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Bridge numbers. I like bridge numbers. Bridges that cross canals and railways (and motorways for that matter) all have numbers. Names are good, but numbers give you a sense of where you are. On canals they are an essential navigation aid. But bridges over rivers don’t need numbers. The difference between things you go over as opposed to things you go under I guess. Still, I’m counting these bridges over the Tees. Cow Green Dam Wall isn’t technically a bridge, so Birkdale Bridge is no.2. It’s a litle way to no.3.

We left the river below Birkdale Bridge as it plummeted down Cauldron Snout. This cascade is more a series of cataracts over a 180m length – making this the longest waterfall in England. There’s a good clamber down the entire south side over the dolerite pillars of winsill so plenty of places to admire the power of the water as it plummets down a total of 60m. Even on relatively dry days, as the water is regulated at the dam it’s always an impressive sight.

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There used to be a little wooden footbridge across the falls – about halfway down.  This would have given an incredible view of the torrents below. Before the reservoir was built, the river ran round a long sweeping crescent picking up speed so by the time it reached the top of Cauldron Snout it was already wild and raring to go. The wooden bridge disappears from the maps by the 1940s and a track bridge appears about where the dam wall is today. But never both together. The amazing moving bridge. There’s more of these to come further downstream..

At the base of the falls, the river meets with Maise Beck – one of its larger tributaries at this end and corners beneath the cliffs of Falcon Clints. This next section along the shadow of Cronkley Fell is wide and flat. The river here is very wide given how young it still is. It’s very shallow but very fast. From here to the top of the next waterfall, High Force – about 6 miles away – it’s got 100m to fall so it’s on a bit of a sprint while it can. The landscape here is classic glacial pasture. big wide and relatively flat land with steeply rising fells beyond. Thousands of years ago this valley was scoured out by the receding ice flows. Long before that, these carboniferous rocks stretched across to the much older Lake District and formed a border with the still separate Scotland. It’s a very old landscape indeed.

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As the land flattens out, so the farms start to appear. First up on the left is Widdybank Farm. As remote hill farms go, this is particularly remote.Yet along the banks of the river the pasture area is flat and fertile. Great for cattle, but still too exposed and high up to grow anything meaningful.

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There are no bridges for miles, but the river is wide and shallow and during the summer months certainly fordable at any number of points.

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Further along on the north bank are the remains of a pencil mill. Here the sedimentary rocks were ground down and  pressed into moulds to make pencils. The mill opened in the mid 19th Century and produced pencils – know locally as ‘widdies’ until 1890.

The river winds and widens until near the far end of Cronkley Fell we find Cronkley Bridge. Bridge no.3 in my book. This is a simple steel girder span over two intermediate stone pillars with a wooden deck. It’s flat and utilitarian and is probably 1950s. The main feature is its length – about 40m. We won’t see another longer bridge for over 30miles. You would normally build a bridge at its narrowest point. It’s certainly the cheapest way to build one. I imagine, as the river is shallow and with a flat rocky bed, this would be an ideal fording point, but a bridge has been marked here on maps certainly from the mid 1800s.

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I had planned on following the river towards High Force about a mile downstream, but a loose and very vocal dog at one of the farms clearly had other ideas, so that bit is another for a revisit. Cronkley Bridge is on the Pennine Way so it’ll be a bit busier later in the year. Also, from March the wading birds return to nest on these high moors. Today it’s almost silent, but by mid April the air here is filled with the strange whoops and warbles of Curlew and Lapwings, the buzz of snipe and the cackle of grouse – over 3/4 of England’s native Back Grouse live in these barren hills of the North Pennines.

But that’s bridge no.3 done. The next four are all walking distance from where I live so familiar territory for a bit…

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The idea of building a bridge out of paper goes back a little while for me. It’s been one of those projects that’s been sat on the back burner so long it was in danger of completely drying out. And if it wasn’t for a random DM on twitter one Sunday evening, it might still be there.

It was some years earlier that a discussion with some of the lovely folk over at James Cropper – a paper manufacturer based in the Lake District – turned to thinking “what could be made out of paper?” At the time they were interested in pushing their brand values of bespoke production, colour and environmental credentials. We’d done some pieces for trade fairs and I’d started doing some small-scale temporary pieces in the landscape for photographs. The thing about brainstorming is that you can come up with ideas and not worry about how practical or realistic they are. I think I said it would be great to do something structural – like a wall, or a building, or a bridge.. or something along those lines, and that’s often how so many of my pieces start life. I open my mouth without thinking, and as soon as I’ve uttered the words they somehow echo and linger. And I start to dwell on them. Yes, a bridge. That would be amazing if we could do that. Obviously I had no idea how to do it, but the idea seemed to stick.

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red paper boxes on Ullswater. 2010.

