a good drawing by David Hill, was published. These drawings were used in conjunction with my own, to make the model. Take a length of plastic soil pipe. The scale chosen for the boat was 1:12 th, so a 6 inch diameter plastic soil pipe was used for the basic centre shape of the hull which is a parallel tube. A section was removed lengthways which allowed the pipe to have its diameter reduced to 5 3/4ins representing the 5ft 9ins size on the original. The keel, which is formed from plywood panels, covers the joint of this section. The hull bow and stern continues as a series of tapering conical sections, these were machined on a lathe from solid fruit wood, constant checking being required to ensure the angles remained correct. The joining of these sections to the tube was achieved by machining an accurate flange that fitted snugly in the tube, this makes sure that all remains square and true. A side profile plate is let in to the bow, it extends slightly forward from the tapering cone, and is set vertical, the casing panels are built onto this plate and are constructed

3 from thin plywood, formers fixed to the top of the tube helps keep the lines of the casing true as it progresses aft. The rearmost part of the casing becomes very fine as it reaches the upper tail rudder bearing and was, for this reason, carved from solid timber then faired into the plywood. The keel shape was extended forward and aft and attached to the tapering hull sections, this completed the basic shape of the model, which was then sanded and polished making the master. Weld lines were added at this point by using evergreen plastic strips, these were sculptured with a scalpel to obtain the desired effect. From this master a fibreglass mould was taken with a removable centre section to gain access to the insides and then a hull produced, this was developed into the model now described. The hydroplane bearing fairings, and the skeg shape were made by using a thin central core of black plasticard cut to the profiles on the drawing, and then building up the thickness either side with a material called Foamex (this is a brand name for a plastic foam used by signmakers) then carved to shape. The black card centre gives an accurate base line to work to and ensures uniformity. After making these components, they were moulded and cast in polyurethane resin. Brass bearings with a soft-soldered 3/32in brass locating spigot were let into the ends of the fairings, skeg and upper tail moulding. This allows a certain amount of adjustment to be made when setting up the rudder and hydroplane. When all was square the bearings were glued into place and any gaps filled and sanded to shape. The accuracy in fitting these parts squarely to the hull is very important as any misalignment will cause the rudders and hydroplane to not operate correctly. Also there are aerofoil shaped braces between the fairings, which need careful fitting to ensure they align properly

4 As mentioned before some of the hull drainage and vent holes have not been reproduced on the replacement plating of the original boat, extra research was necessary to find out where these holes and openings were. Only a few photo s of X- 24 were found to be of use, probably because very few are available, and some are credited to be X-24 but other evidence suggests otherwise. The various hull drain and vent holes were accurately marked and then cut out. A fine file was used to do this. It is important to make sure they are all perfectly in line, as any discrepancy will be very noticeable. On the top of the casing there are two distinctive large openings for the hatch accesses, these are cut out then the whole top surface was plated over with panels of 15thou Plasticard sheet with all the vent holes and other details represented in them. The hatch covers are turned on the lathe from plastic and detailed with hinges, handles and operating levers. Two short vertical tubes representing the hatchways are fixed to a dummy pressure hull shape that is screwed to brackets fixed onto the interior of the removable centre section, this gives the impression of depth when viewed inside the openings. There are two hinged plates that were made in brass because they needed to have strength and be operational. These give access to the locating pins that are arranged at either end of the removable centre section to lock it in position. The use of elastic bands make them close tight to the casing, tensioning the hatches. External fittings. It might be of interest to describe some of the external fittings and to describe how they were made. On the topside of the casing, diagonally opposed, are two lifting lugs. These were carved from a block of styrene and details added from smaller plasticard strip. A mould was made in silicone rubber and the lugs were cast in polyurethane. Tubular steel deflection guards, which are represented by bending brass tubes to shape, protect them, the ends are flattened to allow them to fit snugly against the hull. A small platform was added which acts as a step on the full-size boat. There are also some very fine details in this area constructed from plastic tube and brass, these are all connected with the side cargo release mechanism. On the portside of the model is the induction trunk, a moveable tube that can be brought up to the vertical position to enable fresh air to be drawn into the boat. It also acts as anchor point for the commander to stand against when the boat is being conned on the surface. On the model this trunking is constructed from aluminium tubing with a right angle bar epoxied on, this bar is also to allow the induction trunk to rest on the top of the casing when in the down position. A series of 1mm holes are drilled around the top inch of the induction trunk, they act as a coarse filter to stop any large foreign bodies from entering the boat The periscope standard was turned from plastic stock and details added from plasticard, the forward night periscope mounting was also made this way, between these periscopes is an observation scuttle, this is a clear plastic window with a frame, imitation bolts were made from shards of plastic hexagonal shaped rod. I find this method of using plastic rod sliced up to make bolt heads preferable in many cases to actual bolts, (and it s cheaper). There is a protective guard over the periscopes constructed in a similar way to the lifting lug guards.

