DIY towed generator

[GILow]

Originally Posted by martinworswick

i've not read all the posts so this may have been mentioned but i believe if your using any prop that is designed for thrust then you have to turn it around for it be efficient as a generator when being towed.

Actually, good effort. I don’t think that one has been mentioned. If it has, I missed it.

Thinking about it, and the shape of the prop and how the blades increase in pitch, it makes good sense.

[GILow]

Originally Posted by alctel

You could also try placing 'wanted' ads in various sailing forums. That's how I got my tow genny cheap last year.

Nice idea, but I suspect that here in Oz it would be a long wait.

Anyway, I’ve gone with the F&P approach now so the die is cast.

[jmh2002]

Not sure if you are familiar with the 'Angry Ram' YouTube channel in NZ, but he is living off grid and does some F&P stuff, among other alternative energy related things.

He also uses mobility scooter parts for various things (electric wheelbarrow anyone?)

You will have to search through the vids, but maybe useful:
https://www.youtube.com/user/Buddhanz1/videos

Oh, he has a 2nd channel which is more relevant:
https://www.youtube.com/user/AngryRamNZ/videos

https://www.youtube.com/watch?v=gUmDvENKPig

https://www.youtube.com/watch?v=mP0YBwE5ZNs

https://www.youtube.com/watch?v=jM0ER3N4Fy0

https://www.youtube.com/watch?v=co3bR9Go24I

[GILow]

Originally Posted by jmh2002

Not sure if you are familiar with the 'Angry Ram' YouTube channel in NZ, but he is living off grid and does some F&P stuff, among other alternative energy related things.

Thank you. Yes I do know his stuff and he is terrific. His was the first video I saw about the F&P conversion that convinced me. So straight-forward and clear in his descriptions. No sales pitch, just good common sense.

And his mad ram is hysterical. How can such a laid back and calm guy end up with such a freaked out sheep?

[jmh2002]

Ok great

Originally Posted by GILow

And his mad ram is hysterical. How can such a laid back and calm guy end up with such a freaked out sheep?

Oh, the ram was wild originally and just happened to be living on his property, and even now I guess you could say that Rambro and family are only semi-domesticated.

Beware of the Ram

[GILow]

Originally Posted by jmh2002

Oh, the ram was wild originally and just happened to be living on his property...

Oh, that makes more sense. I've only glanced at one or two of the videos, when I have time I will watch them properly and get the full Rambro history.

[GrowleyMonster]

Not practical. Mount a couple of solar panels instead. And a wind charger if you like.


You could possibly mount a pulley on your propshaft, if your gearbox will take kindly to freewheeling. Many don't and prolonged freewheeling will damage it. But assuming you can, then you want to change to a fixed prop or controllable pitch. In trail shaft mode the prop and shaft turn, and energy is transferred to the motor mounted piggyback over the shaft via belt or belts. A double or triple pulley and vee belts works okay, a flat belt a bit better but possibly harder to find spares or replacements and they would cost more. A 5kw BLDC/PMAC motor would work for this. Permanent magnet motors can produce sparks and limit your use of gasoline or propane aboard if the motor is mounted below. The controller in regen mode will output fairly clean DC, but probably not at 12v so you will want a 36v or 48v bank. Power 12VDC loads with a DC/DC converter. As a plus, you can flip a switch for electric propulsion for docking or other low speed or short duration maneuvering. AND when you run your engine, you can adjust regen to charge the batteries at whatever rate you decide is practical. One con is having to break the shaft at a coupling to change belts. If you kept a few spares around the shaft tied back in such a way that they do not touch it, you would have ready spares and could go a lot longer without having to break the shaft. There is chain drive, too, but this has its own set of issues. Anyway what I have described is actually a diesel/electric parallel hybrid propulsion/charging system. It would cost you around $3k or less, assuming use of cheap but rugged golf cart batteries. And a lot of work, connecting, building a battery box, fabricating motor mount, etc.



Keep in mind that this is not free energy. The more you take from the trailing prop, the more you slow the boat. And the power produced will be far less than you probably envision. The load on the diesel when engine charging though, could actually be a good thing if like most boats you are overpowered and the diesel is just loafing along. Diesels work best at their optimum speed and load. However, you will see an increase in fuel consumption with the increased load. The major benefit of tailoring the load is in prolonging engine life between rebuilds. This would be particularly true for turbocharged engines, BTW.



To get an idea of worst case scenario for slowing the boat speed, think of a fixed prop with the shaft locked. The heavier you load the generator, the more closely the drag will approximate this. The lighter the load, the easier the prop can turn and the less resistance it will offer to the water it travels through.



The easy way would be to mount a solar panel or two. This would make a much smaller hit on the boat's performance. Solar works really well for charging, with modern MPPT charge controllers. All the fine engineering is already done for you. Just hook it up, test it, and you are good to go.



Most any shade tree engineering project using any of the various motor types mentioned will give you some output, as long as no field current is required by the device operating as a generator. The issue will be in efficiently rectifying and converting the output to the desired voltage, which will change according to what state of charge the bank is in. You would probably want to manually regulate output, after familiarizing yourself with your bank's preferred charging algorithm. Efficiency will generally be pretty low, a small output in relation to the boat's speed loss. One exception... if you commonly reach and exceed hull speed, actual and not calculated, where the boat is actually fighting its own bow wave, your sails are producing more energy than the boat can use effectively, and so the drag would in that situation be much less of an issue. You would in a sense be recovering wasted energy.

