Propelling to fossil freedom – simple and cheap

Hydro generation covers an essential part of a sailor’s energy need, next to solar panels and wind generation. This third way of supplying stabilizes your energy household. It is like sitting on a tripod instead of a chair with only two legs. When you are sailing and meanwhile the propeller generates electricity, you feel that unexplainable fossil freedom.

Ya sailing: fossil freedom

Hydro energy is free energy, who does not want that? I tell you: too many sailors. 

Hydro energy is safer than a windmill (mostly set too low, so dangerous blades), than a solar panel (can blow away in a storm). Of course, it is also safer than a fossil fuel generator (fire, unhealthy).  Who does not want that? Again: too many sailors. 

Every cruiser, especially the long-distance cruiser, can get the energy really simple, and for low costs. You just connect an alternator to your propeller and you let it run when you sail. We will explain how.

To start with the result: there will be an alternator in your engine room, driven by a V-belt, which runs over a pully around the propeller shaft. When the propeller runs, it will make the alternator run, generating electricity, and a (built in) rectifier will give the voltage your battery needs (most yachts have 12 Volt).

Hydro generation is here to see: a pulley around the shaft (right arrow), a V-belt, and an alternator (left arrow) delivering electricity to your electricity system when the shaft runs.

Balancing RPM, (1) the alternator

The alternator is the most critical thing, so we start here. Most car alternators will start to generate electricity when making 800 rotations per minute (RPM). This so-called cut-in RPM, just tells you it would deliver its first Watt. We want more Watts; practice is to start from 1000 RPM.

If you buy an alternator, check some things:

  • The rectifier. For most yacht systems it must be 12 Volt. Then it delivers till 14,5 Volt to load your battery completely.
  • How heavy the alternator is. If it charges over 80 Amperes at 12 Volt, then make sure it has a double pulley (and double V-belt)
  • Check the diameter of the pulley. It should be rather small; about 50 mm.

Now we go to the next step: how many rotations does the propeller make? Then we can we determine the final step: how many times bigger must the pulley on the propeller shaft be, to get that 1000 RPM? 

Balancing RPM (2) the propeller

A propeller will start delivering a constant strong rotation when the boat sails over 4,5 knots. We take some extra and make it 5 knots. (If you are interested in the theory, Betz’s law tells you all about how much speed is needed to make a propeller run, in water, in wind, whatever)

Now comes the fun part. 

There are two ways to learn the RPM of your propeller: by measuring it, or by calculation. Best is to try both methods.

First the measuring method. 

You set sail and measure the RPMs when you sail e.g. 5 knots. You can buy an expensive RPM meter of 50 Euros or you measure it as follows:

  • take a 20 cm line. 
  • Tape 5 cm of it on your shaft in the engine room
  • When your shaft makes rotations, the end of the line will hit the hull skin: TICK
  • Take the Dictaphone on your mobile phone
  • When your yacht makes 5 knots, push the recording button
  • After exactly 1 minute, you stop recording. 
  • Play the Dictaphone and you see a spike every moment the end of the line makes the TICK
  • Count the number of spikes and you have the RPM of your propeller when sailing 5 knots.

Now the calculation method. 

The number of rotations depends on the pitch of your propeller. You can read that on the propeller. This says for example: 14” X 16”. The first number: 14” stands for the rotation diameter of 14 inch. The 16” is the pitch. This 16-inch (or 0,4 meter) pitch means, that it will theoretically go 16 inches (0,4 m) forward in one complete rotation. 

Suppose you make 5 knots. 

5 knots is 5 X 1852 m = 9260 meter per hour. This is 9260/60=154,3 meter per minute. 

So, your prop would make 154//0,4 = 385 rotations in a minute. So, it’s RPM would be 385. 

But… water is not wood where a screw exactly follows its pitch. Water is ‘’thin’, ‘flexible’. When a propeller delivers propulsion, it pushes a boat forward, but also it pushes water to aft. It ‘slips’. An optimal propeller has 50% slip. 

This makes the propeller’s RPM 385 *2/3 = 257 RPM. 

Believe it or not, if you now check it with the measuring method, you see your results get pretty close to each other. If you measure less RPMs, you have more slip and so perhaps too much resistance. This can be a rough propeller, or friction in the reduction box or the bearing. If you have measured more RPMs, then this is great for your hydro generation, but you could have the disadvantage that the propeller doesn’t work well when you give much RPMs for propulsion.

To the right pulley size

OK, we have now:

  • An alternator that must run 1000 RPM with a speed of 5 knots. 
  • A propeller making about 250 RPM at a speed of 5 knots. 

So, the pulley of the propeller must be 4 times larger. Given the pulley diameter of an alternator of 50 mm, it means that the pulley on the propeller shaft must be 20 cm. 

Most boats have that desired 10 centimetres under the prop shaft, but first check it before you start building. If not, there are alternator pulleys smaller than 50 mm. That saves you triple on the prop shaft pulley.

Next week we focus on efficiency and a more sophisticated system. 

A bridge too close

There is a plan to build a bridge over the river Guadiana, to connect Alcoutim, on the Portuguese side, and Sanlucar de Guadiana on the Spanish side. We wonder if the bridge is a good idea. Because we adore the undisturbed beauty and silence of this place. Will it help these little towns? We are concerned that this bridge will not bring them the desired economic development. Then it would just be a waste of money, spoiling all that makes this place special.

The Spanish Sanlucar de Guadiana seen from Alcoutim…..
and Alcoutim in Portugal seen from San Lucar Guadiana.

