One afternoon we came back after a walk and found our neighbour making a beautiful sketch of Ya!
Daniel showing his sketch of Ya on the pontoon of Sanlucar de Guadiana
Daniel simply said: “it takes me an hour and it makes me happy. When I draw I feel that everything around me disappears and the time stops, it is a pleasant and harmonious feeling”
And it shows: what a beautiful sketch!
Daniel’s sketch of Ya
Daniel (Instagram: @dandibujador) belongs to the collective Urban Sketchers (Malaga). They are a global community of artists who practice drawing in locations in cities and towns, telling the story of the environment and its people.
A long, long time ago there was a town where everybody lived happy. They called the little place Happytown. Just like in many towns in the country, the people’s wealth grew. Then, the garbage in Happytown grew and started stinking. And also, it caused diseases. What to do?
Remove to the landfill They moved all waste further away. The government of Happytown took care for it with landfills. Everybody recognises that is a pity that all this garbage removal and pieces of land cost money and taxes. But also, everybody thinks it is necessary to handle the problem. When the consumption grew further, also the amount of waste grew. First the government expanded the landfill, but it simply became too much to put on the landfills.
Remove to landfill and air So, after a long debate, the government decided there should be a garbage incinerator west of Happytown. It cost some extra money but it was worth it. Well, the Happytowners living closed to it were not happy, because of the smoke, but they moved. And most people could afford cars, so in the weekends they went to nature areas and spend their time there.
The Happytowners’ wealth grew further and everybody could live in bigger houses and could buy more stuff. So, there was more garbage. And also, a second incinerator, but that doubled the garbage costs.
Recycling As a result, recycling started in Happytown. The main chunk of garbage is the green stuff, vegetation and so on. Each household in Happytown got a separate container. This could be transported to a composting place. And yes, it costs the Happytowners more square miles of land, and also more transport costs and more taxes, but as a Band-aid, the Happytowners can get free fertile soil. Anyhow, it kept the problem contained.
Later new containers came into Happytown. But now on every street corner, to ease off the cost of the infrastructure. There was a container for glass, divided in green, white, brown and blue glass. A container for cloths: cotton, polyester, linen, and one for mixed fabrics. The container for batteries was the most difficult one, because there are about 15 sorts of them, like PbAcid, NiCad, NiMn, FeMn, LiIon, LiFePhO4, and so on. The government issued a list of all of that, but that was hard to understand. But most people could find somebody with the technical education to help you with that. Which is important, because there was a camera on the container to monitor if people complied to it. And next to all extra effort, the taxes to pay all this, rose further. These taxes kept on rising, because the soil under the old landfills was polluted with all kinds of chemicals, for example, from the batteries. So, this had to be cleaned up.
Still, the welfare of Happytown grew. This extra money was necessary, because if you wanted to go for a nice walk in nature, you had to go by car now. Now that all people had big houses, the roads had to be wide for all the cars in Happytown. When the wind came from the wrong direction, everybody could smell the incinerators. All these fumes are especially bad for your children, and who would hurt them with dirty air? So many people of Happytown went to the beautiful hills of Simpleshire. They mostly stuck together in a camping, and they called it Happycamping. Because they were happy again in the weekends.
Simpleshire. As if the time stood still there. All peace and quiet. The people lived in little houses. An occasional car. Many people could perhaps not afford such car, but they also did not need one. Here they did things the other way. The Happytowners were amazed to see how they dealt with the garbage.
Rethink The first thing a Simpleshire man does when he wants to have something, is: think. He asks himself questions like: “Do I really need this?” Or: “Do I need this thing, but then a bit different?” That’s why a Simpleshire household is simple, free of all unnecessary stuff.
2. Refuse If a car salesman comes to the door, they simply refuse. “Sorry, I don’t need a car. In case I need one, I am member of Simpleshire Wheel Share.” The same goes for a lot of other stuff. You just share it, or exchange things. This rethinking and this refusing prevent most of the garbage.
