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 a tight reaching sail, that was developed in the Whitbread Round the World Race by Robert "Hooky" Hook for Paul Cayard's successful EF Language. In that race it replaced the jibs for light upwind work in addition to many off wind angles. The luff is as straight as possible, and the sail is flatter than other asymmetric spinnaker. Due to the flatness of the code 0, it is usually made with a high modulus luff line for supporting strength, and of a heavier, less stretchy fabric than normal for a spinnaker. Due to the tight luff and flat cut, the