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Create Power While Under Sail

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Want to keep your sailboat's batteries charged without a generator or running the engine? A hydrogenerator might be the solution.

Modern hydrogenerators are lightweight and generate an impressive amount of battery charging power.

Sailors tend to use their engines far less than the average powerboater, and this creates an immediate problem of how to satisfy a boat's electrical needs. Lighting, electronics, refrigeration, and entertainment systems all require electricity to operate — all demands placed on the boat's battery bank. Solar panels, wind generators, and diesel generators have their place, but all have drawbacks.

I faced such a challenge many years ago on my first Atlantic crossing. We wondered how we were going to keep the batteries charged. By today's standards our electrical demands were modest, but we had no diesel generator. We calculated that we would need to run our main engine for two to three hours per day, a very inefficient and noisy way to charge the battery bank. Solar panels were rejected solely on cost, and there was no convenient place on the old ketch for a wind generator. Ultimately we settled for a "towed generator" — a small propeller at the end of a stiff line was trailed behind the boat, which turned a generator mounted on the back deck of the boat.

Watt and Sea's hydrogenerators are usually fastened on the transom. The lifting up and down is similar to a rudder blade's handling.

Modern iterations of the hydrogenerator are far more compact and easier to deploy. There are several manufacturers, but all use the same basic principle: they transform water flow energy into electricity using an alternator. Looking like a cross between a small outboard motor and a retractable rudder, modern systems are capable of putting out impressive amounts of power with minimum drag. In fact, all the boats in the last Vendée Globe race used hydrogenerators for producing all of their electrical energy needs. This made crucial weight savings by not requiring a heavy generator and the associated fuel tank.

Watt and Sea Hydrogenerator

In this video, you can watch one of the popular Watt and Sea units being towed behind a fairly modest sailboat. At 8 knots of boat speed in 14 knots of wind, the unit is putting out an impressive 16 amps of power. Price depends on which unit you choose, but expect to pay around $3,000 for a complete system.

• Watt and Sea
• Sail-Gen – Dedicated Water Generator
• Hydrogenerator Save Marine H240

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A marine surveyor and holder of RYA Yachtmaster Ocean certification, BoatUS Magazine contributing editor Mark Corke is one of our DIY gurus, creating easy-to-follow how-to articles and videos. Mark has built five boats himself (both power and sail), has been an experienced editor at several top boating magazines (including former associate editor of BoatUS Magazine), worked for the BBC, written four DIY books, skippered two round-the-world yachts, and holds the Guinness World Record for the fastest there-and-back crossing of the English Channel — in a kayak! He and his wife have a Grand Banks 32.

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Yachting Monthly

• Digital edition

Everything you need to know about hydrogenerators

• Sam Fortescue
• December 13, 2023

Design developments have made hydrogenerators the most efficient form of sustainable auxiliary energy for yachts. Sam Fortescue reviews the latest innovations

The potential of hydrogeneration has been well understood for decades, but it’s only over the past 15 years that the idea has started to become properly commercialised. In essence, it’s a very simple concept: the boat’s motion through the water turns an alternator which generates electricity to recharge the onboard batteries.

‘Every yachtsman owns a sophisticated wind energy machine in the form of the yacht itself,’ explains Peter Andersen of Eclectic Energy, which manufactures the Sail-Gen and Duogen hydrogeneration systems. ‘Hydrogeneration provides a simple way of converting a small part of the power harnessed by the yacht’s sails directly into electricity.’

Because water is a much denser medium than air, a small hydrogenerator fitted to the transom of a yacht can potentially produce a great deal more energy than if a larger wind turbine was fitted to it.

‘Kinetic energy increases proportionally to the cube of the velocity,’ adds Andersen. ‘That means producing 300 amp-hours per day or more is a realistic prospect while cruising at 7-8 knots with a hydrogenerator fitted. And it’s the reason why more and more boat owners are now opting for water generation, although it’s still not as popular as it should be.’

By contrast, a tradewind run with a wind turbine might yield just 80 amp-hours per day, because the apparent wind on a run is lighter. Good performance might see 40W output from 10 knots apparent. Similarly, solar panels only produce a fraction of their rated output for most of the day, so you’d need a large array to match the return of a modern hydrogenerator.

A blend of all three will, of course, give the best outcome for different conditions at anchor and under way – but on passage, it’s hard to beat the benefits of a good hydrogenerator.

Watt&Sea’s hydrogenerator is a flexible option

Speed v drag

The speed versus drag issue has always dogged hydrogeneration technology, mainly because hydrogenerators only put out meaningful energy once a boat reaches speeds of five knots or more. However, the increasing use of hydrogenerators on the international offshore racing circuit has started putting paid to most of those concerns, with all manufacturers now agreeing that the extra drag of the impeller in the water is negligible. It also becomes non-existent once the boat reaches hull speed.

The main issue for cruising sailors is the boat speed required to obtain meaningful energy from a hydrogenerator, which is mostly a question of the diameter and pitch of the impeller. Just as you need to ensure that an auxiliary propeller is matched to both the power of the engine and the speed of the hull, so the impeller on a hydrogenerator must be correctly sized for the speed of your boat under sail and desired power output.

The pitch also needs to be set to offer the optimum angle of attack for the boat’s likely range of speed through the water. That’s why leading manufacturers offer a choice of impeller, or at least an adjustable one.

Hydrogeneration is the most efficient form of sustainable auxiliary energy for yachts

The Watt&Sea is the most flexible in this respect. Its two models (300W and 600W maximum output) can be equipped with a 240mm diameter impeller or a 280mm unit. The difference in output is striking: at five knots boat speed, the smaller one produces 100W, while the larger one can manage 120W. Over the course of a day, that amounts to an extra 40 amp-hours on a 12V system.

The smaller impeller has a maximum boat speed of 11 knots, which will be enough for most cruising monohulls. Only sporty catamarans would need to consider the smaller 200mm impeller with its 13-knot top speed. Faster than that and you’d need to look at a race model with a variable pitch.

Charging performance

Apart from price, the factors differentiating the various brands on the market are their charging performance and mounting system.

Eclectic Energy is the only manufacturer whose generators rectify the current on board to produce a DC output that can be wired directly to the batteries. This has the benefit of simplicity, but requires beefier cables running all the way from the generator to the batteries.

The Duo Gen hydrogenerator from Eclectic Energy

Watt&Sea’s hydrogenerator puts out a three-phase, low-amperage alternating current that runs through a DC converter. The converter monitors the battery voltage to determine whether it is in the higher power absorption phase or the lighter float phase of charging. After that, an electromagnetic brake stops the impeller if it’s spinning too fast and becoming dangerous.

Swi-Tec’s charge controller funnels all the power from the generator into the batteries until they reach a predetermined voltage. At this point, the MPPT (Maximum Power Point Tracking) algorithm reduces the charge to nearly nothing, a buzzer sounds to alert the skipper and the impeller brakes itself automatically. It can then be changed to ‘freewheel’, allowing the propeller to rotate freely.