3. Reduce But there is more yield. These Simpleshire people just take not more than they need. This sounds like common sense, but they really do it. So they insulate the fridge and save 50% of energy, and costs. They leave 2 minutes earlier from home and drive 90 km/hr in stead of 130. This saves 20% of petrol, and costs.
4. Reuse And, if they have stuff they don’t need, they check if somebody can reuse it. Cloths and toys for kids, car parts, etcetera. It may take some time, but for all sorts of stuff there is a buyer, especially with internet. Sometimes a small repair is needed, but that gives space for negotiation.
5. Recycle But in the end, of course they also have garbage. Most of it is green stuff, vegetables and grass and so on. They keep it in a separated corner of the garden, where it rots. It is too small to really stink.
The rest of their garbage is very little, about 10% of what the Happytowners produce. There are still the rechargeable batteries which are dead after 50-100 times. Every 5 years a car picks them up and brings them all to one spot to be sorted out and recycled.
6. Responsible containment Then, what is left as garbage, is nearly nothing. Therefore, they have a small landfill, which will not even be full for the next centuries. They keep track on what comes in. They registrate it. The keep control, because Simpleshire people want to prevent polluted soil or ground water. They don’t want to compromise the future of their children.
The Happytowners saw that. All people, all companies and the government in Happytown started acting in this following order:
The incinerators in Happytown were not necessary anymore and the air became clean again. People rethought about working at home in stead of standing with their cars in the traffic jams, nose picking and irritating each other. So many people sold their cars. and shared them. The big roads around the town were not necessary anymore. So they made a park there instead, all around the town, which they called “Simpleshire Park”. All Happytowners walked and camped there in the weekends and if a child asked its parent about the name of the park, the parents told them this fairy-tale.
And all Happytown people, all families and companies, lived and worked happily ever after.
We carefully hoisted our lead-acid batteries into the dinghy of a fellow-sailor. He is happy to re-use them, and we are happy that they don’t have to be recycled yet. So, we are both happy. The alternative would have been to sell them as old lead, but we prefer re-use to recycle.
Why did we decide to replace the batteries? Well, we noticed our lead-acid batteries got more difficulties in loading and unloading. They also needed more energy for themselves, so they were less efficient. Also, because we could not travel during COVID, we decided to use our time on Guadiana river to replace the batteries. After giving it some thought we knew we wanted to change to lithium-ferro-phoshae. Lighter and much more efficient. So, in January we ordered batteries and… lead.
Work in progress: taking the old batteries out and replacing them with the new ones.
The 24 lead-acid batteries that have served ‘Ya’ faithfully for the past 7 years not only served for energy storage, but also for ballast.To prepare the battery-banks for the new batteries, we had to take the old ones out, They weigh 60 kilogrammes each so we were very glad Hadrien helped us.Afterwards, we have been living with 1400 kilogrammes of batteries on our side decks for a few weeks. We connected them and used them for cooking etcetera.Because the new batteries weigh only 300 kilogrammes instead of 1400, we had to put in extra lead to keep Ya’s stability.
To be exact, we have put in 24 pieces, in total 991 kilogrammes of lead. We were allowed to use a little less than we removed because the weight could be put lower in the boat.The new batteries arrived in time.We prepared for the structures to keep the new batteries in place.Peter carefully put together lots of connecting pieces for the new batteries.Above the lead, a construction to keep the new batteries stable and dry.And, in the spot where we had 1 lead-acid batteries, we can now fit in 4 lithium-ferro-phosfate batteries.Slowly but surely the new batteries find their way to the battery-bank.Peter makes sure the batteries will keep in place also when sailing.A demo-construction of 2 sets of 3 LFP-batteries.
The next phase is the that we have to connect the battery-banks to all our energy-input systems (solar, hydro, wind). We hope to be able to tell you how we did this in one of our next blogs.
Orcelle: this first design is already more than 10 years old (source)
Wallenius Willemsen explains why cargo needs to shift to wind power
Nowadays, cargo companies search for alternative ways of shipping. Of course, you can think of wind assisted shipping. But you can also think of completely fossil free shipping using wind, sun and waves. Check this and understand why, all of a sudden, Ya feels very real, but also, very small…
Sail Cargo Ships
The “Wind Challenger Project” reduces fuel consumption by using sails and engines. For more information. https://www.mol.co.jp/en/sustainabili…The B9 concept uses wind energy. This delivers 60% of their power. The rest comes from engines that are powered by bio-gas. (source: www.b9energy.co.uk)
The WASP has the ability to load and unload cargo by herself since the masts can also be used as cranes. The WASP will make use of the trade winds.