[smacksman]

We used an Aquair wind/water genny crossing the Atlantic. Gave about an amp a knot and cost only a quarter of a knot to drive it. The prop towed about 30m behind on multibraid line and the prop always had fresh teeth marks on it when hauled in. I have heard some people lost the whole meter long steel prop and shaft! Hang the genny off the stern rail with rope ties which will absorb noise. Make sure the rope attachment to the genny shaft is a sewn eye to a shackle and not a knot. Any out of balance here will vibrate badly under load. The Aquair was about 300mm dia and weighed a ton! Cost a lot but did the job.

[GILow]

Originally Posted by GrowleyMonster

Not practical. Mount a couple of solar panels instead. And a wind charger if you like.


You could possibly mount a pulley on your propshaft, if your gearbox will take kindly to freewheeling. .

Mate, with all due respect, it is clear that you have not actually read a thing I have written. You've made a whole lot of suppositions that simply don't apply because:

a) I already have buckets of solar
b) I already have one of the best (old) wind generators ever made
c) I will have a feathering prop that does not support shaft generation mode.

I've also explained in some detail why I want this minor addition to the charging system and how it will be used. (very rarely, as in only when running down wind at night)

You've got some strongly held beliefs on electric propulsion, fair enough, and I am happy to defer to you and others in that area. But I think you'll find they simply have no bearing on this project as I have framed it.

Matt

[GILow]

Originally Posted by smacksman

We used an Aquair wind/water genny crossing the Atlantic. Gave about an amp a knot and cost only a quarter of a knot to drive it. The prop towed about 30m behind on multibraid line and the prop always had fresh teeth marks on it when hauled in. I have heard some people lost the whole meter long steel prop and shaft! Hang the genny off the stern rail with rope ties which will absorb noise. Make sure the rope attachment to the genny shaft is a sewn eye to a shackle and not a knot. Any out of balance here will vibrate badly under load. The Aquair was about 300mm dia and weighed a ton! Cost a lot but did the job.

Smacksman, than you for this post, it constains some terrific metrics and advice.

I had not yet considered how I would attach the rope to the shaft, so I have filed your caution about balance.

Another thing that interests me is that the F&P motor is also around 300 mm in diameter, thought that is without any kind of home made weather-proofing cover. I was going to try to mount it below decks, but your noise/vibration comments have given me pause for thought. Either way I will test it above decks for the testing phase which may tell me more about whether I have will have a noise problem.

You say the amp-air came with a 30 meter tow line. Would you say that was adequate, or if you were making one from scratch (as I will be) would you have made it longer or shorter?

[newhaul]

Originally Posted by GILow

Mate, with all due respect, it is clear that you have not actually read a thing I have written. You've made a whole lot of suppositions that simply don't apply because:

a) I already have buckets of solar
b) I already have one of the best (old) wind generators ever made
c) I will have a feathering prop that does not support shaft generation mode.

I've also explained in some detail why I want this minor addition to the charging system and how it will be used. (very rarely, as in only when running down wind at night)

You've got some strongly held beliefs on electric propulsion, fair enough, and I am happy to defer to you and others in that area. But I think you'll find they simply have no bearing on this project as I have framed it.

Matt

are you still located in Adelaide ? I have an off gridder friend just outside Melbourne that might be able to help you set up something fairly cheap .
I could ask him

[GILow]

Originally Posted by newhaul

are you still located in Adelaide ? I have an off gridder friend just outside Melbourne that might be able to help you set up something fairly cheap .
I could ask him

That would be great thank you.

Over the weekend I bought an old F&P washing machine and have converted the motor to the 4 x 3c star generator configuration but if he has had experience with these conversions I would appreciate his wisdom on whether I should be using an alternate config.

Also, I plan to go/stay off the grid when I move to a farm in Tassie in a few years, so these sorts of contacts are often priceless. Particularly when trusted old sites such as the Alternative Technology Association's forum have been down for nearly a year.

Matt

[newhaul]

Originally Posted by GILow

That would be great thank you.

Over the weekend I bought an old F&P washing machine and have converted the motor to the 4 x 3c star generator configuration but if he has had experience with these conversions I would appreciate his wisdom on whether I should be using an alternate config.

Also, I plan to go/stay off the grid when I move to a farm in Tassie in a few years, so these sorts of contacts are often priceless. Particularly when trusted old sites such as the Alternative Technology Association's forum have been down for nearly a year.

Matt

he has lots of experience iirc he is a mechanical engineer i will pm his email he has a couple questions and told me it would take about 1o hours to put something together I ventured a guess that your timeframe is more like by spring time

[GILow]

Originally Posted by newhaul

he has lots of experience iirc he is a mechanical engineer

Perfect

i will pm his email he has a couple questions and told me it would take about 1o hours to put something together I ventured a guess that your timeframe is more like by spring time

Yes, and that may be only in my dreams. The boat is currently half gutted, the standing rigging is an untuned mess just keeping the mast vertical before I put the new stays on and my heating project is running about two months behind schedule.

Oh yeah... and lectures started again last week.

[newhaul]

Originally Posted by GILow

Yes, and that may be only in my dreams. The boat is currently half gutted, the standing rigging is an untuned mess just keeping the mast vertical before I put the new stays on and my heating project is running about two months behind schedule.

Oh yeah... and lectures started again last week.

Giles is a great guy I bet he will want to help with several of your projects