The Remoran is perhaps the most ambitious of all, with a charge controller that can automatically detect the system voltage and then apply a ‘smart charging algorithm’. It also interacts with a smartphone app via Bluetooth, allowing you to keep a close eye on its performance and power output.

A Sail Gen hydrogenerator mounted on a yacht’s transom

Mounting systems

While Watt&Sea supplies a pod-based system that can be permanently fitted under the hull, a removable transom fitting is still the most popular choice, allowing the unit to be removed and stowed when not in use. Alignment, though, will have a significant impact on a hydrogenerator’s performance, with the best results coming from a clean, clear flow of water. Manufacturers therefore recommend an offset mounting outside a direct line with the rudder.

There is a balance to be struck, however, as heeling can make one tack more productive than the other. On twin-rudder boats, a central mount works well.

Swi-Tec and Watt&Sea both offer an optional pivoting mount for fitting to a raked stern, while the Remoran has in-built pivoting as standard, using a spring-loaded knob to tab between different settings and offering a rake of up to 40 degrees. Watt&Sea also offers different leg lengths to suit different installations, while the Remoran Wave 3 has a telescopic leg that can be adjusted by over 30cm.

Watt&Sea unit with an optional pivot mounting for attaching to a raked stern

The Seagen and Duo-Gen take a very different approach to mounting, with a flexible yoke providing a single point of attachment. The alternator is attached at this end, while the impeller is at the end of a 1.6m tube which can be fastened out of the water in a vertical position when not in use. ‘It means the units are not rigidly attached to the yacht but are free to pivot,’ explains Eclectic Energy’s Peter Andersen. ‘This de-couples the impeller from the hull movement, reducing stress on the mounting.’

Main propeller regeneration

While a standalone transom-mounted unit is the most common type of hydrogenerator technology, there is another approach – using your main propeller to ‘regenerate’ electricity whilst under sail.

Oceanvolt’s HighPower ServoProp

Fully electric propulsion from the likes of Oceanvolt and Bell Marine has long had this capability built in, as do systems from Torqeedo and ePropulsion. But parallel hybrid systems are also available, where an electric motor is installed alongside the engine to both generate electricity and drive the boat electrically. Lynch Motors in Devon has been supplying its permanent magnet DC motors to the Vendée Globe boats for years, purely as a re-generator, and now produces the flexible Red Snapper motor for cruising yachts.

The only problem with a regeneration system is that the pitch required for the propeller to drive the boat efficiently through the water may not always be the same as the pitch for optimum regeneration. ‘The lift surface on a propeller is on the wrong side for efficient extraction of energy from the water,’ explains Eclectic Energy’s Andersen.

Manufacturers have tackled this in different ways. Oceanvolt has developed its ServoProp for saildrives, which electronically adjusts its pitch depending on speed and function. The latest incarnation allows total 360-degree blade mobility and faces forwards, which increases efficiency, albeit at greater risk of collision damage. At six knots, it produces an astounding 1kW of power.

Bruntons has another solution with the cleverly engineered Autoprop, which automatically pitches up to match the boat speed. Its Ecostar version of the prop can generate 200W at five knots and up to 1kW at 10 knots when connected to an electric motor.

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hydro-generator

Discussion in ' DIY Marinizing ' started by HuwFernie , Jan 8, 2012 .

HuwFernie New Member

Anyone ever tried to make a generator to mount behind a sailing boat? There is one made by Watt and Sea http://www.wattandsea.com/en which started me thinking about re-wiring and re-propellering an electric trolling motor but I'm getting stuck at figuring out how much power I'd be generating. I've also thought about building one from scratch which sounds like an interesting challenge. We have a 24v battery bank of 320Ah and run our boat at around 10 - 15 Amps with most stuff on; so the 500w from the commercial option looks good. I'd like to give this a go out of interest but I'm out of my depth with the motor choice. Any help would be appreciated. Huw  

gonzo Senior Member

There isn't much to change on a trolling motor with permanent magnets. The propeller would ideally have a high pitch to be more efficient. You need to decide what your usual cruising speed is and select the pitch accordingly.  

pistnbroke I try

I am sure this has been on before ...you need to make up a metal prop and get twisting with it over the side of a power boat going at your normal cruise speed. Your problem is you will need a series regulator to control the output to 14.4v which will generate heat and probably be an own design though a solar panel regulator would also be suitable .  

CDK retired engineer

You will get approx. 80% of the nominal power of the trolling motor, so if it draws 20 Amps as a motor, it produces 16 Amps as a generator. That power can be used for instruments, lights etc. but for proper battery charging you need a higher output voltage. That means a voltage converter/ charge controller that will skim another 25% from the generator output. So in the example you get 12 Amps.  

Thanks for the info. For charging, is voltage not proportional to rpm so spinning the motor faster = higher voltage? most of the graphs I have seen show a linear relationship (but I'm only looking through google). And from CDK's numbers 25A at the motor would give 20A as a generator and put 15A into the batteries. So at 24v 25A I'm looking for a saltwater, 600w, permanent magnet DC motor. For the charge controller I have seen this: http://www.mdpub.com/555Controller/ which I think will work. I'll have a look and see if there are any suitable trolling motors out there.  

i force or bison in the UK are a good buy ..I dont follow CDKs logic if its a 24v 86lb motor it draws 50A ..so to my mind thats the max the windings will handle continuously ..remember of course a 12v battery will need a regualted 14.4v and a 24 v battery 28.8v.. Whatever your charging system you will not get more than 25 A into a 100AH battery and only for a short time as it will drop fast to 15 A and then on down  

FAST FRED Senior Member

To see the effect on sailing , turn the existing motor to thrust forward and operate it at full throttle while underway. That is the drag creation you will need to live with. No free lunch. FF  

Thanks Fred, I'm not too worried about drag at the moment, I'm more concerned with having to run a generator/engine for charging and not being able to sleep!  

philSweet Senior Member

Yes HuwF, lots of folks have tried. The info above is all basically true, but folks are trying hard not to rain on your parade. As a practical device, it has absolutely no chance of replacing any generator. Turbines and propellers are different animals. Yes, they both have one moving part with one degree of freedom, so how hard can it be? The trouble comes from the fluid, not the machinery. If you insist on thinking of it as a prop in reverse, you won't ever get a handle on it, but perhaps this analogy will help- If the prop is moving the boat at 3 knots, the water jet created by the prop is probably three times this. So that is the speed you would have to tow at to get that sort of power. (Except that doesn't work either, it's actually somewhat worse than this if you are measuring power in/out of the batts). A solar panel is much easier to live with. I can cruise a 38'er on two panels and a 30amp controller feeding three WalMart batteries. (and no drag) Fast Fred's comment about drag was probably intended to discourage you a bit. Mathematically, there isn't any natural relationship between the thrust made and the drag caused by the two cases. It depends on engineering, the drag could be nearly anything. Drag of turbines is usually a secondary issue for turbines. You won't find much info on it. A design for best power/drag will be different than a high nominal efficiency design. I have yet to see a report of any trolling motor producing 2% of its rated amperage behind a smallish sailboat.(peak,yes- average over time,no) I think some of the 20knot Vendee boats used a custom generator to manage the autohelm power draw. Or was it the ORMA boats? Really fast boats. Some practial considerations. Propulsion benefits from the slowed wake behind a boat. Obviously, generation would suffer if towed in the wake. The slipstream a prop creates effectively straightens out the inflow condition seen by the prop. The heave of the boat has less effect than you would expect. On a generator, the situation is reversed, any heave or inflow irregularity is magnified. Just watch any air generator on a pole on the transom of a sailboat. They don't work very well when the boat is underway in a breeze, which is real annoying to people (they also don't work very well when underway and there isn't a breeze ) There's a bunch of info at the electric boat forums. Yahoo Groups has one.  

