electric propulsion

Discussion in 'Propulsion' started by Lew Morris, Jan 26, 2003.

  1. Lew Morris
    Joined: Jun 2001
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    Lew Morris Industrial Designer

    i'd like to build what might be considered a light, 'high performance' runabout in the 12-15 foot range.

    i've reviewed the 'electric propulsion' section on this website, and have also visited the eboat.org website.

    does anyone have hands-on expereince with any of the electric propulsion in general or the motors and/or manufacturers listed this website?

    thanks all...
  2. Guest

    Guest Guest

    Diesel electric propulsion system is common in offshore supply vessels and especially in cruise ships and recreation vessels.

    If the vessel or boat does not have a large hotel electric load, and just need propulsion power, then, it may not be cost effective, but still can be installed.

    Diesel electric system will not be as simple as taking power from the generators to the switchboard and then send current to the AC motor at the head of the tail shaft. Experience tell the operators that motors will not last, due to spikes in the system. If you look at a very small boat, then it is possible to use a generator to charge up a bank of batteries to power the shaft motor.

    The system to make it possible is called SCR, started out in the tug industries and the drillships with delicated high power machinery which must not fail. In Europe they use cyclo- convertors to intercept the power delivery to the motors. In the early days, motors are DC but now they move to select AC.

    SCR is a computerized switchboard. Now cyclo-convertors works in the same principal, but deals with one power unit at a time. SCR takes all the power and converts to DC and reconverts to AC, then, subsequently manage the power supply to the needed power units.

    For years machinery, such as windlass and cranes that will last have DC motors, with AC power feed to contactors to convert AC to DC. But DC motors are more expensive in UK, but not so in France. So it is a case of supply and demand.

    Cyclo-convertors takes the AC power and cleans them in elements and rebuild back to fine sine curve. Then drive the motor in the power chain.

    One point to note that, while more service power can be shared. Propulsion power should be stand alone. If it is a non-class vessel, you are the boss to mix them up. Mixing propulsion power with other hotel power, can only be performed in the good hands of the large electronic/electric suppliers, using their logical approaches in power management.

    Diesel electric offers great flexibility to your boat's layout. Shaft lines will be absent. Propulsion engines are replaced by a series of identical generators.

  3. Lew Morris
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    Lew Morris Industrial Designer


    please re-read the first line of my post; "i'd like to build what might be considered a light, 'high performance' runabout in the 12-15 foot range."

    i grew up in Columbus, Indiana where they build Cummins diesel marine engines and stationary engine/generator sets, but i don't recall one of their products in the 2-5 hp range... which might be suitable for a FIFTEEN foot runabout.

    i've often wondered if there might actually be a market for a 5bhp generator set for use on sailboats. i guess a little Honda genset might be the answer for electric aux propulsion on my little twenty-one foot daysailer.
  4. Peter_T
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    Peter_T Junior Member

  5. 60minmacd
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    60minmacd Junior Member

    Lew, when you say "light weight, high performance", you are talking about the design I am currently working on. You can see my posts--"paddlewheel boats" and follow my progress with the 1/4 scale model. We had a slight delay this week due to hurricane Frances, but should be running the tow tests soon.----John
  6. Dutch Peter
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    Dutch Peter Senior Member

  7. mselle
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    mselle Transportation Designer

  8. Dan B
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    Dan B New Member

    A very intersting concept, Here is alink from a UK manufacturer with a permanent magent motor for vehicle operation. It falls more into the medium sized boat range .
    rated at 20KW continuous.
    controllers for these motors can be found at
    I noticed that a few of the above links used water cooling around the electric motors, I wonder how important this is, when considering a air cooled motor from a wheeled vehicle?
    The system shown in the vetus.nl link for hybrid , desiel connected directly to the shaft of he dc motor, would no doubt use a clutch of some sort, which would be most efficient, a manual clutch or an electric clutch? Considering that a manual would always offer some resistance even when decoupled and the electric would use precious amperage to operate itself!
  9. oldchris
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    oldchris Chris Mannall

    Im looking at the possibility of replacing 6hp inboard petrol engine with an i/b elec motor toothed belt transmission and either wind gen or solar panel recharge on a cycle of about six hours useage perweek and batteries to replace onboard internal ballast.The boat is a 50year old restoration project and will be berthed in an area of extensive wild estuary bird life. Has any one any pertinent observations?
    Old Chris
  10. DGreenwood
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    DGreenwood Senior Member

    oldchris- Depending on how that six hours of usage is spread out over a week, it all sounds feasable to me. Could be done relatively cheap with an electric fishermans trolling motor(adapted to application and a simple battery setup). The charging system is the complicated part. Need more info about available light, deck space, and wind to work that part out.
  11. oldchris
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    oldchris Chris Mannall


    Thanks for yours. The boat in hand is a 24ft x 6'6" 4' deep keel with a quarter shaft installation. These dimensions suggest a max speed of around 4.8mph.
    Therefor application would normally be used for getting on or off mooring ,berthing alongside with remote chance of motoring for an hour or two in dead calms. The vessel is 3/4 flush decked giving enough room for a solar panal array say 3'x3' 1sq mgives400watts? If on average two or three trips a week were planned in summermonths ,southern UK this would seem to provide enough charging rate to keep batteries well topped up.Summer sun gives an average of 8hrs perday.

    Alternatively wind generation though likely to provide more or less 24hr input carries penalty of additional windage when vessel is under sail and lower overall charge rate. Difficult for a non electric man to get a grip on broad parameters. Will keep in touch with results of responses from UK providers of equipment.
  12. oldchris
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    oldchris Chris Mannall

    electric replacement fro 6hp petrol

    Since writing yesterday followed up the following:electric boat design design and propulsion with a futher link to paper by cedric Lynch of Lynx electric motors which give a basic but easy to follow and systematic design programme. Would no doubt help the originator of this subject. RGDS Old Chris
  13. brian eiland
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    brian eiland Senior Member

    Professional BoatBuilder article

    The Dec/Jan 2005 issue of Professional BoatBuilder has a really excellent article on the subject of diesel-electric propusion by Nigel Calder
  14. Wattagan
    Joined: Jan 2005
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    Wattagan New Member

    DC propulsion Motors

    Looking over the posts on electric propulsion and there are some very interesting comments.

    My situation is that I manufacture marine DC generators ideally suited for charging batteries and or driving DC propulsion motors.
    This is the easy part for me and you can see them at www.wattagan.com
    The trouble is finding suitable DC electric motors.
    I have looked at most of what I can find on offer and all are really expensive especially with controllers.

    Has anyone had any success using any sort of commonly available dc motor or maybe adapting an AC motor or Alternator as a motor ?


  15. Unfortuntly the only motors that can handel all the load, speed and be efficient are the brushless ac or dc motors and their drives. $$$$ 10hp was 5K to 7K. Then you need a power system. Not practical for any planing type of boat. Even using the latest and most dangerous LI -POLY batteries, NO way are we going to plane and play. Still a wet fuel and wind hobby.
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