The silent call of the Guadiana

A strong flood takes the sailing ship from the mouth of the river Guadiana, under the bridge near the cities Vila Real and Ayamonte, about 15 miles all the way up to Alcoutim and Sanlucar.  

A sailor arrives here when the flood stream starts slowing down to a nice flow. You feel the calm, the peace here. Time to anchor. Easy, because the Guadiana has plenty good anchor grounds. 

The village of Alcoutim has about 1000 inhabitants, Sanlucar about 400. Both places are located ‘at the end of the country’. Or even at the end of Europe. Well, at least it feels that way. Our Portuguese friends all see Alcoutim as the ultimate place of peace and silence in Portugal. They come here, over the little roads, and for them this area is the place to be. The Portuguese and Spanish tourists come to these far ends to enjoy the silence, the handful of friendly restaurants and bars and the idea to retreat in case you need a real still, buzz free holiday at end of the world.

You can kayak, swim, make a small river cruise. If you want to go to the town on other side of the river, you ask the man of the ferry boat to take you there. 

There is also a cable from the one to the other side. Great for hikers. The Portuguese and Spanish walks are fabulous all year round, not in the least because of the undisturbed landscape and silence.

You can walk several beautiful trails here, all equally quiet. Lovely, even when it’s raining.

Our “Ya” is staying here in winter. For decades, there has been a small sailors population of some 50 sailing boats depending on these villages for their services. Each village has a small dockside, which guarantees an international ambience. 

We like our walks here. The area around Alcoutim and Sanlucar is quiet. As long as we’ve been here, the silence is broken only by the occasional motorboat, a single car passing by, roosters crowing, birds singing, a barking dog and people talking. When the sun shines sometimes there’s music from people playing instruments, alone or together. 

A bridge? 

Once every three year there is a bridge during the Festival do Contrabando  (Smuggler’s Festival). Small scale theatres, arts and artisans on both sides and a temporary bridge connecting the villages. This attracts lots of tourists. 

There is a temporary bridge during the Festival of the Smuggler, and that attracts lots of tourists (photo: Nuno Costa, Sul Informacao).

Now, the Portuguese and Spanish local administration have made plans to build a bridge between the villages. This could help connect both sides. With a car it would take 10 minutes from village to village, instead of an hour. But which local would want that? If you would want to just cross the river, you can also go by ferry. This takes 10 minutes if you include the waiting. In general, there seems to be little exchange between the people of the two villages. The only ones crossing the border seem to be the sailors. There is one Spanish commuter regularly going up and down, and there are tourists, mostly hikers, crossing over by the ferry boat. 

The sparsely populated rural areas on both sides would not generate a lot of traffic. There is already a bridge over the Guadiana in the north (near Mertola), and one in the south (near Castro Marim), both about 30 km away. Sanlucar could benefit from the fire brigade and the health services in Alcoutim, if there wouldn’t be institutional and language barriers to be bridged first. 

The sparsely populated area on both sides of the river is connected by bridges. We have indicated them with arrows on the map: they are near Castro Marim in the south and Mertola in the north. Both bridges are located about 30 kilometres from Alcoutim and Sanlucar.

We are asking ourselves: who is really going to benefit from this bridge. Will there be economic development because of the bridge? From what sectors? There’s hiker’s tourism, some small scale agriculture, no mining or other industry. So, tourism might be one of the viable sectors. But then the question is: what do tourists want? We think the tourist who come to this kind of remote area wants good food, nice walks and a pleasant environment. 

The sound of a pleasant environment

A pleasant environment. Now we sailors and hikers get interested. Especially Peter, as an environmental scientist. He did a small ‘sound check on the spot’, as follows. He made a 10 seconds movie on a popular hiking trail. Just a random movie, so under the film you here the silence, with a footstep, some buzzing flies and a bird. This film-and-sound is recorded some 800 meters from where the bridge might be projected. We expect it will be a bridge with two lanes, with cars passing at 80 to 100 km per hour. So, then Peter put the noise of this kind of road under the same film-and-sound. Here under you see and hear the result. 

The first 10 seconds you hear the environment when you hike there.
The next 10 seconds is what you hear with a bridge near Alcoutim and Sanlucar with traffic.

This traffic noise is not loud. It would comply with the regulations about noise pollution, so don’t worry. But you would hear it. And it completely overwhelms the tiny sounds that a hiker, a sailor comes for, what many tourists enjoy. This region is one of the few where silence is not yet broken. Lucebert, a Dutch poet once wrote: Everything of real value is defenceless.  We would say: the sound of nature is at least vulnerable. Maybe we appreciate silence more because we have lived in big cities and we know what it’s like when you’ve lost it.

A revaluation

So, let us reweigh the plan of this bridge against the loss of silence in this environment. 

In the past decades, the roads to Alcoutim and Sanlucar have greatly been improved; they are small but good. You can easily travel to and from the tourist hotspots of Vila Real de Santo Antonio and Ayamonte on the coast. For tourists, there seems to be no particular added value that a bridge for cars might have. Also, the local inhabitants don’t seem to particularly need this infrastructure.

If you would really like to facilitate cars passing, a reaction ferry like here in Westerhuesen might be a better idea. 

Perhaps an elegantly shaped bridge for pedestrians and bikes might be of true added value. Especially if the bridge itself would be worth visiting, like the hanging Geierlay bridge or the Pedro e Inez bridge in Coimbra. They would have to allow for sailing boats passing through, so the bridge should at least be 20 metres high. Other ideas to strengthen the local economy might also be welcome, like cooperation on cultural activities, development of the regional cuisine, crafts but also attracting digital nomads like the island of Madeira is doing now.

