# Hacking a trolling motor into a towed type generator



## peterchech (Sep 2, 2011)

Has anyone seen this done?

Its cheap, 12 volts, and draws about 40 amps. so if run wired to a diode then the house bank and powered up I speculate it could possibly pump out 10 amps. Total guess.

Might need a bigger prop, or one with a shallower angle, but I don't see why this couldn't work and if I'm right why more cheap sailors like myself haven't done it. It's even cheaper than solar if it works!


----------



## guitarguy56 (Oct 10, 2012)

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


----------



## JonEisberg (Dec 3, 2010)

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...


----------



## JonEisberg (Dec 3, 2010)

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


Damn, that vid should be titled "Tow Generator at its WORST", that is one nasty looking set-up... The prop should not be breaking the surface like that, and whatever line they're using is totally unsuitable, becoming kinked and whipping around like that...


----------



## peterchech (Sep 2, 2011)

JonEisberg said:


> Damn, that vid should be titled "Tow Generator at its WORST", that is one nasty looking set-up... The prop should not be breaking the surface like that, and whatever line they're using is totally unsuitable, becoming kinked and whipping around like that...


I guess the point would be not to tow it with a line, but rather to mount it directly off the transom using its existing shaft as a solid mount.


----------



## tommays (Sep 9, 2008)

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


----------



## JonEisberg (Dec 3, 2010)

tommays said:


> 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...


----------



## tschmidty (Sep 25, 2008)

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.


----------



## chef2sail (Nov 27, 2007)

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


----------



## PaulinVictoria (Aug 23, 2009)

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


----------



## bobmcgov (Jul 19, 2007)

Trolling motors are theoretically a decent match for a tow-driven prop. But there's the real problem people forget when they confuse propellers with rotors: props PUSH water or air, rotors are PUSHED BY water or air. The blade pitch & convexity on any propeller are exactly wrong for generating power. It's alongside the people who set a box fan outside as a "cheap wind turbine" and attach it to a car battery. Wrong power band, wrong blade geometry.

There have been attempts at dual-purpose drivelines -- engine or hybrid-electric driven propeller in one mode, then rotate the blades 180 degrees and drive a PM alternator using boatspeed. I guess they work okay, tho the complexity invites trouble. Intriguing idea, tho -- esp. as more boat owners opt for variable-pitch props.

Nothing this side of dead dinosaurs puts out amps like a good hydro-gen. The prop diameter can be quite small -- water is 100 times denser than air. Drag is an interesting topic: I'd say at the boat speeds at which a water rotor becomes useful (6+ kts), its drag becomes trivial compared to wave-making losses; on planing boats, its drag is trivial compared to available horsepower. At low boatspeeds, the drag would be substantial -- but you may as well pull it out of the water then, because it is only making 3A anyhow.


----------



## guitarguy56 (Oct 10, 2012)

If I were the designer/architect of these yachts I would simply put two inlets allowing water to enter a tube and run the fan/prop/blades that in turn runs the generator... so either way whether the boat is leeing to either side one of the generators is always turning, best when the sailboat is tracking straight you wind up double generating units... the water simply comes in and out the tube... no lines, no unsightly cables, or breaking water as in the video... and probably very little drag... best example would be a liquid flowmeter...


----------



## blutoyz (Oct 28, 2012)

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.


----------



## bobmcgov (Jul 19, 2007)

guitarguy56 said:


> If I were the designer/architect of these yachts I would simply put two inlets allowing water to enter a tube and run the fan/prop/blades that in turn runs the generator... so either way whether the boat is leeing to either side one of the generators is always turning, best when the sailboat is tracking straight you wind up double generating units... the water simply comes in and out the tube... no lines, no unsightly cables, or breaking water as in the video... and probably very little drag... best example would be a liquid flowmeter...