Thanks Phil, I like the brutal honesty! The Watt and Sea web page I linked in my first post is the consumer model of the Vendee used towing generator you mention. It was this that got me thinking in the first place: I've heard reports that it works, but it does cost about $4000! So for something that looks like a laser dinghy rudder with a trolling motor bolted to the end, a new propeller and a little bit of electronics in the boat I figured I could build something for say $400 It's only an idea, and it doesn't look like I'll get enough time to try before this trip. I still find it an interesting idea to play with though. We are looking at a solar option, but it does need a pretty big investment and also a lot of deckspace. Thanks for the idea about Yahoo groups, I'll look into it. Cheers, Huw  

"I'm more concerned with having to run a generator/engine for charging and not being able to sleep!" The really interesting question is can we have a water generator that works in the current , as we are anchored? The only attempt I know if was a gent that took 100ft of canvas 4 inches wide sewed it in a loop and installed (wired) hinged 4x4 thin plywood flaps to it. An auto verticle front spindle clamped on the aft deck with the bearings and a steel wheel. The canvas was dropped over the open wheel,flaps out, and in 1/2 K or so the flaps would open dragging away from the boat , and hinge closed on the return. In a 2K current one could not stop the wheel with foot pressure , so good power was being made. Tho 2K in an anchorage might not be common. Sadly his budget did not include bucks for a better generator than bike units ,so the concept was not perfected. Something low cost and simple might work if refined a bit. GO FOR IT! FF  

GTom New Member

Sorry for reviving an old thread but I haven't seen any recent info on hydro generators. Costs of the commercial models is still far from realistic, asking the price of 4 tons of diesel for a device with a complexity of a 250$ trolling outboard. Anyone actually tried to use a ~500W trolling motor (ebay, 2-300$) for power generation? I understand that they are probably not PM motors, but AFAIK that can be dealt with. Any suggestions for propeller design for a typical 3-7kts boat speed? CDK said: ↑ You will get approx. 80% of the nominal power of the trolling motor, so if it draws 20 Amps as a motor, it produces 16 Amps as a generator. That power can be used for instruments, lights etc. but for proper battery charging you need a higher output voltage. That means a voltage converter/ charge controller that will skim another 25% from the generator output. So in the example you get 12 Amps. Click to expand...

srimes Senior Member

If it's a PM motor with simple resistive speed control then it would generate power whenever it's forced to spin faster than it's powered speed. Then it just comes down to fitting the right prop. Maybe I'll dig my motor out from under the porch and see if I can spin it with a drill and produce power.  

srimes said: ↑ If it's a PM motor with simple resistive speed control then it would generate power whenever it's forced to spin faster than it's powered speed. Then it just comes down to fitting the right prop. Maybe I'll dig my motor out from under the porch and see if I can spin it with a drill and produce power. Click to expand...

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As bonus, the alternator can be used with a wind turbine when anchored. Of course then you have noise 24/7/365 , if the wind is blowing.  

a hydrogen gas fueled triple engine

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Hydrogenerators – on test

If you’re planning to go long-distance cruising you’ll most likely be looking to fit one or more forms of power generation to avoid running your propulsion engine.

Thanks to modern alternator designs that offer increased power at lower rpm, hydro-generators are becoming a worthwhile investment for yachtsmen who regularly sail long passages. Yes, they do create a slight drag on the yacht under way, but only around 0.25kt or so, which is unlikely to worry most long-distance cruisers.

How do they work?

A hydro-generator has an impeller (reverse prop) that rotates when towed behind a yacht. That rotation is applied to an alternator, which produces AC power that is rectified to produce a DC charge for your batteries, in a similar way to a shore-powered battery charger.

Early models towed an impeller on a long line behind the boat, which was attached to an alternator on board. But their trailing impellers were often bitten off by large fish and they frequently tangled up when fouled or if not retrieved correctly. Current devices have an impeller attached to a submersible leg – not unlike an outboard motor.

Modern, brushless alternators with magnets have reduced turning resistance and increased efficiency, enabling them to produce more power at lower revs. A hydro-generator is an effective way to provide constant electrical charge over a long distance. On a 40ft yacht one of these can produce around 200Ah of charge every 24 hours at 6kt, which is enough to run most electrical items on board.

They also require little maintenance, other than weed clearance and periodic checking of the electrical connections.

Swi-Tec Hydrocharger

First this HG produced a high current flow, although not stable as it fluctuated considerably between readings. Hence the charge levels in our results table are derived from a mean between lowest and highest reading for each speed. The control box is liable to overheating, as the fan appears to be prone to failure. Our test team felt the box was more complicated than necessary.

• Verdict 6/10

Watt & Sea

We tried the 600W model with the mid-range impeller as that was more compatible with the others on test. Although not as powerful as the Save Marine and Swi-TEC HGs at the lowest and highest speeds, at a typical cruising speed of between 5-6kt the output is strong and, importantly, stable.

We liked the ease of installation and straightforward operation, including the simple ‘plug-and-play’ charge controller.

• Verdict 7/10

The SailGen is easy to mount and, having the heavy alternator at the boat end, is light and easy to deploy and lift. The dive plane idea works well and, though its real-time output is less than others, being always kept at the correct depth means its charge level is far more consistent.

• Verdict 8/10

The output is a bit lower than SailGen’s, which itself is middle of the range in comparison with all the others, but having the 2-in-1 option of a wind generator could be a real bonus for those planning to make long passages then coastal cruise in windy areas such as the Trades.

Save Marine

We liked the lightness and ease of deployment of the Save device, especially the arm that kept the lines tidy and secure. We also thought the turbine design to be innovative, quiet and very efficient. Finally, we loved the idea of the remote monitoring on a smart device, especially as the charge controller is fully automatic so there are no switches to be flicked or audible alarms to listen out for.

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Hydrogenerator

Hydro generator.

The hydro generation or “creating energy while sailing” function is an automatic feature in all Oceanvolt motors. 

This feature is activated by pushing the button on the Oceanvolt displays for 5 seconds. The display will automatically switch to regeneration mode showing the current generated power, RPM and time until the batteries are fully charged. 

