|Builder:||Armstrong Whitworth, Newcastle upon Tyne|
|Laid down:||1 June 1915|
|Fate:||Sold, 21 February 1922|
|Class and type:||E class submarine|
|Length:||181 ft (55 m)|
|Beam:||15 ft (4.6 m)|
HMS E29 was a British E class submarine built by Armstrong Whitworth, Newcastle-Upon-Tyne. She was laid down on 1 June 1915 and was commissioned in October 1915. E29 suffered an explosion in the battery compartment which killed four men on 9 January 1916. E29 was sold on 21 February 1922.
Like all post-E8 British E-class submarines, E21 had a displacement of 662 tonnes (730 short tons) at the surface and 807 tonnes (890 short tons) while submerged. She had a total length of 180 feet (55 m) and a beam length 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. 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 tonnes (55 short tons) of diesel and ranges of 3,255 miles (5,238 km; 2,829 nmi) when travelling at 10 knots (19 km/h; 12 mph). E21 was capable of operating submerged for five hours when travelling at 5 knots (9.3 km/h; 5.8 mph).
E21 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.
E-Class submarines had wireless systems with 1 kilowatt (1.3 hp) power ratings; in some submarines, these were later upgraded to 3 kilowatts (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.
- Innes McCartney; Tony Bryan (20 February 2013). British Submarines of World War I. Osprey Publishing. pp. 11–12. ISBN 978-1-4728-0035-0.
- Akerman, P. (1989). Encyclopaedia of British submarines 1901–1955. p.150. Maritime Books. ISBN 1-904381-05-7
- "E Class". Chatham Submarines. Retrieved 20 August 2015.
- 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.