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Engineering apprenticeship=== Working for his father, at first on the Great Grimsby Royal docks, then in company with his elder brother Lewis Rendel on the eastern breakwater and new Admiralty pier at Holyhead, he was well prepared for an apprenticeship to his father's great friend, Sir William Armstrong, at his Elswick works. He lived with Armstrong at his house in
Jesmond for three years before completing his engineering education at his father's London office. His father died in 1856 and the brothers George, Stuart and Hamilton all joined Armstrong's company, while Alexander took over the family business.
Rendel gunboats In 1867 Armstrong signed an agreement with a local shipbuilder, Dr.
Charles Mitchell, whereby Mitchell's shipyard would build warships and Armstrong's company would provide the armaments. George Rendel was put in charge of the new venture and he designed the early ships produced by it. These were the
Rendel gunboats (or "flat-iron gunboats" after their physical similarity to a contemporary
flat iron) produced for the
British Admiralty as well as for Italy, Brazil and Chile. The first of these was
HMS Staunch, delivered in 1868.
Forced draught Rendel and
Alfred Yarrow pioneered the use of
forced-draught fans in boiler rooms, significantly increasing the power of marine steam engines at minimal cost in weight or volume.
Naval guns Rendel worked on the design of large naval guns, using hydraulics to reduce the number of men required to work the guns and the space required. This was first tried on
HMS Thunderer, which was able to have 38-ton guns fitted, instead of the 35-ton guns originally planned. His hydraulic systems were subsequently used in all
Royal Navy ships as well as the ships of several foreign navies.
HMS Inflexible In 1871 Rendel was appointed a member of the British government committee on warship design. He played a major role in the 1877 design of the innovative , which was notable for being the first major warship to depend in part for the protection of her buoyancy by a horizontal armoured deck below the water-line rather than armoured sides along the waterline. She was packed with other new features: her guns weighed 80 tons each; she carried the thickest armour ever to have been carried by a British warship, at ; great attention was paid to her damaged stability to ensure she could absorb damage and remain upright and buoyant.
Resignation Rendel resigned from Armstrong's company in 1882, when Armstrong decided to make Andrew Noble sole manager of the Ordnance Department. In fact, Rendel loathed Noble, as did his brothers, who also worked for Armstrong.
Admiralty career He was invited by the
First Lord of the Admiralty, the
Earl of Northbrook to become an extra-professional
Additional Civil Lord of the Admiralty on the
Board of Admiralty in 1882, but retired from this post due to ill-health in 1885.
Italy He was persuaded to rejoin Armstrongs in 1888, in order to manage a new armaments factory, built as a subsidiary, at
Pozzuoli, near Naples in Italy. In 1900 Armstrong died, and
Sir Andrew Noble succeeded him as chairman of the company, now known as
Sir W G Armstrong, Whitworth & Co Ltd. After Armstrong's death, the old acrimony between the Rendels and Andrew Noble came to the fore, with George and his brothers criticising Noble's management of the company. The dispute between the two sides was not resolved until several years after George's death. ==Honours and awards==