5 The two mooring eyes are both made from brass, as is the towing point in the bows and the D shackle connecting the small towing wire. Moving aft we come to the hydroplanes and rudders. The shapes of these parts and their construction are similar to the methods already described for the fairings. A flange on both parts pinned together by brass bolts joins the two rudders, upper and lower; this joint is partially hidden by hole in the hydroplane which the rudder pivot pin passes through. It will be noted that this needs assembling after all has been painted and finished. The pivot pins are 3mm brass rod with a flange to locate them in the bearings. The action of the moving surfaces is by a closed loop system: i.e. a push and pull rod operation. These rods are made from 3/32 brass with the solid clevises filed from 3/16 square brass stock, then soldered to the rods at both ends. A lever is fitted at the forward end; starboard side only, where the actuating rods pivot from, this connects the hydroplane to the module inside the model. All this mechanism is protected by the same tubular guards which have previously been described, the guards are this time actually bolted together using 14BA brass nuts and bolts and are fitted to brackets epoxied into the hull and hydroplane fairings. The Keel There are two distinctive cooling pipes running down both sides of the keel, these are made from aluminium tube with right angle bends returning into the hull made from solid plastic rod drilled to accept the tube. Five saddle brackets with imitation bolt heads hold this part to the hull. Two guards protect this tube when the side cargoes are fitted into their lower hinge sockets, these are made from thin brass sheet, bent to shape and epoxied to the hull. Plates containing four rows of drainage holes and having rivet details added by using PVA glue applied by a syringe, are added to the keel either side of the cooling pipework. Painting and finishing Careful research showed that these boats were painted black overall when operational, but might have had grey topsides during training. My example was to depict X-24, as she was when she returned from the Bergen raids, so a black finish was required. The model was sprayed with a mixture of satin black and matt varnish. Much experimenting was undertaken to ensure the resulting finish looked right. The satin finish was too glossy, and needed toning down, hence the addition of matting agent. Weathering the model, always a delicate subject, was carried out sympathetically to give what I consider to be just enough to put life to the model, at the scale chosen even the stains on the domestic outlets need representing! There would be a degree of oil staining running down from the relevant openings and hints of rust appearing at the joints of the plates. Natural wear on the casing panels is also shown as lighter shades of paint representing the undercoat grey, just showing through the black paint. The towing hawser is a scale size piece of nylon cordage, with eye spliced ends. When sprayed up black and then heavily rusted, it is fixed to the starboard foredeck by clipping to small brackets that are added along the starboard sides. The main attack periscope is made from a length of aluminium tube with the top portion turned down from solid aluminium alloy bar. The night periscope was carved from a block of plastic and a representative lens added. A useful side effect of making

6 the periscopes in this manner was discovered when using them on an earlier model submarine, As the boat submerges the air trapped in the aluminium tube lifts the periscope automatically to the raised position, a small O ring stops the shaft from lifting out completely, when surfacing, the weight of the tubes lowers them down again. This model was designed to use the Craycraft 20inch module as the operating system, and during testing in the tank, (fishpond) this proved to be more than adequate. These boats have a very low freeboard when surfaced with most of the hull being underwater, and subsequently do not need to take on a great amount of water ballast to dive. This module is no longer available as the company has ceased trading; however, any other system could be used to operate the model. A stand incorporating two cradles was constructed to display the model realistically; this was how X-24 was displayed at HMS Dolphin before being restored. These small submarines were once described as looking more like water boilers than underwater weapons of war. Possibly an unfair description as I personally find their lines pleasing. Over the two years spent building the model I have amassed a large amount of information about them and have grown to admire their design. I also have the greatest of respect for the men that served in them during the difficult times when serving with the 12 th Submarine Flotilla. Alan Poole. Picture of model in early stages of construction