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Old 18-05-2011, 16:50   #16
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Re: Ever Refit a Sailboat with an Electric Water Jet ?

I'll write up some plans and run a few experiments. It will be a few months until I can come up with something though. I'll keep everyone informed.

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If you do this your biggest issue will be about efficiency. A propeller is quite efficent if used properly, a good waterjet can be better then a bad prop. I like the idea of having jets facing in different directions. Two ways of figuring it out, study up of try it out.
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Old 18-05-2011, 17:36   #17
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Re: Ever Refit a Sailboat with an Electric Water Jet ?

Your electric power has to come from somewhere, so unless you are using the jet drive just for getting in and out of a marina, you might find it to be uneconomical. I think for keeping green, an electric motor driving a prop would be better. If you engineer it right, when not in use the free wheeling prop turning the motor can act as a generator and keep your batteries charged.
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Old 18-05-2011, 17:50   #18
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Re: Ever Refit a Sailboat with an Electric Water Jet ?

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I'm really not looking for effeciency as much as I am trying to make the boat more "Green". I want to get away from Diesel, and the issues that come along with an internal combustion engine.
If you are realistic about the range that you can get from batteries and how to charge them back up, electric drive with a big slow prop is hard to beat.
Fuel is going to beat batteries for range, I can get ~60 hours at ~6kn out of 210 lb of diesel then a few minutes at the fuel dock do it again, but I don't see myself needing to go 360 miles straight too often, 10-20 miles quite a bit and 50-100 a day sometimes, so an electric drive would work for me most of the time, and if it had a back-up genny would be perfect. But I curently have a happy little Yanmar.
Water jet is a neat thing but for electric I'm not sure. But in some hull shapes it may be the best.
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Old 18-05-2011, 20:09   #19
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Re: Ever Refit a Sailboat with an Electric Water Jet ?

You may be correct...an electric motor might be my best bet. Perhaps I am being too overzealous in my idea of a water jet? Thanks for your ideas. I'll keep all information in mind as I sift through the information. Lou
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Old 18-05-2011, 20:17   #20
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Re: Ever Refit a Sailboat with an Electric Water Jet ?

Hi Astrid, Yes, the turning prop can be used in that manner. Of course, I can utilize a combination of solar, wind and inertia power. Perhaps a three tier system which can utilize different forms of electric propulsion systems. Prop for forward thrust, and water jet for reverse and thrusters? Hmmmmmm?
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Old 18-05-2011, 20:28   #21
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Re: Ever Refit a Sailboat with an Electric Water Jet ?

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Originally Posted by Louann View Post
You may be correct...an electric motor might be my best bet. Perhaps I am being too overzealous in my idea of a water jet? Thanks for your ideas. I'll keep all information in mind as I sift through the information. Lou
I think this may be the case. If you want to make the boat more green, put the money you'd have invested into the engine conversion into your rig. Start by rigging something like a gennaker or screacher that you can use to keep the boat moving when the wind drops below 10 knots apparent.

I'm appalled by the number of sailboats I see motoring in conditions where they could easily be sailing in excess of five knots. This happens for one of four reasons:
* the skipper doesn't have the skills to make the boat go in anything other than 15 knots true on the beam;
* the skipper is too freaking lazy to remove the mainsail cover and hoist the main if he's only going a few miles to the next cove;
* the skipper was so afraid of the ocean that he purchased a boat for how it resembles a bomb shelter rather than how it sails;
* the skipper booked a one-week bareboat cruise, and doesn't therefore have the patience to wait for a favorable breeze.

If you've got a sailboat, sail it. An auxiliary engine is just there to get you into and out of the harbor, and for those rare occasions when you are totally becalmed and your wife is about to give birth.
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Old 18-05-2011, 20:30   #22
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Re: Ever Refit a Sailboat with an Electric Water Jet ?

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Propellors are more efficient at slow speeds than waterjets.

At high speed the waterjet wins.

So on a typical monohull I do not believe the waterjet would be more efficient.
Many years ago I worked in a Yamaha shop (ATV and motorcycle.)

We used to deliver and prep outboards for local delivery... IIRC, the 40hp jet drive used the same power head as the 90hp propeller driven motor.

The jet drive offers better shallow water performance, but the torque needed to drive a displacement hull will likely come at a great cost to efficiency.

I am all for experiments, but I hope you do some math on the conversion before you invest too much time and money.

Good luck whatever you do.
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Old 18-05-2011, 20:35   #23
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Re: Ever Refit a Sailboat with an Electric Water Jet ?