With a normal folding propeller the motor kicks the blades out and centrifugal force combined with the motor controller keep the blades open. The motor controllers tune the system actively at 10 Hz which prevents the blades from closing (too much braking would close the propellers). This is continuous monitoring, the system will adjust the propeller RPM depending on the boat speed. 

The system shuts itself down when the battery is fully charged or if boat speed is too low for efficient hydro generation.

OCEANVOLT SERVOPROP

The patented Oceanvolt ServoProp variable pitch sail drive combines a high efficiency sail drive with the most powerful hydro generator on the market. The unique feature of the ServoProp is the possibility to turn the propeller blades more than 180 degrees. The software controlled variable pitch sail drive adjusts the pitch of the propeller blades automatically so that the power generation and power output are optimal. Combined with uniquely designed blades it delivers optimal efficiency in both forward, reverse and hydro generation. And with the blades set to the neutral sailing position, the propeller creates extremely low drag similar to the drag of a feathering propeller. The benefits of ServoProp include an estimated +30% increase in forward propulsion, +100% in reverse and +300% increase in hydro generation effect.

A normal fixed propeller (that by nature does not have the blades ideally shaped for regeneration) generates less than half the power of ServoProp at a given boat speed. ServoProp is capable of generating more than 1 kW at 6-8 knots. The power generated can be used to power both the propulsion system as well as all the electronics on board without the need to have a separate generator. With this in mind we can definitely start talking about the possibility of a totally self-sufficient cruiser!

The ServoProp is suitable as a propulsion motor for monohulls up to 50 ft & multihulls up to 60 ft. It can also be used as a hydro generator in boats up to 100 ft.

Videos of hydro generation

power created by hydro generation

Oceanvolt systems are optimised for either 2 or 3 blade Flexofold folding propellers & Gori propellers.  Other folding propellers can also be used but they provide 30-50% less propulsion and regeneration power. 

The highest regeneration power is gained with fixed blade & adjustable pitch propellers and also with dedicated systems for hydro generator use, because they allow using a higher pitch/dimension propeller.

The regeneration feature is extremely suitable for catamarans because twin motors means double the energy generation.  Catamarans are also faster, which means that regeneration power capture is higher.

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Towed Water Generators: Are They Worth It?

Jonathan Neeves

A few years ago, I noticed that 2 of the 10 cruising boats I saw docked in Bergen, Norway, had towed water generators, making me wonder whether the Scandinavians have had better luck with these devices than we have. In the October 2017 issue of Practical Sailor, offshore gurus John Neal and Amanda Swan Neal of Mahina Tiare Expeditions share their experience with these systems.

It has been a long time since Practical Sailor tested towed water generators, and the number of choices remains extremely limited. The last towed water generator we reviewed was the Hamilton-Ferris towed water generator . And the last long-term test was of the Aqua4Aeroben made by LVM in the United Kingdom.

The units I saw in Bergen looked like they were the Aquair 100 made by the British manufacturer Ampair. In our article on Choosing a Wind Generator , we mention Ampair, and we describe its wind generator in greater detail our marine wind generator test (available only to subscribers). We have not yet had a chance to test the Aquair 100, but it operates in a similar way to the Hamilton Ferris unit. Both tow a small impeller that looks-and this is one of the problems-like a big fishing lure with propeller blades. As the impeller spins, it turns the generator fixed to the boats stern. Old-timers may remember how much the fish seemed to like those pricey impellers for the Walker Knot Log , even though they were painted black.

One thing I noticed in Bergen was that one of the towed water generators had what looked to be a homemade impeller, and it is quite probable that the original one was lost. This is one of several problems with towed water generators; they get tangled, fouled in weed, snagged, and lost-sometimes eaten by big fish or sharks. I suppose one reason there might be more of these units here in the north country is the waters don’t have as many surface-feeding pelagic species as we have in warmer climates.

Towing isn’t the only option, though. While I was in South Africa a few years ago, I spoke with the local representative for Duogen to try to arrange a test of this product, a combination wind and water generator. At the time, the company was fairly early in the product development, and I was not impressed with the fabrication. One thing I did like was the apparent ease (the key word is apparent, because I did not try this at sea) with which the Duogen deployed: It is suspended over the stern like an electric outboard. In its water-gen mode, it looked very similar to the Watt & Sea hydrogenerators that Practical Sailor contributor Dan Dickison examined during the Velux 5 Ocean Race. These are now available in a cruising version , but they are expensive units, and again we have not tested them.

All of these products have another problem in that they add drag underway. Some owners report speed losses of a quarter- to a half-knot. This isn’t a big deal if they can help keep the ships systems running on a long passage of the kind that John and Amanda routinely tackle on their offshore training sails aboard their Hallberg Rassy 46, Mahina Tiare III .

Call me a skeptic, but when I look at the prices for hydrogenerators and consider how much time they will actually be delivering power to the boat, I think there are much better ways to spend my money. If an efficient and convenient dual-purpose generator comes on the market, I may change my tune. But right now, I think solar, then wind still reign in the world of ship-board alternative energy.

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Cruising 300 Hydrogenerator

CRUISING 300 Hydrogenerator

Cruising 300.

• Technical specifications sheet
• Output Curves

An input of energy up to 300W (24 Amp in 12 V), for more comfort in the respect of the environment !

The CRUISING 300 is usually recommended to boats measuring up to 35 feet :

Available in two lengths in order to optimize the immersion of the propeller depending on the place choosen for the fitting.

Ideal on boats sailing generally from 4 to 6 knots, and consuming around 8 Amps (12 V installation)

Delivered in standard with the 240 mm diameter propeller (output 8 Amps at 5,2 knots), it will produce even more with the 280 mm propeller (8 Amps at 4,5 knots)

Mobile application : converter equipped with a Bluetooth chip allowing the reading of charge data, various technical informations, as well as the adjustment of voltages if necessary (Lithium battery)

Available in 2 versions :

• short (Ref. PK-610-300)
• long (Ref. PK-970-300)

Packs characteristics :

Technical characteristics

Dimensions and weight

Output power curves

Watt Speed in knots

The propeller supplied in standard with the CRUISING 300 hydrogenerator pack is the 240 mm model which allows to produce 8 Amps at 5 knots .

It is the more “universal” model guaranteeing the energy self-sufficiency on most boats with a negligible drag. To produce at slowest speed, the 280 mm diameter is more efficient.

To produce at higher speed to minimize the drag effect, the 200 mm diameter is available as well as the 200 mm with manual variable pitch to be used on applications like MINI 6.50.

General Questions

How to choose the right power : 300W hydrogenerator is designed for boats under 35 feet, and 600W is ideal over 35 feet sailing boats. It also mainly depends on the equipment you have on board !

How to choose the right lenght for my boat : First define the location for your installation onto the transom.

You have to respect 3 rules to choose the ideal location :

• The hydrogenerator should not be in the rudder blade axis to avoid water perturbations. 10 or 20 cm aside from this axis will be fine.
• The leg must be vertical in the lowered position for the production to be optimized : the propeller axis must be horizontal, aligned with the water flow.
• the recommended depth between the surface and the propeller axis is 300 mm(12 inches), even when the boat heels.

