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Old 13-03-2016, 15:33   #31
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Re: Electric motor for sail boat

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Originally Posted by lonesoldier0408 View Post
Funny you mention that. A DC motor powering an AC generator could be the answer. One battery bank being charged while powering the generator. Swap banks and repeat.


Still surrounded by anchors.
Perpetual energy? Works for me.
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Old 13-03-2016, 17:05   #32
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Re: Electric motor for sail boat

Unless you intend to split an atom, all energy on earth comes directly, or indirectly from the sun.
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Old 13-03-2016, 20:19   #33
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Re: Electric motor for sail boat

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Unless you intend to split an atom, all energy on earth comes directly, or indirectly from the sun.
Volcanoes?

The energy in the mantal?

Energy in waves, isnt it from the moon?

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Old 13-03-2016, 20:59   #34
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Re: Electric motor for sail boat

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Unless you intend to split an atom, all energy on earth comes directly, or indirectly from the sun.
Geothermal? Tidal?
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Old 13-03-2016, 22:00   #35
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Re: Electric motor for sail boat

Theoretically, in the future, anti-matter (dark matter) in contact with "normal" matter and then the huge resulting contained reaction (except in one direction) will power future starships between star systems..... There are also designs for space-based sailing ships that would unfold huge metallic foil sails to capture the solar wind emanating from our sun that would power a vessel close to the speed of light to explore other planets in our solar system, etc. Much faster than a Yanmar (wink wink) because it would always be accelerating and there are no hull speed restrictions in space. Future Cruisers?
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Old 13-03-2016, 22:11   #36
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Re: Electric motor for sail boat

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Theoretically, in the future, anti-matter (dark matter) in contact with "normal" matter and then the huge resulting contained reaction (except in one direction) will power future starships between star systems..... There are also designs for space-based sailing ships that would unfold huge metallic foil sails to capture the solar wind emanating from our sun that would power a vessel close to the speed of light to explore other planets in our solar system, etc. Much faster than a Yanmar (wink wink) because it would always be accelerating and there are no hull speed restrictions in space. Future Cruisers?
Do do do do do do do do

Thats the theme from The Twilight Zone
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Old 14-03-2016, 11:08   #37
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Re: Electric motor for sail boat

So..this topic is one that I find intriguing.
If we take the LA storage cells out of the equation, and then look at the current (pun intended) 800 pound gorilla of hybrids. The rail industry claims 476 ton-miles per gallon. https://www.aar.org/newsandevents/Pr...er-Gallon.aspx
I find this to be pretty flippin efficient.
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Old 14-03-2016, 12:15   #38
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Re: Electric motor for sail boat

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So..this topic is one that I find intriguing.
If we take the LA storage cells out of the equation, and then look at the current (pun intended) 800 pound gorilla of hybrids. The rail industry claims 476 ton-miles per gallon. https://www.aar.org/newsandevents/Pr...er-Gallon.aspx
I find this to be pretty flippin efficient.
A well designed hybrid drivetrain can come pretty close to matching a conventional drivetrain. Trains use diesel/electric because a mechanical transmission that could get a 100 car train weighing thousands of tons moving would be huge, expensive and complicated. The electric portion is basically acting as a transmission.

The efficiency of trains has little to do with the transmission type.
- Steel wheels on steel tracks are basically the ultimate in low rolling resistance tires. About the only thing better would be mag-lev.
- Aerodynamics are also huge. 99 of the 100 cars are drafting with 8-10' headways.
- Freight trains also usually limit speed to 40-50mph. Bump that up to typical automotive speeds of 70mph and it can easily double or triple fuel consumption due to wind resistance.

If you look at hybrid cars, they typically don't do any better than conventional cars in freeway driving (typically slightly worse). It's in city driving where they can save up braking energy in the battery and release it when they accelerate plus picking up some otherwise wasted energy when idling.

Neither use case is really comparable to a typical cruising boat. Mechanical transmissions are straightforward and reliable for low HP applications. The prop meets little resistance when it first starts turning and cruising boats spend the vast majority of their time under power at a steady speed matched to the optimum engine output.

For electric drivetrains to really take off, we need a reasonably priced high capacity storage system for electricity or we need a drastically more efficient method of electrical production that can be mounted on a boat.
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Old 14-03-2016, 12:42   #39
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Re: Electric motor for sail boat

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A well designed hybrid drivetrain can come pretty close to matching a conventional drivetrain. Trains use diesel/electric because a mechanical transmission that could get a 100 car train weighing thousands of tons moving would be huge, expensive and complicated. The electric portion is basically acting as a transmission.

The efficiency of trains has little to do with the transmission type.
- Steel wheels on steel tracks are basically the ultimate in low rolling resistance tires. About the only thing better would be mag-lev.
- Aerodynamics are also huge. 99 of the 100 cars are drafting with 8-10' headways.
- Freight trains also usually limit speed to 40-50mph. Bump that up to typical automotive speeds of 70mph and it can easily double or triple fuel consumption due to wind resistance.

If you look at hybrid cars, they typically don't do any better than conventional cars in freeway driving (typically slightly worse). It's in city driving where they can save up braking energy in the battery and release it when they accelerate plus picking up some otherwise wasted energy when idling.

