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
Asymmetrical spinnaker used on racing boats, bridging the performance gap between a genoa, which develops maximum driving force when the apparent wind angle is between 35 and 60 degrees, and a spinnaker, which has maximum power when the apparent wind is between 100 and 140 degrees. Due to its geometry, the sail is less prone to collapsing than a spinnaker and does not require the use of spinnaker pole. The sail can benefit greatly and be much larger if the boat is equipped with a bowsprit. Some boats (e.g., the Melges 17), have retractable bowsprits for this sail. A form of asymmetrical