Engineering student Barnaby Walker takes Dr Hugh Hunt for a trip down the river Cam.

Pedal-powered punt cruises Cambridge Cam

When it comes to punting ingenuity, Cambridge's river Cam is no stranger to human inventiveness and the latest effort saw engineering student Barnaby Walker take to the water in a pedal-powered punt.

Punting and Cambridge, as synonymous a pairing as carrots and peas, students and debt, or engineering and ingenuity. Punts first glided serenely/zig-zagged nervously down the river Cam at the turn of the 20th century, when the flat-bottomed Thames pleasure boats were first introduced. Originally built as cargo vessels or platforms for fowling and angling, they had become popular as pleasure crafts in London and were quick to become successful as such on the Cam.

Punt, definition: ‘a long, narrow flat-bottomed boat, square at both ends and propelled with a long pole, used on inland waters chiefly for recreation.’

With its square-cut bow, the punt is designed for use in small rivers or other shallow water and is, therefore, perfectly suited to the river Cam, with its shallow and gravelly river bed and the scenic course it takes as it ambles through the heart of Cambridge, passing beside iconic old college buildings and, further upstream, through the picturesque and tranquil English countryside.

Your traditional punt is roughly 7m long and 1m wide, with sides of about 0.5m deep and an underside that slopes very gently at the front and the back, made with long, narrow planks stretching fore and aft, attached to the flat sides and the treads. In order to allow the wood to swell when it gets wet, the planks are set a small distance apart (traditionally the width of an old penny, about 1-2mm). It has no keel, stem or sternpost and is built with two side panels connected by a series of 10cm-long cross planks, known as treads, spaced about 30 cm apart.

Since a punt has no keel, it draws only about 5cm even when fully laden, making it highly manoeuvrable and suitable for shallow water and can be punted from either end, especially handy in narrow streams where turning round may be difficult. The square-cut bow gives greater carrying capacity for a given length than a boat of the same beam with a narrow or pointed bow and makes the boat very stable and suitable for passengers (aka 'puntees').

A traditional punt has no tiller nor any provision for oars, sails, or motor. Instead, the punter propels the punt and the puntees by pushing against the river bed with a pole, which is normally about 4-5m long and weighs about 5kg. The bottom of the pole is fitted with a metal shoe, a rounded lump of metal to protect the end, sometimes made in the shape of a swallow tail.

So, that’s punting as far as tradition goes. A classic design that has stood the test of time and is as popular now as it ever was, with numerous punt hire and tour companies touting for business among students and tourists alike.

As Jerome K. Jerome put it in Three Men in a Boat (1889), "Punting is not as easy as it looks. As in rowing, you soon learn how to get along and handle the craft, but it takes long practice before you can do this with dignity and without getting the water all up your sleeve."

While you can’t fix it if it ain’t broke, there’s nothing wrong, however, in trying to improve on a classic, right? Punts have always posed an exciting challenge to those with an engineering mind. Over the years there’s been a paddle-driven steam punt, a petrol engine-powered punt, hybrid catamaran-style motorised punts and even a rocket-powered, Chelsea bun-burning punt to grace the gentle waters of the Cam.

Now it’s the turn of fourth-year engineering student Barnaby Walker, who turned the full force of his engineering expertise to a challenge posed by Trinity Fellow Dr Hugh Hunt. Not expecting anyone to take him up, Dr Hunt had advertised an unusual project for Part IIB of the Engineering Tripos. Dr Hunt takes up the story:

“The idea of a pedal-powered punt was first mooted in 2014 by Trinity Fellow Professor Mike Proctor, now Provost at King’s. His initial idea was a solar-powered punt or something very eco. After discussing over dinner one night, we decided to put it forward as a final-year engineering project in 2015.

“I wasn’t expecting any serious takers for this project because it required practical skills with both bikes and boats, as well as some good dexterity with fluid mechanics and Newton’s laws of motion. In Cambridge we often don’t get people like that.”

Barnaby Walker was to prove him wrong.

The engineering student was intrigued and set to work immediately, combining his maths and computer modelling skills, together with his design acumen in considering how to power the punt, assessing its stability and building balsa-wood models.

“It was a great challenge. I was drawn to it as I’ve sailed quite a bit and I’m a very keen cyclist - I rebuild bikes in my spare time," Walker explains.

Barnaby worked with Trinity punt men Paul Joyce and Ed Few to adapt a 28-year-old punt called French Hen to take on board two paddles, like miniature paddle-steamer wheels, to be powered by the pedalling of a bicycle. The biggest challenge was in adapting and modifying the punt to this new source of propulsion.

“The scariest bit was launching it," says Walker. "As always with engineering, you can do all the calculations and modelling beforehand, but when it comes time to actually turn what you have done on paper into reality, there is the sense that you may have missed some crucial detail. The feeling of relief when it was launched and the punt was a success was a great feeling.”

For Dr Hunt, the project combines the inventiveness, creativity and problem solving that underpins engineering.

“Engineers look at the world as it is and see if it can be made different – and hopefully better!", he says. "In Cambridge we tend to take ourselves a bit too seriously and sometimes it’s good to let loose on something a bit mad. We’re especially looking to capture the imagination of the next generation of engineers and young people are attracted to nutty ideas like this.

“This was great fun, but also an excellent challenge. You don’t have to do very serious projects to learn a lot – as Barnaby has proved.”

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