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Old 17-01-2016, 01:43   #226
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Re: Tug of War - Electric vs Diesel

Of course, in order for the electric motor to be able to provide this 2 or 3 times rated power, there must be a power supply able to sustain the electrical loads, and a controller able to arrange the occasion. This does not seem likely in the typical electrically powered yacht.

Further, the analogy of a tractor pull is flawed, due to the differences in the way the energy is converted to bollard pull. Knobby tires on dirt are a bit different than propellers in water. In the former, application of high torque at zero rpm is useful. In the latter, the propeller must reach a considerable rotational speed to generate pull... different ball games!

Finally, this whole argument is silly, for the "tug of war" has absolutely nothing to do with the normal operation of a sailboat under power. We seem to be observing a bunch of zealots promoting their views rather than a reasonable discussion of the merits of a new technology applied to an old workplace.

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Old 17-01-2016, 14:13   #227
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Re: Tug of War - Electric vs Diesel

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Originally Posted by mcarling View Post
More like five minutes.
That will do a lot of good fighting a strong current/headwind.


Straw man argument. I never made any claims about warrantiesYou made claims about ratings. Manufactures set ratings. Blow thru them and you void warranties. Why do manufacturers do that? Because they know the engines won't last if you exceed the ratings.


No problem. I'll even give you an example that's easy to verify. Sea Shepherd's MV Brigitte Bardot, formerly MV Cable and Wireless Adventurer designed by Nigel Irons blew up an engine by running several hours at full throttle playing cat and mouse with the Japanese whale poachers in the Southern Ocean Whale Sanctuary. Video recording of the event can be watched on Animal Planet's Whale Wars. While I have crewed with Sea Shepherd a couple of times, I was not onboard the Brigitte at the time.So where are the details. Age/hours of engines. Were they maintained? Etc... All you have is a failure without any real details. If you watch these types of shows and don't understand most of it manufactured from drama...well there's not much I can do to help you.


And that proves it doesn't happen???No but it establishes that its a very rare event unlike your implication that open up the throttle all the way and you are ensured of a quick engine failure.


You seem to think I've made some point, or tried to make some point, that I have neither made nor tried to make. Please reread or rethink.You seem to be pushing the idea that electric HP is not the same as diesel HP. That's false. If you have some other point, please share it with the rest of us.


Yes, of course, and I've never suggested otherwise.


I've already clearly stated that it would burn up.So what is the point? You could put a giant turbo on the diesel and get 5 minutes doing the same thing. In actual tractor pulls, that's pretty much what they do but it has no relationship to this thread.


All of that is correct, but not the full story.Please share the rest of the story then.


That's not what happens in real tractor pulls.Last time I went to a real tractor pull, the turbo charged IC engines were the big boys. They dealt with torque issue by spooling the engines up and thrashing the transmissions. Unless you are suggesting adjusting the idle to something on the order of 2500-3000rpm and hoping for the best when you put it in gear, what is your point.


I have not written anything contrary to that.

I'm going to try one last time to explain this at a third grade level, since what I previously wrote was unclear to at least one reader.

The difference between the maximum power than a diesel engine can produce for five minutes versus five days is roughly about 10%. The difference between the maximum power than an electric motor can produce for five minutes versus five days is about 2-3 times. These are facts that can be verified by anyone who knows about diesel engines and electric motors. The rated power of diesel engines is their maximum instantaneous power, which is not very different from their long-term sustainable power. The rated power of electric motors is their long-term sustainable power, which is very different from their maximum instantaneous power.

Nonsense. I used to have a 7.3l diesel in a pickup. It put out 180hp. I knew guys who put a turbo on it and got the HP up around 250-275 and they didn't blow up first time they hammered the throttle. I'm sure you could go with a bigger turbo and get into that same 2-3 times range but just like the electric motor, it will have a 5 min life span. What's the point?

I have not claimed in this thread that electric motors have any advantage over diesel engines for any purpose other than tractor pull competitions, so please stop with the straw man arguments. If you still don't get it, please go ask an expert you trust.Then what is your point? This is a thread about electric vs diesel motors on displacement cruising boat.
As previously stated, it's about the use case:
- For a small passenger car, you can downsize the HP and get similar performance. The IC engine only needs around 40-50hp to maintain freeway speeds. Bump that up to around 70-90hp to account for strong headwinds or climbing a grade but for acceleration, you need torque and there the electric motor delivering max torque from zero RPM offers an advantage. The net result is a small car can go from a 120-150hp IC engine to a 70-90hp electric and the performance differences will be almost unnoticeable.
- For a cruising sailboat, no one really cares about 0-6kt times, if they did a reduction gear and a big low pitched prop would solve the issue. Max HP is called for when fighting a strong headwind/current/wave. In that scenario the diesel is spooled up to the point where it is putting out it's rated HP and the electric has no advantage.

