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Old 09-17-2008, 04:31 PM   #1
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As I continue in my quest to purchase and equip a multihull for a circumnavigation I find myself revisiting the issue of electric versus diesel motors. Last year I demoed the Lagoon 42 Hybrid and found it to be slow and heavy, and was told that it was the additional weight of the batteries and the larger Genset that is required to keep the batteries charged and the fuel that still has to be carried to keep the Genset running so that the batteries can be charged so that the motors can be run. (A chain of events). Anyway when I demoed the Lagoon 42 with its Solomon electric motors we found that the Genset would kick in and run every 20 minutes in less than 10 knots of wind. The propellers which are not folding are supposed to turn at the cost of ½ a knot to charge the batteries but that was not sufficient and the broker assured me that everything was working as it should.

With continuously rising fuel costs, availability issues and a need to be more environmentally friendly we keep looking at electric, but most have told me that electric is not where it needs to be yet to be depended on while circumnavigating.

I like the idea of electric but in all practicality should they fail in the middle of some ocean it is impossible to repair them as they are sealed units (or so I am told), versus a diesel motor that given reasonable spares I could either repair or rebuild.

Back to the electrics, I have been told that they are unreliable, have no worldwide support, and certainly non in some of the more distant locations and according to Lagoon you save no more the 1/3 of your total fuel costs on the electric motors versus the fuel usage of diesels. Why should they be so unreliable, the electric motors that are used in some of the yachts are designed by Solomon who builds the electric motors for most of the electric trains that run in Europe and elsewhere (again or so I am told).

Opinion, ideas and suggestions are most welcome and for those that are cruising or are circumnavigating are there any that have or know of that did so using the electric motor option ?
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Old 09-17-2008, 04:57 PM   #2
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Aside from in icebreakers, I have no experience of electrical propulssion (and that was diesel-electric) but I do feel drawn towrds electrical propulsion as it is environmentally friendly, relatively cheap, almost silent and very reliable in comparrison to the infernal combustion engine.

The Swedish firm of Oz Marine produce what I believe to be the best unit on the market just now - but there again I have not done a lot of research into this.

As battery capacity steadily increases, I am sure we are going to see many more yachts with electrical auxiliaries.

Aye // Stephen
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Old 09-17-2008, 09:45 PM   #3
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I personally agree that the electric propulsion systems available today, are not where they need to be yet in order to be economically viable to the crusier. I have done considerabe research myself on what is available both here in the U.S. and Europe. The Europeans seem to be slightly ahead of the US in R & D of these "Hybrid" systems but still lack feasability for applications such as ours. The "Chain of events" scenario is the same conclusion I came up with.

I believe future development in "Fuel Cell Technology" may be the first to provide the answer, but they are propably 5-10 years from it. I would personally suggest, stick with what works and has been proven. Buy something you don't need a computer tech to troubleshoot and fix.

I decided to sell my pretty, brand new, computer controlled, emisions compliant Cummins turbo diesel ($25k) and go with a 1979 Ford Lehman 6 cyl, 120hp. I can rebuild the whole entire motor with 7 wrenches, 2 screwdrivers and a hammer! Just the way it should be...Oh and I have less than $2k in this motor with all new accessories and spares! A savings of only $23,000! I burn 2.2 gallons per hour at cruise with the old school Ford vs.- 8 gal per hour with the high tech motor. Technology looks great... on paper!

I know you have big decisions to make, just thought I'd throw in my 2 cents worth of knowledge. Whatever you decide, Good luck....Steve
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Old 10-15-2008, 12:15 AM   #4
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I find it difficult to understand why, when sailing in a 10kt breeze, why the generator needed to kick in every 20 minutes. Were you motor sailing with WOT (wide open throttle) ? My understanding of the electric motor/regeneration system, is that you need to have the 'throttle' barely on, so that the prop is spun in reverse while sailing and regeneration can occur, thus topping off your batteries.

