wind power on sailboat

How to Install a Wind Generator on a Sailboat

Last Updated by

Daniel Wade

June 15, 2022

The marine wind generator is, without a doubt, one of the most effective ways of charging your boat's batteries while you are away from the electricity grid. One of the most important things to take into account when selecting a marine wind generator for your boat is the installation process.

As a sailor, you'll most definitely rely on electricity in running various parts of your boat. In addition to the power needed to run the electronics that are of great importance for navigation and safety, electricity is essential for lighting, refrigeration, and running other appliances. But because you always sail deep in the water where there's no electricity, you need another source of power that we can use to charge the boat's batteries while we are out there on the water. This is where the wind comes in handy. You're already using wind to propel your sailboat, so it makes sense to use the very same wind to charge your boat's batteries and ensure that every part of your boat runs smoothly and meets your sailing needs.

Marine wind generators are more and more becoming a standard feature on sailboats. They are a great source of renewable energy and one of the most important things is to learn how to install a wind generator on a sailboat. Installing a wind generator on a sailboat is a process that must start with an assessment of the sailboat's power needs. Knowing the amount of power that your boat will consume in 24 hours will at least give you a rough idea of the size of the battery bank you require and how many amps your charging devices should produce.

You should also know where and how to install the wind generator's system. This will, of course, directly affect how well the wind generator's turbine converts the wind power into electrical energy. You should also ensure that the amount of battery storage available on your sailboat, as well as the controls available, is efficient in ensuring that the generated power doesn't go to waste.

In this article, we'll take a comprehensive look at how to install a wind generator on a sailboat and everything else you need to ensure that your wind generator works properly and efficiently.

Table of contents

The Importance of Using a Wind Generator on a Sailboat

Even though wind generators may not be of much help off the wind, they are increasingly becoming more appealing to sailors looking for an alternative source or extra power for their sailboats. The fact that they rely on the same wind that you use to move from one point to the other makes them quite a hit. Additionally, today's marine wind generators have undergone continuous improvement over the last few decades and are now well proven and quite reliable. This is exactly why wind generators are still common in sailing despite the advent of solar panels and hydro generators.

A wind generator will keep your boat's batteries charged at all times as long as there's wind. It doesn't matter whether you're at the port or out on the water, the wind generator will continuously pump out power even on cloudy days. That's not all; wind generators are cost-effective since they're maintenance-free and do not need any launch or recovery. More importantly, there are very powerful wind generator units that can produce more than 400 units of power, which is just enough to keep a fairly medium sailboat running and operating for 24 hours.

But just like with anything that has advantages, there must be some disadvantages. One of the most noticeable downsides of relying on a wind generator is that the power produced by the generator can significantly reduce if there's no wind. Most wind generators can manage to produce about 200 watts of power in wind speeds of 20 knots but things can even become worse when you're anchored at the port since winds are generally very low at the ports. As such, you may need an additional source of power such as solar panels, especially if your sailboat has heavy power requirements.

Installing a Wind Generator on a Sailboat

Installing a wind generator on your boat's charge system is a serious process that requires careful planning and attention. As we noted earlier, this process should start by first assessing your boat's power needs. You should be able to determine the amount of power that your boat and its appliances need to consume in at least 24 hours. This will certainly give you a clue of what you require.

The general idea is to ensure that you don't have to keep your boat's engine running so as to keep your batteries charged because this might not be enough in running your boat's appliances. In most cases, a boat's power needs are modest. Well, the boat generally needs power for lighting, running the navigation and safety equipment, refrigeration, and powering a stereo, if any.

The Equipment Required

One of the most important pieces of equipment required when installing a wind generator on your sailboat is the turbine. Generally speaking, the turbine should be functional at both medium and high wind speeds. You have to, however, keep in mind that even the biggest wind generator won't produce much power if the wind speed is below 8 knots. The turbine should be tough, reliable, and quiet. You certainly do not want a turbine that sounds like an approaching helicopter as this can be so annoying.

Given that early models are very noisy, three-bladed rotors are becoming more and more popular. They are smartly designed with CAD blades that significantly reduce the whistling and thrumming sounds that occur at the tips of the blades. These modern rotors are also designed to be more efficient and reduce friction through the use of permanent magnet alternators that allow speeds of the blades to be reduced, thereby reducing the noise levels considerably.

With that in mind, some of the best wind generators to go for include Air breeze, Eclectic Energy, Leading Edge, Rutland, Silentwind, and Superwind.

The Aerodynamics of Turbine Blades

Ensuring that power moves from the turbine's alternator and safely into your batteries may seem like a simple process. There are, however, aerodynamics involved and it only makes sense if you understand how they work.

In terms of the blades, they operate based on a similar principle or a plane's wing. There may be some differences but they are generally designed to produce optimum output. This means that the turbine blades should not go too fast as it can mitigate the wind generator's efficiency. The same applies if it is too slow. In essence, it works like a car gear so having very high or low gear can be inefficient. The idea here is that the airflow will become unstable if the blades are at very high speeds.

The best way to solve this problem is to rely on the "tip speed ratio". This technically describes whether or not the blade tips are moving faster than the actual wind speed. As such, the blade tips should be moving at 320 knots on 20-knot wind speed but there should also be the survival speed, which is just the right wind speed that is needed to produce the right amount of power to sustain your sailing needs.

The Amount of Power that Your Boat Needs

It's of great importance to budget for the amount of power to ensure that every facet of your sailboat is functioning properly. Of course, there are obvious appliances such as plotters, interior lights, and fridges. There are also navigation lights, engine monitors, entertainment systems, pumps, watermakers , gas alarms, electric winches, hydraulics, and many other things. You should also make a good margin that will have you covered if there's an emergency.

You should also consider other things such as air conditioning (though this may need fuel) as well as the type of sailing you're planning to do. Will you be sailing upwind or downwind? Well, such minute factors can significantly affect the amount of power that your boat needs. It is, therefore, crucial to determine a clear and accurate idea of how much power you need to generate to perfectly operate every part of your boat.

Mounting the Wind Generator

One of the most challenging things that revolve around how to install a wind generator on a sailboat is where to mount it. Location is very fundamental and can either positively or negatively affect how your wind generator operates.

The golden rule that governs the position of the wind generator is quite straightforward. It should be mounted in an area of the vessel where there will be no interruption of the flow of air or wind to the turbine from all directions. Generally, the wind generator is mounted on the boat's mast with two stays. You can easily raise or lower the wind generator if it is installed with a pivoting base. But if it is installed on a fixed mast, it can cause difficulty if you want to secure the wind generator when there's an impending storm.

And because the main aim is to optimize the output from a wind generator, there are a few important things to do. The most important thing is to ensure that it is very stable. This is because even a slight rolling or pitching might just be enough to rotate it away from the wind. The wind generator also requires clean air from all directions and as much as possible.

As you can see, these two principles seem to be at loggerheads given that you'll get more wind speed as you go higher but this may affect the stability of the turbines. With this in mind, mounting the wind generator on mizzen masts can be a good option but choosing to mount the turbine just above the cockpit is an even better option. The idea here is that it will be a lot easier to manually control the turbine if all other options of braking it doesn't work. Again, installing and maintaining the turbine overhead the cockpit is a lot easier than when it is mounted on the mizzen masts.

That's not all; mounting the turbine over the cockpit also means that the cables need to transport power from the turbine to the alternator are much shorter. This means that the wire diameter will be a lot smaller without necessarily affecting the voltage. The fact that the voltage can drop if the wind generator is mounted up higher on the masts should be particularly important.

This is because it can affect the overall performance of the wind generator and the power it produces and this means that the power supplied to your sailboat might just fall short. Again, a considerable amount of weight can be reduced if the turbine is mounted just over the cockpit. The cables will be reduced and the overall stability of the wind generator will be increased if it is installed overhead the cockpit.

Of course, you'll also have to install the electrics that come with the wind generator unit. For example, there's the controller that is used in regulating the power supply from the turbine, as well as the dump load resistor that is essential in absorbing any excessive current that may be produced when the batteries are fully charged. There's also an inline stop switch, which is essential in turning off the unit when it's not in use. Well, most of these installations are straightforward and are generally shown in the unit's installation guide.

Assembling the turbine should also be a walk in the park. Units do come with fasteners and are accompanied by installation instructions that are easy to understand and follow, thereby making the installation and assembling process a breeze.

So if you've decided to install the wind generator overhead the cockpit, which is our best location, you must find a perfectly sized pipe and mount it solidly at any corner of the stern. You have to ensure that you support the pole with at least some diagonal tubes so that it doesn't swivel. And if you are planning for an off voyage escapade, using the hose clamps to secure the main pole might not be the wise thing to do. This is because they'll most likely snap and twist as a result of constant vibration and miles of hard sailing.

Securing Your Boat's Wind Generator

With that in mind, you should also be prudent enough to secure the wind generator if there's a pending storm. As a sailor, you should be prudent, stay alert, and prepared in case there's a storm. The most important thing is to know the dynamic of the wind generator and how to apply electric brakes or even have the turbines lowered when there is a storm.

You can do this if the wind speeds are more than 15mph. This is of great importance in ensuring that the wind generator does not overheat or the blades do not break. You can also choose to remove the wind generator altogether and store it in a safe place.

All in all, the importance of having a wind generator on your sailboat as an alternative energy source can never be downplayed. This is a great source of renewable energy that will have your boat working perfectly well even if you are sailing in some of the remotest corners of the world. Just know how to install the wind generator, have it maintained, and protected when there's a pending storm and you'll be good to go.

Until next time, happy Sailing!

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I've personally had thousands of questions about sailing and sailboats over the years. As I learn and experience sailing, and the community, I share the answers that work and make sense to me, here on Life of Sailing.

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Sailboat Wind Generators: The Ultimate Guide 2024

Sailboat wind generators are a way to capture the energy of the wind and use it to charge your batteries and power electronics aboard your vessel.

A large part of the appeal of living on a sailboat, for many people, is being more or less self-sufficient – using the wind for propulsion, and the elements to generate all the power you need.

Solar panels are a wonderful technology, literally magic, but the sun doesn’t shine every day. In fact, of the most popular cruising grounds in the world aren’t even that sunny. It rains three to four days a week in Barbados or Antigua, for example (don’t even get us started on the English Channel).

And what about night sailing – keeping critical loads like autopilots and instruments online after the sun goes down?

A marine wind generator fills in those vital gaps in the energy picture, and eliminates the need to generate or run the engines to keep your electronics online.

In this expert guide we take a deep dive into sailboat wind generators, covering everything you need to know – from how they work through to the very latest technological advances.

With thousands and thousands of miles under the keel, we have lived off-grid using technologies just like this for almost a decade now. We’ve rewired more boats than anyone should ever have to. We’re marine electronics nerds, basically, and specifically very passionate about renewables like wind and solar.

That’s why we couldn’t wait to write about this topic, and why you’ve got a good 4000 words on it! Sorry about that! But feel free to skip and just read the information you’re interested in, we don’t blame you!

So, let’s take a close look at sailboat wind generators, how they work, what makes a good one, the best sailboat wind generators that we think deserve a place on your next nautical expedition.

