Prolyte structure to support Virgin Street of Light


A spectacular light show, supported by a Prolyte truss structure, was installed by Underbelly in the heart of Edinburgh’s Royal Mile for the festive season. Stretching 97 metres from the City Chambers to the Tron Kirk, the structure is over 18 metres high at its tallest points and features more than 60,000 lights.

Live entertainment specialist Underbelly has been a presence in Edinburgh for many years. The result was a dynamic light installation, based on the architecture of Edinburgh’s famous St Giles Church. It offers an immersive experience in which tens of thousands of light sources synchronise with evocative live recordings from local Edinburgh Choirs: The Edinburgh Gay Men’s Chorus, Edinburgh Police Choir, Edinburgh Royal Choral Union and Edinburgh Festival Chorus.

The Underbelly production team set to work, as head of production David Watson explains: “First and foremost we had to work out how to build a freestanding structure to support the modular wooden frames that carried the lights. We couldn’t attach anything to the surrounding buildings, as the Royal Mile is too wide. As Anthony said, the support structure had to deal with the changing camber of the street over a length of 97 metres and be suitably resistant to the Scottish winter, so it was no mean feat.”

Watson worked closely with structural engineer Ivo Mulder - now of IM-STEE, but before of Prolyte Group. The team elected to build the main structure using Prolyte standard pieces where possible. Ronnie MacLennan and Catalyst Event Production Services then supplied the Prolyte products and rigging services. Mulder and Watson augmented this with a number of bespoke elements to achieve the desired angles for some of the canopy pieces. “We only had three or four weeks to pin down exactly how the Street of Light was to be built. David and I designed it together,” explains Mulder.
“Ivo is a genius when it comes to proving the structural integrity of temporary constructions,” says Watson. “We were working on a job in Hong Kong when Dave showed me the drawings for Street of Light,” says Mulder. “I knew we would need a substantial support structure, safe for winds up to force 10. Scaffolding was a possible solution but it can be quite imposing. For Street of Light we wanted something relatively transparent - we didn’t want to take anything away from the effect of the lights.”

“To keep costs down we wanted to use as many standard Prolyte parts as possible. It was challenging. We didn’t know for sure how much the wind would influence the structure so we based our initial calculations on a completely covered surface, which it obviously was not. The calculations from this gave us ballast requirements of around 20 tons on each of the main arches, which was completely unfeasible. We had to re-think how we could reduce the wind loading but keep it safe. In the end we managed to halve the requirement to ten tons of ballast on either side of the main arches and 4 ton on each leg behind it. We have since experienced 70 miles-per-hour winds and the structure has been absolutely solid.”
Each of the 26 legs in the installation is connected to bespoke jacklegs, which enabled the team to level the installation along its full length. In the central circular structures, where effectively the legs have no bracing between, the ballast has to hold it square as well so each leg has around 4.5 tons. In total, 130 tones of ballast secures the whole installation.

Designed by Puglia-based Italian firm, De Cagna, the framework is artisan in nature. Over 60,000 light sources, split into various switched circuits and attached to modular, skeletal pinewood cut-outs, are secured to a free-standing Prolyte Truss frame. The installation had to be robust enough to withstand the city’s unpredictable winter weather. Wind speeds in the city can reach up to 100 miles-per-hour and, depending on wind direction, the Royal Mile can become a giant wind tunnel. In addition, it’s not uncommon for the city to experience four very different weather systems in a single day.
With a schedule of two shows per-day over 25 consecutive days, there was little time for maintenance so the installation had to work from the get-go. With up to 11,000 visitors from 49 countries visiting the event per-day and sharing everything they saw on social media, achieving the structural integrity required and proving it to the relevant authorities, without compromising the artistic effect, was crucial.

Hannah Muddiman, the recordings coordinator, sums up the event perfectly: “Attending the Street of Light launch events and seeing all the hard work come together so spectacularly was fantastic - there was real excitement in the air. These days we don’t often hear choral or classical music in public spaces. Hearing this music - real people singing songs by Freddie Mercury, Handel, Daft Punk, Dolly Parton and Karl Jenkins – in a public space and watching so many people enjoying it and responding with such delight - open mouthed, sharing it with loved ones, singing and dancing along - was a highlight of the year for me. Seeing the choirs so proud and enjoying listening to themselves in such an exciting setting was magical.”



Selling a roof system is a complex procedure, a roof system is an investment for the long term and the owner needs not only to know how to build it correct and safely, but also should be aware how to use it most efficiently on future projects. The support we get from Prolyte really makes the difference

Jean Paul Gaspard Audioconcept C.A., Venezuela