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Old 06-07-2008, 08:25   #16
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There are some real advantages - there is instantaneous power when you need it, no need to start engines. The engine controls can be mounted pretty much anywhere, or be portable - he's thinking about mounting them on a belt so he can walk around the boat with them - would make mooring up single handed easier
44,

Add to this full torque at low rpms and best of all, quiet or at least much quieter motoring, few moving parts, low maintenance etc.

Electric propulsiion fascinates me and I would dearly love to go electric but after several years of reasearch came to the conclusion that at this time it's just not practical for a large cruising boat. The Ossa system would be a possibility but is way out of my price range. Gideon's Green Motion is another that bears watching but again, not within my means. I looked into the re-e-power systems but they develop less torque than Arjan was able to achieve on his "Roktat" (a similarly sized and probably equally lightweight cat) and he was still underpowered even at 72 volts. I fear that your friend may be dissappointed, although I hope that he is not.

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Old 06-07-2008, 08:52   #17
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Cruisers & Sailing Forum is an easy way to search for specific topics on this site, and if you've decided on a multihull sailboat with an inboard engine, you will want to read the several discussions of shaft drives vs. saildrives, cats vs tris, shoal draft keels vs boards, etc. Opinions vary [understatement] and are never in short supply!

I think you are on the right track. A '68 Suburban is a bit more challenging than repairing and maintaining the engines typically found on multihull sailboats. See if you can find a short course in diesel engine repair for boat owners in the Norfolk area. In addition to learning about the engines, you will have an oportunity to meet like minded people.

New and Used Yachts for Sale - YachtWorld.com is a good place to explore the variety and costs of cats and tris, but don't get put off by the seeming preponderance of megabuck vessels; there are some true gems out there that might fit your purposes at a merely horse-choking price tag.
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Old 06-07-2008, 09:36   #18
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Originally Posted by klevalt View Post
Thank you for all of the information you have provided! I guess I am lacking a key bit if information here... the multi-hull will be a sail boat... how does this change the scenario?

None at all, I believe all who responded assume you're talking a sailing multihull. I agree with the poster who said if you're useing electric to get in and out of port or very local day sailing, electric could suffice. The one advantage I do see is as Sunspot said, it's instant power at the flip of a switch. But that's no trade off if you're considering any kind of long distant sailing, electric just doesn't have the long run times you can so easily get and need from diesel power. I'd hate to be looking at a stiff current with no wind with my Amp meter buried to the left. I had a good soaking a few years back with another boat I had and the diesel engine had a good bath, not submerged but soaked to the gills. After the bail out and some wiping down she fired right back up. I'd freak if an electric motor and it's asscociated wiring got the same bath. When I got back I gave her a good fresh water bath and oily wipe down and changed a few electrical connections and it ran another year or so until I sold it and it still serves the new owner well. I still say (Being a comercial electrician for years) this technology is years off of serving the long distace cruiser.
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Old 06-07-2008, 09:39   #19
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Does anyone have any knowledge of lithium-manganese batteries? These seem to be about ready to come on the market, an they may have a favorable impact on the viability of electric propulsion. They are much lighter in weight than lea acid batteries, and seem to be much more stable than lithium ion batteries. Below is a link:

torqeedo: Produktbeschreibung

(Kalhoff Electric bikes use lithium manganese batteries and a good description of the technology can be found here: Electric bicycle batteries - what you need to know about Lithium ion batteries for electric bikes

Also, Genasun is developing a lithium-ion battery that has been used in the 2007 Mini-Transat:

Genasun
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Old 07-07-2008, 01:04   #20
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I think Gideon uses these expensive batteries for their capacity to weight, he's very careful with weight.
You may intend to sail but the engine is your back up plan. The old sail ships came to grief because there was no back up plan.
You will need to motor for a couple of days. That needs diesel. A diesel electric drive is more flexible in terms of location, can be lifted for sailing, and is no more expensive as new. Battery capacity can be very low too, depends on marina to sailing distance but more on the domestic demand. Running the motor for an hour a day while you do mains voltage cooking is not a big deal. Gen Sets are available, I saw 1500 watts at about 4000 sterling, all packaged in a sound box. Drive motor pods (try gideon,he installs them) you want a submersible motor, the sewage industry uses then a lot, and a matched prop. Some second hand units are available, depends on your budget and experience.
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Old 21-07-2008, 02:09   #21
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OK, help me out here, I have been told by competent people that for a 40 to 42 foot cat not to accept less than 2 30 HP diesels because anything less is insufficient, and unsafe. that is 60 HP*746 watts per HP = 44760 watts or approximately 45KW. The last I checked none of the boats were coming with a 45 KW generator to power the motors, and the batteries would not handle a 2 hour trip up river much less all day against the wind and current. I have heard the story about being more efficient, but my yanmar book shows that the prop and the engine are perfectly matched at full horsepower, I do not buy that the electrical system outperforms the mechanical system at full power. So which is it? are the diesels way oversized? or is the electic way undersized?
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Old 21-07-2008, 04:28   #22
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Quote:
Originally Posted by decktapper View Post
OK, help me out here, I have been told by competent people that for a 40 to 42 foot cat not to accept less than 2 30 HP diesels because anything less is insufficient, and unsafe. that is 60 HP*746 watts per HP = 44760 watts or approximately 45KW. The last I checked none of the boats were coming with a 45 KW generator to power the motors, and the batteries would not handle a 2 hour trip up river much less all day against the wind and current. I have heard the story about being more efficient, but my yanmar book shows that the prop and the engine are perfectly matched at full horsepower, I do not buy that the electrical system outperforms the mechanical system at full power. So which is it? are the diesels way oversized? or is the electic way undersized?

The electric to diesel comparising works different, we have powered a FastCat 435 with 2 x 4.5 Kw and the actual top speed under power is 6.5 knots with a loaded and clean cat
with 2 x 9.6 kw we expect a top speed of 8.5 knots on the FastCat 455 loaded to 8.5 tons
that is the same speed as we get out of 2 x 29 hp Yanmars in other words
9.6 Kw will give us the same power as 22 Kw diesel power . much of this has to do with the losses from the crankshaft to the prop and the high torque always available on the electric motors.
The first Green Motion Fastcat will be launched in 2 months and if you are interested we can keep you posted.

Greetings

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Old 21-07-2008, 05:42   #23
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Gideon,

Perhaps the point of the advice that Decktapper refers to is that the 2x30 hp engines are needed to be able to safely maneuver the boat in high headwinds and choppy waves. You didn't mention the wind and sea state conditions under which you achieved 6.5 kts top speed.

I know from experience that I can achieve hull speed (7.6 kts) in my monohull at 2800 rpm in calm conditions, but with 50 kt headwinds and waves, I make no way whatsoever, and can just barely keep the bow into the wind at max rpm (3100) on my 56 hp Yanmar.
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Old 21-07-2008, 07:25   #24
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Originally Posted by Hud3 View Post
Gideon,

Perhaps the point of the advice that Decktapper refers to is that the 2x30 hp engines are needed to be able to safely maneuver the boat in high headwinds and choppy waves. You didn't mention the wind and sea state conditions under which you achieved 6.5 kts top speed.

I know from experience that I can achieve hull speed (7.6 kts) in my monohull at 2800 rpm in calm conditions, but with 50 kt headwinds and waves, I make no way whatsoever, and can just barely keep the bow into the wind at max rpm (3100) on my 56 hp Yanmar.
In both cases with Diesel and with the electric motors we measured in no wind and flat water conditions however with wind on the nose with both , the drop in speed is considerable more with the diesels as it is with the electric motors.Force 7 on the nose gives
5.5 knots for the electric 2 x 4.5 kw version and 6.5 knots with the twin 29 hp diesel .
This probably has to do with the lower revving larger props on the electric version.
With the 2 x 9.6 Kw retractable electric version we expect better speeds with wind on the nose than with the diesels for the same reason.
I have not had 50 knots on the nose with the electric motors yet but with the 29 hp yanmars it is the same as with you , almost no headway with 50 knots