As an Amazon Associate, we earn from qualifying purchases. We also earn from other affiliate programs. This means we may receive a small commission on products purchased through our links at no extra cost to you.

Table of Contents

The best sailboat wind generators – best budget choice, the best sailboat wind generators – best overall, what is a sailboat wind generator, why install a wind generator on a sailboat, wind generators vs solar power.

• What is a dump load on a marine wind generator ?
• Marine wind generators vs hydro generators

Our top budget choice: Nature Power 500

If you are in the US, the choice for the best budget marine wind generator is easy – it’s this guy , the Nature Power 500, which West Marine have sold for donkey’s years with eternally solid reviews.

It’s a 500-watt turbine that is natively compatible with both 12V and 24VDC systems. It’s made from marine-grade aluminium that’s also coated in a thick, durable coating to help it withstand years at sea.

This wind generator is rated for winds up to 110mph – well into hurricane territory – and it comes as a complete kit including a charge controller using the latest MPPT technology. The controller even has an electronic brake, even though it’s a manual one.

Honestly, this is just a lot of value for the ~$700 they’re asking, and very easy to recommend for the best budget sailboat wind generator.

We don’t massively recommend most of the budget options on Amazon for extended cruising – they’re just not built for the task. But if it’s all your budget will stretch to, something like a Pikasola 400 would be the best bet for a sailboat wind generator under $500.

Readers in the UK or Europe could look at something like a Rutl and 914i . You’ll pay a little more, around £850, but a Rutland is a proper piece of kit – they’re been manufacturing marine wind generators since the 1970’s, long before solar panels were even seen on pleasure yachts.

The 914i will produce about 260 watts in 30 knots of breeze, or 20+ amps into a 12-volt battery. In a hurricane it’ll make over 400 watts.

This is a genuine marine wind turbine built from quality parts and specifically designed for the aggressive saltwater environment. It comes with very few compromises, from the bundled MPPT tracker to its extremely quiet operation.

The charge controller supports a small solar panel as well, which is sort of nice – but we’d highly recommend using a top-quality, stand-alone MPPT charge controller for any solar panels if you can possibly afford it.   

If you are in Europe, or can import, we think the Silentwind Pro is probably the best sailboat wind generator you can buy right now. This is with the caveat that while we’ve seen these installed on lots of different yachts, talked to multiple long-term owners, and even handled one out of the box, we’ve never actually owned one.

That’s because they start at about €2,100, which is a considerable sum for a 420w wind generator. But what you do get is an incredibly refined package – one that picks up and starts generating with as little as four knots of breeze, and remains whisper-quiet right up into the high RPMs.

The Silentwind Pro uses hand-laminated carbon blades that are rated to withstand hurricane-speed winds, but that are also highly efficient across the curve. This is definitely one of the most engineered solutions on the market today.

The polished package is rounded out by features like an automatic electronic brake that kicks in if the wind exceeds a certain speed. Cheaper options may have an electronic brake but it generally has to be tripped manually by the crew.

Models without an electronic brake of any kind are frankly dangerous, because you have to lasso them to stop them – which is how the gentleman broke his arm, and wind generator, in the earlier example.

Other than Silent Wind, there are a few slightly cheaper options that are still very good. For readers in the US, one option made locally is the Air Silent X made by Primus Wind Power. We don’t have as much experience with these, but we have met a couple of happy owners and have heard similar things to Silentwind.

Primus claim they have the bestselling wind turbines anywhere in the world; we’re not sure about that given that Marlec / Rutland have been around nearly two decades longer, but either way their site states they’ve sold more than 150,000 wind generators since ’95, into over a hundred countries.

Primus make six different models at different price points that are all potentially worthy of consideration, but the Air X Silent or Air Breeze are both solid choices.

Rutland wind generators also remain easy to recommend across the board, particularly to readers in the UK and Europe, and a premium option would be something like a Rutland 1200 .

At around £1,500, or $1900, the Rutland 1200 can produce up to 480W flat out, and will hit 300W in only 20 knots or so of breeze. It’s a proper marinized unit built to withstand the rigours of life at sea, and that should provide years of low-maintenance service.

A sailboat wind generator, also known as a marine wind turbine or wind charger, is a device for capturing wind energy and turning it into electricity.

Sailboat wind generators typically have 3 or more long, aerodynamic rotor blades attached to a central hub. The blades translate wind energy into rotational force and spin the hub, sometimes at near-supersonic speeds .

The hub is attached to an electrical generator – a lot like the alternator on an engine – that generates electricity as it spins.

A wind turbine is an electrical fan operating in reverse. The fan takes electricity and uses it to spin a motor, attached to a hub and some blades, creating wind.

A wind turbine takes wind energy and uses it to spin a hub attached to generator, creating electricity.

You can actually just spin any DC motor to generate electricity , but it helps a lot if you pick one that generates the flavour of electricity you’re after.

Brushed motors are appropriate for generating DC, whereas a brushless motor is better suited to AC voltage applications.

A handful of marine wind turbines, mostly older ones, do use a brushed motor set up to produce a voltage that can directly charge a 12 volt or 24-volt battery.

Brushed motors are called that because they literally have a core of metal brushes that drags along inside outer, magnetic stator. Those brushes wear out over time and need to be replaced. They’re in something like a starter motor that works intermittently, but putting them in wind generators was always a bad idea.

They’re also noisy – which is a major consideration in a device that is going to run overnight, above your head, while you sleep, every night.

Brushless motors have so many advantages over brushed, from their efficiency to their lifespan to their reduced mechanical noise. As such, most wind generators produce AC electricity and then rectify it to DC at the regulator in order to charge the battery bank.

This means you will normally have three wires leading from the wind generator on your sailboat to the charge controller. It also means you definitely don’t want to connect those wires, carrying AC electric, to your DC battery bank, without passing them through the charge controller first.

Wind generators offer a lot of advantages – notably the ability to work day and night, and in both sunny and stormy weather.

Solar panels are great, but they only work during the day – and on sunny days, at that. They’re also affected a lot by the seasons, because in winter there are both less hours of daylight, and the sun is lower in the sky, its rays have to travel further and they strike the panel at an oblique angle. And, it’s cloudy or rainy nearly every day.

Regardless of season, as we’ve explored earlier in this guide, some of the most popular sailing destinations don’t actually have reliable sunshine – but all of them have reliable wind.

Not so with sailboat wind turbines, which work just as well on sunny days as stormy. They often generate even more power in winter, on days when solar might be producing at 10% or less.

This effect makes wind generators a big enabling technology for grey-weather sailing, from extending your sailing on into the “shoulder season” and benefitting from empty bays and anchorages, to exploring unconventional cruising grounds such as the Scandinavian fjords.

Besides stormy and overcast days, wind generators will keep on producing at night. This is particularly helpful when night sailing with the radar, AIS and full nav suite running, maybe plus an autopilot, and then all your domestic loads like your fridge and freezer. Even if you’re just at anchor, it’s nice to wake up with topped-off batteries every morning.

This doesn’t apply if you have a modern boat with ample battery storage, but when we were just getting started in sailing, we would frequently have half-flat batteries by morning.

Not only does this shorten the life of the bank, it occasionally even meant we struggled to pick up the hook in the morning – which is a bit of a safety hazard. Again, this is mitigated by wind.

None of this is to say that you should ditch solar power for wind. Solar power has many wonderful properties, explored below, and the two technologies actually complement each other very well. If you have a large enough vessel, we fully recommend you try to integrate both into your power plan.

Wind and solar are both very useful technologies to the cruising sailor, each with its own set of advantages and disadvantages. Their pros and cons in fact offset each other and synergise quite nicely, compensating for each other’s weaknesses.

As such, we’d argue it’s less about deciding which is better, and more about figuring out whether you can incorporate both into your power plan somehow.

Nonetheless, let’s have a look at how solar power and wind generators compare and contrast, and some of the pros and cons of each technology.

Advantages of solar power vs wind power

Solar power’s major advantage over wind is that it’s “solid state”. This means it has no moving parts to wear out, and requires almost no maintenance.

In fact, solar panels will generally sit and faithfully do their thing decade after decade with almost zero human interaction. A common standard nowadays is for panels to retain 90% of their producing power after 20 years .  

There’s a 10kW solar array in Switzerland that’s been feeding directly into the grid since 1982; it’s over 40 years old and going strong.

Solar panels benefit from wiping down once or twice a year, but other than that, they’re a totally set-and-forget technology.

Many sailing destinations have ample sunshine, with long hours of direct sun throughout the sailing season.

Solar is also cheap and plentiful nowadays, and panels come in all shapes and sizes that can fit almost anywhere on a yacht – including a handful of solar panels you can walk on, although those are not cheap.

Overall, though, solar is much cheaper than wind watt-for-watt. You might pay $0.50 per watt for a good rigid polycrystalline solar panel and charge controller. A wind generator may well run to $2000 for 400w – that’s $5 per watt, up to ten times more expensive. And the wind generator has moving parts that can require replacement.

Another often overlooked advantage of solar panels is that their solid-state nature makes them very safe – there are no moving parts to catch a finger in, or spinning blades that could strike a member of the crew. They just sit and silently do their thing, year after year.

Disadvantages of solar power vs wind power

Solar only works when the sun shines. The sun, as we’ve pointed out earlier, doesn’t always shine. You might be surprised by how cloudy places like the Caribbean can be – some islands have rain up to 50% of the time.

Some popular sailing destinations, like the English Channel, average about two hours of sunshine per day, with rain or overcast skies on 75% of days annually ( no, seriously ).

There’s always night sailing, as well. If you’re night-sailing, you may well have tools like radar and AIS running for safety, plus other loads like an autopilot and anything like fridges and freezers running below.

If you only have solar power, and no wind, you may have to run the engine to make it through the night – or invest in a large battery bank that can keep up until morning.

Marine wind generators are an excellent way to bridge the gap. It can be windy at any time of the day or night, and very often the cloudy or stormy days are the windiest. It’s only sunny during the day, and only some days, so this is a major disadvantage of solar power when compared to wind.

Another disadvantage of solar panels is that they lose power quite dramatically when shaded, and sailboats unfortunately have a lot of tall, shade-casting objects. These include the mast, the boom, the sails and anything like radar or Starlink dishes .

Somewhat paradoxically, solar panels also lose power as they get hot in the sun, meaning the normal, everyday conditions in many exotic destinations can actually reduce their efficiency by double-digit percentages. They are happiest somewhere cold with lots of sun, like on top of a mountain – not in the tropics.

Advantages of wind power over solar power

The wind doesn’t rise and set like the sun – it can blow around the clock. Okay, technically, the sun rising and setting down does change the temperature and create all the wind on earth.

But the wind often continues after the sun goes down. In fact, when you’re on a boat, on the water next to land, the wind usually just reverses at night .  

It’s often windy on the water on sunny days because all wind is caused by pressure flowing from high to low, and the main source of those differing areas of pressure is heat from the sun – particularly, say, where the adjacent land and water heat up at different rates.

That’s how wind is made on sunny days. But it’s often windy on non-sunny days, too, because it’s just about air rushing between those areas of high and low pressure, hot and cold air. As such, cold fronts can bring wind too.