Taking in account those 3 points, the 610 mm or 970 mm leg will be chosen.

Watt&Sea recommends servicing every 2 years or every 10 000 miles. It should be noted that, regularly, you can :

• remove the propeller and clean the conical fitting
• check all the cables, to be sure it’s not cut , spoilt or pinched (what could damage the energy output, and generate some noise)
• check the good condition of the plugs (corrosion can damage/stop the power passage and the energy production)

Mechanical installation

Eletrical installation.

Accessories

Removable mounting kit for transom

Universal support for all kind of transoms

Cruising hydrogenerators range.

After-Sale Service

Cruising 600

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Choosing a Generator for Your Sailboat

• By Ed Sherman
• Updated: November 14, 2018

You can’t take it anymore: Your 1990s vintage cruising sailboat didn’t come equipped with a factory-­installed air-conditioning system or an alternating-current generator to power it and the other AC appliances you’ve brought aboard. Since you’ve owned the boat, though, you’ve turned into a real believer in global warming as you try to sleep through sweaty nights on board, and finally you’re ready to pull out your wallet and do something about it.

So, where do you begin? The first step is to analyze how much electrical power you are going to need. Since your boat had a basic shore-power system when you bought it, you already have some idea of your small-appliance usage, things such as hair dryers, the coffee maker and maybe even a small TV. But now you need to think in terms of running this same gear while at anchor. Additionally, if the standard-equipment shore-power option for your boat at the time of purchase was a 30-amp service, as is most often the case here in the United States, you might discover that it’s inadequate to run that new reverse-cycle air-conditioning system you’re dreaming about.

This is an area where, in my experience, a lot of boat owners go into denial as they discover that more power consumption adds considerable cost. Everything you’ve read about marine electrical systems so far tells you that air conditioning and refrigeration use a lot of power. But how much? The good news here is that these units have become more efficient in recent years and the power needs are not as great as they were when your boat was new. As an example, a modern 18,000 Btu reverse-cycle system from Dometic Corp. will need about 15 amps of AC power to get the job done. A 10,000 Btu unit is going to draw around 8 to 10 amps, depending on your location and whether you are heating or cooling.

Analyze Your Needs

The first step is to do an honest load analysis to see how much electrical power you will need. This is typically measured in thousands of watts, or kilowatts. The operative phrase here is: Don’t cheat. If you want to luxuriate in air-conditioned comfort 24-7 while cruising, it’ll cost you. Unlike powerboats, most cruising sailboats come equipped with liquefied petroleum gas stoves and ovens, so one of the major power consumers (an electric galley) is not a concern here.

All said, you are probably going to be looking at generators in the 4 to 12 kW size range. The typical owner of a 40-something-foot sailboat who wants to power up a reverse-cycle air-conditioning system, small galley appliances, a refrigeration system using either AC or DC power, a water heater and a battery charger is going to want an 8 kW generator. Larger boats that might end up having a clothes washer and dryer, larger reverse-cycle heating and cooling unit and water heater can easily end up in that 12 kW output range. The American Boat and Yacht Council offers a free trial membership with access to the relevant electrical power ­standard (E-11), including a complete load analysis worksheet for those who are so inclined and want a detailed account of their electrical needs. Simply go to abycinc.org to gain access via the consumer section of the site.

A quick way to determine your AC power needs is to look for the mandated label on each appliance. It is required to tell you either the operating voltage and amperage draw or the operating voltage and wattage.

Either way, a simple equation can be applied to get the info you need: Volts multiplied by amps equals watts; or watts divided by volts gives you an amperage value. Add the number of watts each device requires and you will get an idea of what size generator you’ll need. Remember that it takes 1,000 watts to make 1 kilowatt. Understand that this method will actually give you a result that does not take into account the fact that you might not be running all of your appliances simultaneously. The ABYC load analysis method found in the ABYC E-11 standard offers some diversity adjustments that are more conservative and reflective of the real world.

Although modern ­generators are not as sensitive to running with a light electrical load, most installers will tell you that running them at 70 to 80 percent of their maximum capacity is better for the engine. The risk here is carbon buildup in the engine’s combustion chambers if run with a light load for extended periods. So, this is a case where significant overkill is not such a good thing.

Practical Concerns

In addition to the electrical load you need to meet with your new generator, you should also be considering its weight and physical dimensions. Will the generator fit into the space you have available? The units I compared (see “Generators by the Numbers,” page 82) ranged in weight from a low of about 270 pounds for the 5 kW Fischer Panda to a high of just under 700 pounds for an 11.5 kW Kohler. This amount of weight dictates that when installing a generator on a monohull, you’re going to want to keep it on the centerline of the boat. Typically, this works out well because most sailboats built from the early ’90s on will have adequate space aft of the propulsion engine to fit in new generator. Multihulls offer more options on that front.

What might be a concern with the monohull is service access, not only for the generator itself, but for things like the propeller shaft stuffing box and shaft coupling. I’ve inspected many boats where the only way to access a leaking shaft seal was to lift the generator out of the way!

Wherever you end up installing your new generator, you need to be able to gain access to all the service points on the unit.

The physical dimensions of the generator could end up being a game changer too, so you’ll need to measure your boat’s available space carefully and compare that to the specifications for the units you are considering. You will also need to determine whether the unit will fit with a sound shield installed or not. Understand that some of the generators offer a sound shield as an option only. The presence of a sound shield, or your ability to insulate the space where you are going to have this generator mounted, could make a difference not only in size requirements but also noise issues while running.

As an example, comparing a Fischer Panda unit that comes with a standard sound shield, we get dimensions of 23 inches by 17 inches by 22 inches. A similarly rated Cummins Onan unit, which also comes with a standard sound shield, is 26 inches by 23 inches by 21 inches. A Westerbeke with a similar rating but with optional sound shield measures 36 inches by 23 inches by 25 inches. That 13-inch spread in length between the Fischer Panda and the Westerbeke could mean the difference between a doable install in the space available on your boat or not.

Finally, wherever you end up installing your new generator, you need to be able to gain access to all the service points on the unit. Can you get that oil filter off as installed? Can you access and change the water-pump impeller without needing an emergency ­chiropractic visit? These are questions that will need answers.

Power Perks

Several features related to newer generators are worth considering. One is whether the unit is equipped with digital controls that may also allow for self-diagnostics and integration to onboard networking that you or a former owner may have installed on the boat.

From a maintenance standpoint, you’ll also want to know whether the water-cooling system for the engine driving your generator is raw- or freshwater cooled. Raw water might save money initially, but will cost in the long run.

Buyers Beware

I can’t emphasize this enough: This sort of upgrade does not qualify as a do-it-yourself project unless you have ­considerable mechanical skills and experience, and labor will be a major addition to the overall cost of the installation.

Also, when you compare different units, study the supplied components carefully. Does the unit come with a remote display and control panel? What additional parts will you need? These will likely include an exhaust system, starter battery and cables, and raw-water supply hoses and a seacock. And don’t forget about wiring the generator ­into your existing, or possibly a replacement, AC ­distribution panel board. These items can add considerable cost above and beyond the generator prices shown in “Generators by the Numbers.”

