HMS E42

Like all post-E8 British E-class submarines, E42 had a displacement of 662 long tons (673 t) at the surface and 807 long tons (820 t) while submerged. She had a total length of 180 feet (55 m)^[2] and a beam of 22 feet 8.5 inches (6.922 m). She was powered by two 800-horsepower (600 kW) Vickers eight-cylinder two-stroke diesel engines and two 420-horsepower (310 kW) electric motors.^[3][4] The submarine had a maximum surface speed of 16 knots (30 km/h; 18 mph) and a submerged speed of 10 knots (19 km/h; 12 mph). British E-class submarines had fuel capacities of 50 long tons (51 t) of diesel and ranges of 3,255 miles (5,238 km; 2,829 nmi) when travelling at 10 knots (19 km/h; 12 mph).^[2] E42 was capable of operating submerged for five hours when travelling at 5 knots (9.3 km/h; 5.8 mph).

E42 was armed with a 12-pounder 76 mm (3.0 in) QF gun mounted forward of the conning tower. She had five 18-inch (450 mm) torpedo tubes, two in the bow, one either side amidships, and one in the stern; a total of 10 torpedoes were carried.^[3]

E-Class submarines had wireless systems with 1-kilowatt (1.3 hp) power ratings; in some submarines, these were later upgraded to 3-kilowatt (4.0 hp) systems by removing a midship torpedo tube. Their maximum design depth was 100 feet (30 m) although in service some reached depths of below 200 feet (61 m). Some submarines contained Fessenden oscillator systems.^[2]

• Koerver, Hans Joachim. Room 40: German Naval Warfare 1914-1918. Vol II., The Fleet in Being. Steinbach, Germany: LIS Reinisch, 2009.
• Hutchinson, Robert (2001). Jane's Submarines: War Beneath the Waves from 1776 to the Present Day. London: HarperCollins. ISBN 978-0-00-710558-8. OCLC 53783010.