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Old 01-30-2008, 08:27 AM   #81
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Electric Boat Engines

Nope, you're right. Most cruising sailboats have a steering vane AND an A/P. An A/P you can push a button...to go do something real quick. A steering vane has to be "set up" and would be a PIA touse on a moments notice for only a moment.
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Old 01-30-2008, 02:59 PM   #82
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RE: Electric Boat Engines

So what does this have to do with electric boat engines? Having all this great discussion under an incorrect topic will certainly hide it for future visitors. You guys really should start a new topic when it wanders too far from the original topic.
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Old 01-30-2008, 03:43 PM   #83
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Electric Boat Engines

Keith--

You're right. It's sort of evolved from electric boat propulsion to efficiency to prop walk to torque to steering to hydraulic steering to autopilots. If anyone goes any farther with any of these (except electric boat propulsion) it should be opened up as a new topic.
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Old 01-30-2008, 05:03 PM   #84
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RE: Electric Boat Engines

Well, golleeeee. I jst thought this thread was about "electric boat engines" instead we have the biggest collection of polly waffle and misinformation I have ever read. We even got to talk about airplanes, which is no surprise as one contributor who flies a small float plane is an expert on everthing else that flies. Marin you've written at last count (but sure to increase!) 5832 words on this thread alone, most of it conjectural rubbish. So it's time to go off the deep end and look for our new word...... cu there!*
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Old 01-31-2008, 05:14 AM   #85
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Electric Boat Engines

"No argument regarding the need to hold pressure on the helm or tiller of a sailboat. "

Many properly designed sail boats are happy to cross oceans with the helm free, just trailing.


IF I were reinventing the wheel and blowing huge bucks on all electric boat , I WOULD SPEC A TRIM TAB ON THE RUDDER AND USE AN ELECTRIC, sailboat style ram to control it .

Off the shelf and cheap.
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Old 01-31-2008, 09:55 AM   #86
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Electric Boat Engines

Believe me FF, I have thought about that alot.
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Old 01-31-2008, 12:01 PM   #87
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RE: Electric Boat Engines

As most of you know I think diesel electric propulsion is super and I'd like to have it on my boat but there is at least one thing that will keep it in the exotic catergory with very few on the water. People who can service them may be 3000 miles from my boat. Like Marin and FF say DE will remain exotic and rare.

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Old 03-19-2008, 04:45 AM   #88
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RE: Electric Boat Engines

"Let's say that you would normally use two 150 hp Yanmar engines and a 16kw Fischer-Panda generator. If you replaced this with a single 150kw OSSA Powerlite generator and a couple of 100hp OSSA Powerlite motors you would have a lighter system, better fuel economy and about the same "usable" power at virtually no additional cost.... "

I don't understand the above.

If you have two engines 150HP each and you repalce them with one 150 HP, what you have is a system with half the power.

Yes, you can run the generator at optimum speed all the time, yes you can have two big screws in stead of one, yes you can disregard the losses between the diesel engine the generator and the two electric motors because of new technology, but does all this optimization suddenly double the output?
Isn't this a tad optimistic?




-- Edited by Marc1 at 05:46, 2008-03-19
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Old 03-19-2008, 07:15 AM   #89
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RE: Electric Boat Engines

There's a good article on this subject in the current (4-08) issue of Power Cruising. Here's the short form: diesel electric *used to have* a greater advantage because older diesel mains were inefficient when operating at lower loads; the generator, OTOH, can run at its optimum load at all times. But the newer electric diesels are much more efficient running at lighter loads, so much of this advantage has gone away.

Still in favor of diesel electric, however: at lighter loads, transmission loss becomes a significant factor for traditional installations but not for electrics. High output alternators can sap significant power, whereas generators are more efficient at battery charging. Electric engines turn slower and use bigger props which are more efficient. And finally, coastal cruisers who visit marinas often can utilize cheaper AC to charge the batts and run off those for a period of time.

Then there's the issue of maintenance....