Correction: turbine engines get used for the biggest class in actual tractor pulls. Turbocharged are the second most powerful. Not seen an electric at a tractor pull.
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Old 17-01-2016, 15:28   #228
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Re: Tug of War - Electric vs Diesel

Since you continue to misattribute to me points not stated and not even implied in what I've written, there is no point in continuing to attempt dialog.
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Old 17-01-2016, 22:40   #229
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Re: Tug of War - Electric vs Diesel

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Since you continue to misattribute to me points not stated and not even implied in what I've written, there is no point in continuing to attempt dialog.
I'll take that to mean you cede to my points.
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Old 17-01-2016, 22:52   #230
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Re: Tug of War - Electric vs Diesel

Some arrogance creeping in there...

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Old 17-01-2016, 23:00   #231
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Re: Tug of War - Electric vs Diesel

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Originally Posted by mcarling View Post
I've seen marine diesels fail because a skipper decided run a diesel engine at full throttle for a day or more. That's their rated power -- their rated maximum power, not continuous power.

An electric motor run at its rated power should be fine for months. However, it's possible to run an electric motor at 2 or 3 times its rated power for very brief periods, such as for the demonstration video at the beginning of this thread. Try that for an hour and the electric motor will fail. With a diesel, its not possible to substantially increase power beyond rated power the way it is with an electric motor -- except by making major modifications, like adding a turbocharger or nitrous oxide or something like that.

That's one of the often overlooked reasons why an electric motor will generally beat a diesel in a tractor-pull like competition such as the video at the beginning of this thread.
Makes sense. And shows that any advantage the electric motor might demonstrate in the video isn't really applicable to the real cruising world.
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Old 17-01-2016, 23:37   #232
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Re: Tug of War - Electric vs Diesel

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I'll take that to mean you cede to my points.
You have a much more inventive imagination than I do. First you attribute statements to me that I didn't make, didn't imply, and never even imagined. Now you're attributing concessions to me that I have not made. Welcome to my ignore list.

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Makes sense.
Thank you.

Quote:
Originally Posted by 44'cruisingcat View Post
And shows that any advantage the electric motor might demonstrate in the video isn't really applicable to the real cruising world.
Yes, exactly.
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Old 18-01-2016, 00:03   #233
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Re: Tug of War - Electric vs Diesel

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Some arrogance creeping in there...

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Naw, just see this a lot when people muddle up a conversation and then rather than clarify thier points, they get testy and throw out an end claim that it's impossible to have a discussion.

I throw them an end claim back. If they really have valid points, they will clarify.
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Old 18-01-2016, 00:09   #234
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Re: Tug of War - Electric vs Diesel

I disagree. Your statement around ceding points was arrogant, assuming and very likely intentionally provoking.

In any case, it stifles debate and community learning-which is why I'm here, so I find it annoying. For other reasons too.


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Old 18-01-2016, 00:13   #235
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Re: Tug of War - Electric vs Diesel

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Originally Posted by valhalla360 View Post
Naw, just see this a lot when people muddle up a conversation and then rather than clarify thier points, they get testy and throw out an end claim that it's impossible to have a discussion.

I throw them an end claim back. If they really have valid points, they will clarify.
Fwiw, your arguments to him sounded illogical and i can appreciate his frustration with you. You seemed more interested in 'winning an argument' than addressing what his points were. No wonder he gave up with you.
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Old 18-01-2016, 00:14   #236
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Re: Tug of War - Electric vs Diesel

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Originally Posted by tp12 View Post
I disagree. Your statement around ceding points was arrogant, assuming and very likely intentionally provoking.

In any case, it stifles debate and community learning-which is why I'm here, so I find it annoying. For other reasons too.


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my impression too. I wasnt contributing but i have been reading along.
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Old 26-09-2016, 07:40   #237
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Tesla Powered Speedboat

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The video shows a pulling match between 2 equivalent cats, one with 2x 10kW OceanVolts and the other with 29HP diesels.

Assuming this was done legitimately, ie that both boats had full throttle on, this shows the torque advantage of electric motors vs diesel.

