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Old 07-12-2020, 12:05   #241
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Re: Jimmy Cornell goes Electric, with a Cat

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marina, the batteries were down to 40%, but at one point the level had fallen to an alarming 13.5%. What this passage has shown was that in spite of all our efforts to save energy,

On average we found that the two propellers could only produce an hourly net charge of 0.6% of the total battery capacity, equivalent to 336 Watts. The only conclusion I could draw was that in its present form, the regeneration system, and implicitly the entire concept, was not working.
1) You cannot efficiently use a propeller to regenerate power. I'm not sure why people still keep trying to use the wrong tool and are surprised when it doesn't work very well. The blades are cupped the wrong way and it just doesn't work very well and never will. Considering the boat had high performance sailing 12 knots, it could easily recharge the batteries in just hours using a larger water turbine that would also be useless for propulsion.

2) An inboard drive system is inherently inefficient. The typical prop slip is significant and the overall efficiency from shaft to propulsion is below 40% in most cases. This is just the wrong way to power a boat mechanically no matter what the power source is if you care about efficiency. An electrically actuated sculling oar or large high aspect slow turning propeller would use about 1/3rd of the electricity for the same thrust as typical inboard which completely changes the results. You don't need much power to move slowly and motoring at high speed is never going to be an efficient use of power.

3) You don't need electric propulsion at all. slocum circumnavigated on this same course and he had many more hardships and even had to use sisal plant fibers etc... It's possible to sail in and out of marinas 95% of the time and the rest of the time you can anchor and wait a few hours then enter (or don't enter marinas even better). This has been demonstrated over and over again since ancient times.
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An electrical engineer by profession, he was the best person to comment on my predicament. His verdict was unequivocal: “Jimmy, your concept may be right but it is premature.
Considering the electrical engineering is a wide field it's fair to assume he may not be the best person when it comes to energy use and consumption, as he maybe specializes in small digital circuits or something. It's not that "electric is not ready yet" but that these sailors were not and their boat certainly was not engineered to efficiently use energy in a multitude of ways.


This is not a blow against electric propulsion at all, but a lesson of what not to bother doing because it's not efficient or effective.
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Old 07-12-2020, 12:15   #242
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Re: Jimmy Cornell goes Electric, with a Cat

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3) You don't need electric propulsion at all. slocum circumnavigated on this same course and he had many more hardships and even had to use sisal plant fibers etc... It's possible to sail in and out of marinas 95% of the time and the rest of the time you can anchor and wait a few hours then enter (or don't enter marinas even better). This has been demonstrated over and over again since ancient times.
its largely impossible to sail into any modern marina and in fact is often forbidden for larger cruisers

what slocum did and when he did it is about as relevant as Robert Stephenson is to a bullet train

( I read his book and other accounts , slocum was a terrible sailor )
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Old 07-12-2020, 12:30   #243
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Re: Jimmy Cornell goes Electric, with a Cat

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. . .it seems they just didn't properly calculate the realistic usage/demand vs the charging that would be available. That's a huge fail for any boat, regardless of the system being proposed.. . .

What they didn't properly calculcate is the real life average output from regeneration. The output from regeneration goes up geometrically with speed, so abundant power at say 9 knots may turn into nothing at 6 and almost nothing at 7. It's easy to get carried away with the performance in ideal conditions and then forget that this just drops right down to nothing in just a little lighter conditions.



That being said, to rely on regeneration to run domestic systems with no generator on board seems crazy to me. What do you do if you spend a few weeks at anchor, something most circumnavigators do more than passagemaking. There should be a backup generator if there is any question about solar keeping up with consumption; regen shouldn't be in the equation at all. I would not have gone to sea in a vessel set up that way. It kind of beggars belief that someone like Jimmy Cornell would.
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Old 07-12-2020, 12:35   #244
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Re: Jimmy Cornell goes Electric, with a Cat

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Originally Posted by goboatingnow View Post
its largely impossible to sail into any modern marina and in fact is often forbidden for larger cruisers

what slocum did and when he did it is about as relevant as Robert Stephenson is to a bullet train

( I read his book and other accounts , slocum was a terrible sailor )

Indeed.


