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Old 19-11-2020, 07:12   #196
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Re: Jimmy Cornell goes Electric, with a Cat

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UMA is kinda screwed with an electric motor in the Fjords of Norway. Forced to sail when the weather is bad and stuck when the weather is nice but no wind....

40 tacks in 3miles....
Or was it filmed for the camera and nothing wrong with that, made a completely different video subject from the norm on a wet and windy afternoon. What else were they going to do?

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Old 19-11-2020, 07:18   #197
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Re: Jimmy Cornell goes Electric, with a Cat

did you have wind gen's?
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Old 19-11-2020, 07:29   #198
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Re: Jimmy Cornell goes Electric, with a Cat

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UMA is kinda screwed with an electric motor in the Fjords of Norway. Forced to sail when the weather is bad and stuck when the weather is nice but no wind....

40 tacks in 3miles....
Watching that video... I suddenly became very fond of our self-tacking jib
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Old 19-11-2020, 07:53   #199
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Re: Jimmy Cornell goes Electric, with a Cat

Yes, a D400. Worked well for this environment on passage, but at anchor there was either no wind or we were tucked into a cove and blocked from a good part of it. The engine was ran often just to charge the bank... I never had to do that much before.

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did you have wind gen's?
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Old 19-11-2020, 08:50   #200
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Re: Jimmy Cornell goes Electric, with a Cat

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did you have wind gen's?
who you asking?
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Old 19-11-2020, 12:49   #201
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Re: Jimmy Cornell goes Electric, with a Cat

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Watching that video... I suddenly became very fond of our self-tacking jib

Their tacking angles were atrocious. Would putting the dinghy on the foredeck or cabin top have helped, rather than dragging it?
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Old 19-11-2020, 13:26   #202
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Re: Jimmy Cornell goes Electric, with a Cat

Meanwhile, in 2012
Nothing to see here, move along


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Old 19-11-2020, 13:52   #203
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Re: Jimmy Cornell goes Electric, with a Cat

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When we hungout last year, I did warn them about the winds in the fjords.... heck, the entire Norway coast. The thought at the time was for them to get a portable gas generator for this part of the journey.

There's a reason the Viking boats had so many rowing positions .



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I follow Uma and watched this earlier today. 10 nms made good, 30 nms sailed, and 41 tacks in 8 hours. In the rain.

Lesson learned could be bring a generator. But I suspect it better describes why so many sailors migrate to a trawler.

Just sayin'

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Old 19-11-2020, 14:15   #204
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Re: Jimmy Cornell goes Electric, with a Cat

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I follow Uma and watched this earlier today. 10 nms made good, 30 nms sailed, and 41 tacks in 8 hours. In the rain.

Lesson learned could be bring a generator. But I suspect it better describes why so many sailors migrate to a trawler.

Just sayin'

Peter
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To be honest with you, that trip would have been a lot more fun (in fact it could have been a great sail with good wind and flat water) with a boat with great windward performance. Put the dingy on the foredeck, and dress warmly.

We sailed in places and conditions like that for years on the coast of Vancouver Island or inland in the fjiords there, and loved it. We had a diesel motor when we wanted it, good heat and lots of excellent sailing.
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Old 19-11-2020, 14:56   #205
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Re: Jimmy Cornell goes Electric, with a Cat

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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.
We have an ex commercial fishing trawler and still have the 52 inch 4 blade fan and nozzle.
Yesterday , clicked in gear at 750rpm we were doing 5.1 knots
Of course it is not the sort of thing you want to be dragging around on a sailing vessel.

Other similar sized boats with same engine and gearbox ratio have removed the big fan and nozzle and run higher rpm/burn more fuel to achieve same speed.
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Old 19-11-2020, 15:14   #206
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Re: Jimmy Cornell goes Electric, with a Cat

Simi,


I totally get why a sailboat goes with tiny props, and then make them folding on top of that. I'm not giving up a knot or more of speed for ANY prop, regardless of how fast it makes me under power! LOL


I even get the compromise on flat bottom power boats, where the prop is the deepest (and most vulnerable) thing on the bottom -- there is a tradeoff to go big.


