Construction Navale
Ultra-fast aerodynamic boats

Actualité

Ultra-fast aerodynamic boats

Construction Navale

After unveiling its prototype ultra-fast aerodynamic boat in 2015, Advanced Aerodynamic Vessels sold its first passenger versions earlier this year.

Designed and built in the strictest secrecy, the innovative composite-hull prototype is 10.5m long, with a beam of 7.4m, a 40cm loaded draught and an air draught of 3.4 metres. Displacement is 3 tonnes light and 4.5 tonnes with a full load. Equipped with two 200hp Mercury Verado motors and space for six passengers, it is designed to exceed 40 knots — which suggests, according to our models, that a 25m version should achieve a speed of 60 knots — while at the same time boasting high energy efficiency thanks to aerodynamic lift.

“The higher the speed, the lower the fuel consumption.” In short, this was the design challenge A2V set itself. “The basic idea arose from the observation that no current designs under 70 metres are capable of high speeds (say, over 40 knots) without significantly compromising fuel efficiency,” said Lionel Huetz, Director of R&D at A2V. “The only vessels that operate commercially at these speeds, despite high fuel consumption, are fast ferries, and even they are only profitable when carrying a large number of passengers. And there aren’t many of them.” Moreover, the design principles applied to fast ferries are not currently applicable to smaller boats, given the sophisticated construction techniques and high maintenance and fuel costs.

A2V has identified several potential markets for its concept. These include, says Lionel Huetz, “getting people to and from offshore oil platforms and wind farms and government actions at sea requiring rapid interception — one example being the policing of unmanned vehicles — and even water taxis.”

 

A2V's team (© : A2V)

A2V's team (© : A2V)

 

Hydrodynamics and aerodynamics combined

Lionel Huetz and Matthieu Kerhuel, Managing Director of A2V and a fellow graduate of the École Centrale de Nantes engineering school, set to work in early 2013. “We combined our experience in fluid mechanics, naval architecture and composite materials to good effect.” Lionel Huetz’s experience comes from six years’ work with offshore racing yacht specialists at the Marc Lombard design bureau which has also invested in the project. “Working with yachts gives you a real feel for the way boats interact with air and water. You also learn a lot about composites, an area where several French companies have proven experience.”

Gradually, the idea of combining the benefits of hydrodynamics and aerodynamics took shape, resulting in a boat that flies, so to speak. Or, more precisely, a boat that uses aerodynamic lift to progressively transfer weight from the water to the air. The faster the boat goes, the greater the lift — and a lighter boat consumes less fuel. “Many are familiar with the concept of boats that fly, or water-skimming aircraft, like the Russian Ekranoplane,” says Matthieu Kerhuel. “What we wanted to demonstrate is that this approach could be applied to a more practical type of boat; one that would be easy to build and maintain and have low fuel consumption, thus profitable all round.”

 

 

Lift at all speeds

“The hull shape is designed to ensure maximum lift even at low speeds,” says Lionel Huetz. The aerodynamics and hydrodynamics have to work together. “First and foremost, the boat has to be compact, simple, reliable and rugged, without the need for additional electronics or complicated crew procedures.” This is why our engineers adopted a solution based on passive stability. The whole boat is designed to maximise aerodynamic lift.

“We began working with digital simulations in June 2013.” The team did thousands of hours of calculations not only to model the hull form, but also its interactions with the elements. Once the hull form had been established and tested, the engineers started work on the habitable spaces and equipment. “By this stage, we had confirmed that our weight and lift estimates were consistent with the design principle.” In November 2013, Hydrocéan, a Nantes-based firm specialising in hydrodynamics, went through all the calculations and confirmed our results. The design concept worked.

Bringing the design to life

“From then on, the challenge was to transform the concept into a boat.” Accessibility, safety features, and stability were all important. “The part that is least visible, but that preoccupied us the most was the hydrodynamics. Creating lift under the hull is straight-forward enough, but our objective was not just high performance. We wanted a real boat that met all the relevant safety and stability criteria. And we certainly didn’t want a boat that rose quickly out of the water with less than full control over its trajectory. We drew on High Speed Craft specifications published by the DNV GL classification society.” Each new weight estimate called for a new set of trajectory computations. ‘It still works!’ became something of a refrain. The company then decided to build a 10‑metre prototype — in other words, the smallest in the range it hopes to develop, the largest being 40 metres long. With input from the Marc Lombard design bureau and Fernand Hervé, the shipyard in La Rochelle, A2V took the project from the drawing board to the construction phase, launching the first model in March 2015.

