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Old 16-07-2012, 00:13   #16
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Quote:
Originally Posted by goboatingnow
Towed water generators are in my direct experience very poor generators. They tend to produce far less then advertised. Solar is by far the best IMHO

Dave
My parents are pretty happy with the ampair tow unit they have. Pretty much runs the auto pilot and all the other electrical loads while the boat is doing 5-6 knots. However it can start skipping out at 8 knots or so.

But I agree with you, hard to beat solar for all round usefulness.
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Old 16-07-2012, 08:24   #17
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Re: Water Generator Concept Thread

Quote:
Originally Posted by goboatingnow View Post
Towed water generators are in my direct experience very poor generators. They tend to produce far less then advertised. Solar is by far the best IMHO

Dave
Dave,

Look up the Watt and Sea. I think it is for the faster cruising boats but it seems to deliver quite good Amps then.

Technology advances.

Hugs,
b.
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Old 16-07-2012, 11:22   #18
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Re: Water Generator Concept Thread

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Originally Posted by Snowpetrel View Post
My parents are pretty happy with the ampair tow unit they have. Pretty much runs the auto pilot and all the other electrical loads while the boat is doing 5-6 knots. However it can start skipping out at 8 knots or so.

But I agree with you, hard to beat solar for all round usefulness.
Aha, that's a useful snippet...thank you.
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Old 16-07-2012, 12:27   #19
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Re: Water Generator Concept Thread

Originally Posted by goboatingnow
Towed water generators are in my direct experience very poor generators. They tend to produce far less then advertised. Solar is by far the best IMHO Dave

I have to totally disagree!
I also had an Ampair towed unit and on both of my Atlantic crossings and always got 5-6 amps an hour 24 hours a day- wonderful trade winds sailing.
As far as skipping is concerned - they also sell a weight to attach to the propeller bar to keep it in the water. Only had to use it once.

And to retrieve the propeller I brought a large split funnel sold by I believe Ferrous Products that you sent down the line, stopped the prop from turning and then became very easy to retrieve the towed unit.

So from my personal experience nothing beats a towed generator producing amps while sailing. On my list for my new boat right after a steering vane.
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Old 16-07-2012, 12:47   #20
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Re: Water Generator Concept Thread

The only problem with solar dependability is the damn sun. It doesn't always shine when you really need max output. The smaller boats in this years Single Handed TransPac Race have all had to revert to hand steering because it was overcast for much of the race. On my TransPac a couple of years ago, didn't see the sun for 10 of the 15 day passage. Batteries were getting pretty low by the time the panels finally got direct sunlight. Anything that obstructs direct sunlight, especially in the critical 10am-2pm time frame seriously reduces PV output. Even a slight haze will cut output 50% and a full overcast reduces output by 80%. If you're sailing exclusively in the tropics, solar panels can provide quite reliable power. Sailing in more northern latitudes and/or getting down to the tropics may leave you sorely lacking in electrical generating capacity.

It really depends on where you are sailing, the amount of realestate you've got for solar panels, and your electrical demand. I've got 260watts of solar generating capacity and it won't keep up with my modest needs , no refrigeration or autopilot, under overcast conditions. Would probably be only holding it's own on full sun light days if I had refrigeration which leaves the A/P drain out in the cold. I'd be hard pressed to find more room for additional PV panels where they wouldn't be shaded so really can't increase my PV generating capacity.

Windmills are great but don't work all that well sailing downwind. The relative wind over the fan blades may not be enough to generate much power. On my TransPac, seldom saw 10k relative wind running ddw at a pretty steady 5k boat speed. Most windmills don't really produce much power till relative wind gets to 15k or more. As you sail more into the wind, relative wind issues become less of a factor but I'm a cruiser and love downwind sailing.

For passage making electrical generation in all conditions, a towed electrical generator has a big advantage for generating power. As long as the boat is moving, you can count on generating some power and the faster you go the more electricity it generates.
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Old 16-07-2012, 12:48   #21
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Re: Water Generator Concept Thread

FWIW, the nattiest little idea I have ever seen was on a Swedish boat called Liva. He had mounted a leg of an outboard through the hull, permanently. It was off centre, and the prop faced forwards. He had beaten the prop to be more efficient as an impeller. It was a weed free design. The leg was glassed into the hull, but making a metal flange would be easy. There were only small hull penetration for the bolts, and the shaft.
Next he mounted a permanent magnet generator on the top of the shaft. The gearing provided by the existing O/B gearbox was about 2.5:1 and the gear lever still worked to be able to stop the shaft spinning. I do not know any performance data, but he seemed happy with it. It was his main underway source of power.
Just an idea for you...
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Old 16-07-2012, 14:21   #22
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Re: Water Generator Concept Thread

Quote:
Originally Posted by sy_gilana View Post
FWIW, the nattiest little idea I have ever seen was on a Swedish boat called Liva. He had mounted a leg of an outboard through the hull, permanently. It was off centre, and the prop faced forwards. He had beaten the prop to be more efficient as an impeller. It was a weed free design. The leg was glassed into the hull, but making a metal flange would be easy. There were only small hull penetration for the bolts, and the shaft.
Next he mounted a permanent magnet generator on the top of the shaft. The gearing provided by the existing O/B gearbox was about 2.5:1 and the gear lever still worked to be able to stop the shaft spinning. I do not know any performance data, but he seemed happy with it. It was his main underway source of power.
Just an idea for you...
Great idea. Wonder if an old electric trolling O/B would work or even an old weedeater.
figured out my design for a stationary one last night. Now I just need a small motor to try and build one.
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Old 16-07-2012, 15:41   #23
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Re: Water Generator Concept Thread

