British Motor Torpedo Boats 1915-45

This is a Portal Page, long overdue, on British small crafts, boats of ships broadly assimilated to the “Motor Torpedo Boat” Family. In reality, MGBs and MA/SBs, used for ASW or general patrol would might to differ. This post starts with the WW1 CMB types that already dented the use of older, larger classic torpedo boats, by inventing a new and miuch master, nimbler and cheaper type of vessel that is still with use today and definitively buried the Torpedo Boat type in the Royal Navy. This naval durst, embryonic in WW1 was continued in the interwar, albeit at a smaller, experimental space, and really flourished in WW2 with hundreds built, embracing the coastal ASW vessel, the SAR boat, and reinventing the gunboat. Time to sail with the Royal Navy’s “naval dust” and see what they have to say about their contribution to victory… Note: Since the topic is wide, this is part I, there will be an update for Part II.

Development

The birth of torpedo launches and craft.

The invention of the torpedo was one of the largest game changer in naval history. Being able to sink a vessel with a single device, without exposing too much the carrier vessel, unlike traditional manned explosive charges, went all the way back to the XIXth century, but it only existed under its self-propelled form via the work of Luppis and Whitehead in the 1860-70s. By the mid-1870s many nations already had embraced the concept of spar torpedo launches and were ready to embark on new types of ship capable of launching torpedoes. This subject already had been well covered notably in the lineage of British Torpedo Boats. Some, like the 3rd class midgets, were already quite small so could be carried by a mothership, such as Hecla or the dedicated HMS Vulcan.

But the concept soon died out. In 1914, the Royal Navy still fielded several squadrons of torpedo boats, now much older since the 1890s saw the birth of the destroyer. The last class were the “coastal destroyers” of the cricket class (photo), later reclassed as torpedo boats. These were officially the very last torpedo boats of the Royal Navy. Indeed, only France and axis powers (Japan, Italy and Germany) in the interwar and WW2 still embraced the concept as a complement to destroyers and originally to take advantage of loopholes in the Washington treaty and London conferences about 600t vessels of war.

Still, the torpedo by itself being a relatively small offensive device, like mines, there was no reason not to imagine a smaller, cheaper vessel than traditional ships. The only issue, already tried with small torpedo boats in the 1880s, was their tactical use, as they were barred from open seas, especially the north sea and its weather. These boats were just too small for operating there in good condition. However for shore/coastal operations, tradtional torpedo boats still in use by Britain in 1914-18 seems like a waste of personal and resources (they burned a lot of coal). Thus, aside the Cricket class and their TB-13 sub-chaser sub-class, the 1900-1905 160 Footers were the only ones still patrolling, but many in the admirakty questioned their utility.

On the other hand, operations in calm sea area, like on the Dardanelles in 1915, showed the utility of smaller boats for patrols. For example, if the RN had been able to sent small patrol crafts in the straits by night, they could have spotted the minelayer Nusret laying its mines, avoiding costly and high profile battleship losses the following day of bombardment. But small, fast crafts, would have been able as well to better survived coastal artillery, just dodging fire, or penetrating the straits by night and cause havoc in Turkish shipping and fleet. The issue then was range. Latter when the Germans sized important bases on the Belgian coast, small crafts would have been useful to perform interdiction missions there.

WW1 British Coastal Motor Boats

Generalities

The British Coastal Motor Boats (CMBs) were a remarkable class of fast attack craft developed during World War I. They represented one of the earliest practical uses of high-speed, small naval vessels for offensive operations—essentially early predecessors of modern fast attack boats and torpedo craft. The concept emerged around 1915–1916, when the Royal Navy sought a way to strike German naval assets in heavily defended coastal waters—particularly in the North Sea and Baltic. The idea was championed by John Thornycroft and his company John I. Thornycroft & Company. These boats were designed to be small and lightweight, extremely fast (up to ~40 knots, which was very fast for the time) with a shallow draft, allowing operations close to shore.

Unlike traditional torpedo boats, CMBs were intended for stealthy hit-and-run missions, often at night. Size was typically 40–55 feet long, powered by petrol engines (not steam turbines), giving rapid acceleration and armed with two small (18 in or 45cm) Torpedoes launched from the stern but machine guns for defense. The could be carried aboard larger ships and deployed close to enemy coasts.
The stern-launch system worked by dropping the torpedo tail-first into the water while the boat sped away—avoiding the need for forward-facing tubes.

