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Green motor for revolutionary catamaran

News International-French

23 Apr 2011

Sailing-class catamaran manufacturer African Cats has just announced the development of a new generation of catamarans – the Green Cat. These crafts are propelled by a revolutionary new motor that uses no fossil fuels and generates its own power from the waves.

(Published on November-December 2008 – JEC Magazine #45)


The Green Cat is a luxurious and spacious sailing-class catamaran that can reach top speeds. The difference is that it is the only sailingclass catamaran without a fossil-fuel engine. Instead, it is powered by an environmentally-friendly electric generator and motor – the Green Motion electric propulsion system. This innovation allows sailors to power their catamarans in an environmentallyfriendly way.


“Apart from propelling the craft when there’s no wind, this motor powers the air conditioning, the heating, the lights – it provides electricity for the whole boat,” says company founder and Director Gideon Goudsmit. “The Green Motion system also produces its own power: when the catamaran is sailing under wind power alone, the motor becomes a dynamo, generating and storing electricity. And when the battery’s full and there’s plenty of wind, the motor can be lifted out of the water for a more streamlined shape and faster sailing.”



Critical weight

This combination of luxury, highpowered sailing and green electric power is unique to the Green Cats. “We’ve been building light, fast and luxurious catamarans for seven years,” says Gideon, “and although they were lighter than other sailing-class cats, our cats still needed the impressive power-to-weight ratio of a fossil-fuel engine to get them moving.” To combat this problem, African Cats have reduced the weight of their catamarans from 8,900 kg to just 5,000 kg. Without such a light structure, it wouldn’t be feasible to use electric motors. An electric motor that could propel a normal catamaran would be huge, increasing the craft’s weight even further and slowing it down so much it would hardly move. What’s more, with luxuries like cappuccino machines and king-size bedrooms onboard, each cat would have a very heavy interior. This meant that, to reduce the craft’s weight enough, not only did every piece of furniture and each little accessory need to be super light, but the weight of the craft’s entire structure also needed to be vastly reduced.


To make their ultra-lightweight catamarans, African Cats use:
  • vacuum infusion to construct each structural component – not just the hull,
  • Twaron fibre instead of glass fibre for reinforcement,
  • a unique foam that absorbs 78% less resin,
  • lightweight epoxy resin instead of traditional polyester resin,
  • a spray-paint coating instead of a heavy gel coating, saving 8% in weight.


Creative solutions

African Cats first looked at using vacuum-infusion technology to reduce weight. With this method, each layer of the hull is assembled inside a mould and sealed in a vacuum pack before the resin is added – a technique that reduces weight and cuts pollution. But this didn’t reduce the catamaran’s weight enough, so African Cats decided to develop their own approach. “Our new vacuum- infusion method uses a unique foam that absorbs 78% less resin than conventional materials. And unlike other yacht builders, we use vacuum infusion for every part of the craft, not just the hull.” They also replaced conventional hull materials with lightweight modern alternatives. “For example, we replaced the traditional glass-fibre reinforcement with Twaron para-aramid fibres, because Twaron has a much lower unit weight and is much stronger than glass fibres. This has significantly lightened the hull, and we’re currently looking for ways to use Twaron in the decks as well. Without this kind of high-performance material, our catamarans wouldn’t be light enough to make the Green Motion motor feasible.”


More Information...
  • African Cats’ catamarans are between 12 and 16 m long: all beds are king-size and the state rooms large.
  • While conventional sailing-class catamarans weigh from 11,000 to 13,000 kg, African Cats’ catamarans weigh as little as 5,000 kg.
  • An African Cats catamaran can sail 480 km – that’s as far as from Barbados to Miami – in 24 hours.



JEC Composites Magazine: For what reasons mainly did you opt for Twaron and not for another fibre?

GIDEON GOUDSMIT: We chose Twaron fibre to increase the impact resistancy and lower the weight of the total hull structure.


JCM: What is the percentage share attributable to Twaron in lightening (8,900 kg to 5,000 kg)?

G.G.: The weight saved is around 10 % or 900 kilos, compared with the use of a different fibre.


JCM: Is there a important surcharge (in term of cost)?

G.G.: The extra cost is around €4500,00 per yacht or around 1% added to the total cost.


JCM: Do you think it is possible to generalize this approach?

G.G.: Yes I am sure it is and it would be advisable to increase the safety in ocean going yachts.


JCM: Do you think you can lighten your catamaran yet?

G.G.: We keep on trying to lower the weight even more but it becomes very difficult.