An Ecological Catamaran?

Mikael, Dan, Gautier at Windelo stand discussing ecological sailboats

Last weekend I visited the Cannes boat show to see the Windelo 50 catamaran. It is a beautiful and innovative performance catamaran — which is great all by itself. It is also, however, marketed as an ecological catamaran, which sounds fantastic. But what does that really mean?

So Isn’t Sailing Green?

Sailing, on the face of it, would seem to be a really green activity. After all, sailboats are propelled using renewable wind energy, and even Greta Thunberg did it, crossing the Atlantic twice by sailboat, instead of any other means of transportation, with the sole objective to travel without emissions.

The reality, however, is (unfortunately) a bit more complicated.

Plastic Construction

Firstly, most modern industrially built sailboats are constructed using a combination of materials that aren’t very ecological at all. These materials, to be found in most modern hull and deck structures, are glass fibers, resins (polyester, polymer, and/or vinyl ester resins, and PVC (polyvinyl chloride).

Or to put it more simply: a lot of plastic!

A lot of plastic that comes with a big carbon footprint during the production phase, and also a lot of plastic that can’t be recycled, so it usually ends up in a landfill somewhere.

A typical hull or deck sandwich construction with a gel coat outer layer, a PVC foamboard in the middle, surrounded by two layers of fiber/glass-reinforced plastic.

Manufacturing sailboats (as well as other boats, of course) the way we are doing it right now, using glass fiber and plastic, is unfortunately not very sustainable at all.

Motoring with Fossil Fuels

Secondly, cruising sailboats usually come with one or two diesel engines, and a substantial amount of sailboat usage isn’t in fact propelled by sails at all, but rather by good-ol’ diesel fuel.

Take us, for example.

Before our previous season, our boat had 368 hours on the engine and it had been moving (SOG > 1 knot) for roughly 700 hours. Some of the engine hours were certainly used to charge the batteries. A lot of all our sailing, though, was motor sailing, not using just the wind to propel the boat forward.

During that same time we traveled about 3,226 nautical miles (5975 km), and with that, we can make the slightly unnerving consumption calculation:

0.154 liter per km is 15.4 liters per 100 km, or about 15.27 MPG.

So, on average, to cover the same distance we sailed for our first two seasons, we would have burned the same about of fossil fuel using a luxury SUV.

Jeep 2021 Grand Cherokee Grandhawk, MPG city 11, highway 17.

If we compare motoring at 5.5 knots (using about 2,5 l/hour of diesel) directly with covering the same distance on road, the comparison gets really bad. We end up with a consumption of about 25 l/100 km, corresponding to 9.6 MPG. That’s like a Hummer H2, basically.

Hummer H2, MPG 9-10 (source: Wikipedia)

“Why?”, I hear myself asking. Why did we use the engine so much?

No wind, or too little wind. That is the best answer I can think of.

We never turned on the engine to avoid tacking upwind, but mostly to get a bit more speed in whatever direction we were going. When the speed dropped down below three knots, and the ETA moved one or two days forward, it often felt better to go a bit over four.

Life Cycle Assessment

Putting it all together, the sailboats of today tend to come with quite substantial carbon footprints. Especially, when you have to use the engine a lot, either for propulsion or for charging the batteries.

According to one life cycle study, roughly 30% of the footprint is made when constructing the sailboat, about 60% when actually using the boat, and the rest can be attributed to distribution logistics and waste disposal.

The study estimates the whole life cycle footprint (from birth to demise!) for a theoretical 40 ft sailboat to 45.82 tonnes of CO2 equivalent. We, with our style of sailing, produced about 1.2 tonnes per year just by running the engine, so I suspect that the estimate is painting too bright a picture.

There clearly is a need for greener sailing, so let’s see what the Windelo people have come up with.

Windelo’s Sustainable Approach

Loving the planet is also caring for the wellbeing of the planet. That’s what I have thought for a long time, and I’m excited that Windelo seems to think the same.

Our love of the planet has been the driving force behind our environmentally friendly boats. We board innovative boats, built mainly of recycled and bio-sourced materials.

Windelo, Our Ecological Approach

In practice, they are addressing the sustainability challenge in three different ways:

  1. Build light and performant boats to minimize the need for motoring and— when motoring is needed —minimize the energy needed to move the boat forward.
  2. When constructing the boat, replace, as much as possible, carbon intensive GRP and PVC with sustainable materials.
  3. Replace the diesel engines with a hybrid-electric propulsion system to minimize the carbon footprint of motoring.

Sustainable Performance

To decrease the amount of motoring needed (see our track record above) you need a boat that performs well using its primary engine, the sails.

I don’t have any real-life performance data (yet!), and Windelo doesn’t have any (at least public) VPP polar diagrams to share, but looking at the base specification, the boats seem really well designed for the task.

It also helps to know that the designers of the new Windelos, Christophe Barreau and Frederic Neuman, have (separately or together) produced a lot of legendary designs before: the Outremer 45, 4X, 4E, 51, 5X, the Marsaudon TS4, TS5, and the list goes on.

In fact, the Windelo 50 looks very similar to the Outremer 51, when looking at the base specifications. Another good indication that the performance should be good.

Outremer 51Windelo 50
Length51.3 ft50.0 ft
Beam24.8 ft26.0 ft
Displacement (light)11.2 tonnes11.2 tonnes
Mainsail92 m291 m2
Jib40 m243 m2

The proof is in the pudding, however. While I do hope that — should we have the opportunity to become Windelo owners — we’d manage to reduce our footprint significantly by sailing more and motoring less, it’s something that remains to be seen. (And validated with real world data!)