This makes wind somewhat more of an always-on technology than solar – especially in the places that sailing boats are found. There is usually wind offshore, and often in the anchorages too as it rolls off the hills . In some parts of the world, such as those affected by the Greek Meltemi , it blows straight 30’s weeks on end.

Overall, sailing boats are just usually found in places with abundant wind energy, so there’s a lot of synergy between sailing boats and wind generators. And we’ve pointed out, many exotic sailing destinations in the world have more wind than sun, and that’s before we get started on sailing somewhere like Scandinavia.

A wind generator has a small footprint compared to a solar panel, although it does need a large exclusion zone around it for safety. Wind generators are sometimes mounted up the mast, but we don’t generally advise putting a large, pendulum-like weight at the end of a 50-foot-long lever arm if you can avoid it as it may negatively impact the motion of your boat.

Disadvantages of wind vs solar power

Wind generators do have some drawbacks compared to solar. The obvious one is that they have moving parts, which both present a hazard to the crew and require replacement or regular maintenance.  

The worst-case scenario is a crewmember being struck by the blades. The tips of something like a Silentwind Pro can spin nearly a hundred times a second and get close to breaking the sound barrier.

Here’s an example of where someone accidentally clipped their arm on a sailboat wind generator and it both shattered their arm and sent the turbine blade flying across the cockpit. The author notes that they had also seen the wind generator explode a seagull prior to this incident.

Much of this is mitigated by putting the wind generator outboard and features like electronic brakes, so you don’t need to stop it with your right ulna as the gentleman above did. The upshot is that wind turbines are dangerous in a way that solar panels are not.

The constant motion also generates wear and tear. It used to be worse, back when we used brushed DC motors – but the bearings in brushless motors do eventually wear out too, and they benefit from regular greasing a bit like your winches. It’s just an extra thing to maintain.

It can be too windy for wind generators, too. It can’t be too sunny for solar panels (although it can be too hot). Many modern, top-end marine wind turbines have that electronic brake built in to compensate for this, but you still have to shut down and stop producing when it blows a gale.

Another disadvantage of wind is that it’s really expensive compared to solar on a watt-for-watt basis. Good polycrystalline panels paired with a brand-name MPPT controller might come to $0.50 a watt at the time of writing, while a leading wind generator works out at $5.00 per watt.

This is compounded by the fact that wind does often produce on quite a concave power curve. That is to say, you need a fair amount of wind to produce anything at all, and probably need gusts into the 30-knot range to start to see your rated wattage.

Another often-overlooked point is that if you’re sailing downwind, you are robbing the wind generator of air. If you are sailing downwind in 15kts of breeze, making 7kts, the apparent wind speed at the generator is only 8kts – which might not even be enough to start generating.

Finally, wind generators can be noisy. Again, brushless motors have helped with this significantly, but there is still the rushing of the air over the blades, and any eccentricity in the bearings or blades will send maddening, resonant tremors down the pole and directly into your sleeping quarters at all hours of the night.

The latest wind generators make use of things like acoustic decoupling, a fancy term for having a rubber dampener between the end of the pole and the deck, to mitigate this.

What is a dump load on a wind generator?

A dump load , also called a dummy load or diversion load, is something used in wind power to get rid of excess power when the batteries are fully charged.

One of the small downsides of a power source that runs night and day is the potential to oversupply electricity and overcharge the battery bank.

As an electrical generator supplies more and more power, it gets stiffer and stiffer to turn. The power has to come from somewhere, and it’s felt as resistance – producing a braking effect.

If you suddenly take that braking effect away by disconnecting the battery bank, the wind turbine will start spinning at very high speed, causing anything from rapid and excessive wear on the bearings through to a catastrophic failure where the blades shear off at supersonic speeds.

In order to prevent this from happening, the charge controller has the option to switch between charging the battery and supplying power to a dump load .

The dump load can simply be a big resistor. It will heat up as the wind generator spins on, and safely apply a brake to it by literally just wasting power as heat.

You can probably guess where this is going. Another option is to use an element specifically designed to heat up, and use it to heat water. You can easily buy DC immersion water heater elements for $20-30 , connect them in the place of the dump resistor and use them to make hot water with the excess power instead.   

We’ve often daydreamed about using it to make ice or run a teeny tiny aircon unit as well.

Some of the top-end sailboat wind generators will automatically apply an electronic brake and safely stop the blades when the bank is full, and it varies from model to model whether they simply have that as an option, or it replaces the dump load entirely (including useful ones, like making hot water).  

Do not be tempted to use the dump load to charge a second battery, such as a starter battery, when the first bank is full. If you do, you will encounter problems once the second battery is full and the turbine starts to freewheel.

If you do want to charge several banks at once, or one after the other, you want a split charger connected to the main charging output instead, and a highly resistive load that can run indefinitely on the dump load output.

Marine wind generators vs hydro generators  

Hydro generators are another way of capturing the energy of the wind and turning it into electricity. But instead of capturing the flow of air, a hydro generator is dragged through the water behind a boat under sail.  

The elephant in the room here is that a hydro generator is only going to work when the boat is in motion. A wind generator, on the other hand, keeps on producing while you swing around at anchor.

The average cruiser spends around 90% of their time either at anchor, on a mooring ball, on town quays, or in marinas. This is because the everyday business of cruising is not so much about sailing as it is about fixing the boat, going ashore for provisions or parts, waiting for a weather window, or exploring the place you sailed to, socialising with the other yachties you just met, barbecuing on the deck, and so forth.

The wind generator works through all of that, night and day; the hydro generator only a fraction.

So why does anyone use hydro generators at all, then?

The answer lies in the fact that a traditional trade-wind circumnavigation, by far the most popular way to “sail around the world”, is almost all downwind .

As a result, you are often “running away” from the wind when you sail around the world, which has the effect of subtracting your speed from the true wind speed and deducting that much power from your wind generator.

Thus, if you want to sail around the world on say, a performance catamaran, it might make sense to drag a generator behind the boat instead of in the air. That way, its performance is tied to your boat’s speed through the water rather than the apparent wind.

An adjacent use-case to this is people who “sail around the world” in the sense of not stopping, or stopping very little. Someone sailing non-stop downwind around the world, particularly on any kind of record attempt, would probably get a lot more of out of a hydro generator.

Another place hydro generators are seen is in the regenerative systems of systems like Oceanvolt . In these sophisticated systems, the propellors of the boat itself work as hydro generators by spinning and capturing energy as they’re dragged through the water under sail.

This feature is even starting to show up on electric outboards, such as the ePropulsion Navy series.

In summary, wind generators are the most practical choice for the average cruiser, multi-year circumnavigator or liveaboard sailor. Unless you love sailing so much that desperately want to go and tack around for four hours to charge your batteries – in which case, more power to you.

Wind generators can form an incredibly useful part of the renewable energy mix on board a sailboat.

While wind power on a sailboat works out many times more expensive than solar power, watt-for-watt, it makes up for this by generating power day and night – and often making even more power at times when solar falters, such as during storms.

Cruising sailboats that only have solar power will be forced to generate or motor if it’s cloudy for days on end, something that happens at least once or twice a month somewhere like the Caribbean.

Solar, naturally, doesn’t produce at night either, so if you have a lot of electrical loads running overnight your battery bank can take a beating.

A common example of where you might get caught out is night sailing with the autopilot, radar, AIS and instruments all running, in addition to your regular loads like the fridge.

Wind generators might usually be sized to produce less than a solar array because of cost, space and weight considerations, but they have the potential to run all day and night and in any kind of weather, and as such they often punch above their weight in terms of the overall energy generation picture.

Electrical loads might slow down a little overnight, as the crew sleep and lower temperatures mean fridges and freezers don’t work as hard, but it’s not uncommon for the overnight draw on a sailboat to be 8-10 amps or more. It adds up, by morning. 

Wind represents an excellent bridging technology for nights and extended cloudy spells, naturally producing the most when solar fails – such as during storms. 

A sailboat wind generator is most effective when paired with solar and a good lithium battery bank , allowing you to generate in all conditions. day and night; and to store and retrieve that energy efficiently even at high currents. 

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Better Sailing

Best Marine Wind Turbine Generators For Boats

Unless you are happy burning endless amounts of fuel, a marine wind turbine is an essential item fr an offshore cruising sailboat. In this article, we will be taking a look at some of the best wind generators for your boat.

Today’s cruisers carry so much electrical equipment that wind turbines, solar PV arrays, and hydro-generators are becoming more and more common. The marine wind turbine has been around for several decades now and has gradually been refined to give a much higher degree of efficiency. Better alternators, CAD-designed blades, life-sealed bearings, and smart charge controllers make the latest devices more reliable, quieter, and safer.

Things To Consider When Shopping For a Marine Wind Generator

Horizontal axis vs. vertical axis wind turbine.

The majority of marine wind turbines are horizontal axis devices, either upwind or downwind driven. These are powerful and, as such, need speed and/or charge output limiters, or they can burn out the batteries and self-destruct in storm-force winds. Vertical axis turbines are more suited to trickle charging – usually connected to one or two batteries up to 200Ah capacity. The blade design means they are unidirectional and thus have no need for a bulky tail fin to point them into the wind. They are also considerably quieter than most horizontal turbines and much easier to mount and install.

What Blade Design Should Your Wind Generator Have?

Modern turbines usually sport a one-piece, cast aluminum body and, commonly, three aerodynamically designed plastic/composite blades. One of the first of these models, the original Air-X, worked exceptionally well, particularly in high winds. However, it was so noisy that neighboring boats frequently complained, leaving the owner the option of turning it off or moving well away from other boats. Since then, CAD-inspired blade design has significantly helped to reduce ambient noise levels, although none could be termed silent.

Once your battery bank is fully charged, additional energy from the turbine needs to be dissipated, or the turbine stopped. Low power vertical-axis models don’t usually produce enough to warrant fitting a regulator, but the more powerful models all need some form of charge limiter to prevent overcharging. The simplest form of regulation is to switch it off when no further charge is needed. If you electrically disconnect the turbine, however, it can either damage the alternator diodes or carry on spinning at an even higher speed, so most are electrically ‘braked’ by shorting out their output wires, and a high-current switch is usually provided for this action.

If you leave a turbine running unattended, you’ll need an automatic regulator, and there are two systems commonly available. The first lets the turbine continue to spin and produce power, diverting any that isn’t needed into ‘dump’ resistors to burn off the excess as heat. While effective, it is pretty rudimentary, and you have to be careful where you mount the bulky resistors, which can get quite hot. Alternatively, some use this unwanted charge to pre-heat the hot water tank via an immersed element. Other turbines incorporate ‘pitch control’, comprising feathering blades that either flatten out or turn edge into the wind to regulate turning speed at high wind speeds.

Charge Controllers

A variety of automatic charge controllers are available, some more sophisticated than others, and you don’t necessarily need to use one from the same manufacturer unless it specifically states that you must. A basic model has a voltage-sensitive on/off switch that will trigger at a pre-set threshold battery voltage. The more useful controllers have a built-in display for monitoring turbine output and battery condition. Some can also accept and distribute charge from other sources, such as solar or hydro generation.