KTH built a model of the Oceanbird. (source: Wallenius Marine)
Test: Oceanbird (scale model) in sea basin (source: Wallenius Marine)
Wallenius Wilhelmsen will build the Orcelle Wind.
Neoline in France seeks orders for a 136-metre vessel. This can also be used for transporting cars or farm machinery. This carrier could cut emissions by 90%. Source: www.neoline.eu
Wind and Solar Ships
Eco Marine Power uses rigid sails for wind and solar energy. The sails can be used with other green ship technologies.
Wind, Solar, Wave and Hydrogen
Orcelle combines sustainable forms of energy. Sails, solar panels and waves generate the energy the ship needs. Also, the ship can produce hydrogen. This way, it can store energy for later use. First, Wallenius Wilhelmsen will build the Orcelle Wind (see above).
NYK uses a combination of common sense and new designs to innovate.
Sky Sail Ships
The kite reduces the load on the engine and lowers fuel consumption. Therefore, it is now used on several types of cargo ships with good results. Click here to find out how skysails work.
Wind assisted sailing ships
Rotors are special vertical spinning cylinders using the Magnus Effect. These rotors can be quite high,so Sea Cargo decided to use tilting Rotor Sails. (source: Norsepower Ltd)
New technologies can lead to a fuller shift to wind. For example, the development of wing sails. And, for instance the America’s Cup inspires for tougher, lighter materials. Another example: better long-term weather forecasts will allow for better route planning. This way, ships can avoid storms or doldrums.
In short: cargo shipping is heading for the future!
We buy stuff from all over the world for prices next to nothing, and its transport costs next to nothing. Next to nothing? Well, the fossil sea transport creates lots of environmental impact. This will cost our next generations an enormous amount of money, health, lives and wellbeing. Therefore, this article is about alternative shipping methods. Sailing cargo methods!
Our next generation working together in the yards of a classic square sailing ship (source: Tres Hombres).
One of our partners of the very first hour is Fair Transport, a Dutch enterprise since 2007. Three young, professional sailors wanted to change shipping cargo. So, they bought an old mine sweeper. Through sheer positivism, energy and with the help of volunteers and sponsors, they converted her into the brigantine “Tres Hombres”.
Captain and co-founder Andreas Lackner explains what Tres Hombres is all about in 1 minute.
Since 2010 she sails cargo between Europe and the Caribbean. She carries a maximum of 40 tons of organic and traditionally crafted goods like, cocoa, coffee, honey & canned fish, and, of course, the delicious Tres Hombres rum.
The brigantine ‘Tres Hombres’ is the pioneer of fossil free cargo.
Tres Hombres is the first fossil free cargo ship. It is hard to find sailors who do not know her!
The 20 meter‘Nordlys’ doubled Fair Transport’s fleet; she covers the coastal shipping.
The fleet has been doubled by the Nordlys (video). The Nordlys carries a maximum of 25 tons of organic and traditionally crafted goods like wine, whisky and olive oil.
To the deep sea trade with larger ships
In Costa Rica, a group of young sailcargo shipbuilders are working on ‘Ceiba’, a topsail schooner of 33,5 meter, able to carry 250 tonnes.
The fossil free cargo sailing needs bigger transports over the largest waters. Like the tea clippers in the 1800s, sailing from China and Australia to England.
So, it is time for the Ecoclipper www.ecoclipper.org. She will be a prototype for a line of fast, traditionally built, emission free cargoships.
The ship will be a steel replica of the Dutch clippership Noach, originally built in 1857 in Kinderdijk. It has been stated by historians that the Noach has been the fastest Dutch sailing vessel ever!