The starboard daggerboard is placed close to the center of the hull for better performance. It allows the interior a better flow as well. Small (or big?) differentiation from the Outremers.

Sustainable Construction

To (eventually) replace the old ones, Windelo is using some really exciting new materials in their construction process.

It’s cool, or even mythical cool, as one of our children would say.

Basalt Fiber

First, instead of glass fibers in the laminate layers, they use basalt fibers.

And what on earth is that?

Turns out that basalt is what volcanoes spew out as lava, after this basalt lava has cooled down and formed basalt rock. More than ninety percent of all volcanic rock on Earth is, in fact, basalt, and more erupts from active volcanoes as we are speaking!

Producing basalt continuous fibers from basalt rock is, apparently, rather straightforward: you melt the rock, and then extract the fibers.

The end result, basalt fiber mats that are stronger than glass fiber, produced with a much lower ecological footprint, and can be recycled.

From rock to fiber. (Picture from
Recycled Bottles

Secondly, instead of using PVC foamboard as the core material in the sandwich layup, Windelo uses a mix of PVC and recycled PET plastic.

Ideally, I think, all PVC should be replaced with recycled materials. At the moment, however, and due to structural reasons on one hand, and weight-saving demands on the other, that isn’t yet possible.

Progress is being made, though, and already about fifty-six percent of all the foam core of the Windelo 50 is made of recycled plastic.

The “raw” material, recycled PET bottles.
(📷 Grendelkhan)
In the leftmost jar, crushed bottled, then molten plastic beads, and finally the end product: a PET foamboard.
(Picture from
Blue areas are green areas, meaning where the recycled plastic foam is used.
(Picture from
Sustainable Wood

Last, but not least: all the wood used in the interior is FSC certified.

And it looks nice!

A fresh, Scandinavian atmosphere in the master cabin.

Sustainable Propulsion

The largest part of a sailboat’s ecological footprint comes from actually using the boat and burning fossil fuels for propulsion and producing electricity.

Windelo’s approach here is what the auto industry has been (successfully) doing for a while now: go electric.

Or, rather, hybrid-electric, as a stepping stone towards ultimately, someday, achieving fully carbon-free propulsion.

The concept isn’t unique, but Windelo is at the forefront of yacht manufacturers offering hybrid-electrical propulsion, not as an expensive and experimental add-on, but as the default and only means of non-sail propulsion.

Their system is not the Oceanvolt system (see Sailing Uma for recent experiences of that!). It is a modular system that is designed by themselves, but obviously put together using components and software from other manufacturers. (They are not building their own electric engines!)

A good choice, I suppose, if you want to not be “married” to just one supplier, but able to pick and choose the best components from a market where the technology is rapidly evolving.

The current Windelo 50 is sold with one electric engine in each hull (standard engine 20 kW, bigger 24 kW), with one or two propulsion battery banks (27 kWh or 54 kWh), and with one or two diesel generators (17.9 kW or 35.8 kW).

The control station. Both engines are off, luckily, since we are moored!

On the power generation side, the engines support hydrogeneration (no data, yet, about how well they do it), and you can get up to 4.7 kW of solar panels.

For the final push over the cliff, you can have up to two wind turbines (0.4 kW per turbine) on the boat.

If you choose those, however, you should also grow a big and bushy beard, I think.

“Welcome back to civilization!” some awestruck onlooker will say, sincerely, after you have motored (silently) into the harbor and performed a smooth docking maneuver.

4.7 kW of solar. You can walk, or even dance on the panels if you want!

Is the Windelo 50 an Ecological Catamaran?

Circling back to the original question, is the Windelo 50 an ecological catamaran?

I think the answer requires answering two separate questions: does the Windelo 50 accomplish the ecological goals it sets out to do, and even if it does, is it still a more ecological choice not to buy any boat at all?

As to the first question, I’m feeling optimistic.

On paper, and after having seen the boat “live” a couple of times, and having chatted a while with one of the founders of the company, I am confident they will achieve what they set out to do: a sailing catamaran that is much more ecological than the mainstream competitors, and a sailing catamaran with a sustainability mindset deeply rooted in its DNA.

I really look forward to getting more data supporting the realization of this goal, and perhaps also some data showing where more progress is needed. (Waiting for that first sail, that is!)

The second question is decidedly more complicated.

Even if the total lifetime footprint is 50% better, it is still 50% as bad, and far from, let’s say carbon neutral. Building a more ecological boat will produce more emissions than building no boat at all.

I think, that when we as a society (and humanity) attempt to keep the planet livable for us and other species, it is more likely that we will succeed by upgrading than by downshifting. By upgrading our current capabilities, production methods, and consumption patterns towards sustainability, instead of— to put it a bit bluntly— turning off the lights.

In that sense, what Windelo is doing, is essential in building the lifeline from our now, to a future, where we live a life without using unsustainable fossil fuels.

Designing, building, and having the vision and determination to create a more ecological sailing yacht, it is the necessary first of many steps to come, and key to the whole journey.

I, Dan, and Gautier. The PET and basalt fiber demo stuff in the foreground. When this photo was taken, we were actually talking about the importance of building more ecological boats. True story! (📷 Elke Aun)


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