A bridge for pedestrians or cyclists could be of added value, like the Geyerlei bridge (sources: justgo and pixeo)

What to do?

Concerned locals have started a website with information and a letter you can sign (in English, French, Portuguese and Spanish).

Everybody who is related to this area (also as a tourist) can leave his or her opinion at the


Good Food

Every day we make beautiful walks, just where we moor or drop our anchor. As a bonus, we find amazing food on our way.

The picture above shows a selection of vegetables, herbs and flowers from our friends’ garden in Calstock. This was in August last year.

In September, in Brittany, we were stunned by the delicious, fragrant passionfruit and the quinces that nobody seemed to want. Which is weird, because quinces are perfect for stews and marmelades.

The flower  of the passion fruit…

….and the fruit itself. You pick the ripe ones from the plant, it is the most delicious fruit you can ever get.

Bunches of quinces, ripe on the trees and inviting to pick,

In October, in Portugal , we saw a gem-like fruit that seemed much too beautiful to eat….

it was the fruit of the Medronheiro (Strawberry Tree).

From November, we walk in the area of the Guadiana river, the border river in the south of Portugal and Spain. Winter is actually a beautiful season to walk. It is pleasantly cool with 15 degrees Celsius.

In area around the Guadiana we see lots of almond trees along the roads and in the fields, with plenty of almonds.

You have to try first before picking them; some trees have sweet almonds, but some bear the bitter ones that you should be careful with. 

The olive trees were heavy with olives in all varieties. 

We met fellow sailors who have produced their own virgin olive oil. It took them three weeks to obtain 2 liters, but: it can be done. 

For cooking and making infusions you can find fabulous herbs anywhere. 

Fresh sage


Ever since we got on the Guadiana River, we have been seeing the orange trees, loaded with fruit. Harvesting season runs from September to March, so there is no hurry.

Walking along the Guadiana river, the orange trees invite you to pick a piece of fruit. 

In Februari, after some rainfall,  the oranges start falling off the trees.  And if no one comes to pick them up, they rot in the fields.

These are the most juicy oranges in the whole world. And water’s always near, which is important according to a widespread European fairy tale on oranges. So, in the open fields, we pick and eat as many oranges as we like. We cannot think of a more sustainable way to stay healthy.

Fossil in paradise

We feel privileged to be on Guadiana river. We are on the Spanish side now, where there is no shore power, but a magnificent view on Alcoutim on the Portuguese side.

Sunny Alcoutim (Portugal)

Until, after some days of fog and rainy weather, we noticed our batteries were on lower capacity than was to be expected.  Trouble in paradise! Was this only the lack of sun and wind?

Gloomy weather on Guadiana River

We realized that our batteries were deteriorating after 7 years of faithful service. Not unexpected, but nevertheless: bad news. Especially because we have a lot of them.

Onboard of Ya we currently have 24 lead-acid batteries

But, never waste a good crisis. We have been carrying around 25 liters of gasoline and a small generator the size of a sewing machine for in case of emergency.  With too little sun and wind and lacking shore power, we decided to start using it.

One of the smallest generators available

During the circumnavigation we never had to use the generator, the trip was truly fossil free. The gasoline is now 5 years old. So, we had to filter it several times before we could use it. 

Fossil in paradise

We are grateful that this now helps us through the windstil, cloudy periods on the river. And we are grateful to our neighbours for not complaining about the noise. But, oh boy, what a nuisance, this fossil in paradise. It stinks, it disturbs the peaceful quiet on the river and we have had to repair it 2 times already because it had hardly been used. 

Generators need maintenance

We pray for the sun to shine and the wind to blow so we can use the generator as little as possible. As we write this we see the meter jump to charging 400 Watts on wind and sun so this is a lovely day.

Ya in Sanlucar de Guadiana with the SilentWind (our camera is quicker than the human eye, it was spinning!)

We have started the search for new batteries to be able to continue our fossil free life.

In one of our next blogs we will tell you about our search and all that comes with it.

Nortada brings silent wind

The Nortada, the Portuguese Northern Wind, brought us to the Algarve. We have been here for a while now, happy victims of the Guadiana Glue. Since our wind generator broke down, we wanted to select a new one. Which one? In this article we compare the three most used quality wind turbines: Air Breeze, Superwind and SilentWind.

Airbreeze (with SilentWindblades), SilentWind and Superwind

We compare these three wind generators because they are universal. They can handle all batteries, can be combined with solar panels and other generators, and they are available in 12, 24 and 48 Volt. They are often used on yachts and they are all good, high end generators.

We chose for the SilentWind for its light weight, low noise, the power in also the high range, and the low maintenance.

The yield is in the height!

If you really want a wind generator to deliver, then it needs height. Don’t put it on a 3 metre pole on your boat, but put it higher than 5,5 metre, away from wind obstacles. Then it delivers double, because that is where the wind blows.

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This is the Zaan at Zaandam from Claude Monet. The 17th century Holland was packed with windmills, used for all sorts of industry. They determined, when higher than 5,5 meter, the wind became significantly stronger. This rule could very well be sufficient on yachts.