Greetings
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Old 21-07-2008, 09:31   #25
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Does anyone have any knowledge of lithium-manganese batteries? These seem to be about ready to come on the market, an they may have a favorable impact on the viability of electric propulsion. They are much lighter in weight than lea acid batteries, and seem to be much more stable than lithium ion batteries. Below is a link:

torqeedo: Produktbeschreibung

(Kalhoff Electric bikes use lithium manganese batteries and a good description of the technology can be found here: Electric bicycle batteries - what you need to know about Lithium ion batteries for electric bikes

Also, Genasun is developing a lithium-ion battery that has been used in the 2007 Mini-Transat:

Genasun
The biggest concern with Lithium is the management of the charge/recharge cycle. If a lithium cell becomes compromised(damaged), or is charged / discharged too quickly - it becomes highly explosive. For this reason there is no way on earth you'd convince me to put a lithium ion battery on a boat. A Lithium magnesium Battery would be more stable than a Lithium Ion, and a Lithium Phosphate would be the most stable. The Torqeedo you suggested seems a decent choice. I'd preference the Valence Lithium Phosphate as an extra measure of safety. But having used Lithium Ion Batteries in my RC Planes, I learned first hand the dangers of Lithium Ion technology and after my first fire, I studied the technology quite a bit. Call my view tainted as a result, but no battery manufacturer will ever convince me that Lithium Ion is safe in a seawater environment. To much opportunity for disaster imo...

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Old 21-07-2008, 09:53   #26
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Hud and Gideon: I think you have touched on a critical point, headway in 50 knots. I know of several popular sailboats that can't do that, or even keep the bow into 40 knots of wind. Perhaps this is one of the reality checks that distinguish blue water cruisers from coastal sailors. We should discuss this further. What IS a realistic expectation?
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Old 21-07-2008, 10:03   #27
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Originally Posted by decktapper View Post
OK, help me out here, I have been told by competent people that for a 40 to 42 foot cat not to accept less than 2 30 HP diesels because anything less is insufficient, and unsafe. that is 60 HP*746 watts per HP = 44760 watts or approximately 45KW. The last I checked none of the boats were coming with a 45 KW generator to power the motors, and the batteries would not handle a 2 hour trip up river much less all day against the wind and current. I have heard the story about being more efficient, but my yanmar book shows that the prop and the engine are perfectly matched at full horsepower, I do not buy that the electrical system outperforms the mechanical system at full power. So which is it? are the diesels way oversized? or is the electic way undersized?
I had a 47ft cat with 2 x 25kw gensets powering 2 x 35 hp electric motors. It was certainly not overpower. The electric motor rpm - torque curve can be adjusted relatively easily, unlike the traditional diesel. So at low rpm, docking etc, high torque was available. However at the high rpms you are still limited by the total hp available therefore it was not much different than 2 x 35 hp diesels.
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Old 21-07-2008, 10:10   #28
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One point I forgot to mention above. 1,000 rpm was max on electric motors so it did have more torque at top end than comparable 35 hp diesels and therefore fitted with larger and higher pitched props. So there was some efficiency gains from that.
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Old 21-07-2008, 10:12   #29
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Hi klevalt,
I love your idea!!! I had the same thought myself a couple years before diesel prices went crazy. I almost did it for my 47' crab crusher of a cruiser, now I wish I had.
The major problem no one is facing is 5 knots is a lot for electric engine. But what is your hurry? What is wrong with crossing the equator at 1 knot? You will get there in the end. With a tri you will have LOTS of room for solar panels. The problem with diesel electric systems is most operate at 120 volt DC which means with all those batteries--- you still have to have house batteries!!!! So what is wrong with 24 volt system? (24v because the wiring is smaller and lighter and big trucks operate on 24v so you can still get lights, refrig, etc.
A German 30' circumnavigated with an electric engine. He had a back up honda 500--it was years ago. No Problems.
Check out my sight for other ideas in my book--- Boat Repair in Exotic Ports around the World (It is written on the lighter side-- but we all need a laugh or two once in a while.)

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Old 21-07-2008, 10:17   #30
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I think with 50 knots on the nose one should still be able to move forward with 2 knots as a minimum
That way at least the boat is still steerable and that is our aim for Green Motion .

Greetings
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