If you wish to motor sail under any wind conditions and still get some regeneration, you can do it by setting the 'throttle' such that the prop is spinning forward at the same speed as the sails are producing ie effectively a 'zero sum' equation. Therefore when the boat picks up speed for whatever reason, such as wind gusting, the boat surfing down a wave etc, the prop (and therfore motor) will then spin in reverse for the duration and provide some regeneration capacity. It should be possible on a long cruise (theoretically anyway) to never use the genset, unless becalmed.

I have done a fair bit of research into the concept of electric motors for cats and think the concept is brilliant for low cost, sustainable cruising. An electric motor has just one moving part - the shaft, while an ICE (internal combustion engine) has hundreds, many needing relacement often and expensively. With an EM all you have to replace are the brushes every few years at a cost of say $20 or so, - and you can do it yourself in 10 minutes. Just imagine - No fumes, no greasy engine compartments, no oil changes, no mechanics bills, no grease under fingernails = happy wife = happy life, and last but not least SILENCE !!.

The cost of batteries and things like ultra capacitors are coming down all the time, thus making the idea more "do-able"

Don't give up your quest - I suggest you look into procuring the best technology for each part of the electric motor system and DIY (Do it yourself) If nothing else, you will understand your system thoroughly and know how to fix it if things don't work as they should.

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Andrew
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Old 04-30-2012, 09:41 PM   #5
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Default Diesel or electric

I have done a masive amount of research and reading on this subject and i believe that the one major consideration is the batery bank. Most electrical motors run quite effectively on 144 Volt and the genset also add to extra weight as is fuel. These being the downsides the upsides is realy worth it. If one offset this weight by reducing weight on other goods and your boat can cary this weight you will have home on the sea. All the luxeries you can imagine and as a bonus no noise no diesel fumes to deal with. When one bring service intervals and related cost into the equation electrical propulsion win hnds down. Back charge from drag is a bonus and should not be a dependable factor.
Correct discharge of bateries will determine batery life and i have found that on average discharching 60% will give my batery bank a five year life span. The genset is so configured that it kicks in at 40% automatically and the diesel consumption is far less than a 48Hp Yanmar running for one hour at 1800 rpms.

I am fitting two 12Kw electric motors with 12 forklift bateries which at 260AH will give more amps than most houses get from their utility suppliers. The genset is a 22Kw genset and will produce ample Kw to keep the motors going for a long time if the wind dies down.

I hope that somwhere in this writing you will find some answer to your search.
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Old 04-30-2012, 10:43 PM   #6
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Interesting in concept yet I wonder if this is the full story when it is all priced and weighed out mile by mile? The weight of the (forklift type?) batteries is enormous and converting diesel-generated torque into Ah-storage in batteries and then back again to motive power will have some losses. My guess is perhaps 15-25% loss in all, remembering the theory is always better sounding than the practice.

Best life expectancy for batteries, even with deep storage types, is to around 40-50% discharge depth relative to capacity. In the relatively warm waters cruisers tend to frolic in the life expectancy of the cells is reduced further. ( like 50% for every 10deg temp rise at the higher average temps )

To prevent shorting out with minor flooding of the bilge, the weight of high-mounted battery banks will be detrimental to boat trim as well, something to think about even with a cat which suffers from overloading much more than a heavy-beamed mono-hull cruiser.

Do you have some links that show some figures for weight/power ratios? I'd be interested to study that. Currently I'm running full solar on both the boat (45') and an off-grid dwelling and just found it's actually quite expensive when it's time to replace batteries. Costs seem to go up way ahead of projections and after about 5 years I had two out of 16 ( 6v L16-type ) lead-acids develop a shorted cell on my land-based set-up. And that is with stationary use only! Maintenance cost may well become an issue, is the point.

Electric motors imply copper which with salt air implies green problems, unless all is kept scrupulously clean, dry and insulated. An oily diesel chugger is more forgiving in that regard. Cost-wise, my 16 new 6V L16 will run North of $5k, heavier deep cycle ones will cost 2-3x more at least.