This ‘higher-than-5,5’ metre rule dates from 17th century. They figured this out in the time that building high mills was difficult, while the wind in Holland was crucial for the industry there. In those days, the Zaanstreek was the innovation centre of Holland, the dominant and richest country of the world. It was full of windmills, for sawing wood, grinding grain, and they were pumping the water out of the polders around Amsterdam. They could use every sigh. This ‘higher-than-5,5-metre’ rule nowadays is interesting for us sailors.

The diagram on the left shows the windspeed windward of an urban place. On the right, you see the diagram of the wind speed on the lee side. A windmill must be put much higher than the disturbing buildings to catch good wind. (Source: Fernando,J .(2010). Fluid Dynamics of Urban Atmospheres in Complex Terrain. Annual Review of Fluid Mechanics, Vol 42, s365‐389)

Check the picture above. The wind blows from the left to the right. On the left side you see a diagram of the ‘clean’ wind. The wind is there if not too close to the surface.  The wind blows over the buildings and creates turbulence above it. On the right side you see the influence of these obstacles.  For good wind, you have to be far above that ‘stuff’. This also underlines the +5,5 meter rule from the 17th century, when obstacles in the field were not higher than the cattle and the grain. And this corresponds with our yacht: a hull on the water, with a railing and stuff on deck. So we’d better stick to that +5,5 meter rule.

If ever you want to remember anything about the yield of windmills: the height is essential. A cheap windmill put on 7 meter, gives a a far better yield than a high-end windmill put on 3,5 meter.

From here we go into the nuances and details.

The windmill on the Ya is over 7 metres high. There’s metres free of obstacles, and you need that to get good wind generation

More height – less weight

A sailing yacht should not capsize. The ‘Ya’ is an ocean approved yacht and complies with the highest standard; even with the mast top blown into the waves she still self-righting. So, all high things on board are necessarily light things.

There are two pretty light wind generators. The lightest is the Air Breeze (5.9 kg). SilentWind a bit heavier (6,8 kg). Heaviest is the Superwind (11,5 kg).

The Superwind is too heavy for a yacht like the Ya; we would have to put it two times lower and this is close to nonsense. But it is a good turbine for a bigger yacht.

The power – it is in the range, not at the peak

The peak power number only gives an impression for a first orientation. All three wind generators are in the range of a couple of hundred Watts. Instead of the peak power, you must look at the power curves. Then you understand the power of a windmill and what suits you.

The Air Breeze (red line) may be the smallest in peak power, but this light mill delivers already 75 Watt at 15 knots wind speed, which is of great value in the leisure sailor’s wind. And there is an extra power peak in the 6 and 7 Beaufort (when there is mostly overcast, so no solar power). You always sail in strong winds? Take the Air X Marine (blue line).
The SilentWind continues its increase till 28 knots of wind. This When over 7 Beaufort, it supplies an awful lot of electricity. In this graphics you also see that generating on high voltage is more efficient; the 48 Volt version yields nearly 25% more than the 12 Volt version.
The Superwind is heavier and delivers slightly more from the first cut-in, and from 25 knots of wind (12 m/s) it delivers 350 Watt continuously. The internal regulation dictates that the 12, 24 and 48 Volt versions all deliver the same 350Watts.

Shrieking, madness….and then silence

We are cruisers. We love nature and the silence. We want our wind generator to deliver energy, not the noise.

All three windgenerators have 3 blades. This is a compromise between efficiency and noise. Interested in the technological reasons why? Rosie explains it simple and straight here.

On the Ya we started with the Air Breeze with the standard blades. From the first cut-in, it started making noise. First you like it, because it delivers. But when it really starts delivering and nears the 15 knots of wind, the blades produce a high shrieking sound. The first neighbour started to complain. At 20 knots of wind the neighbours got angry.

Then we discovered the silent blades. Made in Portugal by SilentWind. A high-end product, just as the price of over 300 Euros. But it was worth every penny. Now the same Air Breeze was making a bit of a whistle till 10 knots, a more serious whistle with more speed, and when the wind is somewhere between 15 and 20 knots, the wind generator’s noise drowns into the ambient noise of the wind blowing through the rigging of the boat.

The Air Breeze with the original blades. When equipped with the blue low noise SilentWind blades, you maintain a good relationship with your neighbours.

Now we have the SilentWind. When the rotation is slow and you listen well, you can hear the sound created by the magnets or the new bearings. At 8-12 knots you hear a light low whistle and when faster it becomes a friendly lower tone with more volume. When over 15 knots, the noise drowns into ambient wind noises.

The Superwind you will not hear from 20 knots of wind. I listened many times to this mill in several situations in light winds, and it is really low noise. But nothing beats the SilentWind.

Brakes and no brakes

All three can be switched off manually, for example when there is not enough wind. The switch simply makes a short circuit. The Air Breeze and SilentWind also use this short circuit brake to prevent too much speed, which is near hurricane.  Before the blade tips would reach bullet speeds, spin out of control and could be ripped from the turbine, the electronics create a short circuit and the blades will slow down to a near stop.

The SuperWind solves this differently, with smart blades. From 25 knots the blades automatically start to adjust their pitch and the rotation speed will not increase. So, in a severe storm, when there is not much sun for your solar panels, the Superwind keeps on generating energy for you.

One could say that the extra moving parts of the Superwind blades have more chance to fail than the simple fixed set of blades of SilentWind and Air Breeze. But this elegant mechanical solution is perhaps safer than the electronic shut off, because also electronics can fail.

