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  #31  
Old 12-04-2009
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Quote:
Originally Posted by sailingdog View Post
While electric power may make sense for a daysailer, it isn't a good idea for a cruising boat. If the boat requires moving under power in hazardous conditions for prolonged periods of time, the real problem is that the electrical bank can not be easily replenished. If the generator is large enough to power the motor without the aid of the battery bank, then there is little in the way of weight or energy savings.
Sailingdog is right. I have some knowledge of electric propulsion systems as I recently built and drive a 1974 VW Beetle that has been converted to battery-electric drive. I put 10,000 miles on it, and it has a top speed of 70 mph so it was highway capable. The best range I ever got out of it was 40 miles. I also investigated an electric outboard on a pontoon boat with solar panels on the roof.

Daysailer: yes
Long-range cruiser? not a good idea.

The problem is simply the batteries. Current battery technology is just not a large enough storage medium (too small of a "fuel" tank). If you get caught in a hard blow, or a situation where you need sustained auxiliary propulsion, you'll be screwed. You would have to positively upholster your boat in solar panels and wind turbines to get an appreciable charge into them without shorepower.

The batteries are expensive. I used 8 volt golf cart batteries. 16 of these ran me about $1500. Golf cart batteries are the ONLY batteries that can stand up to this application. "Deep Cycle" Marine batteries absolutely will not stand up to this kind of abuse, neither will 12v gelcell batteries.

If you have unlimited money to throw at this project, new Lithium batteries are smaller, lighter, and hold more energy. There are several chemistry varients: Lithium cobalt, Lithium sodium, etc. Unfortunately, Lithium batteries absolutely require a computer controlled management system to keep them balanced without destroying them. Lead acid batteries do not because you can safely (for a time) overcharge the "full" batteries while the laggers catch up and achieve full charge. The result is that the full batteries have boiled away some electrolyte and you just add de-mineralized water. You can't add water to a Lithium chemistry battery.

It's a good idea, and I'm not saying you shouldn't do it, but I am saying that you shouldn't do it on a blue water boat or long-range coastal cruiser. A day-sailer that stays near home is most appropriate under today's battery and charger limitations.

I can provide more information, but I think I've gone on long enough.
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  #32  
Old 12-04-2009
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Quote:
Originally Posted by COOL View Post
JCR,
The boat is a custom built Lancer 36, originally
built as a race boat with minimal furniture.
The boat displaces 10,500 lbs on 29' LWL, so
it is very easily driven.
The engine is a Volvo MD 11C with a 110S Saildrive.
When I am able to get the machine started, which has always
been an issue, it will push the boat at 7.5 knots at 2500 rpm.
The shaft output is rated at 17 kW at that speed.
The ratio is 1.66:1.
The current prop is a 2 blade fixed , maybe a 16"x11", it seems
to be too much prop and the acceleration will throw off your
feet when you ease it in to gear. I will eventually go with a
folding prop of some sort.
I am guessing that I will not need a thrust bearing for the belt
drive, but I will build a composite structure to support the
Saildrive, since it was supported by the engine.
i do not know how yet to configure the ground loop
for the electrical system, that was connected to the
engine block.
My expectation is to get into and out of the slip,
we are sailors and not motorsailors.
Cool

I am a little surprised that it takes 17KW to push your boat basically at your hull speed of around 7.2 knots. Any thoughts of changing over to straight inboard when you refit to electric propulsion? I agree you should not need a thrust bearing if you are belt powering your saildrive. Please know that an electric drive is most easily suited for an inboard setup and is very basic and simple once you complete the actual mounting installation. But certainly you can do what you are suggesting. If you need help or just some pointers to help you let me know.

JCR
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  #33  
Old 12-04-2009
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Not to mention the drag.
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  #34  
Old 12-06-2009
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Cool,

You might be interested in this; http://www.sillette.co.uk/elect_saildrives.pdf

Good luck with your repower.
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  #35  
Old 12-07-2009
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Quote:
Originally Posted by JCR View Post
Cool

Any thoughts of changing over to straight inboard when you refit to electric propulsion?

JCR
If you mean a propshaft and stuffing box arrangement,
then No.
The Saildrive is in good shape, and the boat came
with an unused spare just like it. I plan to do the project
in the water. And my ultimate pipedream would be to devise
a retractable drive leg that seals flush with the hull.
Thank you for the helpfull comments.My first, and most
difficult step will be to remove the big hunk of iron.
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  #36  
Old 01-31-2010
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If we could forget about "hull-speed" and spend more time considering a speed that requires far less energy, electric would look much more viable.

First off I don't rely on speed after playing "chicken" with a storm before I finally realize that it has me in it's sights. I preplan my sailing regarding forecasted weather. When I do get it wrong, hull-speed doesn't seem to move me fast enough anyway.

I'm ready for electric and the purported shortcomings(?) that are associated with it, even if it means moving at 2 knots in the duldrums, as long as I can get rid that #$&*#% motor.
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  #37  
Old 01-31-2010
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One absolutely insurmountable advantage that an internal combustion engine has over an electric drive system- instant refueling. We can compare power output and weight and whether we really really need to travel at hull speed until the end of time, but you cannot get around the fact that when you run out of diesel or gas, you can fill up your tank and restart. Sure, you could keep a spare bank of batteries on standby, but that is just one more bank to wire, store, charge, and pay for. It is a hell of a lot easier to store five or ten gallon cans of diesel or gas on board than it is to try to store a spare bank of fully charged batteries.

Respectfully, those of you who are tearing out your engines to install electric drives because you are unable to get your IC engines to run reliably will likely also have big problems with electric drives as well. if you cannot handle the basic maintenance and repair needs of an IC engine, you will be utterly clueless at troubleshooting and maintaining a cobbled together multiple battery electric drive.

And why anyone would spend upwards of $3k to install an electric drive to avoid the $2k cost of making an Atomic 4, Westerbeke or Yanmar trouble-free is beyond me.

Last edited by bljones; 01-31-2010 at 07:21 PM.
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  #38  
Old 02-01-2010
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Quote:
Originally Posted by bljones View Post
One absolutely insurmountable advantage that an internal combustion engine has over an electric drive system- instant refueling.
And why anyone would spend upwards of $3k to install an electric drive to avoid the $2k cost of making an Atomic 4, Westerbeke or Yanmar trouble-free is beyond me.
If you run out of diesel or gasoline in the the middle of the ocean,
you will have no opportunity to refuel until you reach civilization.
With an electric system, you have the ability to regenerate or
recharge through solar panels. It may take some time, but you
still have an option.
If you spend $2000 on an old A4, you will still have an A4.
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  #39  
Old 02-01-2010
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My A4 is 40 years young and just had its first full service and was pulled because the shaft log required a repiar and other PO compleat lack of matiance

We move a C&C 35 MARK I at 7+ knots with a 13.5 HP diesel i would think the prop is your leading issue

It only has a 10 gallon tank as at 14 MPG we never have a range issue
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Last edited by tommays; 02-01-2010 at 03:35 PM.
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  #40  
Old 02-01-2010
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In reply to COOL
If you're offshore I doubt you could charge the battery banks enough for much motive power as you'd have enough trouble gathering enough amps from the sun or wind for daily use. Unless you started a generator and if you're going to have one of those why not just have an engine.
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