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Old 18-02-2020, 11:32   #151
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Re: Jimmy Cornell goes Electric, with a Cat

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Originally Posted by mglonnro View Post
This one fell just out of your search, but kind of related to both your points: https://www.yachtworld.com/boats/201...maran-3495614/

Owner discussing (among other stuff) the electric/hybrid system of the boat:

This is an interesting take on "all electric."


* He has 20KW of motors, probably a bit small for a 50 footer, but not bad.

* He has 35 KWh of battery storage -- but he chose AGM so really he only has 17KWh of propulsion (if he gets to 100% charge). So, he has about an hour, maybe two at some reasonable cruising speed before he hits empty.

* He has a massive generator -- 22KW -- meaning he can actually run the motors at full power for as long as he has fuel.

* He has ZERO recharge capability other than the generator. He either runs the generator whenever he runs the motors, or he runs the generator when he stops motoring. The solar (540W) is for the house battery, and really too small even for that.

* As a bonus, he isn't constrained by the normal "4 kts cruising speed is OK, I'm not in a hurry" mentality -- instead, he can follow the pack and hit 6-8 kts cruise speed.
* One downside is the size of the generator. Most of us don't want to run our engine at anchor as our battery charger because it's too big for the small load. This generator (31hp) is larger than many main engines! In fact, the AGM's when charged at 25% of C (typical recommendation) will only load the generator at 1/3 capacity.
* At full load, the 20KW motors will draw 140A continuous from those 4D batteries. Is a 4D AGM OK with that?
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Old 18-02-2020, 11:41   #152
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Re: Jimmy Cornell goes Electric, with a Cat

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We've read a lot of claims about hydrogeneration in this and other posts along similar topics. To date I've yet to see any real world data supporting these claims.
This is a glimpse of real world data that I found in another thread. Between 9-10 knots of sailing speed and the left prop reports regeneration ~1 kW, the right prop much less. Someone commented that they had info it was a sensor fault, but who knows. They are just numbers on lcd displays, however. Who knows.

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Old 18-02-2020, 16:23   #153
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Re: Jimmy Cornell goes Electric, with a Cat

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yeah cos theres no emissions expelled in building the boat is there???

sorry but this is just yet more hypocritical virtue signalling

the least emissions path by far would be to NOT BUILD ANOTHER NEW BOAT and make do with an existing one.
So, are you suggesting that we completely stop building boats? What next? Stop building cars, planes, houses, bridges...?

Or are you suggesting we keep building these things exactly the way we have always done with no attempt at all to make improvements?

This guy is not going to change the world with his new boat, and I doubt he has ever claimed that. Just because a step in the right direction is only a tiny step, doesn't mean it is not worth taking. It is the people who have the cojones to do something different that move the world forward. The keyboard warriors that bitch and moan about every advancement should probably find themselves a nice cave and a bow and arrow....
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Old 18-02-2020, 16:45   #154
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Re: Jimmy Cornell goes Electric, with a Cat

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When looking at the stats you will find, that almost 50% of the electric energy produced in Germany last year was renewables.
And in what universe is nuclear greener? Looking at the energy spent to built those plants and the repercusions when dealing with the waste, I am not sure...
Yes, if looking at CO2 it appears like they are better...
Actually, Germany's "renewables" are just up to 40% last year, and 40% is a LONG way from 50%. The renewable share would have to increase by 25% to reach 50%.

Not to mention that just because a source is renewable doesn't mean it's "green." Fully one quarter of the renewable source electric generation is from bio sources. The vast majority of the bio sources are biogas (which produces methane and CO2) and wood-fired generating stations. Both of these sources emit CO2 when burned to produce power, and the biogas production process also generates large quantities of CO2 in the process, not sure what they're doing with that. Hopefully capturing it for use in carbonated beverages?