>>Also Read: Best Portable Boat Generators

Here Are Some Of The Best Best Marine Wind Turbine Generators For Sailboats

Auecoor solar wind hybrid system – best marine wind turbine generator on amazon.

The Auecoor Solar Wind Hybrid System is the best system to hook your boat/sailboat with. It is a hybrid system that utilizes both solar and wind power generation. This system is highly efficient, it is designed to withstand heavy wind loads, and it is ready to install on a boat/sailboat. They also produce many models to serve your needs, from 500 Watts all the way up to 2000 Watts in optimal weather conditions. 

All models come with a 400-Watt wind turbine generator, and then you can add as many 120-Watt high-conversion, waterproof and flexible solar panels as you need. This unit is also pretty easy to install. The solar panels are easy to transport, and they come with pre-drilled holes for easy installation. This is my personal favorite kind of setup and the one that I believe is the best for any serious boater. It provides 2 renewable sources of power that guarantee that whether you are making a passage or liveaboard in a nice beach somewhere, you will have dependable power as if you were living connected to the grid.

Air Breeze 200

Although the latest generation Air Breeze, made by Primus Windpower, provides an increased charge output, it is also quieter and should apparently outlast its predecessors. Its low start-up speed (4.2kn) means that, on average, it should be able to produce more energy than some higher-rated turbines over long periods of low-to-moderate wind speeds. Though it only has a maximum output of 200W, its output has been optimized to provide a more constant charge in typical northern European and Mediterranean wind conditions. The new Air Breeze weighs less than 6kg and has an integral electronic charge controller and over-speed regulator, rendering bulky dump resistors unnecessary and making installation considerably quicker and easier.

Leading Edge LE-300 or LE-450

A UK company, Leading Edge supplies wind turbines for both marine and terrestrial installation. The LE-300 and LE-450 are available in 12V, 24V, and 48V versions and are remarkably light, making them ideal for sailing yachts. The output is DC via two wires, and a run/stop switch is supplied that breaks the turbine by shorting the output. The units can also be supplied with charge controllers, a dump load style regulator that allows you to leave the turbine on 24/7 without the batteries overcharging. The three-bladed LE-300 is very light (6kg) and one of the quietest of the three-bladed models. However, its output is poor for a horizontal-axis turbine, although it starts spinning in the gentlest breeze. The five-bladed LE-450 is more powerful (105W at 15-knots) while remaining quiet and stable. Another great feature of this wind turbine is that it is the quietest marine wind generator tested.

Rutland 1200

The latest in the Rutland wind turbine line up, the 1200, is Marlec’s answer to the third generation three-blade, permanent magnet turbine models. More powerful than the 914i, it features a ‘Tri-namic’ blade design, which is said to provide a low start-up speed, very quiet running, and more power towards the top end of the wind scale. With a claimed peak production of 483W (that’s 35.5A at 12V) in 29 knots of wind, the 1200 can also supply a very useful 40W of power in just 10 knots of wind – a more realistic average in most waters.

The 1200’s charge controller has dual outputs for two separate battery banks and can accept up to a 20A solar PV supply. It reduces the turbine speed automatically after winds reach 30 knots, regulating the charge without using dump resistors. It also has an integral start/stop switch and can support a remote display, which connects to the controller via a simple Ethernet cable.

Eco-Worthy Wind Solar Power Kit

What can I say? I just love a good wind-solar hybrid power generator. With this kind of setup, you won’t have any problem charging a 12V or 24V battery bank with this hybrid system throughout the day, in any weather condition. The Eco-Worthy Wind Solar Power Hybrid generator can guarantee enough power for you to remain comfortable on your boat and operate any appliance you need and enjoy your time on the boat. You can purchase any model that fits our needs starting from 400 Watts all the way up to 1,400 Watts. However, always buy a generator that has a higher power output than you think you will need because you almost always won’t be in optimal climate conditions.

The blades on this German-built device are very steeply pitched towards the hub, resulting in an early start-up in lighter airs, and they also incorporate tiny fins along their length, said to quieten them at high speed. The blades have a kinetic rotor pitch control system designed to feather them in very high winds, not unlike the large terrestrial wind turbines. With a charge controller in the circuit, the turbine can therefore be left spinning in all weathers without worry. The output is two-wire 12V or 24V DC, so it could, in theory, be directly connected to a battery bank.

It can also be used with a simple short-circuit stop switch, which will slow it down enough to be tied off. The Superwind 350 can also be supplied with a 40A SCR Marine charge controller, which has two independent, diode-isolated outputs for start and service battery banks and dissipates unwanted energy via two large, wire-wound dump resistors. Nominal power is 350W at 25 knots.

Silentwind 400 Wind Generator

As fitted to all boats in the Volvo Ocean Race and featuring ‘Silent Power Blades’ – hand-laminated carbon blades, successfully tested at hurricane speeds – the latest Silentwind 400+ has improved wind tracking and earlier start-up than its predecessor, the 400. Featuring aerodynamics combined with a three-phase Neodymium-Iron-Boron permanent magnet generator, the 400+ is said to have a start-up speed of only 4.3 knots and a peak output of 420W at 30 percent less rotation speed than other 400W generators. 12V, 24V, and 48V models are available.

The Silentwind has a 3-wire AC output, which connects directly to the matching hybrid multi-stage charge controller that enables trickle charging and the connection of up to 20A of solar PV power. An adjustable boost function increases performance and optimizes the power yield, while the LCD displays all the important charge information. When the batteries are fully charged, the turbine automatically stops or switches to trickle charge mode with a significant reduction in rotation speed. It can also be stopped (braked) manually with the built-in switch on the controller.

Rutland 504 Wind Marine Generator

The Rutland 504 is a small and lightweight (just 3.5kg) mini-horizontal turbine from the UK off-grid power specialist, Marlec. The earlier model (503) has proven to be extremely popular over the years, in both the small leisure craft market and in commercial applications such as remote street lighting and signage, buoy lights, ATON power, etc., and the 504 should prove equally so. Like its predecessor, it is very compact, and its blades are ‘encapsulated’ – i.e., they have a protective ring around them to prevent limbs and clothing from getting caught up in the blades. Its output is better than that of the vertical-axis turbines but nowhere near the more powerful generators listed above. It is, however, notably quieter.

Typical output is around 15 knots of wind is 12W (1A @ 12V), doubling to 24W/2A at 20 knots. It also has a lower start-up speed than the vertical turbines and, although it takes around 10 knots of wind to provide any useful charge, its low-friction alternator compensates for the gusts by ‘smoothing out’ its output. The 504 does require a charge controller if it is to be left unattended.

 Leading Edge Vertical Wind Turbine

The LE-V50 and V150 vertical axis turbines are compact, lightweight, and virtually silent. The V50 measures 270mm dia x 456mm high and is intended for trickle-charging batteries or for running low-power devices. Available in 12V, 24V, or 48V versions, it has a nominal output of 12W but a peak of 70W. In typical waters, this results in an average charge of 0.5-1.0A @ 12Vdc in a fresh breeze. The bigger V150 model has a peak output of 200W but a more typical rating of 24W in wind speeds of 15 knots – double that of the V50. 

Leading Edge wind turbines were originally designed to generate power for industrial data monitoring equipment in very remote areas where there is no other power source; these often supplement solar PV arrays in an off-grid sailing situation.

>>Also Read: How to Charge a Sailboat Battery

Final Thoughts

There you have it; these are the best Best Marine Wind Turbine Generators for your boat or sailboat. Whether you are boating/sailing during your holidays or liveaboard full-time, a reliable power source is necessary. It will always provide you with the necessary power to operate your essential electronics, and depending on the power output you go for, it can fill up your batteries without an issue. Remember that when you are out in the water, it will be near impossible that there won’t be enough wind for a marine wind turbine to generate power, so you will rarely be without power. However, that’s why I always sail with both a wind generator and solar panels on board. 

Peter is the editor of Better Sailing. He has sailed for countless hours and has maintained his own boats and sailboats for years. After years of trial and error, he decided to start this website to share the knowledge.

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Discover the Ideal Wind Speed for Sailing: How Much Wind Do You Need?

Alex Morgan

Sailing is a popular recreational activity that harnesses the power of the wind to propel a sailboat through the water.

The wind plays a crucial role in determining the speed and performance of a sailboat, making it essential for sailors to understand how much wind is needed to sail effectively.

In this article, we will explore the relationship between wind and sailing, along with the factors that affect sailing speed.

To begin, let’s delve into the basics of sailing and how wind powers a sailboat.

Understanding the physics behind sail propulsion is key to comprehending the impact of wind on sailing.

Several factors come into play when determining the speed of a sailboat.

Among them, wind speed holds significant importance.

The force and velocity of the wind directly influence how fast a sailboat can travel.

Other factors such as sail area, boat design and weight, the angle of the wind, and the conditions of the water also affect sailing speed.

When it comes to sailing, there is a minimum wind speed required to get the boat moving efficiently.

This article will outline the minimum wind speeds necessary for different sailing conditions, ranging from light air to moderate breeze.

Different types of sails are designed to cater to varying wind speeds.

Being aware of the types of sails suitable for different wind conditions is crucial for sailors to optimize their sailing experience and performance.

We will explore strategies and techniques that can be employed to sail effectively in light wind conditions.

Proper sail trim, the use of specialized sails like the spinnaker or code zero, as well as mastering tacking and gybing techniques, can greatly enhance the sailing experience in light wind situations.

We will provide essential safety guidelines for sailing to ensure a secure and enjoyable experience on the water.

By the end of this article, you will have a comprehensive understanding of how much wind is needed to sail, along with valuable insights and techniques to optimize your sailing experience based on the wind conditions.

• Sailing with wind power: Wind power is what propels a sailboat forward, and understanding how wind affects sailing speed is crucial for sailors.
• Factors influencing sailing speed: Elements such as wind speed, sail area, boat design, weight, wind angle, and water conditions determine the speed at which a sailboat can travel.
• Minimum wind speed for sailing: Different wind speeds, such as light air, very light breeze, light breeze, gentle breeze, and moderate breeze, are required to effectively sail.
• Types of sails for varying wind speeds: Different types of sails are used to maximize performance in light, moderate, or strong winds.
• Strategies for light wind conditions: Proper sail trim, using a spinnaker or code zero, and employing tacking and gybing techniques help navigate in lighter wind conditions.
• Sailing safety guidelines: Adhering to safety measures and guidelines is essential for a safe and enjoyable sailing experience.
• Conclusion: Identifying the ideal wind conditions ensures optimal sailing performance and enjoyment for sailors.

How Does Wind Power a Sailboat?

Wind power propels a sailboat forward by creating aerodynamic lift when it hits the sail. This lift is generated by the curved shape and angle of the sail. As the wind flows over the sail, it creates a pressure difference, generating lift similar to an airplane wing.

The wind’s force on the sail enables the sailboat to move forward. Sailors can control the lift and, consequently, the speed and direction of the boat by adjusting the sail angle. The wind provides the energy needed to overcome water resistance and propel the sailboat.

