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  #31  
Old 09-11-2012
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Re: Optimal propulsion system

Converted Hunter 29.5 & wouldn't go back.
Best source for good, expert info is:

Electric Seas
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  #32  
Old 09-11-2012
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Re: Optimal propulsion system

David,
Sorry about the short post. I had a nice long one written, but because I tried to post a link, it wouldn't go on. If you have questions, send a personal message to me.
Amazing the passion of those who have opinions based on supposition.
Terry
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Old 09-11-2012
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Re: Optimal propulsion system

Quote:
Originally Posted by miatapaul View Post
Yea, same thing happened to the 200 mpg carburetor in the 1970's!

Though I do find it difficult to believe that we cannot get a lot better millage from cars today. After all I got way over 50 MPG in my 1980 VW Diesel and it is more than 30 years later!
It's not a lost art it's just no emissions laws, a tiny car and no horsepower.

If only we could pair today's engine technology with consumer expectations from the 70's we'd have 50+ MPG cars easily. Unfortunately it doesn't work. Even the most compact cars need 100+ horsepower (like my Fit) to sell.

As for the conspiracy theories I agree 100% with Tallswede. Oil companies have nothing to worry about meanwhile Apple is sitting on a hundred billion dollars and would love to spend a chunk of it on better batteries. Some things are just hard to do - storing energy in batteries is apparently one of them.

Last edited by asdf38; 09-11-2012 at 07:20 PM.
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Old 09-11-2012
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Re: Optimal propulsion system

A good (though very in-depth - make a cuppa first) article discussing battery capacity can be found here:

http://physics.ucsd.edu/do-the-math/...icit-disorder/

For those unfamiliar with his work, all of Tom's articles are excellent. He goes into the details and the actual real-life numbers of all kinds of energy systems.
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Last edited by MattSplatt; 09-11-2012 at 07:38 PM. Reason: typo
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  #35  
Old 09-11-2012
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Re: Optimal propulsion system

Hello there, keep in mind that the Generators AC output changes with rpm in a very unfavorable way. Unfortunately changing rpm changes the AC volts, but most importantly hz. A modern generator needs to run at 1800 rpm's about 60 Hz. if you change the rpm you put the generator under undue strain, (windings in the stator) ( solid-state
voltage regulating system).Changing the RPM on a generator is very impractical. Whatever converts your AC to DC should operate at 60 Hz......Captg
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  #36  
Old 09-11-2012
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Re: Optimal propulsion system

Paul-
"Though I do find it difficult to believe that we cannot get a lot better millage from cars today. After all I got way over 50 MPG in my 1980 VW Diesel and it is more than 30 years later! "
There ARE TDI engines that will getbetter mileage and poewr than your non-turbo-diesel got. The problem is, they are illegal on the US marlet because almost all diesels spew particulates and the EPA is convinced those are carcinogens that also cause allergy and respiratory problems. And it looks like the EPA is right on that one, more evidence keeps saying the same thing.
The EU has allowed them but starting "now" you will see all sorts of new diesels coming to market, most with an extra tank of urea which is injected into the exhaust in order to clean it up. I'd guess that will impact the boat market soon too.
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Re: Optimal propulsion system

Quote:
Originally Posted by davidpm View Post
The way I see it all of the advantages are lost except one.

It's more expensive to install and run and more complicated and may be just as noisy.
If you typically sail 50% and motor 50% and catagorize a light electric assist in the sailing side then maybe you can sail 90% and motor 10%.

Lots of if's.
My wife really hates motoring under diesel.
Sorry I'm late to this party, but I thought I'd add my 2c worth based what I've seen - because it doesn't have to be that way:

First off, the system I've seen was: 11kW AC Gen set connected to battery charger and Danfoss Variable Speed Drive (VSD). VSD connected to ABB 3-phase AC electric motor. The batteries where connected into the VSD with automatic changeover to power the VSD off generator if it was running. All off-the-shelf stuff. This system has the following advantages:

1. The gen-set and batteries (as few or many as you want) can be mounted anywhere that's convenient weight-wise - not just in the tail of the boat, but generally somewhere central, under the saloon table for instance - and can be properly sound-proofed since there's no rotating shafts extending outside the box..
2. The gen-set provides AC power to other things in the boat (fridge, hot water, etc.)
3. The gen-set is compartmentalised: Engine-and-generator-in-a-bow. Removal for replacement or serious overhaul is four bolts.
4. The gen-set runs at constant speed, supplying whatever load the engine, batteries, etc. need. Continuous throttle and fwd/reverse is via the VSD.
5. The 3-phase AC electric motor is mounted low in the bilge and takes up hardly any room at all.

With this system, the generator automatically starts only when the batteries are getting low. The owners usually manually run the gen-set when anchoring (to make sure there is plenty of power for the anchor winch as well as the motor) and again during dinner to heat up the hot water for showers and run the microwave - very civilised!

Disadvantages: None I could see - apart from the cost, which may not be all that much more than a conventional set-up if you didn't mind having less batteries and hence running the gen-set more. The various bits do all take up space so it wouldn't suit a small monohull, but on a bigger boat - or a cat - it's ideal.
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Last edited by Classic30; 09-11-2012 at 09:27 PM.
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  #38  
Old 09-12-2012
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Re: Optimal propulsion system

Well how these systems are put together by engineers is not a full hp generator but one much smaller that runs at best efficiency most of the time. If you need peak power you need to drain batteries.The electric motor is left freewheeling and becomes a generator while sailing to refill batteries.Genset would come on at preset drain point on batteries or by manual start.

The genset etc don't go in the bow.That effect trim to much.

There are several systems in place right now and some Charter cats have/are being produced. Look at there set up for ideas.

We all do different things in life to earn money. Go do that and leave system design to Electromechanical Enginneers.

3 phase ac motors? VSD's? varispeed gensets? There is so much wrong here I won't even comment but if you PM me I will recommend a few books if your interested in the subject in some real way.

Last edited by ParadiseParrot; 09-12-2012 at 07:53 AM.
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Old 09-12-2012
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Re: Optimal propulsion system

The optimal propulsion system was put in place a thousand or more years ago and has been under continuous upgrade since -
Sails
Efficient, and getting better
Quiet
Longest range per unit of consumption.

ParadiseParrot, not to offend, but it didn't take a electromechanical engineer to come up with that. I'm just a database guru and didn't even stay at a holiday inn last night.
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Old 09-12-2012
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Re: Optimal propulsion system

P.s., if you need backup - install a sweep oar and convert some sea biscuits to forward speed.
I believe that propulsion system was designed by the guy / girl who built the garden of Eden.
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