How did your set-up actually pencil out for you $-wise or did you have some special deals or circumstances working for you? Diesel I believe is still the biggest bang for the buck, if you will pardon the pun. I am all for running renewable and alternate energy yet in practice find the harsh reality of facts is often very unkind to our lofty and commendable goals, even as I wish it was not so. Good speed and a frothy wake!

Ivo S/V Linnupesa
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Old 05-01-2012, 02:22 AM   #7
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Guillaume--144V DC--that sounds pretty lethal--so 120VAC rectified, pretty much? Most electric drive systems for yachts are 36V, 48V, 72V, 96V. The company in Maryland (sorry, don't recall the name...), they seem to be the only one that I can think of that advocated for higher voltage systems, but I haven't kept up with what they're doing...

Linnupesa, you've pretty much got it right--diesel is the most cost efficient solution. There are many, many dreamers out there who imagine that they will re-charge their big battery bank and use that for their electric drive successfully. It just ain't so.

The few folks I know today with electric drive motors in use state that they've been unsuccessful with any meaningful regeneration via prop shaft and that solar and wind don't manage to top things up when they really need to use the electric drive (e.g. upwind motorsailing or pure motoring for more than a short while). One fella was trying to bash his way back up Baja and called another friend of ours literally crying "what am I gonna do? I've got no engine and the alt energy just isn't keeping my batteries topped up for my electronics much less the electric drive." That poor fella didn't even have a portable generator on board. Now there's a dream gone wrong.

On the other hand, I know a few folks who had realistic expectations of their electric drive system and they're quite happy. One fellow has a 40' sailboat which he day sails up in Canada--he has a 6kW electric drive motor and a battery bank that he keeps topped up with shore power. He uses the motor ONLY to get in and out of his slip--though he says he's motored for about 3 hours in a calm to get back to the slip. Another fellow uses the electric drive pretty much the way you'd use a hydraulic transmission--he has an 8 kW diesel generator located in one part of the boat and the 9 kW electric drive back at the stern. Happy fellow and operates pretty much at zero float on his battery bank--meaning he doesn't need the batteries in the first place.

That brings us to our own boat's experience--she was built back in 1931 and is thought by many people to be the first hybrid yacht out there. She had a 25kW electric drive motor and two 10kW (gas-not diesel) gensets to run it. A hefty battery bank allowed her to motor for an hour or so w/o genset (as I recall reading about it in a yachting article written in the 1930's). The gensets were installed well forward, with a gas/water separater exhaust and with the electric drive aft. The cockpit was quiet--and that was the goal of the owner. He actually usually used the boat with one or both gensets running and kept the speed so he was zero float on the batteries--so not using their capacity at all. He owned and used the boat extensively with that drive system in place for about 5 years before selling it. He wrote in Yachting magazine the only thing he would have done differently was to get rid of the battery bank and run the engine w/one or both gensets on (depending on whether he wanted 10kW or 20kW available. He could make our 29ton boat do 6 knots on 10kW delivered or 7.8 knots on 20kW delivered.

That electric drive system is long gone--the fellow who bought the boat from the original owner took it out and put in traditional diesel. We've got a new diesel that the owner before us purchased, so it will be many years before we consider something different. We very likely, eventually, put in a system much like the original one but without the huge battery bank

Fair winds,
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Old 05-01-2012, 04:38 AM   #8
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Default Electric or diesel

Lunepesa i cannot fault your contribution and could not agree with you more, paper is indeed a whole lot friendlier than practise.

This whole idea came about when i took delivery from my boat which has a 40Hp air cooled Deutz engine with Volvo Penta z-drive. The motor was fitted in cente of the cockpit floor with a belt driven configuration partly in the in the bilge. The previous owner said he would replace that power configuration as it was a weak moment!

In my ealy research i ran across a Austrian hybrid system which held promise but would be extremely costly as you use a diesel motor coupled to a generator which in turn was coupled to an electric motor all with cluthes so one can select which to use and when to use which.

