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Old 05-11-2016, 10:04 AM   #81
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Only a little.

You wouldn't need a very big outboard to move you along at get home speeds. 15 - 20hp? You may already carry one for your dink.

And this solution would be a lot cheaper than adding a wing engine. Especially if you only have a real need for the wing engine for this one long trip.

I've seen it done on other boats. And while they didn't have nor need the fuel capacity you might, it did work.
Sorry my response was a little curt. I agree that in principle it could work. I do have a 20HP motor for my dink. The problem is that I'd need to carry about 500 gal of gasoline for it to give me the 1000 mile range that I'd need. And I might well want a bladder for extra diesel for the longer crossings.

My plan is to keep going after I reach Hawaii - so I anticipate many long passages.

Richard
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Old 05-11-2016, 10:21 AM   #82
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Thanks - the question for me is based around whether I want to add a hydraulic PTO to my existing 20kW generator for this kind of get home system. Alternatively I could use the 240V it's already generating to power an electric get home motor. It would seem to be a simpler solution - though I'm not sure if it would be cheaper yet.

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The limiting factor for the Eagle hydraulic bow thruster get home is the Perkins 35 hp. If the gen has to be replace a 50+ hp gen set would be installed. I would not size by kw but hp. To me a gen set is two separate items, a engine and a generator. The cruise gen is powered by the main 671 engine. Hydraulic you talking horse power.
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Old 05-11-2016, 11:05 AM   #83
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The limiting factor for the Eagle hydraulic bow thruster get home is the Perkins 35 hp. If the gen has to be replace a 50+ hp gen set would be installed. I would not size by kw but hp. To me a gen set is two separate items, a engine and a generator. The cruise gen is powered by the main 671 engine. Hydraulic you talking horse power.
If I'm adding a hydraulic PTO to the engine that drives the generator then yes - HP would be the unit of power to look at. I think it's around 27HP for the Lugger that drives my NL. But if I add an electric motor and use the electric power output of the generator then kW is what matters. So it's all a question of what power transfer mechanism you are using. In my case I'm leaning towards electric.
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Old 05-11-2016, 01:47 PM   #84
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Sorry my response was a little curt. I agree that in principle it could work. I do have a 20HP motor for my dink. The problem is that I'd need to carry about 500 gal of gasoline for it to give me the 1000 mile range that I'd need. And I might well want a bladder for extra diesel for the longer crossings.

My plan is to keep going after I reach Hawaii - so I anticipate many long passages.

Richard
No problem. I was just thinking out loud and wasn't sure just how often you'd be making long distance runs.
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Old 05-11-2016, 05:43 PM   #85
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If I'm adding a hydraulic PTO to the engine that drives the generator then yes - HP would be the unit of power to look at. I think it's around 27HP for the Lugger that drives my NL. But if I add an electric motor and use the electric power output of the generator then kW is what matters. So it's all a question of what power transfer mechanism you are using. In my case I'm leaning towards electric.
Would be interesting to see what you come up with as far as electric motors. Above 10 HP, most electric 220 volt motors are 3 phase. Maybe a company like Siemens has some special purpose motors in the 15 to 20 HP range. The second probably tougher issue is starting surge load. Unless the motor is a slow starting variable speed, the electrical surge to start that motor in gear, very likely may trip the main breaker. If money is no object, maybe a variable speed prop for soft starting that could also be feathered to reduce drag and keep the shaft from spinning when not in use,

Lots of fun spending other people's money. Now I understand politicians.

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Old 05-11-2016, 08:02 PM   #86
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Would be interesting to see what you come up with as far as electric motors. Above 10 HP, most electric 220 volt motors are 3 phase. Maybe a company like Siemens has some special purpose motors in the 15 to 20 HP range. The second probably tougher issue is starting surge load. Unless the motor is a slow starting variable speed, the electrical surge to start that motor in gear, very likely may trip the main breaker. If money is no object, maybe a variable speed prop for soft starting that could also be feathered to reduce drag and keep the shaft from spinning when not in use,

Lots of fun spending other people's money. Now I understand politicians.

Ted
Yes - most of the motors I've seen for boats are DC with big battery banks. That's not really what I want - though it does solve the soft start problem. I've got quite a few years before I'll really need this so there's plenty of time for technology to catch up.

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Old 05-11-2016, 08:17 PM   #87
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Variable frequency drive (VFD) will solve any "hard start" issues. Proven, off the shelf, common technology.
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Old 05-11-2016, 08:32 PM   #88
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Variable frequency drive (VFD) will solve any "hard start" issues. Proven, off the shelf, common technology.
Are these available for single phase 220V?

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Old 05-11-2016, 09:12 PM   #89
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Are these available for single phase 220V?

Richard
Yes sir. So common you can even find them on Amazon.
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Old 05-11-2016, 09:48 PM   #90
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Are these available for single phase 220V?

Richard

yup. also some models can drive a three phase motor from a single phase source.
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Old 05-11-2016, 10:21 PM   #91
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Yes sir. So common you can even find them on Amazon.
Interesting - though they don't seem to provide high power versions (20kW)

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yup. also some models can drive a three phase motor from a single phase source.
However, as you say, these exist:

20KW single phase 230V to 3 phase 400V converter - 20KW single phase 230V to 3 phase 400V converter Exporter, Manufacturer & Supplier, Yueqing, China

That could be used to power a 3 phase VFD at 20kW.

Thanks for all the pointers

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Old 05-12-2016, 12:04 AM   #92
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The Amazon link was more of a haha. Likely a joke only I could get. Sorry Richard

They can be sourced in any size, phase, voltage you specify. Extremely common in commercial/industrial settings. Handy little devices that make the impossible (or really difficult) happen. Commercial HVAC would not be able to exist in its current state without them.
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Old 05-12-2016, 01:18 AM   #93
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Interesting - though they don't seem to provide high power versions Richard
The biggest VFDs I worked with were 5,000 HP being powering cyclone feed pumps.
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Old 05-12-2016, 07:36 AM   #94
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Are these available for single phase 220V?

Richard
The motor has to be 3 phase. The freq. drive creates the third phase.

We use them on chilled water A/C systems all the time to ramp up the chiller compressors.
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