CMBs saw action in several theaters: Daring raids against German-held ports and shipping. However, early operations were risky and had mixed success due to strong defenses. Baltic Operations in 1919. Their most famous use came slightly after WWI during the Russian Civil War, to attack Bolshevik naval units. In August 1919, CMBs carried out a raid on Kronstadt naval base. Capt. Augustus Agar sank the cruiser Oleg, Claude Congreve Dobson was involved in attacks on battleships. These raids demonstrated the effectiveness of small, fast strike craft against larger warships.

CMBs introduced several concepts that shaped future naval warfare:
Asymmetric naval tactics, small vessels threatening large capital ships, speed over armor, surprise and night attacks. Early form of what would later become motor torpedo boats (MTBs). They directly influenced interwar and WWII designs, including British MTBs and German E-boats. However they still had their drawbacks:
Limited seaworthiness in rough conditions, short operational range, vulnerability to gunfire and dependence on larger ships for transport. But CMBs were a stepping stone in naval evolution: They helped the transition from large fleet engagements to coastal and irregular naval warfare, inspired future fast attack craft used extensively in World War II and demonstrated that technology and tactics could offset size and firepower.

Note that Britain alone was not alone developing these. Germany happily developed its LMs series “motor gunboats” and from LM5 onwards proper Motor Torpedo Boats from LM1 to 20, and up to 33 were unfinished). The French had the V series in 1917-18. Italy was of course the greatest believer in this type, with in addition to modern Torpedo Boats of 130-200t, developed its legendary MAS series, that fit Adriatic waters like a glove. The first two came from SVAN in venice, followed by many, many more classes until 1918. That would be the object of a full portal. The Austro-Hungarians answered with their amazing Veruschsgleitsboote and its Gleitboot series. Russia also developed motor launches and riverine bungoats. Postwar in 1920, Japan purchased Thornycroft boats.

Development of British CMBs

In the First World War, three junior officers of the Harwich Striking Force argued that small motor boats equipped with torpedoes might be capable of travelling over German protective minefields, ships at anchor in their bases, as shown by the Japanese surprise attack at Tsushima in February 1904, a distant cosuing of Pzarl Harbor. the Admiralty gave approval in the summer of 1915, but wrote a staff requirement for North Sea operations. High speed was required, with lightweight and powerful petrol engines: 30 knots (56 km/h; 35 mph) and a good radius of action. Of course they would be armed with lightweight 18-in torpedoes, depth charges and small mines, and Lewis gun. For 30-foot (9.1 m), that could fit in the davits of a light cruiser, it would be about 4.5 long tons (5.0 short tons; 4.6 t).

Thornycroft, already experienced with small and fast boats, sub-contracted that work to Tom Bunn of Rotherhithe, Taylor & Bates of Chertsey, Camper & Nicholson of Gosport, Wills & Packham of Sittingbourne, Salter Brothers of Oxford, Rowhedge Iron Works of Rowhedge, Frank Maynard of Chiswick, J. W. Brooks of Lowestoft. Engines were auto-or aero industry standard internal combustion engines, from Sunbeam and Napier. Thornycroft in 1910 already produced a fast boat, the Miranda IV capable 35 kts, but the admiralty obtained a 40 foot prototype based on the latter, a 40 ft (12 m) variant for trials, judged too small. Still, it led to a first series. The concept was then improved with the 55-footer. It can no longer fit under cruiser davits, but still could be carried on some battleships or dedicated vessels or towed barges, but was far more capable.

The 40-footer CMBs were made of Mahogany plank on frame construction with a single-step planing and a round-form hull. Based on the prototype made for the admiralty in 1915 and based on Miranda IV. In all, 39 were ordered, plus two converted for other uses. They were made by Thornycroft, Tom Bunn, Taylor & Bates, Camper and Nicholsons, J W Brooke, Frank Maynard, Salter Bros, Wills & Packham, and thus, diverged in many details, engines and performances. The first combat action was in December 1916, with the 3rd Coastal Motor Boat Division proceeded to Dunkirk (Lt. W. N. T. Beckett on HM CMB 4). The type was however soon replaced by the 55 footer and ended for training or harbour defence in 1917-18.

