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Motor Gun Boat 81 (MGB 81) is a restored Second World War motor gun boat of the Royal Navy. Built by British Power Boat and launched in 1942, MGB 81 was one of eight new motor gun boats built by the firm in response to the increased need for small, fast vessels equipped with sufficiently heavy firepower to engage German S-boats and convoy escorts.

MGB 81 was designed by George Selman and constructed at British Power Boat’s yard in Hythe, Hampshire. Taking into account the experience of serving Royal Navy crews, the eight new boats were the first to be designed as true MGBs, rather than vessels that had been converted from a previous design. MGB 81 had a hard chine planning hull design and was powered by XXX. It was fitted with a 2-pounder 'pom pom’ gun and a twin Oerlikon 20 mm cannon in a power operated turret.

After its launch in June 1942, MGB 81

Background
During the 1930s, Hubert Scott-Paine, the founder and director of the British Power Boat Company, had evolved the idea of a hard chine high speed planing boat for military purposes. Several innovative designs had been purchased by the Royal Air Force and the War Department, who saw the value of High Speed Launches (HSLs) that could quickly rescue downed aircrew or service their seaplanes. The Admiralty was less interested in fast boats, although Scott-Paine continued to press the importance of fast torpedo boats that would fulfil a similar function to the Coastal Motor Boats (CMBs) of the First World War. Eventually, in 1936, the Admiralty ordered eighteen 60 ft Motor Torpedo Boats (MTBs) from British Power Boat, which formed the 1st, 2nd and 3rd MTB Flotillas in 1937. In 1938, Scott-Paine began developing a new 70 ft design, known as PV 70. The Admiralty were impressed, but instead chose a 68 ft design produced by rival firm Vosper as the basis for future torpedo boats. However, they did place several orders with British Power Boat for newly developed Motor Anti-Submarine Boats (MA/SBs). The Admiralty felt that small, fast vessels equipped with depth charges would be a useful counter to submarines operating in offshore waters. In early 1939, British Power Boat supplied six 60 ft MA/SBs to the Royal Navy. After introducing a 70 ft version based on the hull design of PV 70, a further thirty three 70 ft MA/SBs were ordered on 4 September as part of the Emergency War Programme.

At the outbreak of the Second World War, the Royal Navy was only equipped with a handful of small boats for coastal operations. The 1st and 3rd MTB Flotillas (60 ft British Power Boat MTBs) were hastily recalled from the Mediterranean and the seven that were sufficiently serviceable were sent to Felixstowe. With the addition of small numbers of early model MTBs from Vosper and Thornycroft, by the time Germany's attack on France and the Low Countries began, the Royal Navy had 10 MTBs and 5 MA/SBs ready for operations. However, the Admiralty realised the importance of a fleet of small, fast craft and this number quickly grew. In November 1940, Coastal Forces was established as a division of the Royal Navy, under Rear Admiral Piers Kekewich, Flag Officer Coastal Forces. His Chief of Staff was Augustus Agar, VC, who had commanded CMBs during the First World War and the British campaign in the Baltic in 1918 and 1919.

With the fall of France, the Kriegsmarine was free to operate from ports all along the North Sea and Channel coasts. E-boats were able to make frequent night attacks British coastal convoys that were inadequately protected by small numbers of destroyers and corvettes. The escorts struggled to defend convoys against these small, fast moving boats with their conventional destroyer armament, and MTBs did not carry sufficiently heavy guns. The Royal Navy responded by converting a number of the MA/SBs. Realising that there was little need for anti-submarine work, as the Kriegsmarine was not deploying U-boats in coastal waters, their gun armament was increased and the boats were re-engined. MA/SBs still being built or on order were completed as gun boats. However, the new role placed considerable stress on the MA/SB's hulls. Of particular concern was the stress caused by high speed manoeuvring in rough seas. The addition of heavier weaponry also affected the boat's frames and caused failures in the hull. In November 1940, based on the early operation experience of the 70 ft boats, Vice Admiral Francis Tower, Director of Naval Equipment approached British Power Boat and requested a design for a purpose built gun boat.



By now Scott-Paine resided in North America looking after his interests in the Canadian Power Boat Company, so chief designer George Selman was asked to design the new boat. Scott-Paine was concerned that Selman would not be able to produce a design without his own input, but accepted that his distance from the company's Hythe factory would make it impossible. Design work on the new boats began in December 1940 and Selman's team worked night and day perfecting the hull, armaments and machinery and conducting tank tests. In his biography of Hubert Scott-Paine, Adrian Rance states that the design was finalised in conjunction with Lieutenant Commander Robert Hichens. Hichens had in fact visited British Power Boat on numerous occasions and his discussions with Selman on the subject of the boat's armament and behaviour had presumably allowed the designer to overcome many of the failings of the earlier MA/SB designs.

