Fairmile B Motor Launch Submarine Chasers


In 1942, during World War Two, the British Admiralty commissioned Thesen & Co. for the assembly and manufacture of a variety of wooden life boats and other craft including the famous, small wooden Fairmile B Motor Launch submarine hunters. To this end and as part of its war effort, the firm closed down its widely known Stinkwood furniture manufacturing department and released the skilled artisans employed there for this boatbuilding work.

By the end of the war, Thesen & Co. had supplied 10 “ML 10” craft to the Royal Navy which were sent under their own power as the 49th Fairmile Flotilla (SANF) to Burma and deployed along the Arakan coast. These boats saw much action in support of ground forces and disrupting Japanese supply lines.

They were constructed from imported timber, (using Burmese teak for the decks, with laminated hulls of Iroko, Sapele, Limba and other West African timbers), displaced 60 tons, measured 112 feet in length, and were fitted with two 1200 horsepower Hall Scott ‘Defender’ petrol engines, naval guns and depth charges. They carried a crew of 19, and were designed mainly for the purpose of submarine hunting.

The operation ceased with the end of hostilities but the after-effects of the yard with its craftsmen remained, resulting in the  continued building by Thesens of large wooden fishing craft, yachts and motor launches. Apart from the petrol-driven, depth-charge carrying Fairmiles, the well-known yachts Voortrekker (which came second in the Transatlantic race in 1968)   and  Albatros II (which gained a first place in the inaugural Cape-to-Rio race in 1971) also came from this shipyard.

After the end of the war, there was much sad nostalgia in Knysna when, while still relatively new, these fine Fairmile craft were broken up. Their ship’s bells were presented to the town in memory of the part it had played in support of the war effort.


Noel Macklin founded the Fairmile Marine Company shortly before the outbreak of the Second World War. Based on his experiences in the First World War, and believing that war with Germany was imminent, Noel was convinced that the UK would need large numbers of small craft to protect British coastal waters against submarines. Initially he used his own money to pay for the design and construction of a prototype boat before the Admiralty stepped in to fund the programme. These boats (which became known as the Fairmile A Type Motor Launch) were conceived as wooden kit boats, with the parts made at the Fairmile factory and delivered to local boatyards for assembly.

The design of the Fairmile A was unsatisfactory in a number of ways, mainly related to their hard chine hull form, but a design existed within the Admiralty for a similar sized vessel with round bilges. This vessel was known to have better seakeeping qualities, and as the Admiralty was impressed with the feasibility of the Fairmile concept of wooden kit boats assembled locally, the contract to produce the boat kits was awarded to them. The new boat became known as the Fairmile B Type Motor Launch, and like the A Type, the kits were delivered to boatyards around the UK (and later around the world, including Knysna) for assembly. Each kit was made up of six packages, and each package was designed to fit in a standard 15-ton lorry.

Like the A Type, the B Type was intended as a submarine chaser, and so all the boats were fitted with asdic (sonar) as standard. Their main armament reflected their anti-submarine focus, with 12 depth charges, a single 3-lb gun aft, and one set of twin 0.303-in machineguns. The initial design of the B Type called for three engines, but were reduced to two on production. Despite this loss of speed, it was recognised that the reduction in power did not materially affect the boats ability to perform its designated role of protection against submarines. Petrol engines were chosen because pre-war searches for suppliers of high power diesel engines suitable for marine use had proved fruitless. Petrol engines imposed a much greater fire hazard than diesel engines, although the fire extinguisher provided on the boats proved its effectiveness. The fuel capacity of 2305 gallons was sufficient to give the boat a range of 1500 miles at 12 kt, and had a top speed of 20 kt. On occasion, extra fuel tanks were fitted to the deck to significantly extend their range, and in this configuration they carried out long sea passages, still maintaining excellent seakeeping qualities in most weather conditions.

A far-sighted specification was that these boats could be reconfigured for different roles with 48 hours notice. To meet this requirement the boats were fitted with steel strips, with tapped holes. Armament was bolted to the strips, and to change roles the unwanted armament had simply to be unbolted and new armament fitted in its place. In this way the boats could be fitted with a multitude of different equipment, including torpedo tubes, mines, depth charges, various guns and other specialist gear. It was also common to carry hand grenades on the bridge.

The first Fairmile B motor launch was completed in September 1940, and altogether approximately 650 boats were built between 1940 and 1945.  This Launch was a great success, and proved their worth again and again with their versatility and ability to operate in heavy weather.

The Fairmile B Type Motor Launch was originally designed as a submarine chaser, protecting coastal shipping and waterways from submarine threats. In this role it provided good service, escorting many convoys and patrolling the approaches to ports. Later in the war their armament was upgraded on some boats to include a cut-down version of the Hedgehog anti-submarine mortar.

Despite their low speed they were pressed in to service in a number of roles which properly demanded much faster vessels. For example, they were used in clandestine operations, working with the Special Operations Executive to insert and remove agents, although faster motor boats were preferred. Similarly, they also acted as minelayers and rescue boats.

The boats also served with many other nations, with some being sent to the US under lend-lease to provide assistance during the German attack on the US East Coast in 1942, others serving with the Royal Indian Navy, Royal Australian Navy, Royal Canadian Navy, Royal New Zealand Navy, Royal Norwegian Navy, Royal Netherlands Navy, Free French, and the South African Navy.


Please see below to read further on the Fairmile Motor Launches built by  Thesens, often bringing to the surface useful as well as entertaining details of events, which could be found nowhere else.  These eyewitness accounts give a more intimate picture of war-time Knysna than official facts and figures could ever show.


Sources: ‘WW2ships’   written by James Davies


‘Memories of Knysna’ –  researched and compiled by Mrs Margaret Parkes & Mrs Vicky Williams