Text provided by the architects
Solar Gate is a sundial that uses solar alignment to mark significant times and dates in Hull. The super-light innovative two-shell structure is place-specific, responding to pivotal historic events and to the cultural context of its location in Hull’s Queens Gardens adjacent to the ancient site of Beverley Gate.
Questions and Answers
What was the brief?
Tonkin Liu won the international art competition in March 2015 to create the artwork in Hull’s town centre. The architects collaborated with structural engineers at Arup and worked with Hull City Council and local fabricator Pearlgreen to deliver the artwork in the summer of 2017, the year in which Hull celebrated its status as the UK City of Culture 2017.
How is the project unique?
The sculpture stands at a height of 10 meters but is made from miraculously thin 4mm plates. At the centre of the 4 meters wide plan the sculpture is just 1 meter deep, tapering to 100mm at the two open edges. From these edges visitors can see how the structure is formed. Two curving and corrugated surfaces join, without the aid of any additional supporting internal structures.
All of the structural strength is inherent in the sculpture’s shell form. The biomimetic technique is called Shell Lace Structure, invented by Tonkin Liu and developed in collaboration with Arup over the past 8 years. Structural lessons from mollusc shells are utilised, whose curvature, corrugation and distortion provide a direct correlation between form and strength, doing away with excess structure where it is not needed. The single surfaces of the structure are tailored out of flat sheets that are curved and joined to make rigid forms.
Solar Gate becomes an illuminated timepiece at night, with a controlled in-ground lighting system installed inside and outside the sculpture. Designed by Tonkin Liu, the lighting sequence has been programmed to alternate between outside and inside, transforming the sculpture into near-transparency. Around the sculpture a ring of perimeter lighting turns on and off in a clockwise direction, to herald forthcoming events and festivals, including a Hull-wide art event referred to as the “Golden Hour.” Through the exploration of “time,” Solar Gate speaks of the past, makes viewers aware of the present moment, and anticipates future moments in time.
The artwork’s theme of “time” was inspired by events that took place at Beverly Gate in Hull in 1642. On the 23rd of April at 11.00, 17:00, and 18:00, King Charles I was denied entry into Hull three times, by the governor Sir John Hotham. Hull’s act of defiance was regarded as a key event in the English Civil War that lead to the fall of the monarchy.
The gate provided the first formal ideas for the sculpture, which was further informed by Hull’s maritime history. Old photos of sails, mast, rigging, a ship’s sextant, and Hull poet Phillip Larkin’s poem that talks about ‘ships up streets,’ – all these references have been overlaid to shape the sculpture, whose form is boat-like in plan, sail-like in elevation, and mast-like in section. The ship’s sextant, using alignment to mark specific times and dates, formed another reference.
What building methods were used?
Solar Gate uses advanced digital tools to align exact sun angles from particular times and dates to pairs of large apertures on its surfaces. When a beam of sunlight passes through an aligned pair of apertures, it lands on a corresponding disc on the ground, a disc that reveals a significant event for the set of time and date. 16 reveal dates have been selected to celebrate Hull’s history and world events.
Solar Gate was fabricated in Hull by specialist metal fabricators Pearlgreen Engineering from laser-cut stainless steel sheets. These were welded together by a dedicated specialist team to form the two shells that were then spray-painted white and joined together before being move to site as a single piece and craned into place. The sculpture’s strength relies on the meticulous connection of the thin rolled plates. The team, working closely with Arup and Tonkin Liu, invested significant time and care to ensure that this highly intricate structure was executed with complete precision.