If you are planning on cruising far afield with your new generator, you should also think about parts and service availability, not to mention its warranty.

Lastly, if you are planning on cruising far afield with your new generator, you should also think about parts and service availability, not to mention its warranty. As part of my ­research for this article, I looked at units from Cummins/Onan, Fischer Panda, Kohler, Northern Lights and Westerbeke. All five brands have extensive global dealer networks, so ­locating a service center that can help is just an internet search away. As for warranties, I’ve noted them in the “Generators by the Numbers” table. Keep in mind when reviewing this ­information that it is based on likely choices from the ­individual company’s offerings for a boat in the 35- to 45-foot size range. Also understand that the prices quoted are list price. Several of the dealers I spoke with suggested that discounts of $1,500 to $2,000 are quite common. That said, if you spot something you think is a deal, be certain of what you are actually getting, ­especially if it’s at a ­remarkably ­discounted price.

Ed Sherman is a frequent CW contributor, Boat of the Year judge and vice president of education for the American Boat and Yacht Council.

A green alternative

Considering the cost of installing a generator — estimated at $15,000 to $20,000, or possibly more depending on your boat and the power output selected — you might consider some alternatives.

How about essentially silent AC power via a direct-­current-to-alternating-current inverter and adequate storage capacity that relies on the latest high-capacity battery technology?

Marine electrical systems have evolved considerably over the past decade or so, and I’m at the point now where I question the need for an onboard AC generator for most cruisers, though some might still benefit from installing a DC generator to supplement solar-, wind- or water-driven charging solutions.

The current density of high-end absorbed glass mat and lithium-ion batteries has improved by 20 to 30 percent due to their inherent capacity compared to older flooded-cell batteries. They can also be discharged to deeper levels without damage and recharged much more quickly due to high absorption rates. I’m of the opinion that it might be time to look at alternative power if you are willing to spend the kind of money we are talking about with an AC generator upgrade for an older boat.

As quiet as they might claim to be, that incessant drone of an AC diesel generator, not to mention the however faint odor of diesel exhaust fumes, is going to be a reality. It’ll have to run all night if you want that AC keeping you cool.

Instead, you could run the DC generator in the morning to replenish your batteries from an overnight discharge. Or, let your solar panels and wind generator do the job. I like the concept of not having to run an engine continuously to get my AC power.

Generators By The Numbers

*All dimensions are with sound shield; **price includes sound shield; ***price does not include optional sound shield

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5 Best Wind Generators For Sailboats (2024)

Last Updated by

Daniel Wade

January 2, 2024

Wind generators, also known as micro turbines, have come a long way since their first appearance on the cruising scene back in the 1970's. Loud, relatively low output and large bladed, these forerunners of the modern day wind generators were both a mechanical marvel and a source of constant consternation. They were basically a small automotive alternator encased in an aluminum housing, with little thought into aesthetics or longevity. Cruisers equipped with an old Windbugger or K.I.S.S. wind generators come to mind as the loud boats in the anchorage no one wanted to be around.

As we all know, there are very few, if any, automotive products that last very long in a marine environment. A large stock of spare parts had to be stored in case of breakage, and daily maintenance consisted of checking the bearings, monitoring the voltage vs. wind speed for signs of decreased output, and rotating the blades into the wind when the boat position changed.

Today's best wind generators boast such features as CAD designed, self-feathering composite blades that are whisper quiet, brushless magnetic alternators, automatic braking and over-charge protection. Boxy aluminum housings have been replaced with sleek, carbon fiber and fiberglass nacelles.

While you may spend a small fortune on a wind generator that has all of these features and more, you can also opt for more budget friendly models, readily available from Amazon, Home Depot and other on-line retailers. The best wind generators are usually the most expensive, but when you are looking at the lower cost models, remember to add in the cost of wiring, mounting hardware, remote monitoring stations and installation, should you choose not to do the work yourself. Not all wind generators are purpose-built for the marine environment. Buyer beware: a turbine designed for the hobbyist on land will not stand up to the rigors of an offshore passage.

Table of contents

As with any mechanical device you are researching, it is a good idea to learn some of the terminology associated with the product. Not all of us know the meaning of 'swept area', 'power capture' or 'yaw error'. Likewise with the electrical side of the wind generator. Learning about output wattage, amps, and microprocessors can seem like a daunting task, but it is necessary to know these terms before you shell out hard earned cash for a quality wind generator.

Some features of wind generators, such as weather-proof coatings and low-noise operation, are common to all makes and models. The use of rare earth elements like Neodymium, (Nd2FE14B, used in magnetic rotors), can add hundreds of dollars to the price of some of these wind generators, but defiantly do add to the overall dependability of the unit.

Some of the more desirable things to look for in a wind generator are:

• Ease of Operation

Also known as plug-n-play, the simpler the set-up, the better. Choose a model that has built-in controllers, that ???makes for less complicated wiring runs. A remote monitor is handy to check on the status of the charging system without crawling into the battery room, or looking up to see if the blades are still turning. If you are ordering your generator and having it shipped, ask your salesman to be sure it has detailed assembly instructions and perhaps an owner's manual in either DVD or booklet form.

• Low Cut-In Speed 

Wind generators work best when the blades are humming along in 20 knots of wind, but that's not always the case. Low cut-in speed means your batteries are getting a charge in the lightest of airs, if only a trickle charge.

If you happen to be ashore when the wind kicks up, you don't want your turbine to spin wildly out of control. Some generators feature a type of automatic speed governor that slows the blades down before they self destruct. Back in the day, you had to pull down on a cord to apply the brakes, then climb up the mast or mounting pole and manually tie off the blades.

• Over-Charge Protection

A 'brake' also kicks in when the batteries are nearing or at full capacity, to prevent overcharging. Some controllers slow the rotation of the blades, others 'dump' the excess power generated through a resistor and heat sink. Wiring an in line reset-able fuse can prevent damage to your batteries should a malfunction occur within the charging system.

• Portability

If you are one of those part-time sailors who cruises for a few months, then dry-docks your vessel for the off-season, choose a light-weight portable wind generator you can set up at home to off-set your electric bill. In case of a hurricane or other emergency when there is no power for days at a time, your wind generator can power cell phone chargers, laptops and rechargeable battery stations. Removing your wind generator and locking it away in the cabin also deters thieves. Portable wind generators that are light can be mounted on higher surfaces without worrying about upsetting the balance of your boat. The heavier the generator, the lower it should be mounted, allowing for safe passage under and around those spinning blades, of course!

It is also a good idea to know your boat's needs and desires before settling for a low cost, low output wind generator. Everything that runs off a battery, including the DC to AC inverter, should be listed, along with their amp/hour draw, to determine how much power you will need to generate. Compare your toys with your reserve amps of your house battery bank. Do you just have a few LED bulbs and a masthead light to run at anchor? Then you can get by with a low output generator. Are you keeping a keg cooler, stereo, disco ball and Netflix going all night? When underway, are you powering SSB, weatherfax, VHF and radar? Then you need a rack full of batteries, and a wind generator with the capacity to keep them topped off.