So, how does wind power a sailboat? The effectiveness of wind power depends on factors like wind speed, sail area, sail shape, and the angle of attack. Higher wind speeds generally result in increased lift and greater speed. Larger sails capture more wind and provide more force, but finding the right balance is essential to prevent tipping or capsizing.

Factors Affecting Sailing Speed

When it comes to sailing , there are several factors that can affect your speed on the water. From wind speed to sail area, boat design, and weight, even the angle of the wind and water conditions can play a significant role. In this section , we’ll dive into these crucial elements, exploring how they impact the speed and performance of sailboats. Whether you’re a seasoned sailor or just starting out, understanding these factors will help you harness the power of the wind and navigate the waters more effectively.

Wind Speed is essential in sailing and can significantly impact a sailboat’s speed and performance. Here is a table showing wind speeds and their descriptors:

Understanding wind speed is crucial for sailors as it helps them select the appropriate sail plan and sailing strategies. Lighter winds, like calm or light air , may require careful sail trimming and the use of lightweight sails such as spinnakers or code zeros to maintain momentum. On the other hand, stronger winds, like a moderate breeze , can provide more power and speed, but sailors need to be cautious and adjust their sails to avoid overpowering.

To make the most of different wind speeds, sailors should accurately read wind conditions, practice proper sail trim techniques, and familiarize themselves with various sail types suitable for different wind speeds. Following safety guidelines is always crucial for a secure sailing experience.

The sail area affects the speed and performance of a sailboat. It is the total surface area of all the sails used on the boat. A larger sail area generates more power from the wind, allowing the boat to move faster. Sail area is measured in square feet or square meters .

The sail area should match the size and weight of the boat. If the sail area is too small for a larger boat, it will struggle to catch enough wind to move effectively. Conversely, if the sail area is too large for a smaller boat, it may create excessive heeling and become difficult to control.

An example highlighting the importance of sail area is a sailor who participated in a race with a small sailboat. Despite his sailing skills, he couldn’t keep up with other competitors because his sail area was too small. After upgrading to a larger sail, he experienced a significant increase in speed and improved his competitiveness.

Choosing the right sail area is crucial for optimal performance and speed. Consider factors such as boat size, weight, and wind conditions to select the appropriate sail area and enhance your sailing experience.

Boat Design and Weight

Boat design and weight are critical factors that greatly influence the performance of a sailboat. The proper hull shape and keel of a well-designed boat allow it to effectively utilize wind power and smoothly navigate through water, minimizing any resistance and maximizing its speed. It is also important to carefully manage the weight distribution of the boat. A properly balanced boat not only sails more smoothly but also becomes easier to handle, resulting in enhanced overall performance .

The design and weight of a sailboat also play a significant role in determining its stability. A sturdy and well-balanced boat is less prone to tipping or capsizing, thus ensuring the safety of those on board. The weight of the boat has a direct impact on its maneuverability. Lighter boats are highly responsive and agile , enabling quick and effortless changes in direction.

When considering boat design and weight, it is essential to align them with the intended use of the sailboat. Racing sailboats prioritize speed above all else , which is why they feature sleek designs and lighter weights. On the other hand, cruising sailboats prioritize comfort and stability , leading to different design considerations and weight requirements.

Angle of the Wind

When sailing, the angle of the wind is crucial for determining the boat’s speed and direction. The angle of the wind refers to the direction from which the wind is coming in relation to the boat’s course.

To optimize sailing performance, it’s important to understand the impact of the wind angle. When the wind is directly behind the boat, known as a downwind or running angle, the sails catch the wind to maximize speed. Sailing directly into the wind, called a weather or upwind angle, is not possible as the sails would luff.

The most efficient sailing angle is a close reach , where the boat sails at a slight angle to the wind, usually between 30 to 45 degrees . At this angle, the sails generate maximum lift and the boat moves forward with maximum speed and efficiency.

Trimming the sails by adjusting the boat’s angle to the wind is critical. By fine-tuning the sail positions, sailors can optimize their performance and navigate different wind conditions.

It’s important to note that the wind angle is not the only factor affecting sailing speed. Other factors like wind speed, sail area, boat design and weight, and water conditions also matter. Therefore, sailors must consider the wind angle along with these factors to achieve the best performance on the water.

Water Conditions

Water conditions can significantly impact sailing. Factors such as wave height, current, and turbulence all play a role in the speed and maneuverability of a sailboat.

Here are some effects of different water conditions on sailing:

– Calm and smooth waters allow for smooth and efficient sailing. It is easier to control the direction and speed of the boat in these water conditions.

– Rough and choppy waters make sailing more challenging. Waves can cause the boat to pitch and roll, making it harder to maintain balance and control. Navigating through the waves can also affect the boat’s speed.

– Turbulent waters, caused by strong currents or obstacles, pose risks to sailing. Sudden changes in direction or unexpected obstacles may require quick adjustments to maintain safety and control.

Sailors should be aware of the water conditions they will be sailing in and adapt their techniques accordingly. This may involve using different sail configurations, adjusting the boat’s trim, or modifying navigational plans to navigate challenging water conditions safely and efficiently.

Minimum Wind Speed to Sail

Sailing enthusiasts , listen up! We’re about to dive into the exciting world of harnessing the wind to navigate the open waters. Today, we’ll focus on the minimum wind speed needed to set sail and experience the thrill of gliding across the waves. From light air to moderate breeze , each sub-section will unveil the ideal wind conditions required for smooth sailing adventures. So strap in, hold on to your hats, and let’s explore the magical realm where wind and sea collide!

Light air is a term used to describe a very low wind speed, ranging from 1 to 3 knots on the Beaufort scale.

In these conditions, sailing can be challenging as there is not enough light air to fill the sails and propel the boat.

To maintain forward momentum, sailors must adjust the sails to capture any available light air through proper sail trim.

Using specialized sails like a spinnaker or code zero sail can provide an extra boost to the boat’s speed in light air.

Changing the direction of the boat relative to the light air through tacking and gybing techniques can help sailors find pockets of slightly stronger light air.

Sailing in light air requires patience and a keen understanding of light air changes.

Small adjustments in sail positioning and boat handling can make a significant difference in maintaining progress in light air.

Very Light Breeze

A very light breeze, referring to a wind speed of 1 to 3 knots, can still be utilized for sailing despite its gentle nature. To make the most of this very light breeze , sailors must focus on optimizing their sail trim. By adjusting the sails to capture even the slightest amount of wind, they can maintain forward momentum. It is crucial to ensure that the sails are properly trimmed in order to maximize the available wind energy.

In such light wind conditions, using a spinnaker or a code zero sail can be advantageous. These specialized sails harness the slightest breeze and provide additional propulsion, allowing sailors to gain extra speed and maintain momentum.

Tacking and gybing techniques can also help sailors navigate through a very light breeze. These maneuvers involve changing the boat’s direction in relation to the wind, helping sailors find the most favorable angle for capturing wind energy.

It is essential for a successful voyage in a very light breeze to adapt to the weather conditions and adjust sailing techniques accordingly.

Light Breeze

A light breeze , which is a wind speed from 4 to 7 knots, is perfect for leisurely sailing or enjoying a calm day on the water.

When sailing in a light breeze , make sure to adjust your sails and trim them properly to effectively utilize the power of the wind.

It is important to pay attention to the wind angle and modify your course accordingly in order to optimize your speed.

To capture the limited wind energy, it is recommended to use specifically designed for lighter winds.

These sails have a larger surface area and are more efficient.

Techniques like tacking and gybing can assist in maneuvering and maintaining momentum in light breeze conditions.

Sailing in a light breeze can provide a serene and enjoyable experience, enabling you to appreciate the peacefulness of the water and the gentle strength of the wind.

Gentle Breeze

A gentle breeze , also known as a favorable wind condition for sailing, refers to a wind speed range of 8 to 12 knots or 9 to 14 miles per hour . Sailing in a gentle breeze compared to lighter winds makes the activity easier . The gentle breeze delicately fills the sails and gently propels the boat forward, without overpowering it.

When sailing in a gentle breeze , it allows for a smooth and comfortable cruising experience. The boat can effortlessly maintain a steady speed and easily maneuver, making it enjoyable for both experienced sailors and beginners. Key to optimizing this experience is properly adjusting the sails to efficiently capture the wind. Sail controls are utilized to achieve the correct shape and tension in the sails, effectively harnessing the wind’s power and enhancing the boat’s speed.

In addition to sail adjustments, sailors should also take into consideration the weight and balance of their boat. A well-balanced boat performs exceptionally well in a gentle breeze, enabling smoother sailing . Selecting the appropriate sails for the conditions is crucial. Lightwind or medium wind sails are particularly suitable for a gentle breeze as they generate maximum power in these conditions.

Moderate Breeze

A moderate breeze is a favorable wind condition for sailing. It refers to wind speeds ranging from 11 to 16 knots , equivalent to 13 to 18 miles per hour or 20 to 28 kilometers per hour . In a moderate breeze, sailing becomes more exciting and efficient as the wind is strong enough to propel the sailboat with good speed.

In a moderate breeze, sailors can easily control their sailboat. They can trim the sails to catch the wind at the best angle, allowing for smooth and steady acceleration. The boat can reach its maximum speed and maneuver easily.

A moderate breeze is generally manageable for experienced sailors. The boat remains stable, and the risk of capsizing or losing control is relatively low compared to stronger winds. It is still important to follow safety guidelines and be vigilant on the water for a safe sailing experience.

To make the most of a moderate breeze, sailors can adjust their sails for maximum efficiency. Proper sail trim, using a spinnaker or code zero sail , and mastering tacking and gybing techniques can enhance the boat’s performance in this wind condition.

Types of Sails for Different Wind Speeds

When sailing, it is important to use different types of sails depending on the wind speed. Here are the various types of sails for different wind speeds:

• Light Wind (0-5 knots): To catch the minimal breeze in light wind conditions, it is necessary to use a light and large sail such as a genoa or a drifter sail. These sails have a larger surface area, allowing the boat to catch even the slightest wind.
• Moderate Wind (6-12 knots): For moderate winds, a mainsail and a jib are suitable. The mainsail provides primary power, while the jib helps control sail shape and balance. Together, these sails enable efficient sailing in moderate wind conditions.
• Strong Wind (12-20 knots): As the wind increases, it is advisable to use a smaller jib called a storm jib, in addition to the mainsail. The storm jib is designed to handle stronger winds and reduces the force exerted on the boat. This combination provides more control and stability.
• Heavy Wind (20+ knots): In heavy wind conditions, it is recommended to use a smaller mainsail known as a trysail instead of the regular mainsail. The trysail reduces the sail area and provides better control in strong gusts. Reefing the mainsail, which involves reducing the sail’s size by folding or rolling it, is also common in heavy winds.

When selecting sails for different wind speeds, it is crucial to prioritize the safety and comfort of the crew. It is advisable to assess the sailing conditions and make appropriate adjustments. Seeking guidance from experienced sailors or sailmakers can offer valuable insights and recommendations based on the specific boat and sailing objectives. Using the appropriate sails for the prevailing wind conditions enhances the overall sailing experience and ensures a smoother journey.

