The efficiency claims are not that outlandish. Prop design is always a compromise. My 2-stroke outboard has a tiny little prop with a very coarse pitch. Fine for driving a tender fast but very inefficient for cruising with a trailer sailer.
Looking at the Torqeedo, the emphasis has been on efficiency with the result that the prop is a lot bigger and more hooked but... it will probably pick up lobster pots more readily, is probably more easily damaged and probably cannot be swung round 180 degrees. Everything is a compromise.
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 It is a good idea that is good for the environment, light weight and easy to use, but if you want to go more than about 3 mph then it isn’t going to suit you.
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 | TMS Poloshirt winner |
01/02/06 21:17
 Well Cap'n electric motors are not prone to stalling at low speeds like an internal combustion engine is, so granted, they can use a larger and more efficient prop. Incidently, steam engines weren't prone stalling at low speds and they also used large and efficient propellors. So much for the bull about "applying latest knowledge from the field of propeller physics", Navier Stokes and all that. We are still awaiting their calculations to prove their claims.
However the major draw back with electric motors in this type of application is the storage of energy, as I said in a previous post Petrol has a calorific value of about 44 MJ (million joules) per kilogram, therefore burning a gallon of petrol of petrol produces about 160 MJ of energy. Even if we only assume 25% efficiency; that is still 40 MJ. An 80 amp hour battery only contains about 1.5 MJ of energy.
"Oh but a battery is greener" I can hear every one say but where do you recharge that battery? from a charger which is plugged in to a 240v socket which, in case anybody has forgotten, is highly likely to get its power from a fossel fuel burning power station.
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Could be powerd by a wind farm!
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 Now there's a thing. How about a wind farm mast on top, turning a coarse pitch propeller underneath? It could even recharge my AA batteries.
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Well I am not sure that you would be able to put a big enough windmill on to power a batterie of that size. If you had it there to charge it up when not in use, but certainly not charge as you move peter.
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Energy storage is a big point. However, most yachties would use the baby units to drive their tender and they spend their days hooked up to shore power (or if they don't they will have alternatrive generators rigged). In terms of greenness don't even start to pretend that a 2-stroke (or even a small 4-stroke) even remotely approaches the efficiency of a CCGT plant even allowing for energy conversion and grid transmission losses.
Roxy's / Peter's comments are relevant. I spoke to the Torqeedo guys at the show about regenerative battery charging when under sail (only really relevant to the biggest unit which uses external batteries). They are not about to implement this but were thinking about it as a possibility for future models.
If got one, I would go for the biggy with two banks of deep-cycle external batteries. I could keep the batteries trickle charged from solar power. Shore power can be used for overnight charges as required. For reassurance on longer passages, the best option would be to lug a little 2-3kw genny and charge the second bank off whilst running from the primary. How many people are going to use a 5HP outboard for making serious passages though?
The end result would cost a lot more, but would have the reassurance of a reliable power source that is available at the flick of a switch and silent running. If I was looking to replace my outboard now, this convenience would probably mean the package would start to be worth the additional outlay.
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I think if I needed to buy an out board, though I would consider one of these, I would probably go for a coventional one, if for nothing else - this is about twice the price of it's competitiors.
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| TMS Poloshirt winner |
02/02/06 13:14
Cap'n:- "---In terms of greenness don't even start to pretend that a 2-stroke (or even a small 4-stroke) even remotely approaches the efficiency of a CCGT plant even allowing for energy conversion and grid transmission losses.---" Did I say it did? The point was that you were still burning fossel fuels to provide the electricity
Cap'n:- "---For reassurance on longer passages, the best option would be to lug a little 2-3kw genny and charge the second bank off whilst running from the primary. How many people are going to use a 5HP outboard for making serious passages though?---" So much for green issues, think of all that extra weight that has to be propelled through the water! Why not just burn the petrol in the 5HP outboard then??
Roxy:- "---I would probably go for a coventional one, if for nothing else - this is about twice the price of it's competitiors.---" Yep, for that outlay you could buy the conventional outboard and the genny!
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On the green issue, even if you were to get out and swim and your kicking legs were the propulsion, humans still have flatulence and methane is a green house gas.
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Sorry for the late reply, Chas, was away for a while.
“YOU'VE YET TO PROVE THIS AND I BELIEVE I WILL BE WAITING QUITE SOME TIME!!!” It won’t be too long. What we are stating is that our 800 watts engine has a comparable effective output power of a 2 HP combustion engine and that it has higher overall efficiency than other electric engines on the market. Independent tests will be published within the coming season by various magazines in Europe.
THE NAVIER-STOKES EQUATIONS ARE THE FUNDAMENTAL PARTIAL DIFFERENTIAL EQUATIONS THAT DESCRIBE THE FLOW OF INCOMPRESSIBLE FLUIDS. True, however few people use them to calculate specific applications like propeller designs. Most propellers in the outboard world are designed using rules of thumb coming from experience or based on extensive measurements like Admiral Taylor’s test series.
THE ONE FUNDAMENTAL LIMITATION FOR ELECTRIC DRIVES IS THE STORAGE OF POWER, IE BATTERIES! i DON'T KNOW THE WEIGHT AND OUTPUT OF YOUR BATTERIES BUT PETROL HAS A CALORIFIC VALUE OF AROUND 44 MJ/KG True, petrol has a much higher calorific value than any battery. That is why for longer distances petrol is superior. We would not recommend running on battery power against winds and currents on high sea. However, for shorter range applications, e.g. for tenders, our engines are a very interesting alternative from performance and convenience perspectives (and nature protection perspectives).