The author concludes that much of this has yet to be quantified, but he suspects there's still an advantage for diesel-electric.
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Old 03-20-2008, 04:42 AM   #90
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RE: Electric Boat Engines

"High output alternators can sap significant power, whereas generators are more efficient at battery charging."

Nonsense the power required to operate the noisemaker will be far MORE than the extra fuel burn from running an alt on the operating main engine.

On our old MD3b Volvo , it was easy to see a 300rpm loss starting the 10hp refrigeration compressor , with no rpm loss when turning on 2 - 130A Balmars.


"Electric engines turn slower and use bigger props which are more efficient."

The gearbox folks have at least 6-1 boxes on the shelf , and that will require a prop that will hurt the draft of most cruisers. And have you ever run the PRICE of a 48 inch to 60 inch prop?

"And finally, coastal cruisers who visit marinas often can utilize cheaper AC to charge the batts and run off those for a period of time."

Many of the better marinas (with big power ((usually for air cond)) ) have METETRS and charge far more for power than a utility. "Free power" from the marina is DEAD .

One cant go cruising on someone else's money.



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Old 03-20-2008, 09:24 AM   #91
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RE: Electric Boat Engines

Paralysis by anlysis!!! Keep her tied to the dock, FF!
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Old 03-20-2008, 06:19 PM   #92
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RE: Electric Boat Engines

Yep.

1) It isn't a choice of running a *separate* generator to charge the batteries vs. running an engine/alternator, it's a choice between running a generator in *place* of the engine/alternator;

2) For sure, bigger props will reduce draft and increase cost; the author was only discussing whether diesel/electric could save fuel. On balance diesel/electric is more expensive;

3) Electric power from the untility is still cheaper than diesel power, even if you have to pay for it. Hence the trend toward plug-in hybrids.
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Old 03-21-2008, 03:56 AM   #93
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RE: Electric Boat Engines

It isn't a choice of running a *separate* generator to charge the batteries vs. running an engine/alternator, it's a choice between running a generator in *place* of the engine/alternator;

The smallest most highly loaded diesel engine will always be the most efficient.
Simply ideling the propulsion engine to spin a tiny alternator will always be the big looser.

Shades of the 60-70's where folks would run a 4-107 to make DC to run a fridge!

The best way to have a taxi engine that could run 4000+ hours last 1000!

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Old 03-21-2008, 04:18 AM   #94
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RE: Electric Boat Engines

Hum...someone is confusing the topic or confusing me.

Diesel electric propulsion for a boat means that in stead to have a gearbox attach to the shaft, you have a generator attached to the main engine and an electric motor turning the shaft. There is no talk of batteries of any sort.

The part I don't understand is this:
There is clearly a loss by converting fuel into energy into electricity and back into mechanical energy in stead of fuel into mechanical in one go.

To compensate this loss and gain some advantage we are told that the diesel engine now turned generator can run at optimum load therefore being more efficient than running at all sort of different revs to suit conditions.
Now as an ex diesel generators mechanic, I find this a tad optimistic.
When a generator can be kept running at a set number of revs, the load variation that is a direct result of what the skipper needs at the time will still mean a variation in load and therefore no such mythical suit spot at all.

Now we are also told that you can have two generators, a small one and a big one and so have three different combinations. Low power required, run the small gen set, more power run the big one, even more run both.
Furthermore you can run a number of props off the one generator or the two.

When I can imagine that it is better to run a small engine at full load for low speed, and a bigger engine at full load for higher speed, I can still not imagine how this complicated set up can compensate for it's own complication. I can imagine this to be of advantage on big ships, but on 50' boats?
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Old 03-21-2008, 06:35 AM   #95
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RE: Electric Boat Engines

"Diesel electric propulsion for a boat means that in stead to have a gearbox attach to the shaft, you have a generator attached to the main engine and an electric motor turning the shaft. There is no talk of batteries of any sort."

Maybe I am confused, but I thought that the genset *was* the main engine in this arrangement and you have the option of running the electric motor directly off it, off a battery bank, or off a combination of the two.