Strategies to Sail in Light Wind Conditions

When it comes to sailing in light wind conditions, knowing the right strategies can make all the difference. In this section, we’ll dive into some effective techniques that can help you glide through those calm breezes. From proper sail trim to utilizing a spinnaker or code zero , we’ll explore various approaches to optimize your sailing experience. We’ll uncover the secrets of successful tacking and gybing techniques that can give you the edge you need when the wind is playing hard to catch.

Proper Sail Trim

Proper sail trim is crucial for optimizing performance and speed while sailing. To achieve proper sail trim, follow these steps:

• Adjust the mainsail using the halyard, cunningham, boom vang, and mainsheet. This will help control the shape and angle of the mainsail .
• Trim the headsail using the jib sheets . Aim for a smooth and even shape, without any wrinkles or luffing.
• Ensure that the headsail matches the wind angle. Use the telltales on the headsail as a guide.
• Make necessary adjustments to the sails throughout the sail to accommodate changes in wind direction and speed. Continuously maintain optimal trim.
• Balance the mainsail and headsail by adjusting the sheets and sail angle. Find the right balance for your boat.

By following these steps, you can ensure proper sail trim for maximum power and efficiency. Remember to continuously monitor and adjust the sail trim with changing wind conditions. Happy sailing!

Using a Spinnaker or Code Zero

Using a Spinnaker or Code Zero while sailing maximizes speed and performance in light wind conditions.

To understand the benefits of using a spinnaker or code zero , refer to the following table:

Using a spinnaker or code zero significantly enhances your sailing experience by maintaining speed and maneuverability in light wind conditions. Experts recommend using a spinnaker for sailing downwind, as it boosts speed by capturing more wind. On the other hand, a code zero is a versatile sail that allows efficient sailing at angles closer to the wind.

Tacking and Gybing Techniques

Understand the difference between tacking and gybing techniques. Tacking is when you change the boat’s direction by turning into the wind, while gybing is when you change the direction by turning away from the wind.

To execute a tack , release the mainsail sheet and turn the boat’s bow through the wind. As the wind changes sides, quickly release and pull in the mainsail sheet to catch the wind on the opposite side.

When performing a gybe , ensure there is enough space behind the boat to safely complete the maneuver. Slowly turn the boat away from the wind, as the mainsail swings across the boat to the other side. Control the movement of the boom to avoid sudden jolts.

Timing is crucial when employing tacking and gybing techniques. Steer the boat smoothly and efficiently to maintain momentum during the maneuver.

Practice these tacking and gybing techniques in different wind conditions to gain proficiency. Light winds require finesse and precise movements, while stronger winds may necessitate quicker adjustments.

True story:

I remember a time when I sailed on a calm summer day. The wind was light and variable, providing a perfect opportunity to practice tacking and gybing techniques. As we turned the boat into the wind to tack, there was a momentary lull before the wind filled the sails on the other side, propelling us forward. With each maneuver, our timing improved, and we glided smoothly through the water. It was a valuable experience, highlighting the importance of mastering these tacking and gybing techniques to navigate effectively in different wind conditions.

Sailing Safety Guidelines

When sailing, prioritize safety. Follow these guidelines:

• Always wear a life jacket or personal flotation device (PFD) on the water for safety, especially in unexpected incidents.
• Check weather conditions before sailing to avoid risks from strong winds and storms.
• Maintain your boat well to prevent mechanical failures while sailing.
• Inform someone onshore about your sailing plans, including destination and return time.
• Stay alert , watch for other boats, obstacles, and hazards to prevent accidents.
• Follow right-of-way rules and navigation regulations to avoid collisions.
• Carry navigational tools like a compass, charts, and GPS for safe navigation.

A true story underscores the importance of following safety guidelines. A group of sailors didn’t wear their life jackets while sailing. Even with calm weather, their boat capsized due to a strong current. Thankfully, another boat rescued them. This incident highlights the significance of prioritizing safety on the water.

Some Facts About How Much Wind Do You Need To Sail:

• ✅ The ideal wind speed for comfortable sailing is 5-12 knots. (Source: Our Team)
• ✅ Absolute beginners should aim for wind speeds under 10 knots to prevent capsizing. (Source: Our Team)
• ✅ Heavy offshore boats can handle wind speeds of 20-25 knots. (Source: Our Team)
• ✅ Wind speeds of 25 knots and above are considered rough for small to mid-sized boats. (Source: Our Team)
• ✅ Checking the forecast before sailing is crucial as wind gusts can be up to 40% faster than the average wind speed. (Source: Our Team)

Frequently Asked Questions

1. how much wind is needed to sail comfortably.

The ideal wind speed for comfortable sailing varies depending on factors such as the boat type, skill level, and personal preferences. Generally, wind speeds between 5 and 12 knots are recommended for a comfortable sailing experience.

2. Can novice sailors handle higher wind strengths?

Novice sailors are more comfortable in lighter winds. It is advisable for them to start with wind speeds around 6 to 10 knots to learn the basics of sailing. As they gain experience and confidence, they can gradually handle higher wind strengths.

3. How does wind impact different boat types?

Different boat types have varying ideal wind speeds. For example, smaller dinghies and catamarans perform well in lower to moderate wind speeds, while heavier keelboats can handle stronger winds. It is important to consider the boat’s design and characteristics when determining the suitable wind speed for sailing.

4. Is it dangerous to sail in high wind conditions?

Sailing becomes dangerous at wind speeds of 20 knots or higher. The risk of capsizing or damaging the boat increases significantly. It is important to prioritize safety and avoid sailing in high wind conditions, especially for less experienced sailors.

5. How can I check the weather before sailing to avoid emergencies?

Checking the weather forecast before setting sail is crucial to avoid poor weather conditions and emergencies on the water. Utilize weather forecasts, online resources, or mobile apps to stay updated on wind strengths, squall winds, and other weather patterns that may impact your sailing trip.

6. What is the Beaufort Wind Scale and how is it useful for measuring wind strength?

The Beaufort Wind Scale is a measurement system used to gauge the strength of the wind. It ranges from 0 (calm) to 12 (strongest storm). This scale helps sailors assess wind speeds and make informed decisions about whether to postpone a trip, adjust sail configurations, or navigate through different wind strengths.

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Choosing a Wind Generator for a Sailboat – Complete GUIDE

Nothing denotes a salty off-the-grid ready yacht more than the sight of a wind generator mounted on the stern. Once, these were the main component of a sailor’s renewable energy arsenal. 

But today, as is the case with wind generators for RVs , the technology has fallen behind the fantastic strides that solar panels have made. Today’s solar panels are less expensive and more efficient than ever before, while wind generator technology hasn’t progressed much in the last 50 years.

Still, there are limited times when wind generators make the most sense on sailboats. Here’s a look at who could benefit from one and five of the best options on the market.

Table of Contents

Is a wind generator right for me, how much power do i need, alternatives to wind power, things to look for in a marine wind generator, 5 great marine wind generators.

Before you dive into the whirlwind of information out there about marine wind generators, take a step back for a reality check. Wind generators were the standard-bearer for years onboard sailboats, but in the 21st century, their usefulness has all but been replaced by solar panels. Solar is efficient, silent, and completely maintenance-free. 

As a result, the usefulness of a wind generator is now much more limited. There are many pros for wind generators—but most of them can be negated by one simple fact–the amount of usable power they produce is significantly less and more expensive than solar. 

Furthermore, the two times when a wind generator does make sense are not conditions typically encountered by most cruisers. Wind generators are only effective for significant power when the apparent wind speed on deck is more than 15 knots. That’s apparent wind speed on deck—meaning most downwind sailing in winds less than 22 knots true or so would be out. 

And then there are anchorages, where sailors hope that a wind generator will help them live off-the-grid to avoid a generator or engine recharge. How many anchorages have you recently sat in that had a constant 15 to 20 knots of undisturbed wind blowing through them? Most of the time, we’re trying to get out of conditions like that, not anchor in them. 

There are some parts of the world where these conditions are the norm. Caribbean trade winds and high latitude winds make wind generators more attractive. Those sailors stuck in the “horse latitudes” in between will find their wind generators silent and motionless most of the year. 

The other time that adding a wind generator makes sense is when there is simply no other renewable energy option available. A wind generator can mount in many ways on nearly any type of sailboat. It has a tiny footprint, unlike a large solar array. 

The bottom line is this—only add wind power when you have absolutely no space left for solar. If you’re maxed out on solar, a wind generator can give you a little boost. But another solar panel will consistently outperform a wind generator—unless you’re that rare sailor whose anchorages of choice feature steady and uninterrupted 20-25 knot winds.

Pros and Cons of Wind Power for Boats

• 24-hour per day operation (as long as it’s windy)
• Small installation footprint, compatible with most sailboats
• Good options when solar panels cannot be used due to mounting problems or shading (especially on ketches)
• Very low power generation in most conditions
• Ugly and bulky, mast and mount included
• Not effective when sailing downwind (like most tradewind sailing)
• Not effective in protected anchorages
• Maintenance intensive, moving parts and bearings wear out
• Limited controller options, many not compatible with LiFePO4 battery systems
• Expensive compared to solar

When calculating your requirements for off-the-grid living, the math does not lie. The problem is not lying when you do the math. You can find many calculators and spreadsheets online to help you make the basic calculations.

First, you need to know precisely how much power every electrical consumer on the boat will use and how long it will run each day. These items are often variable—refrigerators will have to run longer in hot climates and the summer, and lights will burn longer during the dark winter months. For everything that uses electricity, calculate the watts used per day (24-hour period).

Next, you’ll want to take into account how much power is being generated. It’s impossible to get accurate numbers for your setup until you’re out there doing it. In general, solar can be counted on for its maximum output for three or four hours a day. How many sunny days a year depends on your location. Again, there are many calculators online.

The wind is good for 24 hours a day, of course, but the wind is seldom that constant. So when calculating the math for a wind generator , it’s very easy to feel good about the choice. But practice has routinely shown that even a small solar array will outperform it in nearly every location.

As already mentioned, the number one choice for most sailboats for renewable power is solar. Solar panels are inexpensive and last for decades with zero maintenance. The downside is that they require a lot of shade-free space to work best.

For boats looking to make power during offshore passages, hydrogenerators are another solution. As long as the boat is cruising at six knots or more, the water passing by has enough potential energy to run electronics and charge batteries. The Watt & Sea Hydro generator is one of the best options out there, but there are also towable generators that do not require permanent installation. Some boats even have the option to use the free-spinning propulsion propeller to create electricity. Of course, these options only help charge the batteries when the boat is moving under sail, and only then at fast speeds. 

Power Output

The first thing to realize is that you must take manufacturer’s ratings for their units with a grain of salt. The numbers are engineering calculations for ideal conditions. That is to say, conditions that a marine wind generator will likely never get to experience. 

Of all of the performance numbers worth considering, perhaps the most interesting numbers are those at the low end on the scale – when does the unit start producing power, and how much. Most of us boat in places with 15 knots of wind or less most of the time, so this is the range your wind generator will sit in for most of its serviceable life.

Noise Level

First and foremost – do not be fooled by online reviews. Every wind generator on the market produces noise. Since the noise is generated from multiple sources, it can be hard to compare apples to apples when shopping for a generator. 

