Emirates Spinnaker Tower two large, white, sweeping metal arcs, which give the tower its spinnaker sail design. The steelwork was fabricated by Butterley Engineering. At the top is a triple observation deck, providing a 360° view of the city of Portsmouth, the Langstone and Portsmouth harbours, and a viewing distance of . The highest of the three observation platforms, the Sky Deck, has only a wire mesh roof, so visitors are open to the elements. The windows extend above head height, so it is not possible to get a view unobstructed by glass. A glass floor is located on the first viewing deck
Spinnaker because it somewhat resembles a parachute in both construction and appearance. This should not be confused with the spinnaker chute which is a hull fitting sometimes used for launching and recovering the spinnaker. A purported etymology has the first boat to carry this sail being a Cowes yacht named "Sphinx", from which "Sphinx's Acre" and eventually "Spinnaker". A spinnaker is used for sailing with the direction of the wind. Symmetrical spinnakers have large amounts of camber, making them nearly hemispherical. Both lift and drag propel the boat forward when moving with the wind. Reaching spinnakers have less camber as they