Twelve were ordered in January 1916 and all were delivered by mid-August 1916, after Thornycroft had submitted designs based on pre-war hydroplanes. The hull was a stepped planing type and the torpedo was launched tail-first over the stern. The original specification called for CMBs (a camouflage designation) to be light enough for hoisting in light cruisers’ davits, but only the ‘scout’ Diamond was used for this purpose. CMB 40 became a nominal depot ship and was renamed Osea in June 1918. A further 16 boats of the CMB 121 group were cancelled in November 1918. Five were converted to Distant Controlled Boats (DCBs), including two 40-footers not previously taken into naval service MB 1143 and MB 1256, which became DCB 4 and DCB S). The survivors were mostly sunk as targets or sold post-war, only CMB 12 lasting unül 1935, CMB 4 was lent to the Imperial War Museum from 1921 to 1928 and then preserved at Hampton, and is now once again in IWM hands at Duxford.

Class (fate): Thornycroft, Hampton – CMB 1 (lost off Ostend 19.6.17), CMB 2 (lost by fire 9.7.18), CMB 3 (converted to DCB 3 7.18), CMB 4-CMB 7, CMB8 (scuttled 27.9.17), CMB 9 (converted to DCB 1 7.18), CMB 10 (lost by fire 7.5.18), CMB 13 (converted to DCB 2 7.18), CMB 40 (sunk by air attack 11.8.18), CMB 41, CNB 42 (sunk by air attack 11.8.18), CMB 47 (caught fire after air attack 11.8.18), CMB 48, CMB 50 (scuttled 19.7.18), CMB 55, CMB 56, CMB 112, CMB 121-CMB 123 Tom Bunn, Rotherhithe – CMB 11 (lost by fire after collision, 2.11.17), CMB 12 Taylor & Bates, Chertsey -CMB 43, CMB 49 JW Brooke, Lowestoft -CMB 44, CMB 45, CMB S9 Frank Maynard, Chiswick – CMB 46, CMB 53, CMB 54 Salter Bros, Oxford -CMB 51, CMB 52, CMB 60, CMB 61 Wills & Packham, Sittingbourne – CMB 57, CMB 58. Launched 1916.

⚙ 40 ft CMB specifications
Displacement	5 long tons (5.6 short tons; 5.1 t)
Dimensions	45 ft (14 m) o/a
Propulsion	1 shaft, various petrol engines
Speed	35+ kts depending on engines
Range	Same as above.
Armament	1× 18 in (450 mm) Torpedo, 2–4 Lewis guns, DC/mines.
Crew	2-3

Enlarged versions of the 40-footers were ordered in mid-1916. They were generally similar, but to identify the wide variety of engine types used they were given the following suffixes:
A = Thornycroft V-12, S00bhp = 35 kts
B = Green 12 engine, 5S0bhp = 37.06 kts
C = Sunbeam engines, 900bhp = 41.19 kts
D = Green 18 engines, 900bhp = c40 kts
E = Thornycroft Y12 engines, 700bhp = 40.96 kts
F = engines (unknown make)
BD = Green 12 engines, 500bhp = 35.10 kts
CE = engines (unknown make)
CK = engines (unknown make)
DE = Green 18 engines, 900bhp = 40.67 kts
ED = Thornycroft Y 12 engines, 700bhp = approx. 40 kts
The BD, CE, CK, DE and ED boats all carried two 18in torpedoes, the others one each. Disposal was much as the 40-footers, with six lasting until 1932.

Class and Fate
Thornycroft of Hampton: CMB 14A to CMB 17A, 18A (lost collision 12.04.18), 21B, 24A (Lost Konstadt 18 08 19), CMB 25D, CMB 26B, CMB 27A, CMB 28A, CMB 31BD, CMB 33A (sunk in action off Ostend 12.4.18), CMB 34A, CMB 364, CMB 65À, CMB 764, CMB78E, CMBS80C, CMB82C, CMBS83CE, CMB87B, CMB 93E-CMB 97E, CMB 113CK, CMB 120F.

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Taylor & Bates, Chertsey – CMB 194, CMB 68B, CMB 73B, CMB 74B, CMB 84C, CMB 86BD, CMB 114D (caught fire and sank 4.23), CMB 115DE

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Camper & Nicholson, Gosport – CMB 194, CMB 68B, CMB 73B, CMB 74B, CMB 84C, CMB 86BD, CMB 114D (caught fire and sank 4.23), CMB 115SDE

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Camper & Nicholson, Gosport —CMB 20A, CMB 37A, CMB 39B, CMB 69A, CMB 70A, CMB 72A, CMB 75B, CMB 77À, CMB 79A (lost at Kronstadt 18.9.19), CMB 81C, CMB 98ED, CMB 99ED (lost by fire 1920), CMB 39R (lost by fire 28.4.18)