The Pardeys were the most recent long range cruisers to try doing without an engine at all. They got towed into harbours.


If you don't mind relying on towing, then by all means -- do without an engine. I consider the engine to be mission-critical safety issue, myself, even if I am a pretty decent sailor. The wind don't always blow, and sailing a vessel of any size into a harbour in whatever conditions you may find, is foolhardy even if it is not prohibited somewhere.


In olden days when sailing ships did not have mechanical propulsion, they often waited days or weeks for the wind to be right to leave or enter a harbour. And were often wrecked when they couldn't sail out of some difficulty (look up the term "embayed").
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Old 07-12-2020, 12:42   #245
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Re: Jimmy Cornell goes Electric, with a Cat

Yes to many of the previous poster's points.

This really is a shocking embarrassment for all parties concerned.

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Old 07-12-2020, 12:49   #246
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Re: Jimmy Cornell goes Electric, with a Cat

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Yes to many of the previous poster's points.

This really is shocking embarrassment for all parties concerned.

Yes, this.


Jimmy Cornell has about the largest following in the cruising world. Or at least, the largest following commanding deep respect. There are serious You-Tubers out there, but they may not have the same respect. And Jimmy is working with a decent budget, where he's not cheaping out or DIY'ing a system on the go.


Jimmy should know what is needed. And OceanVolt should have (over)designed and installed his system for free. This was both a supreme marketing opportunity, and a colossal marketing failure.


If it worked, they could point at him for years to come. If his experience, funds, and the committed effort of OceanVolt failed -- I shudder to think of it.


Who here thinks that on our more limited lay-person budget and experience could get a functional system from OceanVolt after seeing this failure? Not me!
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Old 07-12-2020, 16:49   #247
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Re: Jimmy Cornell goes Electric, with a Cat

So let's see. Cornell expects 800 watts regen per hour from each SD15 at 8 knots sailing , and gets that in sea trials, but gets 532 watts per motor at average speed of 8.2 knots on passage. Fair enough, I agree that is somewhat disappointing compared to spec., and deserves investigation.

So instead of 1.6 kW x 24 hours = 38.4 kW regen per day, he gets 24 kW per day from regen.

Has it escaped everyones attention, including Jimmy's (with all due respect), that if he is burning through 24 kW of power per day to run his boat, something is very wrong? If he didn't have regen, he'd be running a 6 kW genset 4 hours a day, every day??? And this is AFTER he has turned off the 2 fridges, not boiled any water, and adopted as many "spartan measures" as he could?

Maybe he turned off the fridges but forgot to switch off the breaker to the Jacuzzi?

Also he says that they produced in 10 hours of regen 5.32 kW. So he has regen from only one motor? Why?

And the 5.32 kW represented "9.5% of our total battery capacity."

So he has in excess of 53 Kw of battery capacity?????? That is HUGE and very hard to believe. So in effect he is draining over 50 kW from his batteries to run his boat????

I would suggest there is more to this than meets the eye, at this point. I would like to see the boats energy budget, something seems very wrong.
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Old 07-12-2020, 17:13   #248
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Re: Jimmy Cornell goes Electric, with a Cat

Beakie,


Can you please try and watch the units? Actually, EVERYONE! A battery is not rated in kW, but kW-h. Generation, at an instant, is measured in kW, but generation over some time (10 hours) is in kW-h. So, 1.6kW x 24 hours = 38.4 kW-h (not kW).



Saying 5.32 kW is 9.5% of battery capacity is meaningless. I can run 5.32kW on my 800Ah batteries (actually, no, I'd burn the cables and the 1kW inverter...), but only for about 45 minutes. If I ran a 5.32 kW load for 1 minute, it would be about 2% of my capacity.


I am QUITE CERTAIN he is not draining 50kW from his batteries. At 12V, that would be about 4,000A, and very few cables are that large. Perhaps his daily drain is 50kW-h, although that is still 160A constant drain, still a huge load.


Your conclusions are reasonable (I think) but would be so much easier to follow if your units were proper.


Mixing power units (kW, A, hp, etc) (yes, A are not really power unless you know the volts) with energy units (kW-h, A-h, hp-h, etc) is really confusing.


