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Norwegian boat builder Brødrene AA and reinforcement maker Devold AMT were the joint winners of the JEC Innovation Award 2005 in the marine category. Their project involved developing a family of carbon-fibre passenger boats, in a spin-off of the prestigious Swedish Visby-class stealth corvettes for which Devold AMT developed and supplied the carbon fibre reinforcement materials.
(Published on October-November 2005 – JEC Magazine #20)
An important message to the composite industry is that today’s ship-owners and operators are not looking specifically for boats in composites. They are simply interested in reduced risk and a return on their investment. These topics were central in the development program that led to the award-winning product family. Building in carbon-fibre sandwich proved to be the right solution, as it provided the best return on investment compared with aluminium or glass fibre. From all points of view, the common denominator in the comparison is spelled W-E-I-G-H-T!
Half the weight of aluminium
Weight is a function of the building materials and technical solutions used and of the speed requirement. A carbon fibre catamaran weighs half as much as a comparable aluminium boat, for example. Replacing the hull material launches the design process into a weight-saving spiral: a lighter structure requires a smaller engine; a smaller engine requires lighter gears, shafts and propellers. Even fuel tanks are downsized. Except for the structure, all these weight savings also bring about a cost reduction that nearly offsets the higher cost induced by the more expensive building material.
Within the range of watercraft, the advantages of reduced weight have been utilised diff e re n t l y. The Rygerdoktoren ambulance boat delivers 44 knots of speed for the same fuel consumption as its predecessor at 28 knots. The Rygercat harbour shuttle ferry, with more than 200 port stops a day, greatly benefits from reduced weight in terms of manoeuvrability and acceleration/deceleration. And with a cruising speed of 35 knots, the Rygerfjord conventional passenger catamaran has the lowest fuel consumption of all Norwegian fast ferries.
For a high-speed catamaran cruising at 35 knots, the weight saving would be 35 tons. This is more than the weight of the passengers, and so the power requirements drop from 14.6 kW/ passenger to 9.6 kW/passenger. Despite a slightly higher investment, the owner of such a ship benefits from the longer service life and reduced operating costs – in sum, a winning combination, to judge by the commercial success enjoyed by Brødrene AA since the concept was introduced in 2002. Today, eight vessels are in service in Norway, with five different ship operators.
Without doubt, carbon fibre will play an important role in the future of passenger ferries. There are several reasons why introducing these innovations is taking time, however. Few shipyards have the combination of skills needed to manufacture in CFRP, for one thing, and conservative ship owners prefer to see proof of lifecycle savings before starting to renew their fleet.