Speaking of batteries, make sure the wind generator you purchase can charge all the different batteries available. Even if you only have wet-cell lead/acid marine batteries now, you may upgrade to AGM, Gel or even LiFeMgPO4 (Lithium Iron Magnesium Phosphate) batteries in the future. Some wind generators and their controllers are not advanced enough to charge these newer power sources.

Unless you are well versed in the application of electrical theory and DC current, you probably don't know much about wire size and current loss. Even the best wind generator will not function as advertised if the power can not get from the blades to the battery. If you have a long run from your generator to the battery bank you intend to charge, make sure your wires are correctly sized to prevent line loss from resistance and over heating. Most installation manuals will have a wire chart included for DIY installations, and there is always a help line to the manufacturer.

Here are four out of the dozens of wind generators out there that have positive reviews and some of the most desirable features.

1.) Superwind 350, 353

This German manufactured turbine features their patented Auto-Feathering Overspeed-Avoidance System. This is basically the same method a helicopter uses to gain lift, and settle back down. As the wind speed reaches 25 knots, the blades 'feather', or dump air, making them less efficient, and slowing their speed. As the wind lessens, the blades re-pitch, becoming more efficient. This action delivers a steady flow of charging current to the batteries, without going into a shut-down mode to prevent overcharging, as some models do. The Superwind generators also can be combined with solar panels and conventional diesel generators. The Superwind generator family also uses a brushless A/C stator for maximum control of noise and radio interference while the unit is producing power. Two sets of bearings in the 350 make for smoother operation and overall longer bearing life. Available in 12v, 24v, or 48v outputs. At close to 30 lbs, these units are well built and dependable. With a price tag right around $2,700 for the Superwind 350 kit, you can expect German Engineering at it's finest.  https://www.superwind.com/superwind-350-353/

2.) Automaxx

The Automaxx line of wind generators comes in 12v, 24v 48v models, in outputs from 400w up to 1500w. Survival wind speeds are listed at 110mph, but we hope you would never have to put that spec to the test. With very low cut-in speeds of less than 6mph, you will get charging amps on the slightest breeze. All their models come with auto-braking and manual braking system protection, over charge and over-speed protection. The 3600 rotation of the power head keeps the unit into the wind, even when you are docked or med-moored. Simple plug and play setup with an internal MPPT (Maximum Power Point Tracking) charge controller makes the DB400 an easy to install unit, while their other models feature a remote charge controller. Works well when combined with solar chargers. At 16.75 lbs., it is lighter in weight than the Superwind, and it's seven times less expensive at around $400.00 for the DB400.

https://www.automaxxwindmill.com/

3.) MarineKinetix MK4

One look at this brand's marketing home page is like an advanced course in wind generator physics. The list of specs for it's models is truly impressive. Not only do they boast all the latest technologies featured in their product, they explain all the scientific jargon they use in terms us simple sailors can understand. They have been providing wind generators to the sailing community for 8 years now, and have a devoted following.

If you need to know the difference between $400.00 wind generators and $1,800 units, check out the product overview section of their website.

The MarineKinetix brand has the the industries best 3 year limited warranty, so they must be pretty sure about their product.

The 12v models of this brand are currently out of stock, due to parts supplier back-orders, but if you are in the market, there are plenty of 24v and 48v units in stock.  https://store.marinebeam.com/marinekinetix-mk4-marine-wind-generator/

4.) Rutland 1200

One of the quieter wind generators out there, the U.K. made Rutland has a long track record of dependability and customer satisfaction. A manual switch is used to stop the blades when high wind is expected, there is no auto-brake. The Rutland can be combined with solar panels up to 20A, and can be also be used with deep cycle gel or AGM batteries, and there is a remote digital display available. One of the Rutland's best features is it's Tri-namic Blade profile design, which achieves low start-up speeds, silent operation in any wind, and maximum power transfer from wind to rotor. Overall good performance and features for the $1,600.00 price tag. https://www.emarineinc.com/Rutland-1200-Wind-Turbine

5.) DuoGen-3

Wind generators are a fairly common sight in most anchorages, and towable generating devices have been around for some time. The DuoGen-3 combines the two into one multi-use charging system. Underway, the high strength carbon fiber mast is lowered down to submerge the blades. At anchor, the unit functions like a typical wind generator. The results are impressive. In the water mode, the DuoGen-3 generates 200 Watts @ 16 amps cruising at 8 knots. Wind generators do not do well sailing downwind, so this may just be the answer. Available in 12v and 24v versions. Charging regulators are not included, so monitors and controllers have to be matched to the unit and sourced locally. https://eclectic-energy.co.uk/

Choosing the right wind generator for your vessel should be a pretty straightforward process, once you have an idea of your needs, the area you will be cruising in, and how long you expect to be 'off the grid'. If one generator is simply not enough because of the size of your battery banks and the load you put on them, you may need to purchase a pair of turbines. Customer support and availability of parts may be the determining factor in your purchase. Talk to other wind generator owners, and get a feel for what they have experienced with their current of former wind generators.

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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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Hacking a trolling motor into a towed type generator

• Add to quote

You might be thinking something like this? I see a lot of drag for a small sailboat...  

guitarguy56 said: You might be thinking something like this? I see a lot of drag for a small sailboat... Tow Generator at its Best - YouTube Click to expand...

I have no idea whether it would be practical, but I would guess your estimate of 10 amps is exceedingly optimistic... I use a towed generator from Hamilton Ferris, a fantastic piece of gear. I'm always surprised more cruisers on passage don't use water generators, though they do inhibit your ability to fish... However, as effective as they are, mine generally puts out roughly 1 amp per knot of boat speed, perhaps a bit more above 5-6 knots... I probably see spurts close to 10 amps periodically, but getting that sort of performance consistently out of a cobbled-together arrangement with a trolling motor seems unlikely to me...  

I know a local person that runs the class 40 dragon and there top shelf land/sea or whatever water generator does NOT become efficient until there above 8 knots at which point the output is massive  

No doubt you're thinking of the hydrogenerators from Watt & Sea... VERY pricey, the cruising version is still over $5K, if memory serves... "Call for Quote" is rarely an encouraging sign... (grin) Watt and Sea Cruising Hydrogenerator Bernard Stamm recently was forced to retire from the Vendee Globe, due to the damage/failure of his water generators... Every boat in the race is using them, that's how dependent these guys (and girls) have become upon them...  

The problem is that using a motor as a generator is that the voltage output is dependent on RPM so below a certain RPM you will not get any charge. Which is why motor charging systems use an alternator, which provide a more consistent voltage. And you would definitely need a bigger prop or at least a hi-thrust version. A better system would be a prop driving an alternator but would be much more DIY. A quick google will show you that it is not really feasible.  

