Like a plane without wings

Like a plane without wings

With its revolutionary new passenger boat Clémentine, French boat manufacturer A2V has built a vessel that can go at twice the speed for half the fuel. And it’s fitted with Scania engines.

With its bold futuristic look, the Clémentine is unlike any other vessel. Designed and manufactured by Advanced Aerodynamic Vessels (A2V), this 25-seater passenger boat is equipped with two Scania 600 hp DI13 engines, selected for their reliability and low weight.

The operational speed of today’s small workboats is extremely limited by the exponential increase in fuel consumption in relation to speed. Oversized engines allow higher speeds, but at the expense of much higher fuel consumption and reduced payload, leading to an economically and environmentally unsustainable cost per passenger.

Lionel Huetz.Frederic Boyadjian

On a conventional monohull or multihull vessel, the fuel consumption per passenger at 50 knots relates directly to the dimensions of the boat. The larger the vessel, the lower the fuel consumption per passenger when the boat is fully loaded. This explains why, so far, high speed has been limited to routes that have enough passengers to require large vessels.

However, the A2V technology is a gamechanger, with a fuel consumption at 50 knots (independent of vessel size from 12 to 30 metres), of approximately 9 litres/100 km per passenger, for a capacity range of 10 to 100 passengers. “That nearly corresponds to the fuel consumption there is when travelling by car,” says A2V’s Managing Director Lionel Huetz. In comparison, the best crew boats typically consume more than 30 litres/100 km per passenger and travel below 40 knots

New aerodynamic concepts

This project is also visionary in applying new aerodynamic concepts. “We started working on a wing shape attached to a coherent and compact aircraft and transposed this idea to a seagoing vessel,” says Huetz.

Thanks to its shape, the weight of the vessel is transferred from the water to air, making it almost like a flying boat. From a blank page to the prototype, A2V’s naval architects and CFD specialists worked for nearly two years computing and simulating, to develop the revolutionary shape that safely transfers the boat’s weight from water to air. With public and private funding, a prototype, named Lilli, was completed in 2015.  The design was reminiscent of an airplane wing resting on the water. The trials of the prototype fulfilled all expectations and A2V was ready to market a product that was thoroughly tested and conformed to theoretical concepts.

The required propulsive power of the vessel depends mostly on the weight carried by the water. Reducing this weight is therefore the key to greater efficiency. A frontal view of the Clémentine clearly shows its airplane wing silhouette closed on either side, which makes it look like a catamaran. Underneath this structure, air is slowed down from 40 to 10 knots creating an overpressure, while above the structure the air circulation generates a depressuring effect.

This phenomenon pulls the superstructure upwards and lifts the vessel higher in the water so that it glides over the surface of the waves, even at reduced speeds. “We managed to optimise the air drag around the ship so that, just like an airplane, it does not act as a brake but actually smooths its passage,” says Gianluca Guelfi, a naval engineer and A2V partner.

The required propulsive power of the vessel depends mostly on the weight carried by the water. Reducing this weight is therefore the key to greater efficiency. A frontal view of the Clémentine clearly shows its airplane wing silhouette closed on either side, which makes it look like a catamaran. Underneath this structure, air is slowed down from 40 to 10 knots creating an overpressure, while above the structure the air circulation generates a depressuring effect.

This phenomenon pulls the superstructure upwards and lifts the vessel higher in the water so that it glides over the surface of the waves, even at reduced speeds. “We managed to optimise the aerodynamics around the ship so that, just like an airplane, it does not act as a brake but actually as a lifting source,” says Gianluca Guelfi, a naval engineer and A2V partner.

“The Scania engines saved us 300 kilos each”

A2V relentlessly chased weight savings by redesigning systems, pooling equipment and reducing pipe lengths. The choice of engines was made in the same spirit. “The Scania engines saved us 300 kilos each. The coupling to the jet did not require a multiplier thanks to the engines’ rating. They can operate for many hours at a high rotational speed,” says naval engineer Fabio D’Angeli.

On the fuel side, the consumption per kilometre was halved: “With the same engine, we go twice as fast. The consumption per kilometre is therefore halved. We are gaining speed while reducing our carbon footprint and fuel costs,” says Lionel Huetz.

The first customer was absolutely convinced: Peschaud signed the order for the Clémentine in January 2016. Straight from the shipyard, Clémentine will join the part of Peschaud’s fleet that specialises in logistical support for oil rigs. In the African country of Gabon, the vessel will be used to transfer personnel from Port Gentil along the Omboué river to oilfields that lie 300 kilometres inland.

AV2 has identified coastal surveillance, passenger transport, pilot boats, offshore traffic and sea taxis as potential markets. “We’re launching a new generation of boats with an especially favourable outlook, especially small swift and profitable units,” says Huetz.