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Wills & Packham, Sittingbourne – CMB 22B, CMB 30B, CMB 63BD, CMB 64BD, CMB 116D, CMB 117D

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Salter Bros, Oxford – CMB 23B, CMB 62BD, CMB 67A (lost at Kronstadt 18.8.19)

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Rowhedge Iron Works -CMB 294, CMB 35A, CMB 90BD-CMB 93BD Frank Maynard, Chiswick – CMB 32A, CMB 38B, CMB 68BD, CMB 714 (missing 15.10.18, believed foundered after collision off Belgian coast), CMB 85C, CMB 88BD

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Builder unknown – CMB 89BD. Launched 1917 (CMB 14A-CMB 18A) – 1919 (except CMB 1180-CMB 120F 1922).

⚙ 55 ft CMB specifications
Displacement	11 long tons (12.3 short tons; 11.2 t)
Dimensions	60 x 11 x 3 ft (18 x 3.4 x 0.91 m)
Propulsion	2 shaft 750–900 hp (560–670 kW)
Speed	34–42 knots (63–78 km/h; 39–48 mph)
Range	c200 nm
Armament	2x 18-in Torpedoes, DCs, Lewis Guns
Crew	3-5

CMB M103 at Chatham dockyard hangar.

Larger versions of the 40-footer were ordered in 1916 and in early 1917 Thornycroft created a 60-foot (18 m) allowing a heavier payload, two torpedoes or a single torpedo and four depth charges, dropped from side cradles and capable of 35–41 knots (65–76 km/h; 40–47 mph). Thhey remained at prototype stage and led to the 70ft CMBs, with Twelve 72 ft long CMBs ordered in early 1918 for minelaying, each carrying seven magnetic mines, or up to 6 torpedoes. Five were cancelled and the last three survived long enough to see the start of the Second World War: CMB 103 MT (Camper and Nicholsons) was preserved as a museum ship, now at The Historic Dockyard Chatham.

Twelve minelaying CMBs were ordered in January 1918, capable of laying seven “M Sinker’ magnetic mines, or an alternative load of six torpedoes, but five were cancelled, CMBs 105-CMB 111. Post-war there were a number of experimental hulls, probably part of this programme, but completed by the builders for trials work. MB 1265 was reported to have been towed from Woolston to Pembroke DYd for completion and MB 1535, building at Hampton, had triple 18in.torpedo-troughs, 3 twin Lewis MGs and DCs, and was driven by a 24-cylinder Green engine. The variations in engines were: M = Thornycroft Y 12 engines, = 25.96bhp MT = Thornycroft Y24 engines, = 36.6kts CMB 102MT became depot ship Hornet in 1923 and survived the Second World War, with CMB 103MT and CMB I104MT, but the other two were deleted in 1920-21. Thornycroft, Hampton -CMB 100M, CMB 102MT. Thornycroft, Woolston (completed by Portsmouth DYd)-CMB 101M Camper & Nicholson, Gosport -CMB 103MT( (served in Second World War and preserved as relic), CMB 104MT. Launched 1919 (except CMB 103MT and CMB 104MT 1922)

Class: Ordered 4.15 from Elco, Bayonne, NY (placed through Canadian Vickers) — ML I-ML 50 p) Ordered 6.15 from Elco-ML 51-ML 550 DO Ordered 7.17 from Elco – ML 551-ML 580, Launched in 1915 (except ML 551 group 1918). T7) 0 ML 19, ML 40, ML 52, ML SS, ML 64, ML 110, ML 424, ML 149, ML 197, ML 230, ML 247, ML 253, ML 254, ML 255, ML 278, ML 356, ML 403, ML 421, ML 431, ML 474, ML 534, ML 540, ML 541, ML 561 were war losses. ML 114-ML 117, ML 38, ML 390, ML 392, ML 3%, ML 396, ML 400, ML 402, ML 404, ML 442, ML 444, ML 446, ML 448-ML454, ML 456, ML 458-ML 460, ML 462, ML 464, ML 469-ML 472, ML489, ML 491-ML 493, ML 5S43-ML Sd, ML 547-ML 548 were transferred to the French Navy and renumbered in V 1-V 73 series. ML 18, ML 62, ML 121, ML 152, ML 191, ML 196, ML 434, ML 521, ML 566 were lost after the Armistice. ML 97, ML 127, ML 229 were sold in damaged state, A total of 200 were sold in 1919, 127 were sold in 1920, and all but 8 were sold by 1924.