It has been tried, & the idea of a ducted or nacelled turbine does have much to recommend it. But imagine the fun when you suck a grocery bag into your intake, and you have to clear a shrouded, plastic-tangled rotor which may well be below waterline.... Can't put an intake screen over it, because the needed degree of solidity will massacre your flow rate. Which, BTW, it always the problem with all ducted, low-pressure turbines. The plumbing adds a shocking amount of drag and turbulence. That creates back pressure, so the water flowing over the skin of your hull decides to go right on by the intake. Bzzzzt. You'd need a proper manta-mouth scoop to overcome that, & I wager the drag on the boat would be many times higher than a naked propeller trailing behind. Which, if it eats a Kroger bag, can be hinged up, cleared, and lowered back down.


----------



## tschmidty (Sep 25, 2008)

Here is an interesting page with some good info on using an alternator.

Using an Alternator in Renewable Energy Projects

You know this would be fairly easy to rig up something like this, with a floating paddle wheel set up and the whole thing pivoted where it connects to the boat. You would just need to work out the size of the wheel and pulley in order to get the rpms correct at the alternator.


----------



## blutoyz (Oct 28, 2012)

tschmidty said:


> Here is an interesting page with some good info on using an alternator.
> 
> Using an Alternator in Renewable Energy Projects
> 
> You know this would be fairly easy to rig up something like this, with a floating paddle wheel set up and the whole thing pivoted where it connects to the boat. You would just need to work out the size of the wheel and pulley in order to get the rpms correct at the alternator.


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


----------



## JonEisberg (Dec 3, 2010)

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.


Difficult to quantify the drag, but I would classify it as barely noticeable... Just a guess, at between 5 and 6 knots, perhaps a quarter of a knot, at most? Even that estimate is probably high...

I'm a big fan of Ferris products, and I have the conversion kit to turn my generator into a wind-powered generator when at anchor... Takes a bit of time to make the switch and hoist in the rig, but well worth the effort if I'm gonna be someplace for awhile, and I really like the ability to stow all the gear below when not in use...










IMHO, a towed generator is really only suitable for offshore, or off soundings where there's no possibility of snagging a fishing buoy, etc... If you're using one on a coastal trip, you'd best keep a sharp lookout, and take it in at night. Only time I've ever lost a spinner, was after passing on the up-current side of a deepwater fishing float on a passage between Nantucket and Nova Scotia - just a stupid move on my part, you have to remember when you have it deployed, and certainly pass on the leeward or down-current side of any obstruction...

There's a bit of a learning curve in learning how to deploy and retrieve the spinner, but no big deal... All in all, a great piece of gear... Here it is, making good amps one day (and all night long) somewhere in the Bahamas...


----------



## bobmcgov (Jul 19, 2007)

Whup! Time out. Regards any sort of paddlewheel, etc....

As sailors, we understand the difference between a *lifting surface* (when your sails are behaving like wings, generating fluid-dynamical forces) and a *drag body* (when you are sailing DDW and your working sails are just big old bags, being pushed against by the wind.)

Drag bodies stink for electricity generation. As tschmidty notes above, alternators produce better at higher RPMs, & the fastest part of a drag-body paddlewheel (tips of the blades) can never move faster than the water moving past it. You'll be lucky to get 100 rpms out of it, & the hub will be moving maybe 6/10s of a knot.

However. An axial thrust rotor (looks like a propeller) can achieve tip speeds many, many times the speed of the incoming water. The blades do this just as your sails do on a beam reach, by splitting the flow and generating lift over both surfaces. I can't find data on the Watt&Sea hydro-gen, but I'd bet it is spinning several hundred RPM at cruising speeds.










W&S have basically saved us the trouble of brainstorming the perfect unit -- they've gone & built it. Although ... I'm not a fan generally of downstream turbines. Face the blade to the front for maximum output. I am guessing they face it aft for impact protection, which is a fair compromise.

A trolling motor with a correctly-pitched prop might just do, however. A clever person with access to a 3D printer could possibly mirror a thrust propeller & print one out in polycarbonate.

The other thing about hydro-gens, of course, its that they only work when you are sailing. Good for driving the autopilot. But they won't keep your beer cold at anchor.