Every windmill can be pre-set to stop generating electricity when a certain voltage is reached. Air Breeze and SilentWind simply use the same short circuit brake to prevent overcharging. Since Superwind does not have this brake, all the excess electricity is regulated to go into big capacitators that will get warm, or even hot, and will be cooled by the air around it in your engine room. I don’t like that for leisure sailors. In wintertime the consumption is low and the battery full, while the winds are strong. Then, when nobody is on board, the capacitators in the engine room or cabin cupboard get very hot. It doesn’t give me a safe feeling.

The Superwind

Keep your maintenance low

Superwind designed the mill to keep the maintenance low. The blade pitch against too much RPMs and the double bearings are two examples. Great, but all together it became too heavy for us.

Our Air Breeze broke down. It did not work properly in the medium wind range. Was it the circuit board? We lowered the mast, unmounted the shaft, et cetera and took the circuit board out. We sent it to the service. It was renewed. We remounted everything, put the mast up again, and it ran well. One week later, the same problem. We lowered the mast… to cut a long story short, we lowered and raised the mizzen mast six times (Thanks to Piet, Tulga, IJsbrand, Henk, Jaap, Mick, Inez and others). We also renewed a chip up there, and other things.

The electronics of the Air Breeze are extremely simple. Great, I love KISS. But they are in the housing of the turbine. Too high to keep an eye on it or maintain it.

Then one morning, we were on the river Guadiana and I saw a strong breeze running over the water towards us. I looked up the mizzen, and saw the Air Breeze hardly responding. I knew, this was its last breeze. Our Air Breeze was no more. We declared it our late Air Breeze.

After these ups and downs, I learned what had to be down. That’s chips, diodes and circuit boards. They don’t belong in the top of your mast, where the rain and moist and salt from the sea reign and you can’t look after it. If you want to keep your maintenance low, then keep it low. Superwind and SilentWind put the electronics in a box (converter or MPPT) and you mount that box in your engine room or cabin or any other dry place. Ofcourse it can break down, but in that environment the chance is smaller and the (preventive) maintenance is easy there.

Why the SilentWind is Ya’s pick

Weight=height. On the Ya the windmill can be put on 7 meters high, on the mizzen mast. If…. the generator doesn’t weigh too much. The 6 kilograms of the Air Breeze and the Silentwind don’t influence the stability of Ya. The Superwind with its 11,5 kilograms should be mounted half way. But on 3-4 meters height there is simply not enough wind to justify such a high-quality piece of equipment.  

Silence. All three are reasonably silent. (if the Air Breeze has the low noise blades). On the other hand, if you are on anchor somewhere in the middle of a creek enjoying the singing of the godwit, bluefinch and specked spoonbill, and then a light breeze picks up, you will enjoy the off-switch of your wind generator.

Which is the best on low noise? My private opinion is that the SilentWind -what’s in a name- beats the Superwind.

Power range. All three deliver well in the critical wind range we like to sail in, or when we anchor in a more open bay. The Air Breeze is best in ‘our’ leisure sailors wind range and falls back in the higher regions. The Superwind is doing about the same, but is cut on 350Watts from 25 knots. The SilientWind continues in the high range. We are also interested in the production in stronger winds, when the weather is bad and our solar panels don’t deliver. Then the 12 Volt delivers continually 420 Watts. The 48 Volt version -which is of our interest- delivers even 520 Watt, so much better than Superwind (350 Watt) and the Air Breeze (200 Watts). Our battery capacity is big enough, it is seldom full, so let it all come in, SilentWind!

Regulation You can look deep into the regulation. We love KISS, and then the Air Breeze comes close with a simple circuit board built in the mill. SilentWind’s regulation is based on the core business of the wind generator: to take all energy it can get from that wind, from the cut-in speed to the safety limit at gale wind. The only disadvantage is that you have a big MPPT in your engine room.
I do like the blade pitch solution of the Superwind to keep on running smooth in even a hurricane. But I don’t like that the mill keeps running when the battery is full and the capacitators can get hot. Batteries are full when there is no consumption, so mostly when nobody is there. Then we don’t want critical hot things on board.

Low maintenance. A special word to Superwind. They have put a lot of attention to durability and low maintenance. Unfortunately, this is also the reason that it became too heavy to be effective on the Ya.

I see maintenance, preventive or repairs, as a daily custom for the sailor. But our Air Breeze signed its death warrant when it had to be lowered from the mizzen for the 8th time to check the circuitboard. The SilentWind (and also Superwind) keeps this delicate stuff in the converter or MPPT, to be mounted low, e.g. in your engine room.

Conclusion: We chose SilentWind. Please mail if you have any comment. We’re curious what you choose and why!

Plastic waste and art

In Alcoutim, we saw a beautiful creature on the shore. Very big and bright. She is called: LONTRA. 

Plastic Otter, 2020, Bordalo II, created out of plastic waste for the Festival do Contrabando, Alcoutim. Photo: Chris Costa

The artist created her out of waste plastic. He is called Bordalo II. On his website we read why he makes this kind of art. “The excessive production and consumption of ‘stuff’ results in a constant production of garbage (…) and leads to the destruction of the Planet.” Bordalo II uses this garbage as raw material in the construction of small and large scale pieces that he has spread around the world. They bring the universal ‘manifesto’ against waste. 

Bordalo II also makes more provocative art, which you might find interesting. So here are two more pictures:

Selling The Truth, Lisbon, Portugal, 2015. Photo: Bordalo II


Mourning The Oceans, Covilhã, Portugal, 2014. Photo: Bordalo II

We were quite impressed by Bordalo’s work and hope you like it too; his message speaks for itself.