Neither use case is really comparable to a typical cruising boat. Mechanical transmissions are straightforward and reliable for low HP applications. The prop meets little resistance when it first starts turning and cruising boats spend the vast majority of their time under power at a steady speed matched to the optimum engine output.

For electric drivetrains to really take off, we need a reasonably priced high capacity storage system for electricity or we need a drastically more efficient method of electrical production that can be mounted on a boat.
You may have nailed it with efficiency. It is apple and oranges. A prop is at most probably 50%.
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Old 17-03-2016, 10:55   #40
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Re: Electric motor for sail boat

We have 8 batteries powering the engine and a separate bank for house. It's a 48v system. We did remove the fuel tank and have 4 batts in each side of the boat for balance. The AGM batts are about 65lbs each.

Because we live in a very windy SF Bay Area, motoring is only needed to get in and out of the marina. This system would not work for long trips unless you had a gen and solar to recharge.

I will post some photos over the weekend.

Electric Yachts of Southern California is our supplier. No affiliation other than our purchase.


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Old 17-03-2016, 11:37   #41
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Re: Electric motor for sail boat

We went with the 10.0 engine for our 30' sailboat. We displace 8500lbs and the motor produces about 20 horse. It's a 48v system that produces 200amp hours. Our top speed is about 5.5 knots at 2400 rpm. We cruise at about 4.5 knots to conserve just in case. Our range is 10-12 miles.

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Old 17-03-2016, 12:15   #42
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Re: Electric motor for sail boat

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Originally Posted by valhalla360 View Post

If you look at hybrid cars, they typically don't do any better than conventional cars in freeway driving (typically slightly worse). It's in city driving where they can save up braking energy in the battery and release it when they accelerate plus picking up some otherwise wasted energy when idling.

They actually do much better than a conventional car, my Prius will actually get 60 MPG at 60 MPH, lightly loaded and level ground, seal level, steady state.
Logically you would think due to all the increased weight of the batteries and electric motors, controllers etc. that are not being used, it would do worse than a car not carrying all that excess weight, at least that is what I used to think.
There are a couple of reason it gets such good mileage, one reason is they are not Otto cycle engines at all, they are Atkinson cycle engines, which I had never heard of, but is very old technology.
https://en.wikipedia.org/wiki/Atkinson_cycle
which would not work at all if you didn't have the torque of an electric motor to get you moving, and secondly because you have two big powerful electric motors to accelerate you and pull hills, then you can put in a wimpy internal combustion motor as all it has to do is generate enough power to maintain speed.
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Old 17-03-2016, 12:17   #43
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Re: Electric motor for sail boat

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We went with the 10.0 engine for our 30' sailboat. We displace 8500lbs and the motor produces about 20 horse. It's a 48v system that produces 200amp hours. Our top speed is about 5.5 knots at 2400 rpm. We cruise at about 4.5 knots to conserve just in case. Our range is 10-12 miles.

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Out of curiosity, what was the HP and top speed before repowering?

We have a 25hp outboard with a 35' overall & 30' waterline and wide open, we are at around 7.5kts.

Obviously, the actual waterline length and hull design may impact it but I would expect hull speed on a 30' boat to be up around 6.5-7.0kts depending on the water line length and I would think 20hp would be enough to reach hull speed.

Now if you underpowered a 30' boat with say 13.5hp not quite being able to reach hull speed is a distinct possibility.

If you are happy with the performance, that's great but there are individuals claiming magical abilities with electric propulsion and at first blush, this doesn't support them.
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Old 17-03-2016, 12:59   #44
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Re: Electric motor for sail boat

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Our 34 year old Yanmar diesel died a few years ago. She took us on an amazing adventure on the SF Bay. We looked at all the options and decided to repower with electric.

We installed it ourselves and are extremely happy. We have a range of about 10 miles at 4.5 knots. More if we go slower. Since we only use the motor to get in and out of the marina, it works out great.

We are mostly day sailors on our Newport 30. We could not have made a better decision. We plug in at night to recharge. Our engine is from Electric Yachts. We call it Tesla sailing.


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Sailing Uma on youtube have done a similar swap.

Sounds like a good option for use on the bay.

There is a lot more complexity in a good diesel setup. As a former mechanic I have no problem with this but the attraction of electric for your use case is obvious.

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Old 17-03-2016, 13:00   #45
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Re: Electric motor for sail boat

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They actually do much better than a conventional car, my Prius will actually get 60 MPG at 60 MPH, lightly loaded and level ground, seal level, steady state.
.
Forget the brand but the last rental car we got in Europe was prius sized and worked out to around 60mpg when we filled it up before returning it. We weren't in a rush so it was mostly down around 60mph also.

Limiting yourself to 60mph makes a big difference. That last 10mph to get up to 70mph freeway speeds can easily knock 10-15mpg off and it's not at all unusual for the newer econoboxes to hit 40-50mpg per the official numbers, so very believable that if you slowed down to 60mph you would get a boost.

The official numbers for 2015 prius (depending on model) range from 40-49mpg highway and from 44-53 city. As you can see, they do much better in the city and drop back to numbers similar to conventional drivetrains for highway driving.

Also are your numbers based on the lie-o-meter or actual fill ups?
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