My cat has a massive bilge, bigger than most i have seen and a plan is formulating in my mind to reinforce the bilge floor and waterproof and seal a big enough area to hold my batery bank and genset. There seems to be ample space to even fit fans and a small aircon to control/regulate the tempreture with enough vent area. This configuration and location should centralise my weight and keep spread it all about 1.3 above sea level which theoretically should improve my stability. This is not final and i will still run this by a marine engineer and architect friend.

If this configuration is workable it will solve a few problems on a lasting basis and with enoug amps my lifestyle at sea should include a number of niceties i have at home. i.e. dish washer, electric oven etc.

It is true one need to watch weight as boyancy remain the difference between sailing and swimming and lastly perhaps also a very big motivator is the fact that i will be cruisig not racing. Adapting to that from a fast lifestyle might be another animal that would need taming!

So once i have run all this by my marine engineer friend and got his feel and guidance i will most certainly report back. In terms of the electrical configuration to date it seems a 12Kw motor seems to be a adquate size motor with which one can also run with a single motor.

I also thougth the 144 Volt requirement was a bit high but was informed that this voltage motors have a number of advantages like for example fireproof,waterproof and brushless and there is a Stainless Steel vesion also.

Once i have sorted out the bilge idea and determined the actual weight i most certainly will report back as i agree it does sound a bit fishy but boy if workable i will be smiling!
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Old 05-01-2012, 05:39 AM   #9
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Hi Guillaume

perhaps you may want to re-read the comments made a lot earlier in the thread about the commercially made cat where the gen-set needed to run every 20 minutes for a meaningful speed. It is all do-able, really, but does the complexity make it worthwhile and even more importantly, is it efficient? I'm thinking of the early rush to RO water makers.. what was the point of burning a lot of diesel to obtain a few gallons of water with a very heavy, expensive and maintenance-hungry de-salination plant? An evaporative still or extra water tankage might have provided the same results at a fraction of the cost.

As to voltage, the U-boats ran around 300V+. My guess is that because the I squared R losses are reduced at the higher voltages wiring can be of a much lighter gauge and consequently much cheaper. The same applies to the motor armatures and their efficiencies. ( less heating loss )

This high DC voltage is certainly more lethal and will for sure also run a good welding arc if Klutzenheimer drops a wrench across some terminals. Ruins your whole day, that. So, working at sea may take on a whole new and exciting dimension as every shift might well be your last, like in RIP Crispy-Critter. With 12V DC that lethal risk is far less... and death IS final.

But hey, alles sal reg kom ou beesie, nie waar nie? Or did I get the country all bollocksed up now?? Ek is n ou Kaapenaar hier.

Ivo SV Linnupesa
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Old 05-01-2012, 06:42 AM   #10
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Quote:
Originally Posted by linnupesa View Post
Hi Guillaume

perhaps you may want to re-read the comments made a lot earlier in the thread about the commercially made cat where the gen-set needed to run every 20 minutes for a meaningful speed. It is all do-able, really, but does the complexity make it worthwhile and even more importantly, is it efficient? I'm thinking of the early rush to RO water makers.. what was the point of burning a lot of diesel to obtain a few gallons of water with a very heavy, expensive and maintenance-hungry de-salination plant? An evaporative still or extra water tankage might have provided the same results at a fraction of the cost.

As to voltage, the U-boats ran around 300V+. My guess is that because the I squared R losses are reduced at the higher voltages wiring can be of a much lighter gauge and consequently much cheaper. The same applies to the motor armatures and their efficiencies. ( less heating loss )

This high DC voltage is certainly more lethal and will for sure also run a good welding arc if Klutzenheimer drops a wrench across some terminals. Ruins your whole day, that. So, working at sea may take on a whole new and exciting dimension as every shift might well be your last, like in RIP Crispy-Critter. With 12V DC that lethal risk is far less... and death IS final.

