The Duogen on the bottom picture I was intrested in a few years back you can change them from wind or water.....really not many amps achieved ....you could try building your own with a old outboard as a drive unit? Put it opposite side to your current outboard and have it locked down permantily?
What about having an electric outboard with a permant magnet motor, that way you could use the same system to gather electricity.
How a Prius charges itself when it goes down hill?
Regenerative braking would be the idea (had to google it)
use the outboard to move out of the harbor, then up with the sails and sail off, as your going the same outboard is putting back what the maneuvering took out.
I always though it would be valuable to use Magnito tech charging on car wheel drums for electric cars....I guess it's possible but the return energy doesn't compete with solar or 240volt charge currently.
or just get a dedicated solar panel and battery to run the VHF radio and ditch everything else! 
Select to expand quotesouthace said..
My guess would be about 2amps at 6 knots.
I looked at the Watt and Sea model. I came close but it was too dear unless I was planning on doing ocean passages. (the diesel gives me ample charge for doing coastal passage work)
They had a base model that provided a maximum of 24A, and a gruntier version at 48A.
I think from memory it started charging at 2 knots, with a rated output at 5 knots of about 10A. Pretty impressive stats.
I Suppose it just brakes down to
- What RPM you can achieve
- and having a generator matched to that so you can achieve desired voltage and amperage.
If i ever get around to building my electric outboard i recon ill give it a go.
Regenerative drag on an outboard
I guess it's up to the gearing. I had a BMW diesel 8 hp in my last 26 footer she had a magnito charging system to charge the battery. No flywheels or belts! Unfortantly it failed and the replacement BMW motorcycle magi failed as well after fitting. You need high speed to create amps or solar.
You don't get anything for nothing, hydro unit would be too much drag on a 20 footer. Live aboard next to me has panels and a wind generator but uses a suitcase generator on a regular basis.
I looked into a Watt and Sea but they are really suited to faster boats so I stuck with wind and solar
Id be more interested on using the engine propeller pulley on the shaft to an idler pulley to raise the rpm to a suitable alternator and a lot cheaper it old school but it works
Select to expand quoteHG02 said..
Id be more interested on using the engine propeller pulley on the shaft to an idler pulley to raise the rpm to a suitable alternator and a lot cheaper it old school but it works
That will just add a side load to the shaft and suck up extra hp. Even changing to a high output alternator will use more hp. If your going to have to run an engine to charge batteries then an engine/genset that's designed for charging batteries is best.
Does anyone have a system in place that generates energy of the drive shaft while sailing? At 6 knots my prop is spinning quite fast(with motor off) and I thought here might be someway to get something out of that as its just spinning all day and night while sailing
Just an idea.
Select to expand quoteDexport said...
Does anyone have a system in place that generates energy of the drive shaft while sailing? At 6 knots my prop is spinning quite fast(with motor off) and I thought here might be someway to get something out of that as its just spinning all day and night while sailing
Just an idea.
To do it you need a counter shift so you can increase the rotation speed x2 them a belt of an alternator
I'll find a link tonight get and post it
I always lock my prop while sailing I find a spinning prop is enoying.
I would rather have a good wind generator At least that way the noise is removed from the hull.
I've always thought a hydro generator would be the best option for generating power on a voyage.
Here is a link to someone that is sharing their research into shaft and towed systems
www.svsarah.com/Whoosh/WhooshPacificPrepTowGenerator.html
Select to expand quoteDexport said..
Does anyone have a system in place that generates energy of the drive shaft while sailing? At 6 knots my prop is spinning quite fast(with motor off) and I thought here might be someway to get something out of that as its just spinning all day and night while sailing
Just an idea.
An alternator will have to spin at about 3000rpm to charge and when it does will need several hp from the prop shaft. With it geared up to get those rpms it probably wont have the power.
A generator will charge from fairly low revs but will also have a low power output.
Attache an old outboard prop to the end of a piece of pipe and trail that astern on a length of rope with a good swivel at the top end. See what rpm you can get from the prop and notice how much drag there is.
If the water generator was going to be any good we would see them everywhere. Solar is the future along with lithium storage batteries. At least with panels they can also provide some shade if you want. If you want to generate some noise then add a wind generator. At the moment an engine driven generator[240v] is the most cost effective way of having power and charging batteries.
Select to expand quoteRamona said..Dexport said..
Does anyone have a system in place that generates energy of the drive shaft while sailing? At 6 knots my prop is spinning quite fast(with motor off) and I thought here might be someway to get something out of that as its just spinning all day and night while sailing
Just an idea.
An alternator will have to spin at about 3000rpm to charge and when it does will need several hp from the prop shaft. With it geared up to get those rpms it probably wont have the power.
A generator will charge from fairly low revs but will also have a low power output.
Attache an old outboard prop to the end of a piece of pipe and trail that astern on a length of rope with a good swivel at the top end. See what rpm you can get from the prop and notice how much drag there is.