Ecoclipper500 will operate in the deep sea trade: Trans-Atlantic, Trans-Pacific and around the world. She will be rigged with three square rigged masts, carrying a total of 976 m2 of sail area, without mechanical propulsion whatsoever. And, the Ecoclipper500 will ship 500 tons of cargo, 2 times the volume of Ceiba, making it the largest vessel of the fleet.
The Ecoclipper500, a replica of the fast 1857 clippership ‘Noah’, will be the first fossil free ship specially designed for world-around, deep sea trade.
Jorne Langelaan, the initiator of the Ecoclipper, tells his vision within a minute, English spoken with Dutch subtitles
On Ya we live fossil free. While Peter is working on the batteries, Inge experiments with bubbles to avoid plastics and chemical waste.
One of the experiments: tooth paste! Inge uses baking soda instead of tooth paste. This saves plastic, all kinds of unnessecary additions and a big CO2 emission on making the tooth paste.
The bottles with Octocrylene went into the garbage.
Now it is time to check our other cosmetics and detergents.
It is hard to get environmentally friendly detergents in some places.
The warning signs on the back of the bottles tell the story in any language. Obviously, you would want to avoid the ‘skull-and-bones’ and ‘dead-tree-dead-fish’ symbols. Also, the exclamation mark seems worth avoiding. That is, if the icons appear because for some categories it is not mandatory to show the label.
So, what could help? We did an experiment using baking soda. The can we had on board was quite old but still reacted with vinegar (bubbles), so, it would still work.
In these pictures you see how baking soda, vinegar, patience and some extra effort turned the black inside of Inge’s teacup amazingly white. But don’t use it on aluminium, silver, gold, or marble!
Encouraged, we passed on to toothpaste. We buy the ones that do not contain microbeads, but we wondered if we could also avoid using plastic tubes. Baking soda is supposed to work so we tried it. It is really nice how clean it leaves your teeth (see video above)
If you don’t like the salty taste or want to have an added taste like peppermint you can just search for plastic free tooth paste tablets and you will find several sites that provide them.
Deodorant, really?
Baking soda appears to have magic qualities. Would it also work as a deodorant? Inge only likes one specific brand and that is not widely available. So, that was also worth a try. A really easy recipe for deodorant: 1:3 baking soda and coconut oil. Melt, mix and allow some time for cooling down. Use sparingly.
Test results: it smells slightly like coconut, does not irritate the armpits and it stood the odour test of a nice walk in the Spanish sun.
If we replace our toothpaste, deodorant and detergents for the baking soda alternative this will save us at least 4 tubes of toothpaste, 2 deodorants and 2 bottles of detergent per year. Less chemical waste, less plastic, just as clean and fresh, more space on the boat and in addition, some savings. Not bad!
Sunday morning on the Guadiana river. We were about to finish our slow breakfast and we heared some tones of music. We looked outside. Watch the movie and turn on the volume. Enjoy peace and quiet.
Even though we really like the Guadiana river, we want to move on eventually. But, in line with government policy, we would like to prevent contamination. The government however, wants us to get our vaccination in Holland.
We tried our favourite site Rome2Rio and found the quickest way.
Before we go from Sanlucar de Guadiana to Rotterdam we first have to get a PRC-test. So, a bus to and from Huelva. Then, to the Netherlands (provided the border with Portugal re-opens and we can fly from Sevilla). The trip would be: bus-train-plane-train-tram-house-tram-vaccinationscentre-tram-house. And vice versa for the return.
We would make 24 movements per vaccination. We will probably both need two injections each, so that makes 48 travel-moments per person. 48 environments to exchange the virus. 96 for the both of us.
And we thought of all the CO2, (Carbon dioxide) we would emit.
How much is that? What we would produce in extra CO2 equals, for example.:
A yearly electricity consumption of two Dutch households (source Milieucentraal), or:
The distance an average Dutch car makes in 1,8 years (source CBS, Dutch National Statistics), or:
230 train trips Amsterdam – Paris by Thalis.
If you would like to try some calculations for your own purposes, try for example thosesites.