But in your case -- why would anyone remove a perfectly functional prop/drive assembly, to go to a smaller less efficient prop? What are the tradeoffs? Perhaps it is a repower to a more modern engine, where low speed shaft turns are just not an option?
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Old 19-11-2020, 15:22   #207
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Re: Jimmy Cornell goes Electric, with a Cat

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cruising w/ an electric motor but no diesel generator makes little sense. you need a generator for distance and exactly these types of situations imo.

But as soon as you install a big diesel generator, you've just sort of defeated the purpose of electric. Yes, electric is green, and perhaps you save a few hundred dollars a year on fuel. But you still have to buy an engine, maintain an engine, maintain fuel tanks (worse, tanks that hold fuel that is in theory rarely used), and lose the space and weight to an engine. And the engine would need to be nearly as large as any engine the boat would normally use. And you would do all that while also incurring the cost and environmental impact of an electric motor/battery/solar farm (their impact is in China, so not easily seen, but they are not without their own form of environmental damage).
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Old 19-11-2020, 15:53   #208
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Re: Jimmy Cornell goes Electric, with a Cat

I will say I just looked at their video. Were I there, with our boat, with our nice diesel engine, I might have raised the anchor under sail and not have turned the engine on until we were at the destination dock (same plan they had). Those conditions are what I consider "nice sailing," even if a bit too exciting. If they had wanted to leave earlier, but couldn't because of lack of wind, then that's a problem. But I think they left because the weather forecast didn't look good for staying there -- and that would apply to a boat with an engine too. I also suspect that if they wanted to leave on the calm day, 10 miles at low speed "should" have been in their battery range, so they could have done that.



Not that I agree with electric power for a cruising boat. But I don't think the electric power factored into this equation.
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Old 19-11-2020, 19:09   #209
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Re: Jimmy Cornell goes Electric, with a Cat

I think they mentioned something like 2-3 hours of motoring in calm weather. At the end of the video it looks like their battery was at 62%? I'm guessing the lack of good sun is really effecting their power generation. It's going to be hard for the regen to have any real impact on these short hops in the fjords. All these probably lead to some unnecessary anxiety.

Their live chat did sound very one sided, like a cat/mono debate with just cat or mono owners but not both. I think Dan said at one time 'everyone' at anchor is waiting for an engine part which cancelled out their need to wait for weather window.............i dunno about that.
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Old 19-11-2020, 21:39   #210
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Re: Jimmy Cornell goes Electric, with a Cat

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But a fan isnít the source of heat, right? Isnít it just blowing air from one place to the other? So what is the heat source for the air that youíre referring to?

Our boat has a diesel hydronic heater with heat exchanger fans in all four corners and the salon. Unfortunately the heater itself has failed beyond repair. Our dilemma: do we purchase a replacement diesel hydronic heater to take advantage of the existing installation, or do we rip all that out and go with a new heating system? If new, what?
Somehow I missed this reply...

A fan is an excellent source of heat. Even more so than an electric heater on a watt for watt basis because:

An electric heating element is 100% efficient in converting electricity into radiation. However, radiation is not 100% efficient in heating the air in the boat. A portion of that electromagnetic radiation is lost. Low frequency radiation will simply pass through the sides of the cabin without imparting much if it's energy (like radio waves). Higher frequency thermal radiation will impart some of it's energy directly to the air, but a considerable portion of the thermal radiation will get absorbed by surfaces on the insides of the cabin. These surfaces will in turn re-radiate their energy in many directions. Some of that energy will heat the air next to the cabin surfaces, but some of it will be re-radiated away from the insides of the cabin resulting in more energy loss.

Fan's also generate radiation from the coils in the motor the same way that a heating element does. However, fans also generate heat through mechanical friction due to the turning blades hitting the air. This interaction increases the average kinetic energy of the air with no electromagnetic losses.

This mechanical heating of a substance with fans is the same way that James Joule discovered and described the relationship between heat and work.

Obviously, if a human is standing under a fan, the evaporative cooling effect on the human's skin will override the short term 20-80 watt heat output of the fan.
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