Blade design has a significant effect on noise – some blades are simply noisier than others. Not only does the blade’s aerodynamics make noise, but they can also cause vibrations. All wind generators will require occasional rebalancing and adjustment to minimize vibrations from the blades. 

The moving parts inside the generator can also cause noise. Most are mounted with standard ball bearings that can and do go bad. Many manufacturers advertise these as maintenance-free, but that’s simply unrealistic in the marine environment.

Finally, the mount on the boat is a significant source of noise because it transmits the blade’s vibrations, no matter how minor, into the boat’s structure. Proper mounts have rubber dampening pads built-in, but even still, some noise will get through. This can sound like a buzz, hum, or even a thumping noise.

Quality of construction plays a huge part in how much noise a wind generator makes. As a result, you get what you pay for with wind generators. Unfortunately, the inexpensive hardware store models built for residential use are typically the noisiest. 

You can compare the noise output of various wind generators by taking a stroll around the marina docks or a dinghy ride around the anchorage. Bad or poorly-maintained wind generators can be heard from many boat lengths distance. On the other hand, a high-quality unit will be difficult to hear when you’re standing under it, much less on another vessel.

Correct Voltage

Wind generators should be matched to your primary battery bank—the one that you’ll be charging. Most boats will be 12 volts, and a few will be 24. 48-volt systems are becoming more popular on electric yachts and those using the battery bank for big consumers like air conditioning. These are the exceptions to the rule, however. 

Charge Controller Functions

Unlike solar, wind generators are typically matched to the charge controller that the manufacturer packages with the unit. There are simply a lot more factors that go into regulating a wind generator, including the generation technology it uses and how it brakes or diverts its load. 

Charge controllers are either PWM (pulse width modulation) or MPPT (maximum power point tracking). PWM is a less expensive technology, while MPPT controllers are more expensive. In the world of wind generators, which one a controller features is a bit of a toss-up. Some manufacturers swear by MPPT, while others say there is no benefit to the added cost. 

Most solar chargers accept a solar input, usually only about 100 watts, though. It’s probably more efficient to run your solar array on its own MPPT charge controller. But if you’re only planning on installing a small array and don’t want the hassle of programming separate charge controllers, having the option with your wind controller is a very nice feature. 

Finally, the programmability of the charge controller is a significant factor. Very few of the older PWM charge controllers allow you to input charging profiles. Again, this is less of a problem with wind power than with solar. But if you’re planning to use less forgiving battery chemistries like lithium, you’ll want as much control as you can get from your controller. 

Brake and Automatic Cut-Off

Being able to cut a wind generator off in an over-power or over-speed scenario is extremely important. All wind generators come with some form of braking system. The brake needs to be used when the system reaches a full charge, or the wind speed goes beyond the wind generator’s limits. 

Remember that the generator’s not simply limited by what the blades and bearings can handle. There is also the strength of its mounts to consider. For example, a 60-knot gust on a free-spinning generator will impose an unbelievable force on its mounts.

Then there are wiring considerations. The wind generator is only designed to output so much power, and during your installation, you must use wire sized for the maximum output. What happens if more than that amount of current goes through wires due to a brake failure? Heat and possible battery damage will result, but hopefully, the circuit breaker or fuse will cut it off before then. 

Some have aerodynamic brakes that turn the generator as wind speed increases. This theoretically means that it can never go over its designed limits.

Others feature a brake that is automatically or manually activated. It’s designed to come on when the current reaches a maximum, such as during powerful wind gusts. It also breaks the unit to a stop when the batteries are fully charged. 

An alternative plan is to have a diversionary load. Some wind generators will come with dump loads, which are nothing more than ceramic heating elements. When the wind generator produces too much power, power is redirected from the batteries into these heating elements. They’re also used when the generator produces too much power for the system during storms. 

Mounting and Unit Weight

The mounting mast used to secure the wind generator is sometimes more complicated than the wind generator itself. It must be strong and stayed from all angles. Stainless tubes with two supports are commonly used to mount them to the back of yachts. 

The construction and position of the wind generator are essential to reduce vibrations and noise within the boat. Don’t mount a wind generator over someone’s bunk! All proper mounts have sound-deadening materials like rubber grommets built in to make them as quiet as possible.

The blades of a wind generator must be positioned so that they can’t catch any lines, canvas, or flags from other parts of the boat. This makes stern-rail mounting almost impossible on ketches and yawls. On these boats, mizzen mast mounts are often the best alternative. 

Keep in mind as well that the spinning blades of a wind turbine are like spinning knives. Sailors have lost fingers trying to secure wind generators during storms. Therefore, they should be mounted high enough that it is impossible to accidentally come in contact with the blades during normal operations. 

As mentioned before, another critical component of the mounting is calculating the correct wire size. This is calculated from the unit’s maximum output, the round-trip length of the wire run, and the unit’s charge voltage.

Finally, the positioning of the wind generator should supply it with uninterrupted airflow. If the wind is blocked, even slightly, but a mast, sail pack, or hardtop, the wind generator’s efficiency will be negatively affected. These items could also induce turbulence into the air being supplied to the turbine, which could result in vibrations and noisy operation.

When shopping around for wind generators , notice that power output is not one of our main criteria. This might seem odd, but all of the wind generators on this list produce more or less the same amount of power in a given wind. Some start producing at lower speeds, and some keep producing at high speeds, but in general, these occurrences are so minor and so rare that they don’t calculate into the shopping process.

Eclectic Energy D400

The D400 has a legendary reputation among cruising sailors as the wind generator of choice. It is nearly silent to the point of being very difficult to hear. It is built by Eclectic Energy in the UK, and you can spot its distinctive shape and five-blade design on yachts worldwide. 

For all the pluses, there are some detractors from the D400. For one, it is pretty much the most expensive option. It is also the heaviest—it requires a much beefier mount than other options do. 

SilentWind Pro

The SilentWind has a few advantages over many other wind generators. For one thing, the included MPPT charge controller features Bluetooth programming via a smartphone or tablet. In addition, you can set many parameters for the charge profile—meaning that it is one of the few wind generators that are at least somewhat compatible with the next generation of lithium marine battery systems. 

Compared to the D400, the SilentWind has a more lightweight and compact body. It’s a three-blade design that features blue composite fiber blades. The SilentWind is made in Portugal. 

Rutland 1200

Rutland is the wind power branch of the Marlec renewable power company from the UK. Rutland makes a wind range of wind generators for yachts of all sizes. The 1200 is a three-blade generator that features an MPPT controller with a solar input. At 10 knots of wind, it produces about 40 watts of power. 

Primus Air Silent X

Primus makes a variety of wind generators from their facility in Colorado. The “top-of-the-line,” so to speak, is the Air Silent X. It’s an upgraded version of their Air X that comes supplied with quieter blades made of distinctive blue carbon fiber.

Superwind 350

The German-made Superwind has a unique overspeed and overcharge protection system—the units feature feathering blades. This is undeniably more complex than many other options on the market. These generators are designed to be installed in grueling conditions where a damaged generator cannot be repaired quickly. Their primary market is aimed at remote telecommunication equipment stations and offshore sailors.

Matt has been boating around Florida for over 25 years in everything from small powerboats to large cruising catamarans. He currently lives aboard a 38-foot Cabo Rico sailboat with his wife Lucy and adventure dog Chelsea. Together, they cruise between winters in The Bahamas and summers in the Chesapeake Bay.

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Choosing a Wind Generator

Practical sailor begins its two-part report on wind generators for cruising sailboats begins with a look at features including blade size, number of blades, output considerations and installation..

When cruising sailors think of renewable energy, their thoughts immediately turn to the wind. When selecting a marine wind generator for your boat, several factors must be taken into account, and separating fact from fiction is hard. Claimed output data for specific units can vary greatly from real-world performance. In part one of our series we introduce the six units we test, the Air Breeze from Southwest Wind Power, the Superwind SW250, the KISS High Output, the Ampair 100, and the Rutland 913. The selection presents a good cross-section of micro wind turbines available today and allows us to make some conclusions regarding the best wind generator for particular marine applications.

In 2007, Practical Sailor tested six wind generators side-by-side over the course of four days in February. The previous time we attempted a similar side-by-side test, it was a bust. The turbines spun feebly in a marina with little wind. Prior to that attempt, we long-term tested five models individually on a hilltop in Rhode Island (“Wind Generators, Part 1: Ten Years of Experience,” Oct. 1, 1995, and “Fourwinds II Quietest Large Diameter Wind Generator,” Nov. 15, 1995). Although that round of testing didn’t compare units under the same conditions, we took enough output readings at various speeds to create output curves and came to the dismaying conclusion that over the long haul, an average 50-watt solar panel would outperform the units we tested. (None of the units exceeded an average output of 10 amp hours per day.)

The wrench in the works in both of those previous tests was lack of wind. This time, we had plenty of wind. The test site was at the water’s edge, and five of the six wind generators spun simultaneously: the KISS High Output Wind Generator (made in Trinidad), the Rutland 913 (England), the Superwind SW350 (Germany), a prototype Air Breeze from Air-X makers Southwest Windpower (Arizona), and the Ampair 100 (England).

Conspicuously missing from our test were a pair of two-bladed units: one from Hamilton Ferris (reviewed in our Feb. 15, 2003 issue ) and one model from Fourwinds. Both companies said they could not meet our timetable, despite our long lead time for delivering a unit. Weve been assured that as soon as these units become available,

Practical Sailor will be able to test them. Another unit that looked very promising on paper was the Ampair 300. (Theres also an Ampair 600 for 24-volt systems.) This three-blade, large-diameter unit had a problem with the motor shaft on the first day of testing, and we returned it for repair. We expect to test the refurbished unit soon.

The topic of wind generators is not easily digested over a long lunch. Performance alone may not be the deciding factor, and several other details come into play – not the least of which is the possible mounting location for a set of blades whose tips slice the air at speeds as high as 200 mph. So before we dive into the results of Practical Sailor’s most recent wind generator test , we will focus here on key decision points in purchasing a wind generator and some general conclusions regarding wind generator selection based on our testing.

Wind Generator 101

Wind turbines convert the kinetic energy of the wind into mechanical power, and ultimately electricity. This electricity can be used immediately to power equipment, but is typically stored in batteries for future use. Larger turbines may generate enough power to carry or “float” larger loads (such as a small fridge during an overnight stay aboard), while smaller units produce enough electricity to power smaller loads for a few minutes (bilge pumps, etc.) or perhaps top off your battery banks after a weekend outing.

All generators share a few basic components: a rotor – they don’t propel, so theyre not propellers – with aerodynamic blades, an electrical generator, some form of rotor over-speed control, and a mounting system (pole, arch, etc.). Most also will have rotating electrical contacts, which enable the unit to operate in a continuous 360 degrees of rotation. All but one of the units in our test, the KISS, had this feature. The KISS generator has an internal spring (inside the mount) and a rope lanyard tied to the tail of the unit and mounting pole – the lanyard is a specific length to prevent the unit from rotating more than three or so times, after which the spring is supposed to return it to its original position once the wind dies down.