----------



## guitarguy56 (Oct 10, 2012)

bobmcgov said:


> It has been tried, & the idea of a ducted or nacelled turbine does have much to recommend it. But imagine the fun when you suck a grocery bag into your intake, and you have to clear a shrouded, plastic-tangled rotor which may well be below waterline.... Can't put an intake screen over it, because the needed degree of solidity will massacre your flow rate. Which, BTW, it always the problem with all ducted, low-pressure turbines. The plumbing adds a shocking amount of drag and turbulence. That creates back pressure, so the water flowing over the skin of your hull decides to go right on by the intake. Bzzzzt. You'd need a proper manta-mouth scoop to overcome that, & I wager the drag on the boat would be many times higher than a naked propeller trailing behind. Which, if it eats a Kroger bag, can be hinged up, cleared, and lowered back down.


Agreed... it was just a design idea and the working would of course be that of the designer to get it working right... that being said the real way to get energy out of the ocean is to get the voltage potential directly from the seawater... per square meter of electricity the scientists are getting around .1 to 2 watts currently... the polymers being used are being slowly designed to obtain 5 watts per square meter... sure it's not feasible to have some 10 meter by 10 meter polymer mat floating behind the boat to generate 500 watts... I can see the drag this would make... 

It would be interesting what advances come later but at the current technologies we have: solar and gas generator (Honda type generator, alternator on the engine, etc) is the best at generating the electricity we need for the boat... wind energy would be last on the list... pedal power with a generator would be a good temporary solution... anything I missed?


----------



## outbound (Dec 3, 2012)

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.


----------



## guitarguy56 (Oct 10, 2012)

outbound said:


> 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!


----------



## peterchech (Sep 2, 2011)

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 ********

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


----------



## smurphny (Feb 20, 2009)

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


----------



## bljones (Oct 13, 2008)

peterchech said:


> I'm not sure how to make a proper prop for it yet though


I'm liking the thinking behind this idea.

peter, before investing too much effort making a prop, why not just turn the motor 180 degrees? now the blade orientation is reversed (tractor rather than pusher prop). See if it works. if it does provide some output you just have to find a way to increase it.


----------



## bobmcgov (Jul 19, 2007)

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.


See post #14, above. Cutting a tunnel into the hull simpler than a hinged armature off the transom? No. And it WILL suck in plastic, floating line, kelp, very sad fishies ....

But the biggest problem is that, unlike a speed transducer, a 20A permanent magnet alternator attached to hungry batteries _pushes back_. Substantial torque is required to spin one. Add the unavoidable friction from any sort of ducting, and you create a pressure 'bubble' at the tunnel entrance. Unlike the fluid in a steam power plant or hydropower install, seawater is not constrained. It doesn't *have* to go into your little tunnel. It can right on around it. The combination, then, of reduced flow rates and slowed-down incoming water would wreck your output. In low pressure, unconstrained situations, ducting is a net loser. A bare rotor generates less backpressure.

I have thought a hydro-gen could usefully be mounted down low, perhaps even slip-fit into a keel bulb. You get cleaner, heavier water down there. Trick would be protecting it in groundings. A little skeg, perhaps, or a small ring around it. And again, many many sailors these days are opting for variable-pitch propellers, even with their greater cost & complexity. For an integrated system (something other than a transom mount like W&S), you could use a DC motor and variable pitch prop as both your driveline and hydro-gen. A small diesel or gasoline engine, bussed to a LiIon battery bank, would create Prius-like efficiency under power. When sailing, you put the motor in reverse to lock the prop blades that direction, then let the propeller drive your DC motor as an alternator.

Other advantages of this setup: 100% torque at all RPMs. Engine can run at optimal speed all the time, with prop speed controlled by the DC motor. No transmission required. You can situate the engine wherever convenient.

Disadvantages are loss of redundancy -- your drive system is your generating system -- complexity, cost, and the tendency (paging Boeing ) of exotic batteries to overheat in some instances. BTW, this idea has also been done in some high-end boats -- forget the names of the manufacturers. Given solar PV has dropped to $1 a watt and power densities have more than doubled in the past 10 yrs, it is hard for most sailors to justify the cost & complexity of an integrated hydro system. Especially since our boats spend 90% of their time not moving, or motoring.