Discussion?
You sure opened up a can of worms here BigBeakie

I haven't had a chance to read back thru all of this subject thread, but of what I read so far there are a lot of 'closed minds' to the idea of electric propulsion.
So I thought I might throw this one into the pot

Interesting forum posting with video links
All Electric "Tesla" Speed Boat - Boat Design Forums

Quote:
Originally Posted by smasterson
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Old 26-09-2016, 08:04   #238
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Re: Tesla Powered Speedboat

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You sure opened up a can of worms here BigBeakie

I haven't had a chance to read back thru all of this subject thread, but of what I read so far there are a lot of 'closed minds' to the idea of electric propulsion.
So I thought I might throw this one into the pot

Interesting forum posting with video links
All Electric "Tesla" Speed Boat - Boat Design Forums

"]

Looked at the link for the Bayliner conversion. The owner reported a 25 mile range under battery power and 4 to 12 hours recharge depending on the charge voltage.

Great idea for anyone that doesn't ever go more that 12.5 miles from home.

Electric power is great and offers many significant advantages but a couple of major shortcomings.

The two biggest are range and cost. To get range you need to tow a barge loaded with batteries or install a large electric generator. Oh but wait, you installed electric power to get rid of the engine and towing a barge isn't practical at all.

Yes I do know how to sail a boat but there are times and places where one needs power and range or you just can't go a number of places.

If understanding and acceptance of the limitations of electric power means I have a closed mind then I guess I do.
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Old 26-09-2016, 09:12   #239
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Range

That speed boat experiment had quite a large HP installation, and much more speed capability than what I am looking for. That range they attained was surprising to me, and encouraging as well.

I'm looking at a sailing vessel aux,...I'll explain soon.
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Old 26-09-2016, 09:14   #240
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Electric Motor Propulsion for 40 foot sailing catamaran

I am working on a design for a 35-40 foot catamaran that I term a picnic/weekender catamaran. The concept will be somewhat similar to this one I found in Thailand a few years ago. I posted it on several boating forums a few years ago.
Weekender/Picnic PowerCat - General Catamaran Discussion | YachtForums: We Know Big Boats!





This particular catamaran was a powercat. I will be adding a sailing rig to it. I will also adding a trolling/fishing chair area to rear deck area,... so that pictured Zodiac dinghy will be relocated, and the two outboard engines need to be eliminated.

I need to repower this cat design, both for close quarters docking situations, and for some motor/sailing situations.
I have had a very long time interest in the rim-drive propulsion concept.
Rim Driven Propellers - Technical Discussion | YachtForums: We Know Big Boats!
What I have in mind at this moment is how I might adapt this to be my single primary propulsion propeller. I would like to mount it in the aft portion of a of the wingdeck of the vessel, and make it steerable upon demand, and also retractable when sailing. Naturally it requires an electrical supply, which as I understand it under present technology can come from a combination of battery power and a relatively small DE power plant. This power plant would be located in its own insulated (heat and sound) box up on the flat deck of the catamaran.

So here are a list of questions I have at the moment:

1) Can such a rim-drive propulsor be run continuous without overheating? It is my understanding that the Vetus unit can do that now.

2) Whether it is the Vetus rim-drive, or another electric drive motor, is it possible to operate such a 'DE system' with very little battery supplements?

3) How few batteries are required (in the interest to keep added weight down) ?

4) Is it possible to 'direct drive' this 'electric prop' with the DE power plant, or are batteries required.

5) I realize Vetus has its own DE power plant, but it appears that FisherPanda has an even greater selection of small DE power plants. Can these systems be mixed?

7) Should the Vetus rimdrive prove not powerful enough, what are the other alternatives that anyone would suggest??


As an example of why I might be considering this approach, I will offer this personal experience of mine. I was the original importer to the USA of French catamaran line,... the original model was a 37 foot boat called the Louisiane 37. I placed a 9,9 hp Yamaha 4 stroke Hi-Thrust outboard engine on it. It was a limited production outboard they made with an extra gear reduction in the output prop shaft so it could turn a bigger propeller. It worked pretty good as we got 7 knots out of the vessel in calm conditions. The engine was mounted in the center on a rear beam of the vessel, and soft lines were lead from the engine to the rudder arms so when docking the engine would steer along with the rudders. Maneuverability was VERY good. It made me a believer in 'steerable engine', verses twins,...an alternative to consider.



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