DISCOVER Magazine #7

One ring to rule them all

Published in category: Harbour & Terminal

Novatug’s Julian Oggel explains the thinking behind a tug that is revolutionary in all senses of the word

Julian Oggel Novatug
Julian Oggel
Managing Director

So, what’s the big idea? “It’s extremely straightforward actually,” begins Novatug Managing Director Julian Oggel. “The CARROUSEL RAVE TUG (CRT) is a tug featuring a towing point on a carrousel ring, which rotates freely around the vessel’s superstructure. The idea came about in 1997. Dr Markus van der Laan came up with it as an entry into a competition looking for concepts of a safer tug. He patented the idea a few years later. Multraship could see the potential of the idea and began a joint venture with Markus – Novatug.”

And how does this extremely simple idea confer additional safety on a vessel? Well, that’s not quite as simple, so here comes a bit of science. According to Novatug’s website, when the towing line angle increases relative to the longitudinal centerline of the tug, the point of attack of the force on the tug moves with the towing line towards the tug’s side rather than staying fixed amidships. When this happens, the towing point automatically lines up with the centre of gravity of the tug in the direction of the vector of the force and thus neutralises the heeling arm of that force. This event effectively all but compensates the heeling moment (moment = force x arm) to zero and brings about a very stable position due to the fact the towing point on board the tow (which defines the force vector) is higher, creating a righting moment to neutralize the heeling moment.

Which is basically a detailed (and complicated) way of saying you can turn the boat sideways during towage without it tipping over. Something that is good news for the crew – in addition to the fact that these characteristics can be applied to make for a more efficient towage operation.

Port paradox

“There is a paradox that a cargo ship entering port needs to overcome; it needs speed to steer, but it also needs to stop. Being able to turn the tug sideways, safely, means you can use the profile of the hull to steer and/or slow down the vessel – rather like if you stick a paddle in the water on one side or throw a bucket tied to a rope from a rowing boat. This will generate resistance that is enough to turn or stop the boat.

“The conventional method of towing in port is one that works against nature – one that sees the tug using its engines to pull in a different or even opposite direction to the vessel heading in order to impede its progress, while still offering it sufficient speed with which to steer. With the CRT method, we effectively harvest the kinetic energy to steer and brake the tow. It’s an elegant and relevant solution. It’s like kite surfing – it simply uses the laws of physics – hence we say ‘we have a patent on nature’. It’s simple and it works.”

Strong, sustainable & speedy

And, as the tug is not only required to generate towline force with its engines, the function of the engines and propeller is reduced to only controlling the heading and position of the tug – which equals a dramatic reduction in fuel consumption and emissions. Plus, with the increased safety offered by the carrousel, the vessel does not require a beam as wide as conventional tugs. The more slender hull offers reduced resistance and lowers fuel consumption even further.

“We have demonstrated that, by using the energy already present in the assisted vessel, we can reduce overall fuel consumption in a typical towage operation by up to 45%.”
Something which is good, “not only from a cost savings perspective, as it neatly answers growing calls for sustainable solutions,” states Julian.

And it’s fast; with the increased braking capabilities, the whole operation can be sped up, for example between bridges, where a conventional operation would require limited speed throughout.

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Growing need

The CRT is growing in relevance as container ships get bigger, Julian explains. “The CRT allows for significantly enhanced freedom of movement and control. This, in turn, allows operators to take advantage of considerably extended weather windows and the ability to perform manoeuvres that would be impossible with a conventional tug.

These capabilities are very useful in the face of larger cargo vessels.

“In the last 50 years, container ships have increased in size to become almost 15 times bigger. The same cannot be said for the infrastructure in ports. So you have these very large ships trying to navigate and operate in ports that have simply not been designed for the purpose.”

Perhaps understandably, the solution many arrive at is increasing the scale of port infrastructure commensurate with the vessels. This though, says Julian, is not always a viable option.

Building bigger infrastructure is not only prohibitively expensive, it’s not even possible in a lot of cases. And all the while it’s becoming more and more difficult for conventional tugs to assist larger container vessels in terminals.

Rethinking the challenge

“The CRT is not the answer in itself, but it is a part of the solution. It does, though, require a rethink on how we view the situation – in a lot of cases, people think in terms of cost in the limited context of what they think they know, when they should be thinking in terms of value in the context of what the real potential is. The CRT is not a cheap tool when you compare it to other tugs as they exist now. In fact, it’s an expensive tug, but if we adjust the way we look at it – the CRT is cheap infrastructure. Very cheap.”

This is why Julian is talking with the ports about the benefits of the CRT – they have an interest in not being blocked. He gives as an example, a container vessel that recently got stuck in the Scheldt River on the approach to the Port of Antwerp. As the vessel blocked the port entrance for other ships, the situation had a knock-on effect that affected not only Antwerp, but a considerable portion of the international port network in North-Western Europe.

“It’s important that ports are able to see the value of this, the successful navigation of ports can have a substantial effect on profits. The whole idea behind increasing ships to Post Panamax size is to increase throughput. Just one ship equals millions of dollars increase in goods. This is where towage is able to add value. Cargo ships have a 20-year lifespan. If you make every port call smoothly, over the 20 years you can achieve more voyages, and there is the margin – for the container ship operator and for the towage company.”

We have to take a long-term view, if only because a tug will last for at least 20 years too.

Proving the point

Putting the plan into action, in 2002 Novatug started with the refit of the vessel Multratug 12 with a carrousel ring. The experiment was a success and led to the carrousel receiving a Dutch Maritime Innovation Award.

“With the prototype we proved what we said over thousands of real tug jobs. We showed time and again that we could turn a tug sideways – safely – to steer and stop a cargo vessel. Then, after a decade of gaining experience, we decided we needed a purpose-built vessel. We gathered together a number of partners. The challenge was how to bring together all the potential into a coherent and optimised whole – we wanted a partnership that would benefit everyone.”

Robert Allan Ltd. provided the design and Voith provided the propulsion for the vessels. Building the partnerships took place over three years, culminating in Novatug signing a contract with Damen for the construction of two CRTs at the end of 2015.

“I was glad when I knew that Damen would build the vessels. Damen has a culture of building solutions. They have people who can think along and, with a long-term view that matches our own, they are willing to invest in innovations. There’s a good structure.”

Damen delivered the first of the two vessels in January this year, followed by the second in May. Novatug’s business model is to offer the vessels on a long-term lease.

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