Rethink: the local solution
Considering the environmental footprint getting our vaccinations in the Netherlands would create, we started rethinking the situation. Our vaccinations could be restricted to 2 movements for each vaccination. That is: if we were allowed to receive them in Sanlucar de Guadiana. No PRC-tests needed, just a walk to get the vaccination in this village or somewhere nearby. This would prevent a lot of contamination moments, and also save fossil fuel and 3,2 tonnes of CO2.
So, we asked the Dutch Embassy in Madrid for advice.
From the skyscraper in Madrid came a quick and adequate response: “We understand your desire to be vaccinated. We have information from the Andalusian authorities about the steps you can take to be eligible for a call. These are as follows:
– You can use your Dutch or European health insurance card to access the nearest “centro de salud” (a public care center);
– There you can register in the “base de datos de usuario” (user database) as “desplazamiento temporal” (temporary displacement);
– According to Andalusian authorities, this will give you automatic a call for a vaccination, in order of age category.
– If you have a medical indication that puts you in a risk group we recommend that you find out how and whether this can be registered.
For timing, vaccination strategy, and further questions it is best for you to check with your ‘Centro de Salud’, but keep in mind this can be a matter of months”.
So, we went looking for our ‘Centro de Salud’. Would it be the ‘Consultorio Medico’ in the centre of Sanlucar de Guadiana?
The Consultorio Medico of Sanlucar de Guadiana
The friendly nurse told us that it would not be that easy. We had to go to the “Trabajador Social” in Villanueva de los Castillejos, a village 22 km further east. We got an appointment 2 weeks later, at 9:45. There was a regular bus line to from Sanlucar the Guadiana.
At 7:30 AM the bus goes to Villanueva. But the first (and only) return to our little village was at 8:00 PM. So, we decided to do this 21 kilometres return trip by foot, because that was faster.
The social worker in the Centro de Salud in Villanueva de los Castillejos gave us the form. In a restaurant we filled it in after our coffee, tea and a ‘tostada’. We got our copies in the papershop down the road, and we walked back to the Centro. We gave the social worker the form. He explained the rest of the procedure in Spanish, using arms and legs to explain the various paths the form had to go through the bureaucracy. This was a bit difficult to understand.
Famous Spanish breakfast dish: toast with tomatospread and olive oilWe forgot to take pictures of the toast with ham and cheese. But here is a lookalike from a travel-site
This visit could have been avoided if we could have filled in the form online. But the breakfast was great, and the 20 km walk was lovely and very healthy!
The walking route from Villanueva de los Castillejos avoids the main roads and takes 20 km.
Now we are back in Sanlucar and await further instructions from the Centro de Salud. We hope Spain keeps its position as frontrunner of EU-countries vaccinating their population. And, we hope we soon can get our vaccination, our ‘ticket to travel’ in a CO2-friendly way.
In the two last articles we discussed two kinds of hydro-generation.
The first was the alternator-to prop shaft hydro generation: simple and cheap to make. Second was the towing generator . This I would not recommend, because an extra propeller gives extra drag. And astern, the water is highly turbulent, which is not efficient for hydro generation. While the ships propeller is under your ship in a laminar current, so it would be common sense to use this prop instead. And, towing generator costs some 4000-5000 Euros. If you would add this money to a renewal of your diesel motor for an electric motor, you have a good business case. And technically it is very easy to change an electric motor into an alternator.
Most ideal is have the propeller directly on the shaft of the alternator. And this alternator can be switched into an electric engine with one button, bringing you to the harbour and motoring through wind stills. This ideal system is working on the ‘Ya’ and we show you how it is done.
Here the Ya sails with the Parasailor. Great in light winds, because we can easily make the 5 or more knots now, enough for a good yield on hydro generation. (Vernoo Media)
Hydrogeneration starts with the propeller
You can use your existing propeller, but if you think of buying a new one, then read this. The best props for energy generation are large, slow running props. So, the 34 foot-long Ya has two 17 inch (43 cm) propellers. But for a sailing yacht, the drag, the resistance of such big props could be terrible. Close hauled, this drag will seriously increase the leeway. Therefore, the Ya does not have fixed props, but 2 Autoprops, that will go into feathering position when not in use.