There are all kinds of political games being played in the reporting of emissions and power generation. European countries import wood pellets to fuel generating stations, as mentioned earlier in this thread, so somehow those plants emissions are not counted. Pure BS.
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Old 18-02-2020, 17:17   #155
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Re: Jimmy Cornell goes Electric, with a Cat

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The slower shaft speeds possible with some electric drives also allows for larger more efficient props that regen sooner (4-5kts vs. 8kts)
That brings up another point not often mentioned about regen. Many, if not most, sailboats cannot install significantly, or even marginally larger props, due to hull clearance, or in some cases aperture clearance.
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Old 18-02-2020, 19:14   #156
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Re: Jimmy Cornell goes Electric, with a Cat

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That brings up another point not often mentioned about regen. Many, if not most, sailboats cannot install significantly, or even marginally larger props, due to hull clearance, or in some cases aperture clearance.

If high torque/slow shafts/large props were such a huge benefit, we'd be doing them with diesels anyway. You can easily make a large ratio reduction gear that will double or triple the torque, while halving or thirding the RPM, giving all those benefits that the electric crowd want. Of course, they come at the cost of larger prop offset from the hull, higher drag when sailing and (a guess here -- I'm not sure) more pronounced prop walk in reverse. We've had a hundred years or more to develop the ideal trade offs in efficiency, torque, shaft rpm, prop size, etc -- we've about got it right.
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Old 20-02-2020, 06:43   #157
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Re: Jimmy Cornell goes Electric, with a Cat

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Well summarized, Gord! Sometimes one just gets tired with all the misinformation that pops up in online forums almost daily...
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Old 20-02-2020, 15:17   #158
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Re: Jimmy Cornell goes Electric, with a Cat

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This guy is not going to change the world with his new boat,
No he is not, but we need early adopters to pioneer the way.

Unbelievable the naysayers knocking a guy for buying a new boat and just making excuses for their own polluting life styles. At least this guy is having a go, some of you negative nellies should put up what you have done when criticizing.

(Not you cliffhanger, I agree with you and just adding to your comment)
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Old 21-02-2020, 13:14   #159
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Re: Jimmy Cornell goes Electric, with a Cat

Some posts have been removed. READ THE RULES pertaining to being nice.
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Old 21-02-2020, 13:45   #160
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Re: Jimmy Cornell goes Electric, with a Cat

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The amount of fossil fuel used to build is boat will be staggering and , the way forward is to be more savy in our use of resources ,recycle , reuse, keep hold of , there is no need to keep upgrading to new boat, and new cars every three years capitalism and Im better than my neighbours syndrome

I agree totally with Tarian. The amount of resources which are used to build a new boat (or a car) or almost anything we use up and throw away, is astonishing.

To get an idea, try to imagine you building a boat, THE WHOLE BOAT, from yourself, from scratch. The hull, the sails, the keel, the engine, the radio, everything, and I don't mean buying all these pieces. I mean, I give you the workshop and all the tools and the raw materials, and you make everything, the whole thing. How long would it take you? Actually, we all would recognize that it is impossible. Nobody to could do it. There is an immense amount of human endeavor and resources which go into building a boat, yet we just throw them away. Same with cars.

All this consumption. We don't need to. We can keep our same lifestyle but just keep refurbishing and use existing stuff. I have a 41 year old boat. it's fine, excellent actually. I have a wonderful 18 year old car, gorgeous and luxurious and in my eyes it's perfect. I will keep both the car and the boat as long as I am able. I don't need to junk either and get new ones, and I think we shouldn't.
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Old 21-02-2020, 14:45   #161
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Re: Jimmy Cornell goes Electric, with a Cat

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I I have a wonderful 18 year old car, gorgeous and luxurious and in my eyes it's perfect. I will keep both the car and the boat as long as I am able. I don't need to junk either and get new ones, and I think we shouldn't.
And so what happens when your car & boat get to end of life? According to your logic you would have to go without. Or do you really think buying second hand is the answer to global consumption?

To me the issue is not buying new, but the fact that almost all products made today are designed as throw away items, from cars & boats to white goods. It's not wholly the consumer or manufacturers fault but a governance issue.

All mass produced products should be designed with an unlimited lifespan and the total sum of parts should be equal to the cost of the item making them economical to repair.
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Old 21-02-2020, 15:06   #162
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Re: Jimmy Cornell goes Electric, with a Cat

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And so what happens when your car & boat get to end of life? According to your logic you would have to go without. Or do you really think buying second hand is the answer to global consumption?