Altogether, as stated earlier, I probably will not convince you to buy into our concept in writing anyways. So I hope you don’t mind if I spare the effort going forward. As you say yourself YOU'VE YET TO PROVE THIS, on which I agree. The best way to prove this is not by writing messages but by getting some test results. So we will do this, we will keep in contact with the people from The Main Sail, and I think it is best to continue the discussion then.
Kind regards
Christoph
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Gentlemen; and ladies of course,
I am a new member to your forum and wish to give you a little background. I am an American, living in the Netherlands. While I am not a sailor, I am building a small launch and wish to power it with electric propulsion. I have found the most relevant discussion on your forum regarding the German offering called Torqeedo. It seems that there was an early flurry of posts on the subject but nothing more in the last 10 months or so. Has anyone had the opportunity to evaluate the Cruise 2.0 version of this product? Also, for Mr Ballin, has your company explored the possibilities of incorporating a Rice tpye duct? How about additional propellors? I have read on your site that the offering is a 12" with 10" pitch, but on other sites, I have read that there is a 14" prop available? Is this the case?
Again, I am very interested and would be very interested in hearing about others' experiences with this product.
Thanks in advance for any who reply.
Patrick
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 Torqeedo won an award in the DAME design competition at the Marine Equipment Trade Show (METS) at Amsterdam in November, which seems a very strong recommendation!
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Having purchased the Torqeedo we are absolutely delighted. You have to first admire design and construction. Then learn to be happy at low speed, ie just better than rowing back to the slip. This engine consumes very little power, ie drives our Avon with 4 people and luggage from shore to boat and back at a week-end (about a mile each way) and is left with 60% charge. Quite capable of beating a strong tidal flow we are very happy with it and I can carry it on the tube in London!
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Thanks for that recommendation. Always good to know how something works in real life. As to speed, I have to admit a certain nostalgia for moorings when everyone travelled at rowing (or Seagull) pace. I have occasionally been out in a powerful RIB and it was great fun, but they can become irritating, buzzing around and making lots of wash and noise, when you are trying to enjoy a peaceful evening on the water. Do people really need 50hp-plus just to get to the pub?
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| TMS Poloshirt winner |
23/11/07 19:59
 Well I travel at Seagull speed-my 40 yr old 40 featherweight!-a family heirloom and my good luck charm which I am quite happy with-suprised how much discussion an electric motor has invoked-bit like the one about multi v.monohulls! As for powerefull ribs Inverie just north of Mallaig on the west coast of Scotland is sold as the remotest village in mainland UK with the remotest pub-great until you see;hear and feel the super ribs shooting off the Mallaig at 50 knots to meet the night sleeper from Euston full of the green welly brigade!! Would be nice if they were equipped with electric outboards!!!!!!!!!! Phil
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| Edited: 23/11/07 20:01 |
I used a Fladen Maxximus 43lb ft electric thruster against the Upper Thames' summer floods. It drove my hefty fibreglass tender against a flow of around 3knots with ease. Electric outboards are great but I wouldn't recommend the one I used. Not happy with the build quality and it went back to the manufacturers a week later since water got in and rusted the bearings solid. Looking for another next season, but a better make.
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Kudos for handling the excess of caps-lock with patience and politeness. We have quite successfully replaced our troublesome 2HP Honda 4 stroke with an 801 torqeedo without noticing any loss of pulling power, and not having to service it or think too hard about storage is a real boon. So well done torqueedo, it is noisier than I expected and we only use it on inland waterways. The problem is range and cost. Typically we get about 2-3 hours on still canal waters. Where it really has come into its own is on environmentally restricted waterways that we previously had to detour. If you don't want to pollute the water directly, or smell the stench of fuel and deafen yourself with the irritating noise of a 2 or 4 stroke petrol for hours on end and don't mind the limited range per 24 hours then this is the answer. You hardly ever need to run it flat out. I'd like a Cruise 2.0 ( 6HP rated ) but it is 1HP over the statute for here and would require red tape. If only they did a 5HP model or a tie-bar connected twin 801.... I head Briggs and Stratton did a 4HP or 5HP electric, but I've never found anywhere that sells them so this is the best there is ... for now.
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| TMS Poloshirt winner |
28/05/08 16:01
Hi Captain I'm glad you have found a good use for one an are pleased with it. I just had a bit of sport with Christoph over his techncal sales spiel. ---"I'd like a Cruise 2.0 ( 6HP rated ) but it is 1HP over the statute for here and would require red tape. If only they did a 5HP model or a tie-bar connected twin 801...."--- I can't see you having a problem with this. You say your local bye-laws limit you to a 5HP motor. Well, I'm certian that "Cruise 2.0" refers to a motor power rating of 2.0 kilowatts. Now, irrespective of any claims of prop efficiency or being "the equivalent thrust of", a 2.0kW motor is a 2.0kW motor and that equates to about 2.7HP in old money. So a cruise 2.0 should be perfectly legal. If it happens to go like a 6HP job when you need it; then you are on to a winner! Just be aware of how a 2.0kW motor will drain even a 24 volt battery - 83 amps! Cheers Chas
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