----------



## peterchech (Sep 2, 2011)

bljones said:


> I'm liking the thinking behind this idea.
> 
> peter, before investing too much effort making a prop, why not just turn the motor 180 degrees? now the blade orientation is reversed (tractor rather than pusher prop). See if it works. if it does provide some output you just have to find a way to increase it.


I was actually thinking to just flip the prop around at first, since the unit will probably be more stable in a prop-aft position. I have never owned one of these so I don't know if the props can just be flipped around like that, but you're absolutely right, I would try with the original prop first.

Like I said, if anyone has an old or broken one lying around, I will pay the shipping to get it to me ;-)


----------



## peterchech (Sep 2, 2011)

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.


----------



## smurphny (Feb 20, 2009)

bobmcgov said:


> See post #14, above. Cutting a tunnel into the hull simpler than a hinged armature off the transom? No. And it WILL suck in plastic, floating line, kelp, very sad fishies ....
> 
> But the biggest problem is that, unlike a speed transducer, a 20A permanent magnet alternator attached to hungry batteries _pushes back_. Substantial torque is required to spin one. Add the unavoidable friction from any sort of ducting, and you create a pressure 'bubble' at the tunnel entrance. Unlike the fluid in a steam power plant or hydropower install, seawater is not constrained. It doesn't *have* to go into your little tunnel. It can right on around it. The combination, then, of reduced flow rates and slowed-down incoming water would wreck your output. In low pressure, unconstrained situations, ducting is a net loser. A bare rotor generates less backpressure.
> 
> ...


Stuff would certainly get into any device that funnels water but I don't think it would be an insurmountable engineering problem to make something accessible from inside the boat. Maybe a trunk. As long as it did not catch and hold things like lobster line, it could be cleaned by just diving down. Not a problem anywhere but in shark country. Putting another hole in the bottom is ALWAYS a bad idea but it would be for a good cause. The little speed sending units work on the paddle-wheel principle which seems less likely to ingest flotsam than a tube. I cannot believe that with modern engineering, something like this can't be designed into a hull structure.


----------



## eherlihy (Jan 2, 2007)

bobmcgov said:


> See post #14, above. Cutting a tunnel into the hull simpler than a hinged armature off the transom? No. And it WILL suck in plastic, floating line, kelp, very sad fishies ....


Possibly resulting in situations like this: Answers to Physics Questions


----------



## guitarguy56 (Oct 10, 2012)

smurphny said:


> Stuff would certainly get into any device that funnels water but I don't think it would be an insurmountable engineering problem to make something accessible from inside the boat.





> The little speed sending units work on the paddle-wheel principle which seems less likely to ingest flotsam than a tube. I cannot believe that with modern engineering, something like this can't be designed into a hull structure.


Yes... my original intent to have some sort of inlet that scoops water... maybe a 'maserator' forward of the generator unit to break up pieces of junk into small enough pieces it would not jam the blades of the unit... just an idea... 

Another method would be the 'free fall gravity' method of scooping in water into a tank and using the gravity of the water through pipes to turn a generator as in hydropower... water comes in and water goes out... electricity is made in the process... wouldn't have to worry about junk collected and clogging up the inlet... of course this opens the hull to two or more thru hole fittings... :hothead

I prefer a less damaging method and that is solar and some combination of solar and a second non intrusive source of energy... good ideas... the trolling motor method may work but may as well use wind power while under way... same principle... one water, the other in air...:laugher


----------



## tommays (Sep 9, 2008)

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 ?


----------



## peterchech (Sep 2, 2011)

tommays said:


> 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?


----------



## tommays (Sep 9, 2008)

Because on the power in water graph its 5 amps at 10 knots and about 2 amps at the 5.5 knots your most likely to be making 

And the same numbers come up on every unit made they all need to go above 8 knots to start putting a useful amount of power

NOW if they worked well at 5 knots i would be wanting to save the money and DIY myself


----------



## bobmcgov (Jul 19, 2007)

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.