"The part I don't understand is this:
There is clearly a loss by converting fuel into energy into electricity and back into mechanical energy in stead of fuel into mechanical in one go."

I guess part of it is that there's also a loss of energy in the standard setup-- converting engine rpm to shaft/prop rpm, and that loss isn't present with an electric motor.
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Old 03-21-2008, 10:34 AM   #96
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RE: Electric Boat Engines

Yep, Adam, that's how I understand it, also. If it's a true diesel/electric system there is no "main" engine. There is a diesel generator which supplies power to every system on the boat -- including the electric motors that turn the props.

Marc, in your example above, you're not replacing two 150HP engines and the generator with just one 150HP generator. You'd be replacing the two propulsion engines and the generator with ONE generator and TWO 100HP electric propulsion motors.

You could look at it as losing 100HP but I think the larger, more efficient props and the always optimum load and max torque make up for it. Read some of the links on the first page of this thread to see an explanation of why you can get the same results with less HP. Warning: Not every one agrees with the explanations. * I guess that's why this thread is still going strong.
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Old 03-21-2008, 11:38 AM   #97
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RE: Electric Boat Engines

Guys,

Why on god's green earth are we talking about gensets? This thread is about DE and to my knowledge has nothing to do with domestic electrical power. The to systems are only connected by the fact that power to run the computer to control the DE system comes from the batteries/genset. As to the efficency question it seems that if efficency at full throttle is better with DE then the power loss in mechanical to electrical to mechanical is less than the losses in the gear box. Whats this talk about taking on power from dockside plug ins? To my knowlege DE propulsion motors never ever run off gensets or batteries. Maybe I'm not so smart either! Please enlighten me if I'm wrong.

Eric Henning
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Old 03-21-2008, 01:08 PM   #98
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RE: Electric Boat Engines

Eric, the way I understand it, a true "pure" diesel/electric system would have no "propulsion" engine at all.* There would be a diesel generator.* That's the "diesel" part of diesel/electric.* The generator would power the electric motors that turn the shafts and props that move the boat.* That's the "electric" part of diesel/electric.* The generator is sized to be able to supply all the power needs of the electric motors plus any/all house/boat system needs.* So you supply everything with one diesel generator (two, or more I guess, *if the boat is big enough to require that much).

Batteries can be/are added to the equation to supply power at anchor but I don't think a pure diesel/electric system would use them for propulsion.**

Of course I could be*the confused one.*
*
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Old 03-21-2008, 01:16 PM   #99
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RE: Electric Boat Engines

I had a post here about the new "Genset" locomotives Union Pacific has developed that I thought used a diesel generator to charge batteries that operated the drive motors.* I did some more investigating and found that I was wrong.* The Genset locomotive uses several relatively small diesel generators to power the drive motors instead of one huge diesel egnine*and generator.* When the load is high, all the gensets run.* When the load drops after the train gets up to speed, some of the diesel gensets shut down.* The objective is reduced emissions and fuel usage.

So my notion that if batteries can power a locomotive they should be able to power a boat was based on an incorrect assumption.

I did learn that the next generation of diesel locomotives is going to store the energy generated by dynamic*braking in batteries instead of simply dissipating it as heat.* Then the batteries will be used to augment the power from the diesel-electric plant to run the locomotive.* If GE's figures are correct, the fuel and emission savings will be very impressive.* Not applicable to boats, unfortunately, because a boat is essentially always going uphill so the*load never drops off.*


-- Edited by Marin at 22:17, 2008-03-21
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Old 03-22-2008, 04:20 AM   #100
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RE: Electric Boat Engines

"I did learn that the next generation of diesel locomotives is going to store the energy generated by dynamic braking in batteries instead of simply dissipating it as heat."

If you check you may find that the "batteries" are giant capacitors, not the lead stuff in your bilge .

Wet batts charge far to slowly , even on 25 downhill miles down the Rockies to capture much energy.

Capacitors can be recharged VERY rapidly.

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