The Autoprop in its working mode (left) and in feathering position (right).
Also, a fixed propeller is not logical on a yacht, because it is generally designed for one speed. Mostly around 4 to 5 knots, and with an RPM (Rotations Per Minute) of about 1500. But when you are sailing and the prop is in generation mode, the prop will rotate slower. If you could adjust the pitch (the angle of the blades), it would generate more. On a sailing yacht, also the speed will vary. So that would require continuous adjustment. You should adjust the pitch with every gust of wind and every wave running up and down. If the blades were continuously adjusted to the optimum position, it would be the most efficient for generation. (And also, for propulsion.)
Well, the Autoprop is the solution to this all. It adjusts the pitch automatically. Whether in propulsion or in generation mode, if the speed varies, the rotations vary, and the blades will vary the pitch to the optimum position and vice versa. And, when in propulsion mode, the blades are adjusted by the rotations and the speed through the water. This can be seen in the film below:
The Autoprop adjusts the pitch according to speed through the water and to RPM. In its reverse mode it works just as efficient as in forward mode. The Autoprop therefore has the best generation efficiency, because the prop runs in reverse when it generates under sail.
The Autoprop adjusts the pitch on natural physics: the centrifugal force of the RPMs, and the impact of the water caused by the speed of the boat. So, no electronics, no chips or wiring, no hydraulic tubes, nothing. Just physics. The only maintenance is some lubrication every now and then. Isn’t it beautiful? It helps the Ya tremendously on its energy generation.
Want to know more? You find a very thorough explanation with an animation on the Bomarine site (Dutch spoken). The technology for the automatic adjustment is beautiful and makes our tech hearts run faster. But the economical hearts will start beating fast when you see the various tests. The Autoprop belongs to the most efficient props. Yachting did a prop test, or check the German Segeln. Underneath we show the outcomes of the French Voile Magazine.
The French magazine ‘Voile’ tested how many miles a yacht could make with 10 litres of diesel. The Autoprop was the best. It also means it can deliver more on hydrogeneration.
The alternators
The E-Tech engine is also a dynamo – you simply switch to the generation mode with a button or key.
An electric motor with a permanent magnet can easily be switched into an efficient alternator. Just with one button. Technically, this type is basically the same as the old-fashioned dynamo on a bicycle tire. The rotations of the current electric motor (and so the dynamo) do not have to be very high. So, you don’t need a reduction box before your propeller and that makes it efficient, less complex and lower in costs. And a slowly rotating propeller is more efficient, in generation and in propulsion. But on slow rotations, the propeller must be bigger and should be designed differently to be efficient.
The white buttons are for switching the engines on (here for the left motor). When you push the throttle up, it will propel. When you switch on the blue button (right motor), the charge mode is activated and the motor is switched into an alternator. With the throttle, you regulate the resistance: the energy you take out of the running propeller.
If you intend to buy an alternator and electric engine, consider these things that were decisive for Ya’s choice for E-Tech.
Low maximum rotation. The maximum number of rotations per minute can be adjusted by the factory. On the Ya the max RPM is only 1040 RPM, with a pretty high torque (Nm). Slower rotations of the prop have three advantages: more efficiency, less noise, less wearing out. It saves you a reduction box with its resistance and fast moving parts, and less reliability. The motors are brushless. Just like most marine electric motors, they no longer have brushes that “drag” along the rotor. These should be replaced frequently. This feature saves us lots of replacements, because the motors make many hours as generators. Double thrust bearing. A thrust bearing is put in between engine and propeller and absorbs the pressure the propeller emits. This prevents the propeller from exerting its force on the motor itself. A permanent pressure on the engine would cause wearing, so this is prevented. Most electric motors only have a thrust bearing on the propulsion side (to forward). But on the Sustainable Yacht the generating side (astern) is mostly used. So, the propeller does not “push”, but mostly “pulls”. The E-Tech engine is therefore equipped with a thrust bearing on both sides. Synchronous motor. A synchronous motor is ideally suited as a motor and as a dynamo. He can, as it were, “flow” into it. Liquid cooling. A cool electric engine works more efficiently than a warm one.