The miracle of insulation

The Ya spent Christmas on a beautiful spot in the Guadiana river. In the morning, we could hardly believe what we saw: there was a beautiful thin layer of frost on the deck. Apparently, it had been freezing. Inge quickly took a picture and went straight back into the comfortable cabin of the Ya. Contrary to most yachts, Ya hardly ever needs a heater to keep it warm inside, even in wintertime. Is this a miracle? No. We will tell you our secret: it‘s just about three things.

The secret of Ya keeping warm inside in wintertime is in three things:

  1. Insulation
  2. Insulation
  3. Insulation

1.    Insulation – a lot, and neatly built in

Before we started with the carpentry, the hull of the Ya was insulated. This was done very precisely with high quality foam, called PIR foam (not PUR!). It is built up in layers up to 11 cm thick. Every foam plate is tightly closed to the other, with some caulk or PUR in between. So, there are no heat leaks.

Before and after the insulation: Tsjerk built the PIR foam up to a layer of 11 cm thick. As a real ships carpenter, he sealed all seams with great care, so, no heat can leak through and no condensation can occur.

2.    Insulation – PIR as an affordable quality foam

How good is this PIR foam? Well, it is a great insulator and very affordable, and it is self-retardant, so it slows down fire. In the table below you see some numbers.

The Lambda number says how many Watts of heat goes through the material if it is 1 m thick and when there is 1 degree (Celsius or Kelvin) difference on each side. So, the lower the Lambda, the better the insulation. As you can see, the very expensive Vacuum Insulation is doing best. The PF Quod Core (0,015) is second best, but it can only be applied flat, and it is rather expensive. And the third best is PIR: this can be used on yachts. It is also self retarding. Materials like cork or expanded clay are doing much worse. Better not use them on yachts, they also weigh a lot.

On board of steel yachts, often glass wool is used. It is easy to put it neatly in any corner. But, once wet, it insulates only as good as the water in it. And it can go down and hang, a disadvantage. When it is dry, it insulates OK. But PIR does that better and PIR can’t take water (condensation). Disadvantage of PIR is that you need to work very precisely. Every open seam is a heat leak and that also creates condensation.

The final column in the table shows the resistance value (R-value). As the Lambda is a theoretical number, the R-value shows the effective heat resistance when the insulation is used in houses, caravans, boats. The higher the R-value, the better. It confirms that PIR is the best affordable choice.

 MaterialAverage LambdaR-value for 100mm thickness
 W/(m-K) M2K/W at 100mm
Brick (sand lime)0,80,125
Glass fibre 2,5
Core cell foam 2,6
Cellulair glass0,0442,78 
Expanded clay0,044
PF/ Quad Core0,0155,56 
Vacuum Insulation0,004223,8


3.    Insulation – to get comfort

On Christmas night it was minus 3º Celsius. We were having a Corona-proof dinner with some fellow-sailors. It was nice, we had fun, lots of olives and almonds, little alcohol and no heater Then, our friends asked where our heater was. Well, somewhere packed deep down in a bilge; we can’t remember using it. Yet, the atmosphere on the Ya felt as comfortable as in a house, or even better. How is this possible?

Now, let us compare the insulation of the Ya with that of a normal house built in the 70’s or 80’s. How well is it insulated? Or, to put it technically: What is the heat resistance of the house’s walls and the Ya’s skin?

Suppose you live in a house with brick cavity walls and 5 cm of rockwool insulation. The two layers of 10 cm bricks each have an R-value of 0,125. So, this is 0,25 in total. 10 cm of rockwool has an R-value of 2,6. Your house has 5 cm, with an R-value of 1,3. So, for the house the total R-value is 1,3 + 0,25 = 1,55 which is the total heat resistance of your wall.

 Here you see the intersections of the skin of the Ya and a cavity wall of a normal house. The heat resistance -the R Value – of the skin of the Ya is 3 to 4 times higher!

Now the Ya

The skin of the Ya is made of 6 mm of glassfibre, 20 mm of core-cell foam, then 4 mm of vinylester/glassfibre. In addition, on the inside the skin is covered with 110 mm PIR foam.

So, the skin has glassfibre (6mm +4 mm) 10 mm. The R-value of 10 cm is 2,5, so the R-value of 1 cm = 0,25. It also has core-cell foam 20 mm. The R-value of 10 cm is 2,6, so the R-value of 2 cm = 0,52. On the inside: PIR foam 110mm. The R-value of 10 cm PIR is 4,4, so the R-value of 110 mm = 4,84. So, for the Ya the total R-value is 0,25 + 0,52 + 4,84 = 5,61.

The total heat resistance of the skin of the Ya is more than 3 times higher compared to an insulated house. No miracle Ya keeps it warm inside in wintertime.

Sun power for your shower – The spiral heater

Last week you read about the shower bag. Now we describe a system with the Spiral Heater that you can build in on board, even by yourself.
It is a rather simple system, with some technical things, so sometimes boring. But we have a cliff hanger: would the story end up with a beautiful model under the shower head? Male or female?

2.    The spiral heater

The cupper spiral is just visible through the double skinned insulation plastic, that prevents that the heat gets lost.. The sunrays go through it, heat the spiral and the water circulatiing through it.

You can make a 30 cm diameter spiral of thin cupper pipe. This solar spiral heater consists of two spiral pipes connected to each other. It is not that difficult to make. Just buy a 30 meter roll of cupper pipe 6 mm that a plumber uses for oil and butane gas lines. This pipe is rather flexible and with a bit of feeling for the material you ‘mould’ the line in a spiral without kinks. Connect the outside end of one to the outside end of the other, and the flow of the one runs against the flow of the other, which is most effective. In the middle you have to ends: one is the inlet and one is the outlet.