Ive never had a system that worked off the wheel shaft like the one shown above ! but have seen a couple of systems like this before! like this one a couple of them worked really well !! Ive always thought about makeing one up for my boat ! after seeing this one Im sure I will bild one as I have the room on the boat we are getting to be able to do so ! first off ya need room around and under the shaft to make it work !! and with our new to us boat thats one thing we have!! LOL Altho it has a genny and such, this type of almost free electric energy is a real fine thing when ya are cruiseing! if it supplys enough power for the auto pliot, and maybe the GPS I would be a happy man !!! Just my 2 cents
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Old 16-07-2012, 16:31   #24
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Re: Water Generator Concept Thread

I've got 260watts of solar generating capacity and it won't keep up with my modest needs , no refrigeration or autopilot, under overcast conditions.

Wow... Thats an awfull lot of solar power. I am very surprised they didn't keep up with your demand, what were you running? My 80 watts have more or less kept up with my power needs for years. No AP or fridge. Mind you we usually get at least some sunny days a week. And I tilt them to maximize the output. My computer is by far my biggest draw.

One homemade water generator idea I like is to install a generator (or slow speed alternater) and any step up gearing you need into the lazarette with a thrust bearing and watertight seal (lip seal?) going through the transom to a ring on the outside. then just use the ampair style towed prop.

there did used to be a commercial unit like an outboard, does anybody know what happened to it?
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Old 16-07-2012, 16:54   #25
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Re: Water Generator Concept Thread

10 days of overcast with the panels only putting 2-3 amps at high noon and you run the batteries down pretty fast even without refrigeration. I was running AIS, Garmin 3206 plotter, electronic compass from the A/P but the A/P in standby, interior and running lights (mostly LEDs), HF radio for 2-3 hours a day and Pactor 3 modem though that was mostly recieve only, and the VHF radio. Eats up a few amps every hour hour and with only 10 or so amps coming in from the panels with no sun, took it's toll on the battery charge.

Don't count on PV panels unless you are going to sail in areas where you are going to see at least half the days with sunshine in that critical 10am-2pm time or figure on a bunch of panels. Even the downwind slide to sunny Hawaii is largely under overcast skies. Of course, now that I'm here, the panels are taking care of my needs even though they are folded down flat against the pushpit. Of course that's primarily only supplying juice for the lights and occasional time on the radio.
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Old 16-07-2012, 17:11   #26
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Re: Water Generator Concept Thread

FWIW,

On our previous boat I had a home built towed generator. It was based on a surplus permanent magnet 32 V tape drive motor which were commonly available on the surplus market at the time. It had a trunion (sp?) mount on the aft rail, about 50 feet of 1/2 inch double braid line and a prop from a 6 HP Johnson on a three foot stainless shaft. Prop was a freebie from an o/b shop, and was so beat up that they had no use for it. The unit started useful output at about 4 knots, gave about 4 amps at 5 knots and 10 amps at 6 knots. The output went up rapidly above that speed, but the prop would jump out of the water which reduced its usefulness. We found that it slowed us down some. Hard to accurately quantify, but on the order of one half to one knot depending on conditions. Retrieval was difficult. We tried all sorts of tricks including plastic bags, funnels, purpose built metal cones and so on. None worked well enough to bother with, and we eventually settled on simply heaving to briefly to bring it in. This included when sailing wing and wind downwind... just drove the boat up into the wind with sails aback. Once the speed dropped below around 2 knots one could quickly heave it in and get going again before the boat actually lost steerage... usually!

This was in the days before common solar availability, and that simple device kept us supplied with copious amounts of electric power when on passage. I would enjoy having such capabilities today, for our ravenous autopilot is a struggle to keep fed.

There has been a lot of info on the net about converting the pancake motors from Fisher-Paykel (sp?) washing machines into slow speed generators. I wonder if such a device coupled to the leg from a defunct small outboard might not be a viable approach... I'd be interested for sure!

Cheers,

Jim
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Old 16-07-2012, 18:39   #27
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Re: Water Generator Concept Thread

The first thing to check when making a shaft generator is if your tranny is rated to allow the prop to free spool. If not, you could destroy the transmission.
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Old 16-07-2012, 18:42   #28
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Re: Water Generator Concept Thread

We too found the overcast vs. full sun juice delivery from solars dramatic.

The other factor we found to play huge role is the angle between the panel's plane and the sun rays.

Huge differences. Hence our panels tilt now.

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Old 17-07-2012, 06:48   #29
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Re: Water Generator Concept Thread

Huge differences. Hence our panels tilt now.

+1

I was running AIS, Garmin 3206 plotter, electronic compass from the A/P but the A/P in standby, interior and running lights (mostly LEDs), HF radio for 2-3 hours a day and Pactor 3 modem though that was mostly recieve only, and the VHF radio.

Me? I switch the lot off, just navigation lights if I am short. No instruments, no GPS, except for the noon fix and final approach, maybe 4 amphours per day? It's kind of fun and liberating sailing without all blinking lights, but I guess if there was any traffic about a VHF would also be needed and AIS, which must draw quite a bit.
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Old 17-07-2012, 07:01   #30
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Re: Water Generator Concept Thread

The Ferris towed generator was our main power source when running downwind in the trades. Compared to solar panels, it was high maintenance, had to be often cleared of sargasso weed, skipped out of the water when winds were over 25k, but it ran all night and on cloudy days. Retrieval was fairly easy with the split funnel provided by Ferris.
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