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Thornycroft-class file photo [24889]

Thornycroft-class Motor Launch

CountryUnited Kingdom
Length67 feet
Beam15 feet
Draft4 feet
MachineryTwo Thornycroft RY/12 (650hp each) or three Power-Napier Sea Lion (500hp each) petrol engines
Speed25 knots
Range350-600nm depending on engine installation and tankage
Armament1x20mm Oerlikon autocannon, .303 Vickers, Lewis, or Browning machine guns


This article refers to the entire Thornycroft-class; it is not about an individual vessel.

ww2dbaseThe gallant exploits of the crews of the Royal Air Force air-sea rescue (ASR) launches, who bravely sailed out in all weathers to rescue unfortunate airmen who had had the misfortune to ditch in the ocean, has seldom been a topic for World War II historians. At the commencement of the war rescue boats were typically adaptations of existing designs which, despite having a good turn of speed, were not generally regarded as being particularly good sea boats. In 1942 therefore, the Royal Air Force (RAF) Directorate of Marine Craft issued a specification for an improved craft to be designed from scratch specifically for this kind of work. This new generation of ASR craft would introduce greatly improved provision for rescued aircrew, especially for the injured. Endurance and sea keeping qualities were required to take precedence over sheer speed and the new boats were required to have a much heavier defensive armament than had been installed on earlier boats.

ww2dbaseThe Thornycroft followed the British Power Boats Type 1`and 2 into service, the first ones being issued to units early in 1942. They introduced the installation of machine gun turrets located on either side of the wheelhouse with a third turret aft. Although this arrangement was commonplace in the Royal Navy's British Power Boat Motor Gun Boats of the time it was new to the RAF rescue launches. Initially a single Vickers or Lewis .303 machine gun was installed in each turret, but these soon gave way to a lower profile turret housing a pair of .303 Brownings whilst the aft turret was often replaced by a 20mm Oerlikon autocannon. This armament arrangement would remain fairly standard on the ASR rescue launches until the end of the war, although there were occassionally various local modifications in an attempt to further improve what was still considered to be a generally weak defensive arrangement.

ww2dbaseHull construction for these boats was of the hard chine principle, the planking being of double skin mahogany planks on closely spaced sawn frames. Wood was also used for the deck, hatches and the exterior of the wheelhouse. To speed up production, the frames and bulkheads, in addition to the sick bay cabin and wheelhouse "superstructure" were prefabricated.

ww2dbaseBelow the deck were the crew quarters containing sea bunks and double tiered cot bunks together with storage space for the crew's personal gear and other items. A folding table, toilet and wash basin were among the items located in the quarters. Further aft was a well fitted galley where hot soup, tea and other forms of nourishments could be prepared. Above, behind the armour plated wheelhouse, was located a well equipped sick bay, radio room and fairly comfortable officers' accomodation. Aft of the sick bay was the fuel compartment containing three 400 gallon petrol tanks which gave the launch a normal range of approximately 350 nautical miles (with additional long range tanks installed this could be increased to 600 miles). The engine room contained a pair of Thornycroft RY/12 Vee-12 petrol engines (later built vessels would have three Power-Napier sea-lion engines of 500 hp each which gave a moderate increase in top speed). An additional heavy duty generator was installed to provide power for the launch when not underway.

ww2dbaseSeventy-eight Thornycroft launches were built between 1942 and 1944; forty-seven by the parent company and the rest by the Walton Yacht Works. Although the type did not appear to have aroused any particularly nostalgic affection amongst former crews, it did seem to have been a good workhorse and quite stable in all but the most adverse weather conditions. They served in many of the numerous ASR Units located around the British coastline, saw action in the Mediterranean and Indian Ocean, took part in pre-D-Day operations covering the Normandie beaches and contributed greatly during subsequent operations along the French and Belgian coasts. The majority of the ASR launches were sold off soon after the war through the disposal agency and by the mid 1950s their rescue role had been taken over by the Royal National Lifeboat Institution (RNLI) aided by RAF and Royal Navy helicopter equipped squadrons.

ww2dbaseProbably one of the most doggedly determined operations by a craft of this type was that performed by HSL 2507, commanded by Flying Officer William Garrett, on 23-26th June 1944. This launch had been equipped with long range fuel tanks and detached with a sister vessel, from No. 1 ASR Unit based at Lerwick, Scotland, United Kingdom, to Balta Sound in order to support the operations of Coastal Command aircraft patrolling the supply lines to Russia. On that mission 2507 was despatched to rescue the crew of a Canadian Canso flying boat which had been shot down while in the act of depth-charging a German U-boat within the Arctic Circle. Soon after leaving Balta Sound and in worsening weather conditions, 2507 had an engine failure. In spite of this handicap Garrett decided to press on with the rescue mission. Rolling and smashing through the seas on one engine in a frantic endeavour to get to the ditched crew, unable to use the galley to get anything hot, after 17 hours the Canadian crew's overcrowded dinghy was located and the rescued airmen were taken aboard the launch. Sadly the Flying Boat's captain died soon after being brought aboard although he was subsequently awarded a posthumous Victoria Cross. All the other members of the flying crew also received well deserved decorations - the willpower needed to survive in an overcrowded dinghy in freezing Arctic seas whilst waiting to be rescued required more than passing notice. Twelve months after this heroic rescue Flying Officer Garrett too was made a Member of the Order of the British Empire.

John Pritchard, The R.A.F.'s Thornycroft High Speed Launches (Military Modelling May 1978)

Last Major Revision: Sep 2015


HSL 2586 at Walton-on-Thames, Surrey, England, United Kingdom, circa 1943HSL 2641 rescuing downed US Navy airmen whose PB4Y-1 bomber had been shot down by Germans over the Bay of Biscay, 15 Feb 1944

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Thornycroft-class Motor Launch Photo Gallery
HSL 2586 at Walton-on-Thames, Surrey, England, United Kingdom, circa 1943HSL 2641 rescuing downed US Navy airmen whose PB4Y-1 bomber had been shot down by Germans over the Bay of Biscay, 15 Feb 1944

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