A motor torpedo boat is a fast torpedo boat, especially of the mid 20th century. The motor in the designation originally referred to their use of petrol engines, typically marinised aircraft engines or their derivatives, which distinguished them from other naval craft of the era, including other torpedo boats, that used steam turbines or reciprocating steam engines. Later, diesel-powered torpedo boats appeared, in turn or retroactively referred to as "motor torpedo boats" for their internal combustion engines, as distinct from steam powered reciprocating or turbine propulsion.
Though other navies built similar petrol-powered craft, the specific designation "motor torpedo boat", abbreviated to "MTB", is generally used for craft of the Royal Navy (RN) and Royal Canadian Navy boats. During the Second World War, the US Navy built several classes of marine V-12-powered PT boat, whose hull classification symbol "PT" stood for "patrol, torpedo", but which were grouped into motor torpedo boat squadrons.
German diesel-powered torpedo boats of the Second World War were called S-boote (Schnellboote, "fast boats") by the Kriegsmarine and "E-boats" by the Allies. These large craft (well over 100 ft overall) were not known as motor torpedo boats at the time, but later have been grouped with them by some. Italian MTBs of this period were known as Motoscafo Armato Silurante ("MAS boats", torpedo-armed motorboats). French MTBs were known as vedettes lance torpilles ("torpedo-launching fast boats"). Soviet MTBs were known as (torpyedniye katyery; "torpedo cutters", often abbreviated as TKA). Romanian MTBs were known as vedete torpiloare ("torpedo fast boats").
The role of the motor torpedo boat has been absorbed in modern navies by the fast attack craft.
Torpedo boats were designed for missions that variously involved high speed, operating at night, low speed ambush, and manoeuvrability to allow them to get close enough to launch their torpedoes at enemy vessels. With no significant armour, the boats relied upon surprise and agility at high speed to avoid being hit by gunfire from bigger ships.
The Royal Navy started developing particularly small, agile, and fast petrol-powered torpedo boats in the early 20th century, shortly before the beginning of the First World War. Known as coastal motor boats, these were only around 15 tons. They were joined by the Italian Navy's MAS boats, of 20-30 tons displacement. MAS 15 was the only motor torpedo boat in history to sink a battleship, the Austro-Hungarian vessel Szent István in 1918.
In the Second World War, Britain fielded a variety of MTBs, which were operated by Coastal Forces.
Diesel-powered MTBs entered the Royal Navy with the Dark class patrol boat in 1954. The last MTBs in the Royal Navy were the two Brave-class fast patrol boats of 1958, which were capable of 50 knots (93 km/h).
Many boats were designated MTBs. A variety of designs were adopted and built. For instance, a 55 ft (17 m) type, capable of 40 kn (46 mph; 74 km/h), was shown in 1930.
The following is an incomplete list of British motor torpedo boats:
Commander Peter Du Cane CBE, the managing director of Vosper Ltd, designed a motor torpedo boat as a private venture in 1936. She was completed and launched in 1937. She was bought by the Admiralty and taken into service with the Royal Navy as MTB 102.
The installed powerplant of three Isotta Fraschini 57-litre petrol engines delivered 3,300 hp (2,500 kW) which gave her a speed of 48 kn (55 mph; 89 km/h) light and 43 kn (49 mph; 80 km/h) when carrying a full load.
MTB 102 was the fastest wartime British naval vessel in service. She was at Dunkirk for the evacuation, where she served as Rear-Admiral Frederic Wake-Walker's flagship after the destroyer HMS Keith was sunk. She carried Winston Churchill and Dwight Eisenhower when they reviewed the fleet before the Invasion of Normandy.
They were based on the British Power Boat BPB 63 ft (19 m) rescue craft and were originally designed for the Royal Air Force but reduced to 60 ft (18 m) in length. They could carry two 18-inch (457 mm) torpedoes and achieve a maximum speed of 33 kn (38 mph; 61 km/h). The Royal Navy ordered their first (of a total of 18) in 1936. These entered service as MTB numbers 1 to 12 and 14 to 19. In the early days of the war, they were painted with different numbers and photos distributed to the press to give the impression the Royal Navy had more than they actually did. One photo was sent to the American monthly Popular Science showing the number twenty-three.
Although various boat lengths were produced by Vosper for the Royal Navy, the "70 ft" boat was produced from 1940. The design was produced with modifications as MTBs 31-40, 57-66, 73-98, 222-245, 347-362, 380-395 and 523-537.
Using three Packard V1-12 marine engines, they were capable of around 37 kn (43 mph; 69 km/h). Early models carried two 21-inch (533 mm) torpedo tubes, two 0.50 in (13 mm) machine guns and two 0.303 in (7.7 mm) machine guns. They could also carry four depth charges.
Between 1943 and 1945, two Vosper designs appeared, the "Vosper type I 73ft" and the type II.
This design remained in use after the war.
The Fairmile D was 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 patrol engines and could achieve 29 knots (54 km/h; 33 mph) at full load. The boat carried 5200 gallons of 100 octane gas for a range at maximum continuous speed of 506 nautical miles.
These boats were designed by Hubert Scott-Paine for the Canadian Power Boat Company, and used by the Royal Canadian Navy 29th MTB Flotilla. Originally designed as motor gun boats (MGBs), carrying a 6-pounder (57mm, 2.24 inch) to engage enemy small craft, they were re-designated MTBs.
Scott-Paine type G 70 foot boat
After the end of World War II a number of Royal Navy vessels were stripped and sold for use as houseboats. These included MGBs as well as MTBs. Many of these were moored in Langstone Harbour, Littlehampton, Hayling Island and Wootton Creek, although most have now disappeared from these locations. More MTB houseboats can be found at Shoreham-by-Sea (West Sussex), Cobden Bridge (Southampton) and Bembridge (Isle of Wight).