The Watt&Sea is a dedicated hydro-gen. The cruising version will put out 10+ amps at 5 kts boat speed (125W); at 7.5 kts, that output doubles to 260W; if your boat can hit 9 kts, you will be seeing 500W ([email protected]).










That is real output. This unit is not a toy. It IS hideously expensive -- but unlike the Ampair, you get pretty nice engineering for your money. If you have a long waterline & regularly make 3000 mile tradewinds passages, the W&S would be a good fit. If you mostly bob around the Chesapeake in a 27 footer, not a wise use of funds.

For solar PV, monocrystalline, you'd need about 15 sqft of panel surface to see [email protected] That's reasonable if you have davits or a radar arch. Hydro-gen works at night, solar panels work on the hook. Wind sometimes works everywhere, but as someone who has lived with a wind turbine for ten years, I'm not totally sure we want one on the boat. Lucky to see 10A from the typical 4' diameter turbine; you'd need a 20+ mph breeze for that. Good choice for the Eastern Caribbean.


----------



## smurphny (Feb 20, 2009)

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.


----------



## JonEisberg (Dec 3, 2010)

guitarguy56 said:


> 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...


I realize that may be the opinion of others and not your own, but such an assessment surprises me... If nothing else, it does not sound like the opinion of a _sailor_... (grin)

Of course, the effectiveness of wind power is going to depend greatly on where you sail, it's not gonna be of much value in places like the Chesapeake or LI Sound in the summertime... but in places like the Caribbean and Bahamas, IMHO it can be a very effective means of making amps, around the clock, and on a very small footprint on the deck of a smaller boat... A much more effective use of "space" on a small boat than solar, IMHO - although some combination of both is the best solution, of course...

Perhaps it's true that fossil fuels are still tough to beat, but for me, one of the greatest pleasures to spending a winter down south, for example, is in the ability to truly get "off the grid"... Reducing your dependence on diesel or gasoline, remaining self sufficient on wind, solar, and water generation of power can be immensely satisfying, and in large measure what the whole point of cruising under sail is all about, at least for me... Always a disappointment, if I ever have to run an engine simply for the purpose of battery charging...

Again, I'm always surprised that more voyaging sailors don't avail themselves of water power... Water generators always receive high marks in the gear ratings from an event like the ARC, for example, at least from the relative handful of boats that use them... Seems like a no-brainer, to me...


----------



## GrahamO (Apr 4, 2012)

I was thinking of an alternative to my (heavily corroded) Ferris then I found this......










Kills two birds with one stone (although it is remarkable how LITTLE power all that work produces......)

I suspect I can wire it directly into my Ferris panel.

Graham


----------



## peterchech (Sep 2, 2011)

GrahamO said:


> I was thinking of an alternative to my (heavily corroded) Ferris then I found this......
> 
> 
> 
> ...


I would hate to be crew on your boat with that contraption on board


----------



## guitarguy56 (Oct 10, 2012)

All these gadgets... why not do it with your shoes...










Lots of ideas but the real one is the 30-100kw generator that uses solely the power of the boat, sun, wind, or any combination that is practical on a vessel without all the obstructions encountered today with these gadgets... 

I'll wait till then... in the mean time I have two 144 watt solar panels I will install on my dodger and along with my Honda 2000 watt genny... I think I have enough to get by... eventually I'll come up with another solution to add 50-200 watts later...


----------



## JonEisberg (Dec 3, 2010)

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.


I'm amazed Ampair is still in business, that is an amazingly clunky and heavy piece of gear... They are pretty quiet in the wind mode, I'll give them that - but that's probably because they are doing so little...

Anyone interested in a hybrid/convertible setup, Hamilton Ferris is the way to go, IMHO... More productive in wind mode, and far more compact and easier to stow...



GrahamO said:


> I was thinking of an alternative to my (heavily corroded) Ferris...


Corrosion can definitely be an issue with these generators, when in the water mode on the stern rail, they certainly live in a tough environment...

