Sir Eustace Tennyson d'Eyncourt, 1st Baronet

Sir Eustace Henry William Tennyson d'Eyncourt, 1st Baronet, KCB, FRS (1 April 1868 – 1 February 1951) was a British naval architect and engineer. As Director of Naval Construction for the Royal Navy, 1912–1924, he was responsible for the design and construction of some of the most famous British warships. On 20 February 1915 Winston Churchill appointed him Chairman of the Landships Committee at the Admiralty, which was responsible for the design and production of the first military tanks to be used in warfare.

D'Eyncourt was related to the politician Charles Tennyson d'Eyncourt (d. 1861), uncle of the poet Alfred Lord Tennyson. He was also related to Admiral Edwin Tennyson d’Eyncourt.

Design characteristics
In his battlecruisers, "large light cruisers" and the Hawkins-class cruisers, d'Eyncourt evolved a novel hull form: in cross-section the hull was an isosceles trapezoid, with the ship's sides sloping inboard at an angle of 10 degrees from the vertical, while outboard of this, external bulges extended over the full length of the machinery spaces. The result was a hull structure of great strength, and the sloping sides increased the possible spread of impact of shells, thus giving greater resistance to penetration.

The aesthetic side of naval architecture has seldom been given much attention, though it is as much of an art as the architecture of buildings; in general appearance (in terms of harmonious proportion as regards length, beam, and freeboard, as well as the size of the superstructure and funnels in relation to the hull), the opinion has been expressed that d'Eyncourt created some of the most elegant and eye-pleasing warships ever designed, the prime example being the battle cruiser Hood.

Ship designs
D'Eyncourt was not necessarily the principal designer of the vessels listed below, but had ultimate responsibility for them.

Battleships and Battlecruisers

 * Brazilian battleship, later HMS Agincourt
 * Turkish battleship, later HMS Erin
 * Chilean battleships Almirante Latorre, later HMS Canada and Almirante Cochrane, later HMS Eagle (aircraft carrier)
 * Royal Sovereign-class battleship
 * Renown-class battlecruiser
 * HMS Hood (51) battlecruiser
 * Several very large capital ship designs, both battleships and battlecruisers, rendered inadmissible under the Washington Naval Treaty
 * HMS Nelson (28) battleship

Cruisers

 * GRC Katsonis
 * HMS Chester
 * Arethusa class (1913)
 * C class (1912–17)
 * Caroline class
 * Calliope class
 * HMS Champion
 * Cambrian class
 * Centaur class
 * Caledon class
 * Ceres class
 * Carlisle class
 * Hawkins-class large cruisers (1915)
 * Danae-class cruisers (1916–18)
 * HMS Danae
 * HMS Dragon
 * HMS Diomede
 * HMS Enterprise (Emerald-class cruiser)) (1917–18)
 * HMS Kent (County-class cruiser) (1923–24)

"Large light cruisers", later aircraft carriers

 * HMS Courageous (50)
 * HMS Furious (47)

Destroyers

 * R and S-class destroyers
 * V and W-class destroyers
 * Scott-class flotilla leaders

Submarines

 * J class
 * K class

Other types
Monitors, Patrol boats, Minesweepers, Sloops, Gunboats for China Station, Merchant ship conversions into seaplane carrier

Tanks
D'Eyncourt was chairman of the Landships Committee, created by Winston Churchill, which oversaw the design and production of Britain's first military tank. (See also the Mark VIII (tank).)

Writings
D'Eyncourt summarized his World War I work in an article "Naval Construction During the War", published in Engineering, 11 April 1919, pp. 482–490. He also published an autobiography entitled A Shipbuilder's Yarn (London: Hutchinson, 1948).