DC Propulsion on semi- planning hull

Discussion in 'Propulsion' started by myastral, Nov 6, 2010.

  1. myastral
    Joined: May 2006
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    myastral Pan Asian Yacht Service

    Am I missing something:

    I have been looking at using a direct DC drive system for a 71 foot semi-planing motor yacht and I have been able to work out all of the details for the electrical system and it seems rather easy with largely off the shelf parts with out any major drama. As You would expect prior to starting any work I will be consulting with a navel architect and electrical engineer to go over all the numbers prior to spending a large amount of cash.

    My question is will it work with a semi- planning hull shape and will it get on plane ?? I have looked at at few different boat and they all seem to be doing about hull speed and or using variable pitch props.


    I have searched the web site and unless I missed something I cant find any similar project or proposals for starting a project.

    Does any one no of any open source research that has been done on the subject ?? or any idea were to look everything seems to be geared to slower boats and cats so I'm really looking for any information on similar trawler type semi planning boats that may have already been built or any conversions.

    SAF
     
  2. mydauphin
    Joined: Apr 2007
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    mydauphin Senior Member

    YOu must have a many millions dollars sitting around to build an overweight, slow, test boat that you will spend the next 10 years trying to get to work.
     
  3. mark775

    mark775 Guest

    Siemens couldn't do it. Good luck.
     
  4. apex1

    apex1 Guest

    Hmm,

    when this is just half of the truth:
    then you can tell us, instead of asking.........:cool:

    Unfortunately, that is not true.

    Regards
    Richard
     
  5. dskira

    dskira Previous Member

    A precise question to don't waste time for a guy who is bored in front of his computer:
    What is your budget?
    You can't state
    Then ask questions like if you just Google the subject.
    So the only way to check if your are serious, is to ask you the amount of cash you have on hand for the project.
    Daniel
     
  6. Yellowjacket
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    Yellowjacket Senior Member

    Add to the weight of a diesel the weight of the generator and the electric motor and it will be so great that you won't have a hope of getting the boat into a semi-displacement mode, let alone getting it on a plane.

    The only way you could maybe do it is to use a gas turbine for a propulsion engine, but that would result in significantly higher fuel consumption than a diesel.

    In this size class the electric propulsion only makes sense for displacement hulls.
     
  7. apex1

    apex1 Guest

    Not even then............:)
     
  8. mydauphin
    Joined: Apr 2007
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    mydauphin Senior Member

    I did research about 5 years ago on powering my 72' boat via a hybrid power arrangement and can to these conclusions. I narrowed it down to Siemens system.

    1. An high voltage AC system is more efficient than a DC system.
    2. I could save drag by eliminating rudder and steering boat via throttling rpms on twin engines.
    3. Batteries and inverters (speed controllers) would take alot more room than present engine room. The engines thought smaller and not needing gearing are still very heavy. No net weight savings.
    4. I would still need diesel generator and get home engine.
    5. I would have to carry basically a spare of everything since fixing it meant replacing parts.
    6. It was going to cost over $150k just for motors, electronics and batteries.
    7. Reliability long term was not predictable and maintenance would be higher
    8. More electrical high voltage thingys to break, and still needed the diesels.

    So I saved $100k and bought two diesel, trannys and shafts...

    Oh, forgot to mention... This was for a displacement boat... Planning...for get it.
     
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  9. myastral
    Joined: May 2006
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    myastral Pan Asian Yacht Service

    The budget will be about 20% over the cost of 2 C-18 and we plan on using a Kilo Pak micro turbine with a 400 volt DC output, four water cooled DC motors two per shaft into combiner, We did a few test using a 110 HP DC motor powered by a DC generator on a 38 foot boat and the results were fantastic. we are still looking a few options for batteries but Litum Ion looks like the right way to go even at four time the cost.
    The first service on the micro turbine is at 70,000 hours and over 15,000 are now in service at data centers and oil platforms around the world were expecting very stable power.
     
  10. mydauphin
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    mydauphin Senior Member

    Ok, so you say you can do this. How much horsepower to get a 71' boat onto plane? How much does one of these Kilopak microturbines cost? How much fuel does it burn? The c-18 is 1000hp and costs used about $48,000 or $100k new. What are your numbers specifically?
     
  11. myastral
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    myastral Pan Asian Yacht Service

    fuel burn was 10 gallons per hour at 100% load. and as with all simillar system the burn rate goes down a bit depending on the load. but zero load would have no negative effect on the life span of the system. the cost is well with in the scope of the project.

    BUt Im still wondering with a DC motor producing the same horse power would the end result be the same given how the torque is applied to the props ??

    This will be done on a new build not a re-fit or re-power
     
  12. mydauphin
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    mydauphin Senior Member

    whenever you convert energy, forces, etc...there is always a lose. Converting diesel to electricity then converting back to a spinning shaft/torque will always be more inefficient and more complicated. How much for speed controllers needed and electric motors? What size motors are you looking at?
     
  13. myastral
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    myastral Pan Asian Yacht Service

    The total per motor is 210 HP so 420 per shaft this will be over the HP used on the last four hulls allowing for a total loss convertion as part of the whole process.
     
  14. mydauphin
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    mydauphin Senior Member


    So you are saying you built 4 boats. Can we see pictures? 840 total hp will need something like 1000kw in generator capacity. That is a lot of microgenerators and batteries. Are you sure it will fit in 70' boat. A 1megawatt generator will be big, very heavy and expensive.
     

  15. myastral
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    myastral Pan Asian Yacht Service

    As Im sure You can understand I would be unwilling to go into any real details, but we have built 4 of the 70 with stadard Cat propulsion, again I dont wont to get bogged down into detials but if You do a litte checking around you can find all the information you need.
    Im just looking for anyone that has done shaft and props for a simmilar application.

    If You went to the Ft lauderdale boat show You might have seen the yacht Bold Seas ? It use to be called Iasanami, I know for the ten years the boat was based in France it was a diesel electric and I would expect it still is.
     
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