I'm surprised Ham doesn't offer a protective cover as an option, I'd highly recommend making one out of Stamoid, or similar, to anyone considering one of these units, you really want to protect these things from the elements as much as possible...


----------



## smurphny (Feb 20, 2009)

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.


----------



## JonEisberg (Dec 3, 2010)

smurphny said:


> 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...


----------



## bobmcgov (Jul 19, 2007)

smurphny said:


> 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.


Smurf: A secondary 'prop' would work -- best if it were down low, perhaps integrated with the keel. There's a lot of aeration and turbulence near the water's surface and the flat runs of the hull. A freewheeling prop doesn't create much drag, tho with any kind of real boatspeed, a cruiser would want it loaded anyhow.

But a *loaded* prop/rotor creates a good deal of drag. So belting your freewheeling drive shaft as in paragraph 2 would make a big difference in drag, with minimal payback. I think it was MIT that found a locked or loaded prop has over 3x the drag of a freewheeling one. No free lunch: if you are pulling amps off any kind of water generator, you are slowing the boat down. So make damned sure you are pulling real amps, to pay for it.

Second issue, as mentioned in a post above: a propeller is designed to drive water, not to be driven by it. Even turning the prop 180 degrees does not solve that issue, tho it at least puts the camber on the correct side. You actually have to rotate 180 degrees *and mirror* a prop to get a proper lifting rotor for power generation. You *need* a lifting rotor's efficiency, because an inefficient rotor (drag body, like the paddlewheel ideas) would simply cavitate when attached to a serious alternator. It spins like hell in unloaded condition, so you think "Aha! Let's capture that energy!" Soon as you hook it to the batteries, it stops dead. That's where wild-hair schemes and Fluid Dynamics part ways. In a contest between Physics and wishful thinking, my money is on Physics.

P=W/T. Power is Work done over Time. Work is defined as a force operating over some distance -- like an alternator being turned a certain number of revs against the resistance of its energized coils. Your propeller/rotor has to be able to reap enough kinetic energy from the water flowing thru it to equal the watt-hours you want, plus a little. To do that in a reasonable-sized swept area, on a slow-moving sailboat, without totally killing boat speed requires a lifting rotor with very good lift/drag performance. Your basic boat propeller isn't going to cut it.

Finally, you must avoid any kind of offset linkage like pulleys or gearboxes. We are dealing here with fractional horsepower: 250 watts (what you might see from a really good hydro-gen at cruising speeds) is only 1/3hp. An alternator driven by your 20hp diesel engine can ignore the friction loss from a V-belt; renewable energy sources cannot. In wind power, you don't start seeing gearboxes in turbines less than ~30 feet diameter and 25kW. Smaller than that, transfer losses outweigh benefits. Direct drive, large-diameter, low RPM, permanent magnet 3-phase alternators, preferably axial flux. There ... I went and revealed the Dark Trade secrets.


----------



## smurphny (Feb 20, 2009)

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?


----------



## Warmar Republic (9 mo ago)

guitarguy56 said:


> 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!


Hey! I used to work at Boeing too! Way back in the 90's. They, (the management types) used to confiscate the shop aids I made and put them back into my box reincarnated in the machine shop and with a Boeing patent number on them. Got a Zebco 33 rod and reel as a "bonus" for making a scribing tool that allowed a +/- .005 trim to fit on composite panel edges. SMH. 
I want to use a trolling motor as a generator to charge a deep cycle battery while it is anchored in a river or an ocean current. I think I will have to do something to access more water column than is available in the cross section of a trolling motor propeller though. 
Old man river, he keeps on rolling. He must know something but he don't say nothing. 
You and me we sweat and strain body all aching and wracked with pain.
I can handle the mechanical design to grab a larger cross section of the current, but I'm lost when it comes to manipulating the magic pixies to shove them into a battery and let them out again. I would think though that there would be a use case for ultracapacitors for taking on large amount of energy in short bursts of input and then doling it out at a rate that would charge a deep cycle battery. IDK though. For electrical designs, I'm entirely dependent on the kindness of strangers.


----------

