John Isaac Thornycroft

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John Isaac Thornycroft
Spy - J I Thornycroft.jpg
Naval architect and founder of two firms carrying the Thornycroft name; caricature by "Spy" (Leslie Ward) from Vanity Fair
Born February 1843
Vatican City, Rome
Died June 1928 (aged 85)
Bembridge, Isle of Wight

Sir John Isaac Thornycroft (1843–1928) was a British shipbuilder, the founder of the Thornycroft shipbuilding company and member of the Thornycroft family.[1]


He was born in 1843 to Mary Francis and Thomas Thornycroft.

Thornycroft worked for a while at Palmers Shipbuilding and Iron Company in Jarrow-on-Tyne before studying for a diploma in engineering at the University of Glasgow. At Glasgow he studied under Lord Kelvin and Professor Macquorn Rankine.[2]

He established a shipbuilding yard on the River Thames at Chiswick in 1866.[3] He built his first steam launch when he was 19 years old. In 1876, his first vessel for the Royal Navy was a steam torpedo boat, HMS Lightning.

His yard built a steam-powered lorry which led them into the vehicle manufacturing business, the Thornycroft named business lasting until the late 20th century.

Thornycroft worked on means of aiding hull lubrication by air which also led him to the hydrofoil. This led him to develop stepped chine hulls which used for 55 ft British Coastal Motor Boats during the war gave them speeds of up to 40 knots.[4]

In 1904, he transferred larger shipbuilding activities to Southampton. In 1908 he also set up the Hampton Launch Works on Platts Eyot, an island on the Thames at Hampton, Middlesex.

He died in 1928.[5]


This boatbuilding works concentrated on cabin cruisers and speedboats, but also produced small naval craft - Coastal Motor Boats in the First World War and Motor Torpedo Boats, Motor Launches and landing craft in the Second World War.

Thornycrofts closed their boatbuilding operation on Platt's Eyot when they were taken over by Vospers in the mid-1960s. The Southampton shipyard continues to operate as a VT Shipbuilding (Vosper-Thornycroft) company.

Sir John Thornycroft's son Isaac Thomas Thornycroft skippered a motorboat Gyrinus II designed by him to two gold medals at the 1908 Olympic Games.

Sir John Thornycroft was the brother of the British sculptor Hamo Thornycroft and uncle of the poet Siegfried Sassoon.


  1. ^ Herbert B. Mason (Editor). Encyclopaedia of Ships and Shipping. London. 1908. pp. 630-631. Full view available from GoogleBooks.
  2. ^ Institution of Civil Engineers (January 1929), "Obituary", Minutes of the Proceedings 227 (1929): 275, doi:10.1680/imotp.1929.14359, retrieved 2009-01-31 
  3. ^ "Thornycroft, Sir John Isaac". Who's Who. Vol. 59. 1907. p. 1747. 
  4. ^ 1908 Thornycroft Model at The Hovercraft Museum at
  5. ^ Sir John Isaac Thornycroft - 1843-1928. Obituary notice. Proceedings of the Royal Society of London, Series A. Vol. 121, No. 788 (Dec. 1, 1928), pp. xxxv-xxxvii

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