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* the skipper is too freaking lazy to remove the mainsail cover and hoist the main if he's only going a few miles to the next cove
This, by the way, is a great argument in favor of in-mast furling. It takes me about 18 seconds to pull the main out or to put it away. On my first several sailboats, it took me longer than that just to remove the mainsail cover, and almost as long to hook the halyard to the head. And don't even get me started on how long it took to flake the sail, lash the gaskets (sail ties), and re-cover the main.

You want green? Get a main that you'll use every time you take the boat out of the slip.

[Edit] Yikes, I can't believe I just responded to my own post.
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Old 18-05-2011, 20:56   #24
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Re: Ever Refit a Sailboat with an Electric Water Jet ?

Lol! My sentiments exactly! Eventhough I am a fair weather sailer, the only reason i use the engine is to get from slip to open water. I sail on Lake Michigan. It usually takes me 10 minutes get through the channel, and I have only used the motor for 20 minutes straight when my (ex) step daughter was sick and the waves were making her worse. Of course, I do want to have more than I need...like usual...
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Old 18-05-2011, 22:14   #25
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Re: Ever Refit a Sailboat with an Electric Water Jet ?

There may be other considerations with a jet...your not going to getting your prop tangled in any lines.
These folks do some interesting stuff... SCHOTTEL: Technical Data
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Old 18-05-2011, 22:54   #26
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Re: Ever Refit a Sailboat with an Electric Water Jet ?

Quote:
Originally Posted by Louann View Post
You may be correct...an electric motor might be my best bet. Perhaps I am being too overzealous in my idea of a water jet? Thanks for your ideas. I'll keep all information in mind as I sift through the information. Lou
Check out this site for a realistic, honest look at electric auxiliary propulsion in sailboats. It isn't for everyone, but for those willing to be realistic, it is hands down amazing.

Your best bet is going to be with a big, high pitch prop turning slowly. My Catalina 30 is fit with a 12.5 x 14 Acme prop. If you take Practical Sailor, on the page with the interview with James of Propulsion Marine there's three photos, one of which is a prop. That's actually my boat and prop when it was in the yard. Electric motors have full torque starting at 0 rpm, so you really lower slip rate and increase efficiency by selecting a big steep prop. A waterjet just doesn't scale down to our size and speed efficiently. It's possible to make cabinets with a chainsaw, just not very efficiently.

Range can be a problem. One of the more realistic electric boaters is always telling people that the most practical battery pack is about the energy equivalence of a single gallon of diesel. If you're happy burning less than a gallon at a time, you're golden. It's definitely not for people who employ auxiliary sails on their slow powerboat...

The real beauty of an electric conversion is the idea of electric sailing. The motor is basically always running. It takes about 50W of power to spin the prop up to the current boatspeed and eliminate drag. This adds about a knot of speed for sailing. By kicking in about 250W, you can increase sailing speed by two knots. Imagine being able to motor sail with your diesel, except doing it at really low power levels (which is bad for a diesel) and without the noise, vibration, and stink.

As far as charging, solar seems to be the most popular, although the usual caveats of lattitude apply. The usual arguments for and against wind generators are pretty much valid with electric. Regeneration, or regen, is using the prop to turn the motor as a generator. It doesn't really work as well as one would hope. Most folks with boats in my size class are getting somewhere around 80-100W max at 6 knots boatspeed. The hype is there, but the physics just don't work out so well without a bigger, faster boat.

JRM

-- I think electric auxiliaries are going to really take off in the next few years. They aren't the solution to every situation, but they're a *really* good solution to several.
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Old 18-05-2011, 23:14   #27
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Re: Ever Refit a Sailboat with an Electric Water Jet ?

If memory serves there was someone on this forum that was working a fully self sufficient electric sail boat. Perhaps someone who doesn't have old timers disease like me remembers who that was, I am sure there was a lot of good information there. I think a jet drive would be too inefficient for a displacement hull and make docking a nightmare. An electric powered conventional or controlled pitch propeller would work better.
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Old 19-05-2011, 00:06   #28
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Re: Ever Refit a Sailboat with an Electric Water Jet ?

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electric water jet?
Electric?
For the spa?
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Old 23-05-2011, 12:52   #29
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Re: Ever Refit a Sailboat with an Electric Water Jet ?

anyone thought about chucking out their old volvo diesel and replacing it with a modern electric engine rechargable with built in alternator, solar cells and wind generator. Seemingly with new technology your engine with equivalent power weighs max 50 - 60 kg and the dry batteries (4x12volt) producing around totally 130 amp. Total weight including batteries 200 kg. Is this a viable alternative 'cos price is cheaper than a new diesel and there's basically no maintenance. Or is this a sissy proposition only suitable for off shore ? let me have your views. tks paul
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Old 23-05-2011, 13:14   #30
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Re: Ever Refit a Sailboat with an Electric Water Jet ?

Thanks for the information. The research goes on and I'm beginning to think that I'm not that crazy after all!
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