Interwar British Motors Torpedo Boats

History

From 1919 to 1939, were crucial years for shaping the MTB concept, later highly effective in WWII. After WWI, the Royal Navy still saw potential in small, high-speed boats armed with torpedoes, even f the admiralty was not to keen of developing tactics, neither had grand plans for these. Some classes were immediately inherited from 1917-18 concepts, and in general, there was the will to keep a tab on this type as long as other navies invested in them. These vessels were intended to attack larger enemy ships like destroyers or transports notably by night, conduct coastal patrols
and perform hit-and-run missions off enemy ports (which became a reality after the fall of France). They were of course influenced by earlier Coastal Motor Boats (CMBs), showing their value in daring raids like those against Bolshevik forces during the Russian Civil War (technically part of the interwar).

During the interwar the Royal Navy didn’t mass-produce these but instead, worked with private boatbuilders to experiment:

British Power Boat Company (BPB)

Founded by Hubert Scott-Paine, prototypes MTB 1 and MTB 2, Focusing on planing hulls for high speed, became the backbone of early MTB development.

Vosper & Company

Developed advanced hull designs and propulsion systems, Later became one of the main MTB suppliers in WWII. Postwar, merged with Thornycroft.

Thornycroft

Already experienced in naval craft, contributed experimental MTB designs.
Interwar MTBs were still evolving, but typical features included a length of ~60–70 feet (18–21 meters), top speed of 30–40+ knots (very fast for the time) and most of them were petrol-powered typicaly with Napier Lion engines or comparable units. They were armed with two torpedo tubes, typically 18-inch and had light machine guns for self defense. This emphasized speed over protection, relying on surprise and agility. Different hull shapes were tested (hard chine vs round bilge) but engine reliability was a major issue. The Royal Navy also evaluated foreign designs, including Italian MAS boats and German fast craft concepts. This handful of prototypes and trial vessels were cost-effective in case of war. The best designs could be mass-produced.

By the late 1930s, rising tensions in Europe pushed the Royal Navy to accelerate MTB development. Lessons from interwar experiments led directly to envision mass production, improved reliability and seaworthiness and use standardized designs for the coastal forces, key assets in Channel operations, Anti-shipping strikes and Special missions. One great test was the “channel dash” but they ultimaterly failed at it, partly due to heavy weather and partly due to the strong opposition met underway. The object of that section is to detail all classes of motor torpedo boats until the war started.

60 footer.

MTB-1 was designed for the Royal Navy by the British Power Boat Company, in 1935. The naval staff in 1934 estimated the RN was lagging behind in for light torpedo boats, when seeing what Germany and Italy were putting in this field. It was planned to acquire 30 boats of that first class. However they diverged in terms of details due to manufacturer’s input. The first two coastal boats since WWI were ordered on 27th September 1935 by the Royal Navy, to British Power Boat Company at Hythe, near Southampton. Four more were ordered on 19th October 1935 and all were completed by November 1936, with their simultaneous commissioning on 27th April 1937 as the first unit of the Royal Navy Coastal Forces. Three were ordered on 7th December 1936, nine on 11th January 1938 for 18 boats ordered total, all completed by 1939.

MTB-19 as completed with stern through torpedoes, note the stern guides folded up.

The first series were informally called MTB-1(1), had two quadruple 7.72 mm Lewis machine gun mounts, bow and stern, unmasked. Sea trials of June 1937 showed it was reliable but a few issues however were noted. This led to the Canadian MTB-1(2) albeit other sources states MTB 332 class. The main issue of these first series was that their 7.72 mm Lewis MGs had a sheer burst mass but very short effective range of just 400 metres, added to a very long reload time. Their torpedoes were carried internally, and landed in water tail first as for the CMBs, via suspended launch guides. This means like the need to close up very close, then make a U-turn before releasing them. They had also two depht charges in side cradles. Another relative issue was the location of the main fuel tank, just below the main cabin, potentially vulnerable to fire.