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Old 07-12-2020, 17:43   #249
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Re: Jimmy Cornell goes Electric, with a Cat

Thanks for the pick up Harry. I feel suitably chastened, because I know better.

As you know, it is shorthand, and used often. But I was also quoting Jimmy Cornell directly from his post, so he needs a reminder note from you as well.
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Old 07-12-2020, 18:08   #250
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Re: Jimmy Cornell goes Electric, with a Cat

It surely is used often. And most times, I can just read through it, even though years of engineering training makes me want to scream.


No, I won't be chastising Jimmy.....LOL I can't even get into the OCC yet*, let alone have the miles he has.


* Side grumble. Two transatlantics on a boat over 74', so they don't count, a 960 mile trip from Marsh Harbor to Newport is 40 miles too short to count. So close, yet so far...LOL
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Old 07-12-2020, 18:26   #251
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Re: Jimmy Cornell goes Electric, with a Cat

I need to rewatch some of umas videos as well but i think even they didnt have full batteries after the atlantic crossing. My guess is no one until now really rested regen over long diatances and like jimmy said smooth test sails are not reliable.
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Old 07-12-2020, 19:31   #252
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Re: Jimmy Cornell goes Electric, with a Cat

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So let's see. Cornell expects 800 watts regen per hour from each SD15 at 8 knots sailing
Once again you wheel out these cruising speeds that just donít stack up in the real world.

Sure you will see 8 knot averages for a boat this size tearing down wind before a stiff trade wind, but the reality is always different as you will learn once you get a few miles under your belt.

The only reason we hear about boats like this having high seasonal averages is the owners motor heaps.


Check out the average wind speeds in the pacific, you may get a surprise.
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Old 07-12-2020, 19:39   #253
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Re: Jimmy Cornell goes Electric, with a Cat

Your "guess" that regen has not been tested under real world conditions, is laughable. How did you come to that conclusion? Just curious, how many installations do you think Oceanvolt have?

But I would entirely relate with anyone who is wondering, as you understandable are, about not being able to see details of positive OV customer case studies on regen. That's a failure of marketing smarts, not the technology.

FWIW, there is a monohull here in Oz with a Servoprop installation, and they have a problem with regen. The problem is at times they have TOO MUCH regeneration. That can create issues also.
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Old 07-12-2020, 19:41   #254
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Re: Jimmy Cornell goes Electric, with a Cat

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Once again you wheel out these cruising speeds that just donít stack up in the real world.

Sure you will see 8 knot averages for a boat this size tearing down wind before a stiff trade wind, but the reality is always different as you will learn once you get a few miles under your belt.

The only reason we hear about boats like this having high seasonal averages is the owners motor heaps.


Check out the average wind speeds in the pacific, you may get a surprise.
The discussion at hand is a specific boat making an actual passage at a calculated 8+ speed, and complaining about insufficient regen at those speeds. Not sure that Beakie was "wheel[ing] out these cruising speeds that just don't stack up in the real world." It was a real world test that really had those speeds. Granted, it wasn't the typical mom-and-pop heavy cruiser, but this was a real semi-production boat in real conditions.



And no one was speaking of seasonal averages, and this boat in particular doesn't (can't) motor much at all!
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Old 07-12-2020, 20:01   #255
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Re: Jimmy Cornell goes Electric, with a Cat

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Originally Posted by Seaslug Caravan View Post
Once again you wheel out these cruising speeds that just donít stack up in the real world.

Sure you will see 8 knot averages for a boat this size tearing down wind before a stiff trade wind, but the reality is always different as you will learn once you get a few miles under your belt.

The only reason we hear about boats like this having high seasonal averages is the owners motor heaps.


Check out the average wind speeds in the pacific, you may get a surprise.
Once again, you offer opinions that have little value. And in this case you clearly don't know what you're talking about, which I guess shouldn't be surprising to CF members familiar with your posts. I guess, in your case, it would be asking too much that you'd actually read the link given to Jimmy Cornells post.....

It is not me that stated the average sailing speed over 10 hours on Jimmy Cornell's Outremer 45, it was Mr. Cornell himself.

Of course, what would he know about judging sailing performance, compared to yourself?
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