The practice and the numbers
As soon as we sail more than 4,5 knots, we give a little reverse power to the engine, and the Autoprop is ‘soft started’ for generation. We push the Charge switch. With the throttle in neutral, we see the RPM display showing about 300. Then we push the throttle slightly forward and the dynamo starts doing its work. Inside the cabin you can hear a light, friendly zzzzoommmm…. The dynamo gives electricity to the batteries in 48 Volt DC. This sound is not irritating at all. It gives peace of mind. A crew member once said: “Dynamo, Sweet Dynamo” 😉
On 4,5 knots the energy production is not more than some Watts. But on 5 knots the dynamo delivers 50 Watts. On 5,5 knots it nears 100 Watt and when doing 6 knots it is over 150 Watt. Great fun it is when you reach the hull speed of the Ya of 7,3 knots and make over 250 Watts with each alternator.
Brunton tested three Autoprops on hydro generation. The largest (566 mm) works already from about 3,5 knots. The Ya has two 430mm props. (Brunton’s Propellers)
In general, we are leisure sailors. At sea, especially the ocean, you sail your ship conservatively and for the 34 ft Ya a general speed of 5 to 5,5 knots is good. Some people find this a high average, but realize that we also have a Parasailor sail. It gives the power of a spinnaker, but is easy to handle with two persons, even when the wind gets stronger and you want to lower it.
Perhaps you find 100 Watts not much. Well, it is. This runs 24 hours a day, so count on 2,5 kWh per day. This is enough to cook an extensive meal with our induction cooker, oven and microwave. So, we are happy on the Ya. But it must be said that our speed is critical for obtaining this result. I would not recommend to seriously spend money on a prop and dynamo for a leisure yacht shorter than 30 feet, simply because you always have to sail too close to the hull speed for a good energy gain.
In 2012 we collected some statements from electric motor suppliers about the generation possibilities. The impression was created that with a propulsion prop, about 5% of the maximum propulsion power could be generated. That would be 650 watts with our 13 kWatt (2 times 6.5 kW) max power and therefore much more than our practice on the Ya. But still they can be right: you only need a larger yacht! For example, a 60 ft yacht would easily do 8 knots, and then the 650 Watts generation is a piece of cake.
But what really helps is that the hydro generation is the third leg of the tripod of our energy household. Now, there is always energy coming in from somewhere: sun, wind or our sailing speed. And, we have a light, reliable engine in our ship.
In last week’s blog we discussed the alternator-to-prop shaft as the good old way to generate your energy from the waterflow under your sailing ship. But there are more options. Here we discuss the towing options. It is great fun to see them working behind your ship. But are they useful for us cruisers?
A separate towing hydro generator
The general principle of a towing generator is simple: you connect the one end of a line to a propeller, and the other end to the shaft of an alternator. You throw the propeller overboard and when the line stretches, the prop starts rotating, thus rotating the line, and rotating your alternator. When the line is long enough, it evens out the difference of speed the boat has when climbing a wave, versus it gliding down the wave.
Who remembers the Walker log? This was the first use of the towing propeller, but then the prop propelled a clock, showing the speed in knots (sea-miles per hour). The one shown here is from 1905. (Clipper Maritime Antiques)
The yield and efficiency
Just as with any propeller, the physics, precisely defined in Betz’s law , also apply for the towing props. With the right propeller and alternator, and in normal, not turbulent, water, they start delivering from 4-4,5 knots. In the beginning, the yield is poor, just some Watts. The real yield starts from 5 knots and the yield grows steeply with every extra knot.
Just as any hydro generator, most towing generators for cruisers start delivering their first 5 or 10 Watts at 4,5 knots and from then onwards, it rises fast – up to 500 Watts at 8 knots. (courtesy Boat News)
When making a lot of speed, the line will stretch, so it will be higher in the water. The closer to the surface, the less efficiency. This is because the waves cause turbulence in the surface; it gets even worse when the prop sprays water up into the air.