But hey, alles sal reg kom ou beesie, nie waar nie? Or did I get the country all bollocksed up now?? Ek is n ou Kaapenaar hier.

Ivo SV Linnupesa
I totally agree but once more i want to really play all this by a marine engineer friend ... i particularly like that last bit about "RIP Crispy has been!" The 144Volt these guys are advocating is apparently available in 96V too but i will investigate the compromises, aye's and nayes for sure as i am at the planing stage still need finality!

Nope, you are perfectly right i am in SA in fact Richardsbay! Keep an eye peeled i am coming!
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Old 05-01-2012, 07:25 AM   #11
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Quote:
Originally Posted by Guillaume View Post
I totally agree but once more i want to really play all this by a marine engineer friend ... i particularly like that last bit about "RIP Crispy has been!" The 144Volt these guys are advocating is apparently available in 96V too but i will investigate the compromises, aye's and nayes for sure as i am at the planing stage still need finality!

Nope, you are perfectly right i am in SA in fact Richardsbay! Keep an eye peeled i am coming!
What vendor is advocating the 144V or even 96V system?

What is the displacement of your multihull? What hp of normal (diesel) engine pushes through the water at 70% of hull speed? Is that the 40 hp engine? This is relevent-- not one but TWO 12 kW electric drive motors? That is adequate to push my fat, full keel, 29-30 ton boat (47' waterline, 54' on deck) at hull speed. I'm thinking you don't need so much. I'm thinking if you had a 40 hp diesel you're probably looking at two 6kW electric drive motors. And, those can be worked at 36V or 48V.

We were briefly entertaining the idea of putting electric drive back on this boat when we did a major rebuild (started 5 years ago and finished 3 years ago)--and at the time, we found reasonable options available at 48V for electric drive.

If someone hasn't already pointed you in the direction of considering a remote hydraulic drive, ask your marine engineer friend about it. That is another option which is more affordable than electric drive and if you maintain it well, you will likely be happier with it than electric drive. If you already have hydraulic systems on the boat, this may make you pretty happy.

Fair winds,
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Old 05-01-2012, 01:24 PM   #12
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I know this is a bit off topic, but I felt it necessary to step up.
With over 50 years of maritime experience including a circumnavigation under sail, I think you MUST reconsider the idea of attempting a circumnavigation on a production catamaran like a Lagoon.
!) the shrouds are so far aft that the main cannot be let out far enough to do extended running w/o excessive chafe.
2) most production catamarans cannot sail their way out of a paper bag (I've been watching them motorsail all winter in the Windward Islands while I was sailing, & OK, yes I was heeling)
3) If you must choose a multihull do not go for a room-a-ran; there are plenty of multihulls that sail well. You'd better consider having to claw your way off a lee shore in 40+ knots of wind w/o ANY engine as a possibility one day. OK, I'll have 2 engines, you say, but both engines can be rendered inoperable by bad fuel & Murphy's law is a reality.
I could go on for quite a while, & before you classify me as a multihull hater, I must state that I sailed a trimaran 1/2 way (the second half) around the world. But mine sailed! Upon arriving at the Suez Canal, the workers there were shocked that I'd sailed the whole way up the Red Sea (1200 miles hard to windward); according to them, I was the first multihull they knew of that had done that.
There are so many factors to consider when one is searching for a vessel for a circumnavigation, & comfort at sea as well as at anchor is certainly one of them, but the ability to sail your way out of danger should certainly be a priority, I think.
Good luck & I hope we see you out here soon.
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Old 05-01-2012, 07:15 PM   #13
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Guillaume

the weight issues are likely your biggest hurdle. Pushing some numbers I came up with:

1. To run 12kw for an hour you'd need at minimum 12 of type 31 12v/100ah batteries ( rounding up some specs here but 12x100=1200ah)

2. At 72lb each battery that's 864lb, with lace and trimmings like cabling, clamps lets say 900lb total. ( Battery choice just for example as not the best by any means! )

3. A 4kw generator weighs around 200lb, so a 12kw one could be 3-400lb?

4. E-motor weight, my WAG is 100lb at least.

5. Add it all up, 1200-1400lb without ANY fuel allowance so far and you get to ride on battery-o-matic power for 1hr at 12kw/hr. and the batteries are absolutely flat after that.

