B-class motor launch

Launch of Cha 105 in Soerabaja.
Class overview
Name	B class
Builders	Droogdok Maatschappij Soerabaja Marine Etablissement te Soerabaja Indische Maatschappij Palembang
Operators	Royal Netherlands Navy  Imperial Japanese Navy
Planned	16
General characteristics
Type	Motor launch
Displacement	130 t (130 long tons)
Length	45.5 m (149 ft 3 in)
Beam	5 m (16 ft 5 in)
Draft	1.4 m (4 ft 7 in)
Propulsion	2 shafts 1,900 bhp (1,400 kW) Diesel engines
Speed	19 knots (35 km/h; 22 mph)
Armament	1 × 76 mm (3.0 in) naval gun 1 × 40 mm (1.6 in) anti-aircraft gun 2 × 12.7 mm (0.50 in) machine guns 20 depth charges

The B class was a ship class of sixteen motor launches built in the Dutch East Indies for the Royal Netherlands Navy.^[1][2] However, before the motor launches could be completed the Dutch East Indies was invaded by the Japanese.^[3] To prevent the vessels from being captured they were scuttled.^[4] Nonetheless, seven motor launches were salvaged and completed as auxiliary submarine chasers by the Japanese and taken into service of the Imperial Japanese Navy as the Cha 103 class.^[2][5]

The B-class motor launches were built in the Dutch East Indies at the shipyards of Droogdok Maatschappij Soerabaja, Marine Etablissement te Soerabaja and Indische Maatschappij Palembang.^[4] They were designed to be able to perform various roles such as auxiliary submarine chaser, patrol vessel and auxiliary minesweeper.^[6] The launches measured 45.5 metres (149 ft 3 in) in length, had a beam of 5.0 metres (16 ft 5 in) and a draft of 1.4 metres (4 ft 7 in).^[4] Furthermore, they had a displacement of 130 tons and were equipped with diesel engines that could produce 1,900 brake horsepower (1,400 kW).^[7] This allowed the launches to reach a maximum speed of 19 knots (35 km/h; 22 mph).^[7] As armament they had a single 76-millimetre (3 in) naval gun, a single 40 mm (1.6 in) anti-aircraft gun, two 12.7 mm (0.50 in) machine guns and 20 depth charges.^[4][2]

The seven motor launches that were salvaged and completed as auxiliary submarine chasers by the Japanese became known as the Cha 103 class.^[2][5] These submarine chasers were equipped with different diesel engines and armament in comparison to their original B class design.^[8] Four chasers (Cha 103, Cha 105, Cha 107 and Cha 108) were equipped with diesel engines that could produce 1,800 bhp (1,300 kW), which allowed them to reach a maximum speed of 20 knots (37 km/h; 23 mph).^[8] Two (Cha 114 and Cha 115) were equipped with diesel engines that could produce 1,500 bhp (1,100 kW), which allowed them to reach a maximum speed of 19 knots.^[8] While the last one, Cha 106, was equipped with diesel engines that could produce 1,200 bhp (890 kW), which allowed the chaser to reach a maximum speed of 16.5 knots (30.6 km/h; 19.0 mph).^[8] All auxiliary submarine chasers of the Cha 103 class were armed with a single 47 mm (1.9 in) Yamanouchi gun, a 13.2 mm (0.52 in) machine gun, a 7.7 mm (0.30 in) machine gun and two depth charge rails that could carry a total of 32 depth charges.^[5]

• Gardiner, Robert; Chesneau, Roger, eds. (1980). Conway's All the World's Fighting Ships 1922–1946. London: Conway Maritime Press. ISBN 0-85177-146-7.
• Lenton, H.T. (1968). Royal Netherlands Navy. Navies of the Second World War. London: Macdonald & Co.
• Mark, Chris (1997). Schepen van de Koninklijke Marine in W.O. II (in Dutch). Alkmaar: De Alk. ISBN 90-6013-522-9.
• von Münching, L.L. (1978). Schepen van de Koninklijke Marine in de Tweede Wereldoorlog (in Dutch). Alkmaar: Alk. ISBN 90-6013-903-8.