Latter they had torpedo tubes relocated at the bow and the forward Lewis mount was dropped. One supplementary DC cradle for Mk.VII depth charges was installed aft. Of these 18 boats, 10 were lost in action until 1941 and the remainder ended as attendant craft or target carrying boats for training. Another entered the series, MTB-100 converted from M MS51 motor minesweeper of 1938, with a greater beam at 13ft 3in, and six MGs. The 18-inch torpedoes were likely of the Mark XII (450 mm) type. MTBs 1-12 and 14-19 formed two MTB flotillas, the 1st (MTBs 1-6 + 14-19) and 2nd (MTBs 7-12). Appearance

The 1st MTB Flotilla was sent to the Mediterranean, based at HMS Vulcan establishment, Malta but they were recalled back home by December 1939 and based at HMS Beehive, Felixstowe. MTB 19 was detached to HMS Vernon establishement for training at Portsmouth. MTB 6 foundered in bad weather. The operated on the English Channel until lost or replaced (MTBs 15, 16, and 17, hit magnetic mines in 1940). The 2nd MTB Flotilla commissioned in 1938 was assigned to establishment HMS Tamar, Hong Kong. All lost in the Battle of Hong Kong, December 1941. MTB 8 was bombed by IJN aircraft, MTB 12 sunk in action by IJN landing craft. The remainder were scuttled on 26 December.

⚙ BPB MTB-1 to 19 specs
Displacement	18t standard
Dimensions	60ft 4in x 13ft 10in x 2ft 10in (18.39 x 4.22 x 0.86m)
Propulsion	3x Napier petrol 1650 bhp
Speed	38 kts trials, 35.5 kts service
Range	960 imp gal. unknown
Armament	2x 18-in TTs, 1x 4 7.72 mm Lewis 1916 MGs (4,000 rds), 4-6 DCs
Crew	9

White experimental-type (MTB 101). Built in 1936, purchased on the stocks by the admiralty.

Designed by Commander Peter Du Cane, managing director of Vosper Ltd, she was started as a private venture in 1936, launched and completed at Portsmouth in 1937. She was purchased for trials by the Admiralty, entering service as MTB 102 as the “100” series denoting prototypes. She was an all-wooden vessels, a “double diagonal Honduras mahogany on Canadian rock elm”.

specs

Length: 68 ft (21 m), Beam 19 ft 9 in (6.02 m), Draft 3 ft 9 in (1.14 m)
Powered by three Isotta Fraschini Asso V-18 57L petrol engines for 3,300 hp (2,500 kW)
Speed 48 knots (55 mph; 89 km/h) lightly loaded, 43 knots (49 mph; 80 km/h) combat

Crew 2 officers, 10 men.
Armed by two 21-in (533 mm) torpedo tubes, depth charges, machine guns, 20mm Oerlikon.

MTB 102 was the fastest wartime vessel in service, for the English Channel. She saw action at Dunkirk in 1940, evacuating allied troops over 8 crossings, and became Rear-Admiral Frederic Wake-Walker’s flagship after HMS Keith was sunk. In 1943, as “Vimy” she joined the Army’s 615 Water Transport Company, RASC. She carried Winston Churchill and Dwight Eisenhower during the Invasion of Normandy in 1944. She was sold off in 1945 and became a private yacht on the North Sea.

Vosper experimental-type (MTB 108(ii)). Built in 1941 at Portsmouth, England, ordered on 14 November 1940 but destroyed on slip by a night German air attack ofrom the 10 to 11 January 1941.

McGruer experimental-type (MTB 109). Built by McGruer (Clynder, Scotland, U.K.) but ordered on 28 Feb. 1942 and eventually sold incomplete in December 1945.

Also called BPB 60 feet-type they were built by British Power Boat (Hythe, England, U.K.). They were Motor Anti-Submarine Boat, meaning no torpedoes were carried, only depth charges, stored in racks aft and drop collars either sides. These comprised two sub-classes: MA/SB-1 to 5 launched in 1938-39, MA/SB-22 to 39 in 1941. The MA/SB 40 to 45 of 1940 were reclassified as MGB-40 to 45. There were reclassifications, the MGB-6 to 21, 46, 50-67 were all ex-MA/SBs launched 1939-41. The latter were British Power Boat 70 footers, the former were 60 footers.

Thornycroft 75 ft Boats.

Wartime British Motors Torpedo Boats

Introduction

The Royal Navy started the war with a collection of leftover MTBs from Vosper, Thornycroft and British Power Boat (BPB), all small, anti submarine boats called MA/SB for inshore sub hunting. No tactics were devised by the Admiralty but after the fall of France in June 1940, German bases were now just across the channel, and soon Schnellboote raids started sinking ships on the east coast at an alarming rate so a crash program was launched to develop small, coastal warships while older vessels were now forced to develop tactics on the fly when seeing combat. The MA/SBs were re-armed as Motor Gunboats (MGB) and started to tacked the German S-Boats (“E-boats”).

