At a time when the carbon footprint of composite boats is being called into question, the Greenscow 40, designed by the architect Gildas Plessis, offers an alternative. This Class40 concept, built from birch plywood and also used for a Imoca’s preliminary draft, aims to considerably reduce the environmental impact of the boats, while delivering similar performance? Tip & Shaft tells you more.
The last time a wooden boat won a scratch race in a major ocean race was in 1980. It was the trimaran Moxie, skippered by the American Phil Weld, in the sixth edition of the Transat. Despite a few isolated performances since then, the growing mastery of composites has consigned this material to oblivion, along with aluminium, its best competitor at the time. But environmental awareness is now challenging ocean racing, to the point of reconsidering certain practices.
Some classes, such as the Mini 650 and the Ocean Fifty, have taken steps to limit the number of boats produced, but “no significant technical steps have been taken“, laments naval architect Gildas Plessis. He adds: “As we were very disappointed by the response of the nautical and ocean racing industry to the 2015 Paris Agreement, we began a process of reflection with the builder Flavien Gaulard (founder of the Kaori Concept yard, located south of Nantes) with the idea of producing a modern boat, but as low-carbon as possible.” The result in 2018 was the Kaori 5.50, a small scow built from larch, whose construction “emits no more CO2 than its own weight (450 kilos), which is ten times less than a standard polyester unit”, stresses the architect.
The shipyard then pursued this approach by designing the Greenscow 40, a Class40 whose construction, for an owner wishing to combine racing and fast cruising, should begin shortly at Kaori Concept. Gildas Plessis says he is also in discussions with three racers for a 100% racing version, without naming them. “We used a database, which gives a carbon equivalent for each kilo of material used, incorporating a number of criteria. The energy emitted, of course, but also the supply chain and entropy. We did a lot of acquisition and sourcing work to find the right suppliers and the best formula,” he explains.
Birch and basalt fibre
The best formula would be… plywood. The architect has set his sights on birch, 30% heavier than African okoume – the wood most commonly used for wooden boat building today – but is found in large quantities in Scandinavian forests, so is less expensive, including ecologically.
Epoxy resin, on the other hand, is still a must, and while plant fibres (flax, for example) can be used for layering and bonding, the architect considers their mechanical properties to be modest, preferring basalt, a volcanic rock found in the Massif Central and whose woven fibre performs slightly better than E-glass. The problem is that it is banned by Class40, which considers it too expensive, “twice as much as glass”, according to François Angoulvant, the class’s chief measurer and a doctor in composite materials. Could there be an exemption for its use in combination with plywood to encourage decarbonisation? “The door is not completely closed”, he replies.
The fact remains that first ecological gain is the absence of moulds, synonymous with a considerable reduction in the carbon footprint, as shown by the life cycle analysis carried out by the American team 11th Hour Racing on the winning Verdier design in The Ocean Race (now Groupe Dubreuil, with Sébastien Simon at the helm): 28.5% of the 538 tonnes of CO2 emitted during construction came from the manufacture of the moulds, which are themselves made of carbon. On this basis, Gildas Plessis, taking up a design he began for Figaro racer Ronan Guérin in 2012, has also worked on a preliminary design for the Imoca Greenscow also made from birch plywood and with larch rails.
The Carbon footprint? No more than 200 tonnes of CO2, all for extra weight that the architect estimates at just 500 kg (for a total weight of 9 tonnes). He recently presented this preliminary project, which he describes as a ‘demonstrator’, to the Imoca class. While the class president, Antoine Mermod, emphasised “the seriousness and innovative approach”, the sustainability committee of the class declined to comment “as they haven’t had the time to study it in depth”.
Between scepticism and voluntarism
After reading it, Nicolas Andrieu, naval engineer at BeYou Racing and recent winner of the Class40 Transat Jacques Vabre, replied: “I’m not disputing the environmental interest of the approach, but I see at least two biases in it: the first is that the wooden demonstrator is a daggerboard boat and it is being compared to a 2020 generation foiler. The latest Imoca boats with daggerboards, such as Macif (2012), came out at 7.5 tonnes. The current generation of foilers is indeed at 8.5 tonnes, but with 600 kilos of foils, the rest being invested in the structure. You have to compare like with like. As for the European standard on which the calculations are based, I think that the load cases should be multiplied by at least two to take into account the real stresses undergone by the planking of an Imoca”.
Asked about the Greenscow 40, François Angoulvant believes that scow hulls don’t lend themselves very well to the exercise: “When Class40 was launched, some boats were made of wood, and I actually owned one. They were 400 to 500 kilos heavier than the composite ones, which were gusting 300 to 400 kilos to reach the measurement weight. Nowadays, scows need so much structure that they naturally reach this minimum weight. I don’t see how a plywood boat could be competitive, there’s no magic wand.”
For his part, Manfred Ramspacher, organiser of the CIC Normandy Channel Race and the Globe40, in which the first Greenscow 40 could take part, is rather enthusiastic: “At one point or another, we’re going to have to make a move. Gildas Plessis’ boat will be very closely watched when it comes out. It’s in its infancy, and the racers are waiting to see, but I think that the big brands interested in social change will be receptive to the idea of investing in a project of this type.”
The final word is to the project leader: “Our approach is not to say that we have to make THIS particular boat, but it’s a way forward. We just have to keep working to see if it’s possible. And the racers who contact us today don’t care about winning. They just want to be the first to tell the story.”
Photo: Gildas Plessis