To me the issue is not buying new, but the fact that almost all products made today are designed as throw away items, from cars & boats to white goods. It's not wholly the consumer or manufacturers fault but a governance issue.

All mass produced products should be designed with an unlimited lifespan and the total sum of parts should be equal to the cost of the item making them economical to repair.
I really think "almost all products" ARE NOT "designed as throw away items, from cars & boats to white goods" I am amazed at the longevity of things these days. When I was a kid nobody kept cars that were over ten years old. Now my 2002 is still almost perfect.

What is "end of life?" In my case the boat can be endlessly refurbished. No part of it beyond the hull cannot be replaced, and the hull could last 100 years, or more. People replace boats because they can, not because they have to, or they sell them and get out of boating and there are too few buyers for the old boat. That is a shame in my opinion, from a resource usage perspective.

The car is another story. While most of the parts can be repaired or replaced there are some things which would be difficult, such as the proprietary computerized electronics, which, because the car is quite rare, are not available. I could not even get exact replacements for the front shocks.

So, there will come a time when keeping it in perfect condition will be impossible, and frankly, the newer cars offer many more features and efficiency. At that time I will decide that it has come to it's end of life and I will buy a different car, probably won't be new because I don't want to spend that much capital on a depreciating item.

But no, I will not go without because I refuse to buy a new car or boat. But extending the useful life through maintenance and upgrades of the items we consume will be good for the future of the planet, and it really makes me feel bad when I toss out a perfectly good item of any kind. I tend to spend more money to fix an old thing rather than discard it.

Finally, most of us discard the old and buy the new simply because we can. The justifications we use are shallow. Admit it, we buy that car because we want it, not because we have to.
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Old 21-02-2020, 16:12   #163
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Re: Jimmy Cornell goes Electric, with a Cat

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. We've had a hundred years or more to develop the ideal trade offs in efficiency, torque, shaft rpm, prop size, etc -- we've about got it right.
Except it isn't right at all. Look at a fish or dolphin's tail compared to its body size and compare your propeller to the size of the boat.

Larger propellers are more efficient. Most sailboats have very small, too small to be very efficient propellers. Cargo ships use huge propellers.

For some, the engine is only intended to be maneuvering in port. A total of less than 1% of total miles traveled. In this case efficiency is less important and you never use the propeller for extended duration.

diesel engines have an overall poor efficiency. It is really not a surprise most boats do not have an efficient propeller either.
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Old 21-02-2020, 19:19   #164
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Re: Jimmy Cornell goes Electric, with a Cat

I think you may have misinterpreted my comment. When I say that we about got it right, what I mean is that we have balanced the various design parameters for the best choice. You are correct, we could increase our reduction ratio (which would increase torque and reduce speed) then make a much larger and much steeper pitch propeller and dramatically improve our efficiency. Of course, our boats would sail much slower and the propellers would be much more expensive and harder to support and be more prone to fouling. Since, as you point out, we do not motor our boats as much as we sail (or at least think we do), we value sailing performance over motoring performance and design our propellers accordingly.
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Old 21-02-2020, 19:27   #165
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Re: Jimmy Cornell goes Electric, with a Cat

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Except it isn't right at all. Look at a fish or dolphin's tail compared to its body size and compare your propeller to the size of the boat.

Larger propellers are more efficient. Most sailboats have very small, too small to be very efficient propellers. Cargo ships use huge propellers.

For some, the engine is only intended to be maneuvering in port. A total of less than 1% of total miles traveled. In this case efficiency is less important and you never use the propeller for extended duration.

diesel engines have an overall poor efficiency. It is really not a surprise most boats do not have an efficient propeller either.
The propeller has to be big enough to transmit the shaft hp to the water, no bigger, and shaft rpm offsets diameter. I have not seen that there is any agreement that a bigger propeller is generally more efficient.

Maybe the way that a propeller works (rotational) as opposed to the flapping back and forth of a fish's tail means that some factors other than size is at work.

And in the case of a sailboat, we have to remember that the propeller becomes drag when the boat is sailing (less, of course, if folding or feathering).

At any rate, the speed I get from my 13" folding propeller (7kts) from an engine running at 28hp is pretty good. I am wondering what kind of efficiency you think we should be getting?
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