Another factor is the speed differences, that will tangle the line. The speed differs with every wave: climbing to the wave top the yacht slows down, and from the top down, she speeds up. When the speed slows down, there will be more slack in the line, so it can tangle. You can prevent this by using a (stainless) steel line, or an anti-torsion line. This is not cheap, especially the latter one. And both are difficult to coil up, so it will take a lot of storage space.
Here you see -although filmed on one side- how the towing prop works. The speed is rather high, and now the prop starts spraying water up high. That is a waste of energy.
The Duogen is a special thing: this is a wind generator and a hydro generator. You simply change the wind blades for a propeller and let the pole go into the water from the aft of your yacht. The pole is perhaps too short for an effective wind generation (I would recommend at least 5,5, meter high, see here). But the pole is long enough to keep a small angle with the water flow, small enough not to affect the efficiency that much. It may not work as well as a long towing line, even though the length of the pole helps a bit to equalize the speed differences before and after the top of a wave.
The long pole of the Duogen brings the prop a bit away of the turbulence created by the underwatership.
The fin under the prop, together with the long pole, make it possible that also with a lot of speed or in extreme waves the prop stays in the water.
When using the right propellor, the energy yield is a bit less than the oldfashioned alternator-on-prop-shaft. But it is not much more than 10% less.
Towing propeller on the transom
You can also mount a towing propellor on the transom of your yacht. There are many brands on the market. The three main manufacturers (Wattt&Sea, Eclectic Energy and Save Marine) make transom towing prop units that can deliver up to half a kilowatt. If you pick the right propeller. For a cruising yacht of 35-45 feet, the best is a big (40-50 cm) diameter, and a small pitch. Racing yachts can do with the small prop and a higher pitch.
Mounted on the transom, the generator can be lifted when not in use.
The mounting needs serious attention. First, always choose the deeper one, because it runs on laminar flow, and not on turbulent ‘flow’.
close to the surface there is more turbulence, so less yield;
you’d better keep it as far as you can from the turbulent water flow leaving the hull of your ship;
the prop must be really deep when you sail in steeper waves: mounted on the aft, the prop can come out of the water. If it does, it costs you much yield;
don’t mount it in the ‘flow-shadow’ of your rudder or your existing propeller(s), because there is serious turbulence.
These deeper transom towing propellers weigh about 15 kg. Their cut-in is at 4 to 4,5 knots, just as any propeller (Betz’s law) and they can deliver 500 to 600 Watt at a speed of about 8 knots. The racing unit is smaller and can deliver more. They cost about 4000 Euros. With some wiring, adjusting to your battery management and the installation hours, it will be 4500-5000 Euro.
Towing generators – great for ocean racers
Towing generators are fun, for sure. But it is difficult to get a good yield out of it. It lies rather high near the surface. The long rope can tangle, which gives extra drag.
The Duogen, the prop on the pole with a hinge on the aft deck, deals with this problem sufficiently. But it is more vulnerable in heavier weather. The hinge must be very strong, and the weight is considerable if you want to hoist it out of the water with 6 or 7 Beaufort.
The towing generator on the transom is not logical to me. We need laminar flow, and especially directly at the transom is the most turbulence, from the hull of the ship and from the propeller(s) you just stopped.
The question is, why would you first stop the propeller(s) on your sailing yacht and then put another propeller overboard? Note that the propeller you just stopped, is usually of the right size and pitch just for your ship, and located deep, so in a laminar flow. A towing generator on board a sailing cruiser just makes no common sense.
And you pay nearly 5000 Euros for it. If I would like to spend money, I would prefer a mechanic in my engine room just making the alternator to the propeller shaft (see this article ), it will be three or even four times cheaper. OK, the towing generator misses the resistance of the V-belt, but no doubt that this will easily be made good by the better location of your propeller.
The towing generator only makes sense for ocean racers, simply because they don’t have a prop at all (to save drag!).
If you have the extra 5000 Euro to spend, and you reconsider to buy a new engine, then consider an electric engine/alternator. This, including the batteries and all, is cheaper on the long run, and can even be cheaper in the first investment. This is a sophisticated system and straight forward to a maximum yield. Like the Ya has. Next week we discuss this.