If the water generator was going to be any good we would see them everywhere. Solar is the future along with lithium storage batteries. At least with panels they can also provide some shade if you want. If you want to generate some noise then add a wind generator. At the moment an engine driven generator[240v] is the most cost effective way of having power and charging batteries.
And adding a good smart multi-stage regulator for a few hundred bucks to your engine alternator will vastly improve the efficiency and speed of charging from the engine. Quick, simple, and will get you if not all, most of what you want.
Cheers, Graeme
Hunt down a copy of the 12v bible that shows how to convert an automotive alternator to manual operation is probably the best method.
Sorry but I have to disagree about manual control of your alternator. If you're going to the trouble of modifying alternator wiring, you may as well invest a couple of hundred dollars for a smart regulator and keep it all automatic. Google the Sterling regulator.
You will save some money up front by setting it up for manual control, but the day will surely come that you forget to control it and cook your batteries. There is already enough to keep in mind when you're cruising, without obsessively watching the voltmeter to see when to throw the switch back to normal charging!
Cheers, Graeme
Select to expand quotewongaga said..
Sorry but I have to disagree about manual control of your alternator. If you're going to the trouble of modifying alternator wiring, you may as well invest a couple of hundred dollars for a smart regulator and keep it all automatic. Google the Sterling regulator.
You will save some money up front by setting it up for manual control, but the day will surely come that you forget to control it and cook your batteries. There is already enough to keep in mind when you're cruising, without obsessively watching the voltmeter to see when to throw the switch back to normal charging!
Cheers, Graeme
I would not be spending more than $20 and that includes the alternator. If I wanted to charge batteries, deep cycle batteries, I would use an engine/generator like a suitcase generator if I wanted to spend a couple of hundred dollars. I would keep the standard alternator standard and have it charge the starting battery. The so called smart regulators don't seem to have a very good reliability record.
The solar panels I have exceed the battery charging requirements I need on my vessel. For those people who need all the home comforts on their boats I would look at the developments in the home off the grid electricity supply and storage field and adapt them for marine use.
www.google.com.au/search?q=prop+driven+alternator&rlz=1C1ASUC_enAU691AU691&espv=2&biw=2560&bih=955&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwik9LmHjrnOAhXHKJQKHdNpC4IQsAQIOw
some interesting images above
forums.ybw.com/index.php?threads/prop-shaft-driven-alternators.231833/
www.sailnet.com/forums/miscellaneous/22098-propshaft-alternator.html
www.cruisersforum.com/forums/f14/alternator-on-the-prop-shaft-84926.html
bit of reading if you feel like it
www.sailnet.com/forums/electrical-systems/92709-ho-alternator-serpentine-pulley-kit-install.html
lifepart2.info/equipment/prop-shaft-driven-alternator
www.sailnet.com/forums/miscellaneous/22098-propshaft-alternator.html
perhaps a alternator like this one low rpm and high out put
www.windbluepower.com/Permanent_Magnet_Alternator_Wind_Blue_Low_Wind_p/dc-540.htm
The ybw forum thread is the only one worth reading. Remembering that we all mainly sail 4 knot vessels, the rare occasions we can maintain 5 knots to have enough power to overcome the drag and actually generate the power is not worth worrying about. The yacht will also have to have a fixed blade propeller so the people with folding props will have to look at modern technology. The hydro generator is about as effective as the third wheel caravan generator from a few years back, when was the last time you saw one?
Select to expand quoteRamona said..
The ybw forum thread is the only one worth reading. Remembering that we all mainly sail 4 knot vessels, the rare occasions we can maintain 5 knots to have enough power to overcome the drag and actually generate the power is not worth worrying about. The yacht will also have to have a fixed blade propeller so the people with folding props will have to look at modern technology. The hydro generator is about as effective as the third wheel caravan generator from a few years back, when was the last time you saw one?
From friends [yes I do have some] sailing from Europe to Australia say that the Watt&sea are very popular over there!
Select to expand quoteshaggybaxter said...southace said..
My guess would be about 2amps at 6 knots.
I looked at the Watt and Sea model. I came close but it was too dear unless I was planning on doing ocean passages. (the diesel gives me ample charge for doing coastal passage work)
They had a base model that provided a maximum of 24A, and a gruntier version at 48A.
I think from memory it started charging at 2 knots, with a rated output at 5 knots of about 10A. Pretty impressive stats.
Figures quoted above for 5 kn
The average yacht sails at 4 knots [4 knot leadmine]. With a 240mm propeller it's going to generate 30 watts! Roughly 2.5 amps. Lets forget about the hp loss needed to get that prop revolving, lets remember there is no free lunch. So for just under 4 grand the average cruiser is going to get 2.5 amps while he is underway!
Propellers are very inefficient when driven. They operate at about 40% efficiency with major losses at the boss and tips in particular. Dragging one though the water the inefficiencies are still there but with added parasitic losses like drag. For 4 grand I could have a pretty phenomenal solar/lithium battery installation, enough to power a modest home!
Now if you were to develop a paddle wheel generator that would be more efficient but the size required would be a problem.