In February 1941, the designs were submitted to the Admiralty at a conference in Bath. W. J. Holt, Chief Constructor of the Naval Construction Department disproved and Selman expected his design to be rejected. However, Admiral Tower quickly intervened and stated that this was the boat he wanted and therefore the design that would be built. The Admiralty ordered three flotillas of eight boats each, but the following month they reduced this to a single flotilla.

Meanwhile, the modified MA/SB gun boats were developing their role in guarding the east coast. In January 1941 the term Motor Gun Boat (MGB) was formalized and through the year, five MGB flotillas were formed as newly completed MA/SB conversions joined Coastal Forces. The 6th Flotilla in particular, under Hichens, began to perfect the techniques of E-boat interception and escorting MTBs making attacks on German coastal convoys. However, by late 1941, although recognising the clear need for a purpose designed gun boat, the Admiralty believed that the new 'long' Fairmile D boats would more effectively fulfil the role. Hichens knew that the larger launches would be too slow to successfully bring E-boats to action and he believed that the 'short' MGBs were more suitable. In November, having learnt of the imminent arrival of the first of the new British Power Boats, Hichens strongly lobbied the Admiralty to give the craft to his crews, who were already experienced in MGB operations and would be able to make the best use of them. He was eventually able to transfer all of the officers of the 6th MGB Flotilla to the new 8th MGB Flotilla with the new boats and, after a particularly successful action in November using the old MGBs, the Admiralty reinstated their order for three flotillas of the new boats.

Design
Selman's design was for a 71 ft long boat. The hard chine planing hull was essentially the same as that of the earlier 70 ft MA/SBs, but slightly longer and significantly stronger. Girders with cross braced mahogany were used to divide the lower part of the hull and reduce the longitudinal stresses placed upon it by high speed. The hull surface was created with double diagonal planking, but triple planking was used below the chine. The hollow back deck of the PV 70 design was also removed and a reverse sheer introduced to improve forward visibility over the bow.



The boat was designed to be powered by three supercharged Packard marine engines, each capable of producing 1,200 horsepower with V-drives used on the outboard motors. 2600 impgal of fuel were situated below the chart room, with a crew mess deck forward and a small galley and officer's cabin ahead of the engine room. The predicted speed when fully laden with crew, fuel and ammunition, was expected to be 42 or 43 kn, and a speed of 20 kn would allow for a range of 1000 nmi, decreasing to 760 nmi at 30 kn. In a slight or moderate sea state (sea state 3 or 4) the boat was able to maintain a speed of between 30 and 36 knots, in a rough or very rough state (5 or 6) it would manage 20 to 24 knots. In the early summer of 1942, after the first of the new boats had been delivered to the 8th MGB Flotilla, Hichens investigated ways of silencing his boat's engines. After experimenting with underwater exhausts, he met Selman who modified the designs for the remaining boats within three weeks. A slight impairment in steering was overcome by adapting the boat's rudders. As well as significantly reducing the noise of the engines and allowing near-silent running at 15 kn, the new exhausts added up to 3 knots to the boats' top speed.

Selman incorporated a 2-pounder 'pom pom’ gun in a power operated turret on the fore deck. Positioned ahead of the bridge, the weight was supported by two longitudinal bulkheads that connected the deck to the bottom of the hull. Scott-Paine did not believe that the gun would be usable in anything more than a calm sea and some members of the Admiralty agreed, believing that the fore deck would be too wet and bumpy to operate a gun from. Hichens, who had come to realise that heavier armament was needed on MGBs than the small calibre weaponry they had so far been equipped with, believed that a 2-pounder was essential in order to be truly effective. He also considered the Admiralty doubters were wrong, as his own experience had shown that the fore deck was the safest and driest place to be in operating conditions. The boat was also armed with two Oerlikon 20 mm cannon in twin power operated turret behind the bridge, four Lewis guns in two twin hand operated mountings on either side of the bridge, a Holman Projector for anti-aircraft defence, two depth charges and a star shell gun.

Ultimately Selman's design was to prove to be the most successful boat British Power Boat ever produced. It also established a reputation as the best of all the short boats in Coastal Forces and the only one that did not suffer from structural defects. Even Holt, who had initially rejected the design, told Selman in 1944 that the type was 'absolutely second to none in service'. Eventually 96 boats of the design would be built, first as MGBs and then as MTBs.

Construction and service


During the 1930s, Scott-Paine had established efficient procedures for the mass production of boats and an advanced construction system allowed all of the new boats' frames to be produced quickly and cheaply using one metal jig. Even so, MGB 81 was not laid down until 16 December 1941 as yard number 1807.

British Power Boat built and planked their boat's hulls upside down. Once this was complete, the hull was turned over by crane so that the engine machinery could be fitted, followed by the decking, deck houses and weaponary. After she had been completed, MGB 81 was launched on 26 June 1942. She began her trials on 8 July, achieving a speed of 38 kn on Southampton Water and on 11 July she was commissioned into the Royal Navy.

Conversion to MTB 416


Thomas Walter Simpson.

Operations