6. That same weight allows for a 300lb diesel engine and at least 900lb of fuel, say about 130g of diesel. At 6mpg that is 780 miles of powered range, about normal for many cruising boats.

7. Consider next that with electric power you start off with 1200lb at minimum, but end with ALL that weight still there. With empty diesel tanks the smoke-belcher option ends with only the 300lb of engine, the used fuel gained you an extra 900lb of buoyancy. The extra fuel for the generator battery system has not even been added in yet but should of course be comparable in mpg usage.

Such arithmetic may explain why both cars and boats still have a tough time competing with fossil fuel. Hopefully new tech will change that soon. Veggie-batteries and super-capacitors and Li-ion tech have all shown their own drawbacks so far, cheap Pb-acid still is king. It is very commendable to question the "by rote" conventional wisdom and to such scepticism I fully agree, yet facts and numbers have to back up the ideals.

In this vein all new plug-in vehicle technology is really a crock, it simply transfers to an out-of-sight source of fossil fuel in most cases... and wants to make you feel good about it too.

Hamba gahle madoda

Ivo on S/V Linnupesa
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Old 05-01-2012, 07:23 PM   #14
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Capta,

Thanks for your words of experience. It reinforces what I've heard from several (honest) multihull owners I know--they've motored, not sailed, through much of their cruising days. If you read the Bumfuzzle's experiences during their multi-year circumnavigation, what you learn is that they motored--quite happily--alot. Unlike many folks, they're not worried about what other people think--so they admitted when they were simply motoring. Often one of their two engines was on the blink, too. Good reading in their archives online. They now have a monohull, but still prefer to motor.

That brings us to a philosophical viewpoint--the few multihull owners I know of that were truly HAPPY with the SAILING performance of their boats also happened to be minimalists who had very little in the way of creature comforts aboard (forget refrigeration, electric anything other than communications) and they had very, very lightweight boats. Two of them had trimarans. One of those was a 31 footer that the sailor built himself. Lightweight and built for speed, it was cracking and breaking apart on a passage he made from HI to Canada. It was not made for long passages though there are other lightweight bluewater multihulls worthy of consideration, I'm sure.

Last fall, on a coastal passage against winds and currents around Pt Conception, a notorious cape here on the US West Coast, we were traveling near a (approx 50') large catamaran. As we enjoyed the glorious sunshine, tacking, we noted the cat was motoring (no sails up) dead into the wind and waves. We sailed further offshore and tacked--the cat came up on the radio with alarm "what are you doing? is it rougher out there? why did you turn back?" ....we calmly told him "we're SAILING...that was a TACK you just saw." On the other end "Oh..."

If someone is totally into the creature comforts then a (very) large catamaran is a way to get those things while still owning a sailboat. But it must be large enough that it is not overloaded while underway. However, a large displacement hull trawler is worthy of consideration by folks who really want to go far and aren't distressed about the use of power/fuel. Further, a real motor-sailor (monohull) could be the ideal boat for those voyagers. Identifying what is really important to the particular voyager and then making it happen--that's key.

Fair winds,

The lighthouse at Pt. Conception

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Old 05-01-2012, 07:44 PM   #15
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Inkosi, Linupesa,
Maninge sense umslegaas thanks!
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Old 05-01-2012, 08:15 PM   #16
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Thanks every one for all the relevant info, choices are not easier just more informed!
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Old 05-02-2012, 01:56 AM   #17
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Hi y'all - 'Brenda/Yoda/& the quiet 1) & 'Pop's Tanjera' - Beaut photo above - would have been 100% better if there was a wonderful wooden schooner in the pic - don't you think?