Of course, when I started to look at it and do the research I discovered it wasn’t as left field as I thought. Building a bridge out of paper was a standard year one exercise in architecture courses all over the world. An exercise in creating strength from lightweight materials. These however were just models even though some could take the weight of people.

Then there’s the work of Japanese architect Shigeru Ban. In 2007 Ban built a full-sized paper bridge over the River Gard at Remoulin in France. Ban had gotten over the structural and scale issues by using paper tubes. Paper tubes are an inherently strong but lightweight form and work well in both compression and tension along their length. Fabricated steel joints hold everything in place.

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Paper Bridge by Shigeru Ban. image © Mikaël Pors

However, I wanted to do something in just paper. I wanted the purity of a single material. This idea that something as seemingly fragile as a single sheet of paper could be the building blocks of something substantial.Something of real structural integrity. Capable of withstanding the Cumbrian weather and strong enough to function as a footbridge. The solution lay in some of the earliest bridges in the Lake District – packhorse bridges.

packhorse bridge Watendlath Cumbria

In the days before roads trading goods were moved across the country by packhorse – loading up horses and trekking them in convoy across the land. With no wheels to get stuck in mud it was a very versatile way to move things across difficult terrain – as in the case of the Lake District. Where rivers ran too fast to safely ford, simple stone arch bridges were built. Originally these were very basic, using local found stone and built over a wooden formwork, using lime mortar to cement the stone together. Once constructed the formwork was knocked down or burnt leaving a simple arch. There was no wall on either side of the pathway as this would restrict the size of the packs on the horses. The bridges were also used by drovers moving sheep to and from markets. Only when the tracks were upgraded and carts and waggons started to use them were sides added to the bridges to stop them from falling off. Carts also meant bridges had to be wider and more substantial with easy gradients up to the top, whereas the original packhorse bridges were frequently steep arches and only three-foot wide.

I found a great book – ‘An Illustrated Guide to The Packhorse Bridges of the Lake District‘ by Michael Hartwell, and set off to familiarise with bridges in the Lake District landscape.

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The construction of a stone arch is very simple and dates back thousands of years.  Wedge-shaped stones – or voussoirs – are laid over a former. The final, topmost stone – the keystone – effectively holds it all together. In a paper bridge, all the stones are just pieces of paper. Structurally, the internal angles of the wedge shapes result in the vertical force (the load on the arch) being transferred to lateral tension (sideways force where it meets the ground).

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basic calculations for the final bridge

I could calculate how to build it on paper by simple geometry. If I knew the size of the blocks of paper and the radius of the arc I could determine how many ‘sides’ a polygon of those blocks it would take to go across the arc. Knowing the number of sides I could also work out the angle between them that I needed to fill with wedges. As I knew the dimensions of those wedges from the paper size I could work out the size of stacks of different sized pieces it would take to bridge that angle. I needed sufficient different sizes to brace across the gap evenly and also get small enough pieces to get as close to the upper edge as possible. The strength in the arc comes from ensuring the blocks are tight on the bottom edge and are wedged tight across the top edge. It’s also important not to make the mid-sized blocks in the wedge too big as, under load, the bridge would have a tendency to pivot on those points and make it rock. When it came to the bigger models and the final piece, those small packs of 10 or 11 sheets were critical. One too many small pieces of paper in one of the wedge sections might not seem much in the 20,000 pieces of paper scheme of things, but an extra sheet in one block equates to 150 sheets over the whole arch – approximately 40mm – and the whole bridge becomes very unstable.

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drawing of stacks making up a single block and wedge

I think I built the first paper model bridge in 2011. It was very haphazard but it worked and held a fair weight. It was quite a shallow arc made by stacking small pieces of paper over a former and then wedging other sheets in a various intervals until it stayed up. The next model was more refined. I knew then how it worked. Using small pieces of paper left over from a project years before it easily held more than its own weight.

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the first model paperbridge. May 2011

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the first sketch of a paper bridge

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Second model. 2012

By this time it was looking like this just might be possible. I’d even found a location where I thought it would look right – with big Lakeland fells around it, a fast flowing beck underneath and footpaths on either side. There was no point building a bridge that didn’t go anywhere.

But, could I build one that would take the weight of a person? And how would it work outside? What would happen when it rains? Only one way to find out. Build a bigger one.

Croppers kindly supplied me with a quantity of paper cut to approximately A4 size. From these I trimmed smaller sizes to make wedge-shaped stacks. I built this first decent-sized bridge one evening in my front garden. I left markers at intervals so I could take it apart again and keep the paper in blocks. It was March when I built that, so it was getting dark early. I got it all assembled to a certain point and left it until the morning to fine tune it.

