 Background At the beginning of February the St Paul’s Plinth competition was announced by the LFA (London Festival of Architecture) to create a new sculpture on the existing structural framework, built in 2018 to support the St Pauls Gateway installation. The existing St Paul’s Plinth support structure consists of a grid formed by tension wires held between a steel aperture raised around 6 metres from the ground. All designs were to make use of this existing framework as a support structure. The competition looked for entries with a strong visual aspect working on a variety of scales that would appeal to a wide audience as the site is familiar to natives and tourists alike with some stopping off briefly whilst others linger longer. The design was also intended to take into account the LFA’s theme for the 2019 Festival of Architecture ‘Boundaries.’ Initial process Lunchtime concept design We began our concept design for the competition with a round table lunchtime discussion, recording our conversation with hastily hand drawn sketches and doing quick research on phones to add flesh to our initial ideas.The foundation for our design was the existing grid structure that we saw creating a datum or boundary which our design would play with. 
We wanted to create something that would add height to the existing structure moving through the grid from below to above. We imagined a structure that would begin below the grid and grow upwards through it controlling the light and framing a view of the sky above and building that surround it. Considering materials and colour as ways of creating an eye-catching landmark we thought about durability and performance, how to make a big impact with a small move. We found a precedent that resonated with our ideas, Frei Otto’s Diplomatic Club Heart Tent. The way the structure and its cladding came together and interacted with light, colour and the elements gave us inspiration. Installation and maintenance was an integral part of the design brief and helped to whittle down our ideas as we wanted to reduce installation time to a minimum
Rapid prototypeAfter lunch we moved into the workshop quickly selecting some materials to mock up a prototype of our design. Making use of some suitable leftovers from recently completed projects we chose polycarbonate, oak, plywood, timber offcuts and gold faced flooring underlay to construct our prototype fin ready for installation onto our test tension wire. A couple of versions later we had changed the density of materials to better balance the centre of gravity and altered the fixing method to sit more comfortably on the wire before we were happy with the look, feel, size and scale of the fin. We used the protoype model dimensions and materiality as guide for developing our design further through technical and graphic drawings alongside our budget development document.
Design Development Our first step was to draw an individual fin in sketchup. Using the protoype we quickly modelled a fin adjusting some dimensions to produce a more pleasing proportion or to work better with standardised manufacturing sizes and machining tolerances.  Then using an image from streetmap we began a visualisation of a significant view of the site. Whilst creating the visualisation we further enhanced the design by subtly altering the colour and arrangement of the fins within the tension wire grid and decided to orientate the fins to face the longest site line, maximising the visual impact from a distance.
We moved into more technical drawings and drew a plan to scale allowing us to create a general arrangement and pin point the location of 151 fins in 15 shades of colour from red to purple. From plan we moved into section, drawing long and cross-sectional images to test the varying character of our arrangement in these two views, tweaking the individual characteristics and strategic layout until we were happy with our design.  Alongside our drawings a costed budget for the design, production, installation and eventual removal of the design was produced. This was informed by a detail drawing created to demonstrate the method of fixing to the tension wires and helped to identify all the parts involved in creating a secure and durable solution. Submission Our final design had come a long way from the initial ideas we chucked around during a lunchtime chat but still had the same intentions at its core. The proposed installation sees 151 pivoting fins installed on the existing wire grid. Each fin comprised of a lightweight transparent plastic ‘sail’ with a timber counterweight. In the rolling breeze each fin captures the winds energy and transforms it into a rippling, multi-coloured light show. Sunlight, as well as artificial light from neighbouring buildings, street lighting and passing traffic, is focused in a complex, dynamic field of colour onto the ground. Metallic golden tips of each fin capture and reflect light creating an organic shimmer every time a bus passes or a gust of wind rushes through. Conceived from site observations the proposal is based around the interplay of movement between the thoroughfare and the datum produced by the plinth’s grid structure. In line with the theme of the LFA it explores the boundaries between nature and the city, as well as between the city’s highly active ground plane and the apparently empty air space just above, encouraging observers to stop and look up. The design was developed through material modelling and rigorous testing by a range of technical and detailed drawing techniques. Each fin is fully durable and weather resistant, being constructed from a range of plastics and stainless steel fixings, with hardwood elements in oak.  Comments are closed.
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