This Channel war ended with hundreds of small boats that could be built partly if wood or non-strategic materials and from civilian small yards, so they did not taxed the British shipbuilding industry and this resulted in rapid developments, woth initial machine guns replaced by 20mm cannons, then 40mm Bofors, and eventually automatic 6pdr guns just for short and bloody encounters with E-Boats. Other MTBs performed many interdiction missions, especially by night. MGBs on their side ended as “jacks of all trade”.

Some were very large like the Denny steam gunboats (SGB) and others fairly small like the HDMLs operating in and around harbours or busy rivers like the Thames and Mersey. And there is the subject of the “RAF fleet”.The RN considered the mission of its own vessels did not included SAR, or by accidents, yet the RAF, especially with the air battle of July to September 1940 was not keen at loosing experiences pilots and were forced to develop a network of rescue motor boats as well as safe buoys…

British Power Boat Series

The British Power Boat 60 ft MTB

Based on the British Power Boat Co. first two 63 ft HSL (high-speed launch) prototypes, they had been ordered originally and designed for the Royal Air Force for air-sea rescue. The RN staff ordered essentally reduced versions down to 60 ft (18 m) in length. They could carry two 18-inch (457 mm) torpedoes and managed 33 knots (38 mph; 61 km/h) with 18 ordered for the MTB-1 class in 1936, entering service in two series, MTB 1-12 and 14-19. The RN used a simple deception, ordered frequent changes of numbers and distributing photos to the pres to make believe they were far more numerous than the ones actually in service. For example the American monthly Popular Science believed there were twenty-three.

British Power Boat 72 ft MTB

Same vessels but ported to 72 ft in lenght. TFormer MGBs in 1941, converted to MTBs from 1942 by adding two side 18-inch tubes and a 6-pdr gun. 10 tons heavier after conversion but still capable of 39 knots. MGB 115–130 became MTB 434–449, MGB 131–170 were completed as MTB 450–489. In 1943, MTB 490–509 were ordered. They entered the Coastal Forces base st Haslar on 15 August 1944. For other sources like Conways, they are assimilated to the “MTB 412 class”, so with series such as as 412-418, 430-432, 434-500, 502-509, 519-522, all launched in 1941-42.

Follow-up British Power Boat types:

Vosper Boats

Vosper Boats – pinterest

This story started prewar, with several protototypes:

Built as a private venture, the 45-ft MTBs were scaled down versions of larger Vosper design, intended to be carried by larger vessels. MTB 104, 105, 106 and 107, were purchased and tested by Admiralty but found to have poor seakeeping. They were never used in combat, remaining on training and trials. Only MTB 105 saw action: She was carried on the Special Service Vessel HMS Fidelity after a conversion to a Commando carrier, to be deployed in the Far East with T Company, 40 Commando. Fidelity was torpedoed and sunk (Convoy ON 154) and so sank MTB 105, but the crew survived thanos to the on-board floatplane.

61 footer originally ordered by Norway, requisitioned. After Norway was invaded and the government ended in exile, the reconstitution of the Freen Norwegian Navy meant MTB-5 and 6 were retroceded to Norway.

Various lengths were tested by Vosper for the Royal Navy, but the “70 ft” boat was produced from 194, with modifications, in series that became MTBs 31-40, 57–66, 73−98, 222−245 and 347−362.
They all used three Packard V1-12 marine engines, for a modest top speed of 37 kn (43 mph; 69 km/h). They also carried two 21-inch (533 mm) torpedo tubes, and twin Vickers 0.50 in (13 mm) machine guns in a “bin” behind the bridge as well as two 0.303 in (7.7 mm) Lewis machine guns plus four depth charges in cradles. Despite the limited speed, they were very agile and well armed, exported also to Romania (Viscolul class).

The Vosper 73 ft (Type I and Type II) were produced from 1943 to 1945, flush-decked, with a slight sheer forward, so no low forecastle and scalloping like previous boats, making them easier to produce. The type II had a heavier gun armament but two 18-in torpedo tubes instad of four, so technically not classed as MGBs. Pennant numbers were MTB 380-395 and MTB 523-537. The Type II appeared in late 1945 and only served after the war.