Hey 'Pop's Tanjera' for everyone else's sake - more info on your boat - U know - length, width, sail-area, weight - all that stuff ??? - - so we can get a good fix on your hp requirements. Please? Now when you've got it all sorted out, do remember that any transfer of hp consumes large amounts of energy - which is not refunded - not free of charge. This a nice attempt of me to try & say - electrical power being more efficient than diesel motor motive power may 1 day happen but not in my lifetime. Good luck though - mate, you'll need all you can get.

Now Brenda - re boats - dreams - cruising - lifre's values; - - I've fallen in 'lust' again. I needed to do some research into some of Nigel Irens's designs - & stumbled across 'again' SV 'Paradox' - a cruising tri - that I covet - oh - ever so bad - now that's my kind of cruising toy. SO - bye & ciao for now - while I go to work for 18 hrs/day to earn enough to by lotto tickets to win enough money to buy one. WOW - That is sure a lovely floating dream. Ah heck at this time I can't even aford the little 40' tri 'I-T-Cup' in SE Asia that I'm trying to get. But - if I live long enough - IT will happen. Ciao & good sailing everybody. Keep chasing your dreams, james OH & ciao 'Pop's-T' too.
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Old 08-24-2012, 10:25 PM   #18
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Default Electric or Diesel

Does anyone have any knowledge about the electric motor capabilities of the greencats made by Africacats? They have "motogen" retractable drive units and lithium ion battery banks. I scoured their website but couldn't find anything addressing how many amp-hour capacity these boats have or how much the batteries weigh. Thanks.
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Old 08-25-2012, 06:16 AM   #19
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BD

perhaps you may want to find out how much power you will need to recharge batteries and for how many miles or hours they will last.

Battery banks can be made for any capacity, so it is the weight and size decisions you will be doing battle with. Plus cost. The biggest bang per buck is still lead-acid aka golf-cart technology. The gel-cell, Li-on etc. all have some advantages but share the boon-doggle of high cost.

Cats especially like to be lightbodied to be nimble. Going green is commendable but I must wonder whether they make a good test-bed for the technology. Unless the weight issues can be solved first. Or, you only need minimal power for getting into your berth.

Ivo
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Old 08-25-2012, 10:12 PM   #20
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There is no magic.

To push a boat you need energy. Each time you convert energy from one form to another or move it from one place to another, you endure an efficiency.

The energy falling from the sun onto our planet per square meter isn't enough to push a boat.

Wind energy will push a boat. The most efficient means is "sails." A small windmill powering a generator charging a battery which turns a motor which turns a propellor is not nearly as efficient. It will take many hours of wind in the windmill to give you one hour of motoring.

The energy density per lb or per cubic inch of diesel fuel is higher than almost any other energy store.

I can't see that electric drive makes any sense unless you posit a much more efficient means of creating the electricity. If we get cheap, small, safe, light nuclear power plants that will fit on a boat, then I will take another serious look at electricity. Until then I will stick with my diesel.

They are the safest, most reliable, most efficient way of powering a boat except sails. Maybe even including sails.

The big disadvantage of diesel is that it is loud and a bit smelly. Other than that, diesel wins every time by a big margin.

Don't expect improvements in technology to radically change that. Neither windmills nor solar panels can even theoretically become twice as efficient. Moore's law doesn't apply here. Batteries could in theory get a lot better, but even there it's a tough row. They have maybe doubled in my lifetime in energy storage ability. Will another 50 years give us another double? If so they still don't do it. Will we do even better? Nobody knows. Maybe we are near the peak of the art now.

Even with amazingly great batteries you still need a generator and you are back to diesel, so there is no real advantage.

For my money, I say get a good new diesel, insulate the engine compartment as well as possible, carry lots of fuel, and maintain it well and you have the best auxiliary power possible. Then use it as little as you reasonably can.

I can see why people want electric drives to make sense and will go through all kinds of contortions to convince themselves that they do. I think it is self-deception.
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