How the system schematically works, with the spiral heater, boiler and taps, is shown in this film.

Interested? Here is the schematic drawing and the description of the complete system.

In general: the Pressure pump keeps the water system under pressure, so the (cold and hot water) taps can give water. The circulation pump circulates the water first through the spiral heater, to the hot water tap and into the top of the boiler, pushing the cold water under into the circulation system.

We start under with the water tank containing water.

A pressure pump pumps water in the system: the water lines, the spiral and the boiler. From now you can use the cold water tap and the hot water tap (although the latter one is still cold now, but wait).

Then, a little circulation pump pumps the water into the spiral heater. The sun heats the spirals, so the water gets hot.

The water leaves this spiral heater through a line going along the hot water tap further to the boiler. It will be led into the top of the boiler. Hot water is lighter than cold water, so the hot water will be stacked on top. The cold water goes downwards. Down in the boiler there is the outlet, so from there the cold water will be sucked up by the circulation pump. Then the water is pumped to the spiral heater for a new circulation. Easy.

Only one safety issue. If water becomes hot, it expands. The pressure would get too high and it would damage the system. Therefore, there is an overpressure valve mounted in the system. It opens when the pressure becomes too high. Mount it just after the pressure pump. The water coming out, can be led to the water tank, or directly before the pressure pump. (this is not drawn here).

 This pump is a typical robust circulation pump. It works on 12 Volt. It switches on when the temperature of the boiler is lower than the temperature of the spiral heater.

Regulating the heat of the water

The pressure pump has a pressure regulation: if the pressure drops, the pump starts running till the pressure is (mostly) about 2 Bar, the minimum water pressure for drinking water.

The spiral heater and the boiler each have a temperature sensor:

  • If the temperature of the heater is higher than the temperature of the boiler, the circulation pump will start running.
  • If the temperature of the heater is lower than the temperature of the boiler, the circulation pump will stop running.

The shower test

It works!

You can increase the seas’ CO2 absorption

Clean Wave

We must stop the poisoning of the coral reef and the plankton in the oceans. If we do that, plankton and ocean life will restore itself. You can increase the seas’ CO2 absorption. This restores the oceans capacity to solve the CO2 problem.

This unknown world of plankton has a great capacity to restore itself. But, it needs help.

Stop or at least reduce using toxic chemicals

You probably already know that eating organic food and minimizing your energy consumption -like we do on the Ya– helps to make a better world. Perhaps you did not know that some chemicals can have a dramatic effect on climate change. However, the good thing is: you can do something very effective about it yourself. Yes, it takes some effort to read the small letters on the everyday products you use. Also, it will take some effort to find alternative products. But it’s worth it. Take a deep breath, here’s the list:

  • Oxybenzone or benzophenone-3 or BP-3 is top on our list because it’s really bad. This hormone-disrupting UV filter is used in sunscreen and many products exposed to sunlight. For example cosmetics, plastics, paint, rubber, cleaning agents and detergents.
    • Don’t buy sunblockers or other products containing oxybenzone. Tradenames are Milestab 9, Eusolex 4360, Escalol 567, Kahscreen BZ-3. Bring them back or throw them away responsibly. Use alternatives (hyperlink, there’s plenty of them. Or, for example, make your own sunscreen.

1 drop of Oxybenzone from a bottle of sunscreen, can kill 140 billion tonnes marine plankton. 70 thousand tonnes would destroy all life in the oceans, and the global production is in excess of 300 million tonnes. Oxybenzone does not stop working when in the water. They change the wavelength of the sunrays into heat rays and thus kill the coral reefs. The reefs are necessary for life in the oceans.

  • Other harmful chemicals used in cosmetics: this list is very long and you will not like what you see. However, please take some time and check for example on
  • Dioxins mostly exist as by-products of industrial processes such as bleaching paper pulp, pesticide manufacturing. Most pollution comes from combusting electronics and plastics, and waste incinerations.
    • Don’t buy bleached paper. Don’t use pesticides. Reuse and repair your electronics, before you remove them. Try to produce as little waste as you can. Buy only things you love and need and use them carefully.
  • Methyl mercury can be found in nature, so also in coal and biomass, combusted in power plants. Only in the US the incinerators emit 80 ton per year. 
    • Stop using electricity from coal and biomass power plants.
  • DDT Dichloro-diphenyl-trichloroethane) kills marine life. It is meant to kills insects, such as the malaria mosquito. It is advised to use as minimal as possible, but it is not forbidden.
    • If you need to use it (malaria), make sure it doesn’t get into the marine environment (water waste treatment).
  • Plastics contain chemicals and the chemicals mentioned above ‘stick’ to it in the environment. They disintegrate into microplastics and accumulate in organisms that eat it. Also, chemicals ‘stick’ to it. 
    • Reduce your plastic consumption (bags, small bottles etc.) Re-use whatever plastic you have. Make sure it doesn’t end up in the environment. If you can, pick up the plastic waste you see on your way and put it in the garbage.
  •  In 2009 all countries (Stockholm Agreement) agreed to stop using the next substances: 
    • PCB’s (or Polychloorbifynil), used as electric isolation fluid, cooling fluid. 
    • PFOS (Perfluorooctanesulfonic acid), makes fabrics water repellent, for example raincoats.
    • PBDE’s (Polybrominated diphenyl ethers), used for flame retardants. 
    • Has this Stockholm Agreement been translated in your national laws? If not, you can write your MP about it.