Type I Specs

Dimensions: 47 t, 73 ft (22 m) x
Engine: 3x Packard 4M V12 4,200 hp, 40 knots (74 km/h).
Range: 470 nmi (870 km) at 20 knots (37 km/h)
Armament: 4x 18-inch (457 mm) TTs, Oerlikon 20 mm, 2x 0.303 Vickers K/0.50 HMG
Crew: 13

Type II Specs

Dimensions: Same but 49 t and 73 ft (22 m) long
Range: 480 nmi (890 km) at 20 knots (37 km/h)
Armament: 2x 18-in TTs, 57mm QF 6-pdr Mark IIA, 1×2 20mm Oerlikon aft, 2x 0.303 Lewis LMG.

Thornycroft Boats

The first two, MTB 24, 25 were 74 ft prototypes. The design was ordered in 1938. They were powered by three Isotta-Fraschini engines for 37 knots. MTBs 49-56, had four Thornycroft RY12 engines given the start of the war with Italy in June 1940 interrupted the provision, but the new engines were too weak for operations.

A development of the Vosper designs under sub-contract of the Thornycroft design. After construction passed to Polish Navy as S5 to S10, they were armed with two 18-inch torpedoes but had a 6-pdr gun forward, twin 20mm Oerlikon aft, two twin .303 LMG mountings.

Canadian Boats

MTB-460 of the Royal Canadian Navy
These Canadian built boats were designed by Hubert Scott-Paine for the Canadian Power Boat Company, used by the 29th MTB Flotilla, RCN. Originally designed as motor gun boats (MGBs) their main armament was a 6-pounder (57mm, 2.24 inch) to engage enemy small craft, but they received two torpedo boats and were reclassed as MTBs.

SP Type G70 Specs

Dimensions: 55 tons, 72 ft 6 in (21 m) x 20 ft 7 in (6.3 m) x 5 ft 8 in (1.7 m)
3x Rolls-Royce/Packard 14M supercharged V-12 3,750 hp total: 38–41 kn (44–47 mph; 70–76 km/h)
Range: 140 nmi (260 km) radius of action at 25 kn (29 mph; 46 km/h)
Armament: QF 6-pdr, 2x 21-in TTs, 20mm Oerlikon/40 mm Bofor, .303 or .50 Vickers MGs

The Fairmile D were a very large British MTB designed by Bill Holt and conceived by Fairmile Marine for the Royal Navy. Nicknamed “Dog Boats”, they were designed to combat the known advantages of the German E-boats over previous British coastal craft designs. Larger than earlier MTB or motor gun boat (MGB) designs, the Fairmile D was driven by four Packard 12-cylinder 1250 horsepower supercharged petrol engines and could achieve 29 knots (54 km/h; 33 mph) at full load. The boat carried 5,200 gallons of 100 octane fuel for a range, at maximum continuous speed, of 506 nautical miles. Armament varied according to role but could include four 18-inch or two 21-inch torpedoes, 6-pounder and 2-pounder guns, Oerlikons, multiple machine guns and depth charges.

British Gunboats

(To come in an update)







MTBs on pinterest

Read More/Src

Books

Royal Naval Coastal Forces 1939-1945, MTB’s, MGB’s, MA/SB’s, ML’s & HDML’s: A. J. D. North. Almark Publications
Warships of World War II, Part 7: Coastal Forces – H. T. Lenton and J. J. Colledge – Ian Allan Ltd., London.

HM MTB / Vosper 70ft Warship Profile No. 7 David Cobb ROI RSMA

Links

coastal-forces.org.uk
bmpt.org.uk
ww2db.com/ Thornycroft-Class Motor Launch
bmpt.org.uk 25 Ft FAST MOTOR BOAT
uboat.net Thornycroft 75 feet-type class
historisches-marinearchiv.de
PopSci 1932 CMBs
British Mil. Powerboat Team
mbriscoe.me.uk HMS St. Christopher
rmg.co.uk HDML model
The Morgan Giles Register HDML’s
uboat.net HDMLs
ww2talk.com British-built PT Boats
Harbour_defence_motor_launch
en.wikipedia.org CMB
MTB
www.usni.org Motor Torpedo Boats: A Technical Study
By Gordon Adamson and Douglas Van Patten
Time running out to save the last WW2 55-foot Coastal Motor Boat
ptdockyard.com costal forces, generic
seaspitfires.com

Videos

Dr Alex MTBs

Model Kits

britmodeller.com
scalemates Vosper 70ft
Thornycroft 55ft CMB
High speed launch Type 2 63-ft-class
Motor torpedo boat BPB 70-ft-class

3D

Vosper MTB Game-Ready model
More in research.