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first A4 model

Overnight the cloud came down and it was a bit misty in the morning. I just needed to move some of the blocks and add a few more wedges I thought to make a better arc. It was then I discovered what happens when the paper gets wet. The bridge was rock-solid. There was no way I could easily take sections out. When the paper got wet, the fibres swelled. As all the paper was in compression all the swelling pressure went against the abutments as it had nowhere else to go. I left that test bridge up outside the house for nearly three months in rain, snow and occasional sunshine. It didn’t go anywhere.

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The next test build was in the Howgill Fells overlooking the M6 Tebay Gorge. This was the first one over running water. It was a blistering hot day and there wasn’t much water coming down the beck, but I wanted to see how it worked in a more real landscape environment.

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test model in the Howgill Fells. 2012

The colour was a bit cold against the foliage and the bridge seemed to flatten out at the top, but this is what test are for – to find all the problems so they can be solved before you go for the big piece.

From this point on the project hung around for a few years. Both the paper manufacturer and the Lake District National Park were keen to help realise the bridge, for one reason or another things never quite came together at the same time to make it happen.

I’d been showing mock-ups of the PaperBridge in presentations and lectures around the world for a few years. It was always something I used to show my working methods and the potential for public / private enterprise. It aways went down well too – there was something about it that caught people’s imagination. Whether that was the bold use of colour in the landscape, or the ambition, or the engineering.

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visual for paperBridge at Greenside, Glenridding. 2012

Earlier this year I was surveying my growing list of unrealised projects and looking to see which ones I could look to finally get done this year. Looking at how progressed the idea was and what was needed to actually bring it to fruition. The PaperBridge seemed to be pretty much there. It was all designed, engineered, tested, materials sourced, legal and health & safety implications sorted. It even had a location and permissions. I’d even gone through the PaperBridge as an example project when I met with Wolfgang Volz over the winter. All it needed was some money for materials and build costs. Although that doesn’t sound like much, finding funding is always more work than you think, so I pencilled it into my diary as something to start working on in the summer. A standard delay tactic.

So when that random twitter message came through asking if I was interested in doing something in the Lakes, the timing couldn’t have been more perfect. Here was a client looking for something high-profile and ambitious in the Lake District landscape, and I just happened to have something all ready to go. Just as well as the proposal would need costing up and presenting in 10 days, and if successful, delivered in just 10 weeks. Under any normal circumstances that would be just impossible for a project of this scale. I don’t normally put proposals forward to open calls – coming up with project concepts, working out all the logistics and drafting up a budget alone can be a huge amount of work with no guarantee of anything coming off it. In fact I’ve never had any commission come off this way, so I stopped doing it. However, I had everything just sitting there, ready to go – although I had no idea how much it would cost, but sure I could do it within their budget. If only just. it was worth a shot.

On the 22nd February I got an email inviting me to realise PaperBridge as part of a new cultural event in Cumbria and the Lake District – Lakes Ignite. The lead-in time for the paper production and my other work commitments meant there was just a 10 day window it could be done in during May. So that was it. Ten weeks to deliver a full-sized bridge out of paper.

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working drawings for a bridge – not the final one though..

Of course things never go smoothly. The tight timetable meant the National Park people couldn’t re-jig their busy rotas to provide the build help I was hoping for. Due to a locally controversial planning application near the original Greenside location, it was thought best not to do anything on that site this year. That meant looking for an alternative location, obtaining permissions, surveying, re-designing the bridge and re-calculating the engineering.

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redesigning the bridge in the studio

Lots of long days in the studio and late nights with my note-book, bits of paper, cosine calculators, building and rebuilding scale models, revisiting the site as it slowly greened up through the early spring, taking photos, generating visuals and eventually it started to come back together again.

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early mock-up of the bridge in Grisedale

A couple of years or so ago, when we were looking at a 16 – 21 day installation period at the original location a short walk from a car park, we were looking at visitor figures in the region of 10 – 16,000. The Lake District is a great place to do this kind of work – there’s so much quality landscape environment to bounce off. It’s a well-known area and comes with its own unique sense of international branding. THere’s also plenty of other things to offer visitors so an artwork can make part of a great day out or weekend away.One of the challenges however can be the number of visitors to the area – much more than you would expect in most rural locations. While I knew the paper would easily support the weight of people on it – we even looked at the idea of taking a horse over it for a photo opportunity – I had no way of knowing what the effect of 16,000 pairs of muddy boots would do to the surface of the bridge. With that kind of visitor figure we’d need to put invigillators there to avoid bottlenecks of visitors and make sure everyone was safe on it. However, at this new, much more remote location – remember it’s a good 5 mile round walk from a car park – crowds were not going to be a problem. It was going to be something that passing walkers would just happen across. Maybe up to 100 people a day on busy sunny weekends.

I quite liked that aspect of it – a piece so remote and temporary that it became something special for the few who saw it….

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