Powered by outboards (unlike the commercial range which has inboard motors) to measure drag more accurately, the prototype was now ready for trials.

 

The prototype (© : A2V)

The prototype (© : A2V)

 

The prototype at sea

As La Palice port fades into the distance, the power of the prototype’s 400hp motors is obvious. In the cockpit, the sensations are very different from what might be expected. The faster the boat goes, the more comfortable the ride. You can no longer feel the chop, the hulls skim the surface, and there is a true sense of stability as the boat approaches 40 knots without you even realising it. The boat’s response is crisp and clean, and there is no pitch or roll. “She behaves like a yacht. She gains lift with the wind close, off the beam or broad. It is only when running with the wind that she benefits less.”

Crash-stop performance is impressive. The boat stops in just a few metres without ploughing in. “She doesn’t nose into the water too suddenly because there is no thrust. She simply settles gently into the water.” The turning radius is three boat‑lengths, and all turns are flat. “She was designed to be simple, highly manoeuvrable and offer maximum passenger comfort.”

The prototype is heavily instrumented — anemometers, an inertial navigation system, engine sensors — to analyse the boat’s behaviour in all seas and weather conditions. “This will allow us to validate our calculations.” The readings and instrumentation will also be useful for modelling boats of different sizes or for different uses.

While the trials are very positive, A2V continues to improve the design and its patented stepped hull. Surface propellers are also an option.

 

 

First orders

Boat operators have already expressed keen interest in the new craft and, more particularly, its low fuel consumption.

After three years of research and trials, the first sale was announced in May 2016 — to Péchaud, a company that provides logistics support services to offshore oil fields. Their new 15.5m crew boat, which may be the first in a series, will serve platforms off West Africa. The proposed design will carry 25 passengers and have a service speed of 40 knots for a range of 600km.

In the wake of its first order, A2V has received a second, this time from Proyachting, a company based in Evian. This 12-passenger, 11.5m boat will criss-cross Lake Geneva at 50 knots, providing a luxury shuttle service between Geneva Airport and various casinos, hotels and golf resorts. Both these boats are scheduled for delivery in 2017. Like the prototype, these will be built in La Rochelle where A2V has a 1,000sq.m assembly hall and slipway close to the Hervé yard which will produce the composite parts.

 

The Proyachting ship (© : A2V)

The Proyachting ship (© : A2V)

 

Offshore versions

A2V is also participating in a Joint Development Programme with Bourbon and classification society DNV GL. The aim is to develop an offshore crew boat capable of serving platforms up to 250nm from its base port. Because of its speed advantage, boats based on the A2V concept offer a potential alternative to helicopters.

The project aims to define the usage profile more precisely taking into account possible areas of operation, average daily operating costs, and how frequently platform crews are relieved. A2V engineers are basing their work on mathematical models already validated by the prototype, along with sea state and weather data provided by DNV GL. The results of this programme should be available by the end of the year.

Other applications

A2V sees potential applications for its passenger craft in the offshore and luxury yacht sectors and possibly in defence. One idea is to build low-cost, 25m, 60-passenger crew boats capable of 60 knots. Another is to build conventional passenger boats carrying up to 100 people. Luxury yachts is yet another area where the new design could find favour, especially with owners interested in innovations offering exceptional performance. In the military and paramilitary sectors, a vessel capable of reaching 60 knots would have clear benefits in combating terrorism, piracy and drug trafficking. This type could even rival commando boats for the interception of go-fasts and powerful semi-rigid boats which go much faster than conventional frigates and patrol boats. To catch and stop a go-fast, today’s frigates and patrol boats have to deploy a helicopter, provided, of course, they have one.

Written by Caroline Britz, translated by Steve Dyson and Allison Wright. 

 

The prototype (© : A2V)

The prototype (© : A2V)