The good news: if we succeed, the plankton will restore itself

If we can take the brakes off the ecosystem by allowing the plankton to grow, then recovery could be really quick. It would take ten to twenty years for plant biomass to double on land. But, it just takes only 3 days for biomass to double in the oceans! 

Trees take many years to remove CO2 from the atmosphere 

Marine Algae take just a few days to remove CO2 from the atmosphere

Marine Bacteria take a few hours to remove CO2 from the atmosphere and grow 1,000,000 times quicker than terrestrial plants.

And the damage done? Plankton that is killed by toxic combinations end up on the ocean floor. We don’t know the impact of the plastic and toxic chemicals on the sediment. But, it may be that the chemicals and plastic could be locked out and no longer create a hazard. This would be a good news story and would give hope for the future of the oceans.

Start now

If we follow the current strategy of climate change mitigation, we will be too late to stop the acidification of the ocean. In ten years, the pH will reach 7.95 which will cause run-away climate change. If we just could stop the use of Oxybenzone, we could probably gain an extra 10 or 20 years to fix the ocean pollution problem. We must do this now because in a decade it will be too late; the oceans are going to be too acid. And we need healthy oceans to stop climate change.

If we stop toxic chemical pollution and clean up our plastic environment, we will be able to develop a sustainable ecosystem and reverse the effects of climate change. You can stop being worried and start taking care. Do what you can yourself. Use your consumer-power. Help your government reach the climate-goals and question them about the chemical pollution. Create a clean wave!

Motivation is plenty. It is good for the economy. It prevents a climate migration of millions of people. And, if we start now, we can restore the health and beauty of our planet. 

This is the last in a series of articles based on the presentation and articles by Dr. Howard Dryden from GOESfoundation and Diane Duncan from Clean Waterwave Foundation.  For more detailed information and insight please check their websites.

You can read the previous articles on our website:

Why plankton has decreased by 50% in 50 years 

Two causes of climate change 

Ya hears a warning from the ocean 

Why plankton has decreased by 50% in 50 years

Plankton, so important for our oxygen and to absorb our CO2 production, is in danger.

picture showing plankton life with toxic danger in the background

PCB’s, DDT, PFOS, Dioxins, Methyl mercury, oxybenzone or microplastics… We don’t see most of what is harming marine life – and ours.

Since the 1950s, the chemical revolution, it has decreased by 50%, and it continues to decrease with 1% per year.  Reduction of plankton is most likely caused by chemicals that kill the plankton and the coral reef.

Vivid colors of coral become increasingly rare

Even very small amounts of PCB’s, DDT, PFOS, Dioxins, Methyl mercury and UV-filters like oxybenzone are toxic for marine life. Also add plastic to this list, because either these substances are a component in plastics, or they will easily bind to it in the environment. 

46,000 pieces of macro plastic per square kilometer, killing more then 1,000,000 seabirds and 100,000 marine mammals, whales and seals every year.

Microplastics adsorb many of the chemicals and concentrate them by the thousands. Plankton eat micro plastics. This is why the plankton are dying at a rate of 1% year.

This is a shrimp. Every shrimp, fish, or  living organism in the oceans contain chemicals and 1 in 15 contain micro-plastic.

A sour story of the oceans

CO2 is highly soluble. It dissolves in seawater. Then it forms carbonic acid. And with less plants and plankton in the water to absorb the CO2, the amount of carbonic acid in seas grows. Organisms can’t live in an environment with much acid. So, more plants and plankton die, et cetera. 

Before 1950 the ocean was constantly alkalic (the opposite of acidic). But since then, it is acidifying rapidly. The acidification will soon come to a critical point where many life forms cannot survive.

The IPCC worked out several scenarios for the acidification. If we continue our present consumption and production (scenario RCP8.5), the acidification will continue.  Only with the strictest scenario on reducing CO2, methane and sulphur dioxide (RCP2.6) we can turn the tide – if we start now.

Graph showing pH levels with 2 IPCC scenarios (RCP2.6 and RCP8.5)

Before the chemical revolution in the 1950s the pH of the oceans was 8.2 to 8.3. Currently, the oceanic pH is about pH 8.06. The acidification will continue to a pH of 7.9-7.95 in about 25 years. From then, most carbonate-based life forms will not be able to survive.

Dominos falling

With many marine life dying, the ecosystem will change rapidly. Like a set of dominos: when one group of organisms dies, another group depending on it, will die, and so on, through the complete food chain. After a couple of years, we will then lose all the whales, seals, birds, fish as well as the food supply for a big part of our world population.

Magnificent marine life, something we can only watch in aquaria in the years to come?

We humans, at the end of the food chain, lose our life support system. The survival of the next generation, of the humanity, comes into question. This is not supposition, or even a hypothesis. When we continue as we do, the dominos will fall in 25 years. 

This is about us, not only about whales

Plankton are the lungs of the planet upon which we all depend, but toxic chemicals are killing them. 

You and me, we, all the people, in industry, government and households, have 10 years to stop pollution of the ocean. Now we can prevent an immense loss of marine life, and life on earth, including human life. This is not about whales and dolphins, but about you, me and our beloved ones.

So, there’s work to be done. Read about it in our next blog on the warning from the oceans.


If you are interested in more literature, follow our links in the text or check out, where this blog is based on. 

Previous blogs in this series: