page_title: Endurance (1912 ship)
section_title: Design and construction
hierarchical_section_title: Endurance (1912 ship) / Design and construction
caption_attribution_description: Endurance final sinking in Antarctica
context_page_description: Endurance was the three-masted barquentine in which Sir Ernest Shackleton and a crew of 27 men and one cat sailed for the Antarctic on the 1914–1917 Imperial Trans-Antarctic Expedition. She was launched in 1912 from Sandefjord in Norway; three years later, she was crushed by pack ice and sank in the Weddell Sea off Antarctica. All of her crew survived.
context_section_description: Designed by Ole Aanderud Larsen, Endurance was built at the Framnæs shipyard in Sandefjord, Norway, and fully completed on 17 December 1912. She was built under the supervision of master wood shipbuilder Christian Jacobsen, who was renowned for insisting that all men in his employment were not just skilled shipwrights but also be experienced in seafaring aboard whaling or sealing ships. Every detail of her construction had been scrupulously planned to ensure maximum durability: for example, every joint and fitting was cross-braced for maximum strength.
  The ship was launched on 17 December 1912 and was initially christened Polaris (eponymous with Polaris, the North Star). She was 144 feet (44 m) long, with a 25 feet (7.6 m) beam, and measured 348 tons gross. Her original purpose to provide luxurious accommodation for small tourist and hunting parties in the Arctic as an ice-capable steam yacht. As launched she had 10 passenger cabins, a spacious dining saloon and galley (with accommodation for two cooks), a smoking room, a darkroom to allow passengers to develop photographs, electric lighting and even a small bathroom. 
  Though her hull looked from the outside like that of any other vessel of a comparable size, it was not. She was designed for polar conditions with a very sturdy construction. Her keel members were four pieces of solid oak, one above the other, adding up to a thickness of 85 inches (2,200 mm), while its sides were between 30 inches (760 mm) and 18 inches (460 mm) thick, with twice as many frames as normal and the frames being of double thickness. She was built of planks of oak and Norwegian fir up to 30 inches (760 mm) thick, sheathed in greenheart, an exceptionally strong and heavy wood. The bow, which would meet the ice head-on, had been given special attention. Each timber had been made from a single oak tree chosen for its shape so that its natural shape followed the curve of the ship's design. When put together, these pieces had a thickness of 52 inches (1,300 mm).
  Of her three masts, the forward one was square-rigged, while the after two carried fore and aft sails, like a schooner. As well as sails, Endurance had a 350 horsepower (260 kW) coal-fired steam engine capable of speeds up to 10.2 knots (18.9 km/h; 11.7 mph).
  By the time of her launch in 1912, Endurance was perhaps the strongest wooden ship ever built, with the possible exception of Fram, the vessel used by Fridtjof Nansen and later by Roald Amundsen. There was one major difference between the ships. Fram was bowl-bottomed, which meant that if the ice closed in against her, the ship would be squeezed up and out and not be subject to the pressure of the ice compressing around her. Endurance, on the other hand, was designed with great inherent strength in her hull in order to resist collision with ice floes and to break through pack ice by ramming and crushing; she was therefore not intended to be frozen into heavy pack ice, and so was not designed to rise out of a crush. In such a situation she was dependent on the ultimate strength of her hull alone.
caption: Endurance's final sinking, November 1915
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