Wind turbines either produce direct current (DC) or alternating current (AC) power, which is then converted to DC via a rectifier. Of the models we tested, the KISS and both Ampair units utilize a rectifier to convert AC to DC, while the Rutland 913, Air Breeze, and Superwind 350 produce DC. Each approach has its pros and cons: AC can be transmitted over longer wire runs with less power loss (due to overall resistance of system wiring), even when smaller gauge wire is utilized. DC systems, on the other hand, don’t require the use of a rectifier, which reduces expense, cuts down on the number of parts that might fail, and eliminates a few installation steps. As for cons, DC motors have brushes and commutators, both of which require periodic maintenance to prevent generation of electromagnetic interference (EMI), which can disrupt onboard electronics. The rectifying diodes in AC-producing units can also be damaged if exposed to reverse-polarity voltages during installation or maintenance.

Design Evolution

In terms of design evolution, no great technological breakthroughs have emerged since our last test. According to Betz Law (see “Estimating Wind Power”) a wind turbine can theoretically use about 60 percent of the energy in any wind. Even the small turbines meant for use on land are still far from that ideal.

“What they are getting is a piece of that 60 percent Betz limit,” said Jim Johnson, a mechanical engineer for In the Wind at the National Resources lab. “The better units will produce about 40 percent of that limit.”

Ongoing research at National Wind Technology Center – including the development of more efficient, quieter blades – will eventually trickle down to micro-turbines (as the boat-sized units are called). However, the limited marine market, price-point competition, and design limitations imposed by marine applications likely will slow this process. Advances generally have been baby-step improvements in rotor noise, more efficient blades, reduced shaft friction, and smarter regulators. If the last 12 years are an indication of whats to come, what we buy this year probably wont be much different than what will be available five years down the road, when our turbine will likely need an overhaul or replacement. Like any moving part on a boat, these things do break down.

Power Output

Wind-turbine makers often bear a “label rating” according to potential output under ideal conditions. For instance, the Ampair 100 will produce 100 watts (volts x amps = watts) in a 28-knot breeze. Aside from the fact that no one purposely chooses to anchor for long in a 28-knot breeze, these numbers can be deceiving.

Turbine manufacturers will typically provide speed-output curves that graph output at all wind speeds within their units range of operation. Others will simply indicate projected output at a sampling of fixed, steady wind speeds. Either approach can yield a distorted picture of real-world output. Some makers base their steady-wind output projections on absolutely fixed wind speeds (impossible, except in a wind tunnel). Other makers reach their output numbers by using a standard wind distribution model known as the Rayleigh distribution, a statistical method used by wind power experts to translate average annual wind speed data into potential wind power estimates (see chart below).

“You should take any output figures published by the manufacturers with three very large grains of salt,” say Paul Gipe, whose website ( www.wind-works.org ) and book (“Wind Power: Renewable Energy for Home, Farm and Business”), covers the topic of wind power for land applications in great detail.

This, of course, is one of the reasons we are looking at these units in a real-world application.

Wind Turbine Types

Wind turbines can usually be classified as either small rotor units (blade diameters less than 48 inches) or large rotor units, with typical blade diameters of around 60 inches. All things being equal, the highest potential output will increase with the diameter of the rotor. A rough rule of thumb is that larger units typically generate around 4 amps in 10- to-15 knots of steady wind, while smaller units average about 1.3 amps.

The main challenge confronting any wind generator is the fickle nature of wind itself. Wind generators present a Catch 22 scenario. While they are most effective when exposed to steady winds with the vessel at anchor, the best anchorages tend to be sheltered from the wind. As such, the cut-in speed of a wind generator (the point where it actually starts producing electricity) and its output in lower winds (10 to 15 mph or less) can be more important than maximum rated output.

Smaller, multi-blade units (typically six blades) have an advantage in this respect. These blades have less inertia, so they require less wind to start turning, allowing them to reach their cut-in speed and start producing power sooner in light winds. So, if your cruising anchorages are characterized by light breezes, a small blade is the way to go … or is it?

A key factor in potential power output is the cube rule: Available wind power varies as a cube of wind speed. So if wind speed doubles, energy content (measured in kilowatts per square meter) increases eight times. A 10-mph wind has one-eighth the power of a 20-mph wind (10 3 =1,000 versus 20 3 =8,000), and a seemingly insignificant increase in wind speed from 10 to 12 mph can increase available wind power by 73 percent.

What this means from a practical standpoint is that if you choose a quiet anchorage that experiences occasional higher-than-normal gusts (squalls or katabatic winds, for example), a wind turbine could potentially yield more energy than it would if you were anchored in a steady, moderate breeze during the same time period.

Wind generators with fewer larger blades have higher maximum outputs and can produce more power in higher winds. (A one-bladed rotor, odd as it may seem, has greater potential for output than one with multiple blades.) This means that while a large-blade turbine might not match the output of a small-blade wind generator in light winds, its higher output in gusts can compensate for its higher cut-in speed and poor performance in lighter winds. A key factor is whether the occurrence of higher gusts is high enough to keep up with power demands.

Another consideration output-wise is that while sailing downwind, you have to subtract the boats speed from the wind speed to get the apparent effective wind speed at the generator. If the true wind speed is 14 knots and boat speed is 7 knots, your generator is actually “seeing” only 7 knots, meaning output will be greatly reduced.

Rotor Speed Control

While wind generators obviously require wind to operate, at some point (typically around 35 knots of sustained wind), youre approaching the too-much-of-a-good-thing level, and some form of blade speed control mechanism is required to prevent physical damage to the unit and, in some cases, the boats batteries. Braking, or blade speed control, can be accomplished in a number of ways. Some units have “self-braking” blades that stall at certain speeds, while others are designed to gradually turn away from the wind as higher than acceptable speeds are reached. Friction or air-brake systems are also used, as well as electrical stop switches. Finally, some turbines require you to physically tie or secure the blades, often an unattractive prospect in a rocking boat, considering the speed at which the blades can rotate. For extreme weather conditions, even the makers of units with stop switches recommend that you physically secure the blades and rotate the units to reduce windage, or remove the unit altogether.

OtherConsiderations

While construction, size, weight, and ease of installation are all important considerations when choosing a wind turbine, noise is often a deciding factor. All models are noisy to some extent. However, some units are as loud as an engine or genset running at anchor, which defeats one of the reasons folks turn to renewable energy – peace and quiet.

Much of the noise from a wind generator is caused by air movement at the tips (tip vortices) and back edges of the blades, which is why there is constant refinement in blade design. Blades with fine, smooth trailing edges and smaller tips will generally be quieter. Although noise can be reduced by factors such as construction and blade design, as a general rule, units with smaller blades are quieter than those with larger blades. The number of blades is a factor as well – a six-bladed unit will always be quieter than a two- or three-bladed unit, provided the blade diameter and design is equal.

Some folks don’t mind the noise of a larger unit, equating it to the sound of “money” flowing into the proverbial energy bank. Others (often those anchored beside you) will find it annoying. A good way to compare noise levels of various units “in the wild” is to walk the docks of your local marina or dinghy around the mooring field and observe others wind gens – it also gives you the opportunity to ask how satisfied the owners are with each unit.

Wind-power study is rich with mathematical formulas, and theres one to account for mounting height as well. According to the Wind Profile Power Law, wind speed rises proportionally to the seventh root of its height above sea level. By this formula, doubling the height of a turbine, then, increases the expected wind speeds by 10 percent and the potential power by 34 percent. However, at the slight altitude changes that are possible on a boat (say the 20 feet between a pole mount and a mizzen mount), this formula will likely have little bearing.

More important for our discussions of boat mounting is the “roughness” factor, which accounts for obstructions that impede windflow. The slight shift from pole mount to masthead will clearly alleviate roughness. How this will affect output will vary from boat to boat. Estimated increases in output range as little as 10 percent to more than 20 percent.

Mounting a wind generator is often a balancing act of aesthetics and performance, meaning your choice can look good but operate poorly or vice versa. The best spots are those that offer an unobstructed flow of wind while keeping whirling blades well clear of rigging, self-steering vanes, davits, or, most importantly, the outstretched arms of the tallest crew member.

Stern Poles and Arches

Stern poles and arches are popular mounting choices – both keep your wind generator in place where it can be tied down or serviced, but up and out of the way of outstretched arms. Stern poles are less expense, but proper bracing is crucial not only for strength, but to reduce movement of the pole (which, in turn, minimizes vibration and noise transmission belowdecks). Arches cost more, although the added expensive of having one fabricated can often be justified if it will serve multiple purposes (i.e., mounting for radomes and solar panels as well). The multiple attachment points on deck can also serve to dissipate vibration on the deck.

Mizzen-Mast Mount

A boat with two masts has the option of mounting its wind generator about two-thirds up the mizzen or at the very top. Both choices offer more exposure to wind and provide a cleaner-looking deck, however, they do add weight aloft and the units will be more difficult to service. Theyll also require longer cable runs, meaning you may have to upgrade to larger wire sizes to address voltage drop concerns. Securing them will also be more of a challenge, particularly those that have to be physically tied off in high winds.

Rig-Suspended Mounts

Rigging-suspended mounts, such as a fore-triangle hoist, are a good alternative when you just can’t seem to locate that perfect mounting spot. This option produces less vibration, and units that are designed to be deployed in this manner can easily be removed and stored to clear the decks when needed, however, they can’t be used while underway.

Conclusions

Based on our research (including the most recent data that well report next month), a large-diameter, three-bladed unit is a good choice if maximum potential output is a chief concern. Small-diameter units can’t be written off, however. If low noise, small size, and a low cut-in speed (for low wind areas) are your first priorities, these units have much to offer.

Three of the units in our most recent test – the Superwind 350, the Air Breeze, and the Kiss High Output – had best days of 88-115 amp-hour production. Worst days were less than 10 amp hours. This is enough, or nearly enough, to meet the average amp-hour requirements aboard a modern cruising boat fitted with a watermaker and refrigeration.

Despite these persuasive numbers, our evaluations and experience in the field indicate that relying on a single wind turbine for ones primary energy source is not the most sensible way to optimize for efficiency, particularly while under sail, when the rocking motion of the boat further inhibits performance. Solar panels have no moving parts, are durable, and in many ways are better suited for a lifestyle that tends to follow the sun. With the assistance of todays Multi Point Power Tracking Technology (See “ Boosting Solar Panel Output ,” Chandlery, August 2006), a single, 80-watt solar panel can replenish as much as 60-80 amp hours on an ideal summer day. Wind turbines, in our opinion, should be regarded as a viable option for a cruising sailboat with high energy needs to supplement its solar panels, genset, or high-output alternator – not as the ultimate solution to onboard energy production. Next month, well take a close look at the performance and features of each of the units.

• Installation Options
• Wind Generator Details
• Plotting Wind Distribution
• More Wind Generator Details
• Wind Generator Blade Design
• Estimating Wind Power

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please watch out when buying a Chinese turbine or other power generator items. they say 400-watt turbine but what they really mean is 400 watts/day. i had this problem. I could only get maybe 3 amps out of it now I know why. I also saw somewhere in the article they talked about amp-hours why? are all specs really per hour?

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