What is the drag these produce on speed? I have often looked at these and wanted more informatuion on them. Jon could you expand on your experiences with the Ferris one, I have seen them. dave  

chef2sail said: What is the drag these produce on speed? I have often looked at these and wanted more informatuion on them. Jon could you expand on your experiences with the Ferris one, I have seen them. Click to expand...

Get a used electric troller and try it. I think the Watt and Sea ones start at $3200 or thereabouts.  

I will be watching this thread... Not because I need a generator but because this is "old school" problem solving just like my father taught me and I would love to see it work. I will say that if I trip over an old trolling motor I will rig it up for fun.  

A few more pullies and my father would have this setup powering everything AND charging the batteries  

Curious why guitar guy is down on wind. It's come a long way.Much quieter. Been reading Nigel Calder and others. Figured out an energy budget. Decided to go with solar and two D400s with extra alternator output. Don't like diesel generators - noise,more holes in the boat, expensive watts and some thing else to maintain. ?Did I make a mistake? Figured the marriage of wind and solar made sense as usually get one or the other and if the lord smiles both. Ferris is close to where I live. Very nice people and informative.They sell a unit that can be used as wnd or water generator. Seemed it would work well as water generator but thought wind configuration was problematic for my application . Like the idea of rigid water generators- clean, relatively small and light- simple concept. On sugar scoop boats would be easy to mount. Trailing stuff- not so much. Hope they come down in price. Very interesting thread thanks all.  

Outbound... on the contrary I'm for all forms of power... I'm quoting what others have mentioned regarding wind energy not being a good form of energy producing device... I'm sure there are those making the best use of wind together with solar... but for a 'size' factor and stored energy then fossil fuels can't be beat at the moment... the best we could do is use solar energy to break down water into it's two components and use the hydrogen to run a generator but that is super not efficient... if the entire boat was coated with solar cells or some sort of energy gathering paint or surface we could hopefully generate enough electricity for all the needs of the boat and then some... to date nothing is viable... I work at Boeing in the advance research group looking for all sorts of new and wonderful materials to be used on the next generation of aircraft... and trust me we've looked!  

The main advantage of the trolling motor, besides being cheap, is that it is rigidly mounted not dragged. I've trolled while coastal cruising and its a constant concern getting snagged, so I wouldn't want to drag a generator if I could avoid it. Google shows that I'm not the first person to think of this, but most of the google results were trolling motors used as static water generators in fast moving streams, haha mostly by rednecks I'm keeping an eye open now for an old or broken trolling motor (I only need the shaft and torpedo/prop, the control head could be broken) if anyone sees one or has one let me know I'm not sure how to make a proper prop for it yet though  

peterchech said: I'm not sure how to make a proper prop for it yet though Click to expand...

I've always wondered why sailboat manufacturers have not designed some sort of "tunnel" turbine system into their hulls, much like the little speed transducers but on a larger scale. The tunnel could be easily covered for racing/min. drag purposes but would be a great asset to any cruiser. Instead of having a contraption hung off the stern or a dragged propeller which will inevitably snag something or get mistaken for food by a shark or tuna, an in-hull design would simplify the concept. As far as using an auto alternator- they require WAY too high an RPM to produce any usable current. Permanent magnet motors are generally used for low RPM 12/24v power. They aren't cheap because all the homemade wind power folks are looking for them. http://www.windynation.com/articles/wind/making-wind-power-how-choose-right-motor  

smurphny said: I've always wondered why sailboat manufacturers have not designed some sort of "tunnel" turbine system into their hulls, much like the little speed transducers but on a larger scale. The tunnel could be easily covered for racing/min. drag purposes but would be a great asset to any cruiser. Instead of having a contraption hung off the stern or a dragged propeller which will inevitably snag something or get mistaken for food by a shark or tuna, an in-hull design would simplify the concept. Click to expand...

Actually, is there a place on this forum where I could post something about wanting an old or broken trolling motor? I would certainly post the results on the forum whether it works or not.  

http://www.ampair.com/downloads/Aquair 100 Data Sheet.pdf All the work is already done the published output figures are rather pathetic at 2 amps ? I fail to understand the desire to repeat the many well documented failed attempts at producing a meaningful amount of power ?  

The PDF that u linked to claims 5 amps at 6 knots, that's not too bad. A 50w solar panel is only putting out 1.5-2 amps in real world conditions, its still useful no?  

bobmcgov said: Tom: The Ampair is a bit notorious -- poor as a wind turbine, dismal as a hydro-gen (mostly for corrosion reasons.) The same rotor geometry can't be optimized for two fluids whose density is as different as water and air. Click to expand...

GrahamO said: I was thinking of an alternative to my (heavily corroded) Ferris... Click to expand...

I decided to go 100% solar panel last year and built a simple arch to mount 2 large panels over the stern. They produce around 200 watts peak. The key to using just solar (unless you have a lot of space) is to pare down the amp/hrs of the equipment. I went to all l.e.d. lighting, changed to a small, super-efficient fridge, and did a detailed analysis of all my power usage. I'm very conscious of how long I use power hogs like the SSB and VHF and have an energy budget for stuff like that. Extended periods of dense cloudiness can be a problem but I can always fire up the iron genny if push comes to shove.  

Why wouldn't a small secondary propeller/shaft log work? The prop could be a collapsible design, optimized to work producing torque back to a generator. Again, it would have to be something designed into the hull during construction. It just seems like an oversight on the part of boat manufacturers to ignore an obvious need of all cruising sailors. Avoiding the necessity of hanging whatever kind of largely ineffective contraption on the boat, you would think, would be a priority. There is one internal shaft in all boats with inboards- the prop shaft. At least in my boat, it turns at quite a clip when free-wheeling. I've thought about putting some sort of brake on it to minimize wear on turning parts and to stop the "whirring sound". (No, putting it in gear does not stop it.) It would seem that a pulley on the prop shaft could be used to supply rotation to an alternator/perm. mag. motor. The additional drag would be minimal because the prop is creating drag already.  

I don't know, sounds like an awful lot of additional drag to be carrying around all the time, for a form of power generation that's only gonna be used sparingly by the overwhelming percentage of cruisers... Some people already are using some sort of PTO setup using their propulsion shaft, but I haven't heard of it producing particularly exceptional results... It's a mystery to me, why so many people appear to think that simply towing a spinner on a 75' torque line when you want to make some amps underway is such a big deal, or monumental inconvenience, or so fraught with potential problems...  

That's great info Bobmcgov. Thanks for posting it. When I was deciding which windvane to install, Yves Gelinas (Cape Horn unit) sent a DVD of his circumnavigation on Jean-du-Sud. It's a great DVD and won a number of awards. During his trip, towing a "bird" type unit, he lost a number of them to large fish and wound up actually having to construct a new one. Having done a bit of fishing for large fish like Marlin, Tuna, and Shark, I know they are VERY attracted to things making noise and spinning around in wakes. This has got to be more than a small problem when towing anything like this. A 300# Mako could take one of those in an instant and test the strength of the rail it was attached to. Jon, have you ever had a fish try to make lunch out of the spinner?  

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