The perfect Passagemaker III, propulsion

Discussion in 'Boat Design' started by apex1, Aug 26, 2010.

?

Please pick your poison

  1. Trawler: single Mitsubishi

    14 vote(s)
    35.0%
  2. Trawler: twin Luggers

    11 vote(s)
    27.5%
  3. Yacht: single Grenaa Diesel

    13 vote(s)
    32.5%
  4. Yacht: twin Mitsubishi´s

    2 vote(s)
    5.0%
  5. Yacht: twin Luggers

    4 vote(s)
    10.0%
  6. I am fine with less accommodation in favour of a large engine room.

    26 vote(s)
    65.0%
  7. I prefer large accommodation, the engine room is second.

    2 vote(s)
    5.0%
Multiple votes are allowed.
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  1. WestVanHan
    Joined: Aug 2009
    Posts: 1,373
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    Location: Vancouver

    WestVanHan Not a Senior Member

    Apex thanks for info on large,slow turning engines-I knew nothing of them before and they seem to be the best way.

    Doing a little research,I found another Danish company- Callesen which has a 5 cylinder ~575 hp @ 425 rpm engine...and weighs 13 tons.
    They also make their own CPP.

    Hopefully not wandering off thread,but did you choose Grenaa over Callesen due to experience,or not offering too many options?

    For your viewing/listening pleasure:

    http://www.youtube.com/watch?v=tYTwHDLImDY
     
  2. apex1

    apex1 Guest

    Callesen made a 6cyl.* too, but is out of business since over one year.

    Both have been of similar quality, well, Grenaa still is.....And Grenaa makes their own CPP too. They weigh a bit less than the Callesen at 9 tons.

    There are others on the market though.

    ABC in Belgium makes something in that range, SKL Germany, Yanmar, Akasaki, Japan...
    and so on.

    You are not off topic. This is the propulsion thread in the Passagemaker department!

    *I would never put anything but a straight six in such vessel.

    Regards
    Richard
     
  3. mydauphin
    Joined: Apr 2007
    Posts: 2,161
    Likes: 53, Points: 48, Legacy Rep: 575
    Location: Florida

    mydauphin Senior Member

    A few question on these types of engines:
    Are these engines regular 4 stroke diesel engines or something else?
    Do they run on Diesel, or thicker bunker fuels?
    What allows them to run at such low rpm?
    They don't suffer from same issue as regular diesel being run at too low and rpm?

    Several people have told me, and I have experienced it in real life that the straight six is by far the best engine design because it is naturally balance. In my experience it seems the straight six do vibrate than others. Your comments please.
     
  4. erik818
    Joined: Feb 2007
    Posts: 237
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    Location: Sweden

    erik818 Senior Member

    My experience from land vehicles is that the straight six is more silent than the V8. The exhaust flow i more even in a straight six then in a V8, making it easier to silence. The difference to a V8 is exaggerated because those of my friends who own cars with V8 engines don't want to silence it too much, but want the engine to sound like a proper V8. Maybe it's the same with boat owners.

    Another question:
    My guess based on the usual beginner's books is that the displacement for a 24 m boat will be 50 - 100 tons. Is 800 hp really necessary? Wouldn't 200 - 400 hp be sufficient?

    Erik
     
  5. DennisRB
    Joined: Sep 2004
    Posts: 1,270
    Likes: 27, Points: 48, Legacy Rep: 228
    Location: Brisbane

    DennisRB Senior Member

    I am still amazed at a 600hp engine that weighs 13 tons. The engine in a car I built developed more than that with a 3.0L displacement. And weighed under 300kg. It was also a straight 6 (my favorite engine type). I could balance a coin on the rocker cover and rev it to 7000rpm with out it falling off. However its rated output of continuous 650hp is rated seconds not years :D It would probably push Richards ship around 400m at full power before melting a piston. That I assume this is obviously where extra weight comes from in ship engines. Huge capacity and long stroke means very low RPM and very low friction and therefore low ware on lightly loaded engine parts. However I am still trying to get my head around how an engine like this can have better economy than a much smaller engine. I believe friction goes up by the square with RPM so double the RPM means 4 times as much friction, but when the engine is sooo much bigger I'm not sure that low RPM could account for it all specially given the extra weight. I would love to hear an explanation, but I am happy to just believe it anyway. Sorry for going off topic a bit.
     
  6. apex1

    apex1 Guest

    These Grenaa Diesels (and the similar ones I mentioned) are regular 4 stroke Diesels. They burn any oil from 0,8 to 5,5 centistoke (thats #1 to #3 medium destillate, Kerosene to MGO) and vegetable oil of similar kinematic viscosity. MDO with 12 cSt can be mixed in when heated.

    note: the "lower" the quality of diesel fuels (med. destillate), the higher their energy content!
    read: when I burn MGO instead of road Diesel, I need less gallons per mile.

    The bigger the masses the lower the rpm possible.

    Yes the straight six is the best balanced IC engine. No other Marine engine runs as smooth. (a 4cyl Boxer does)
    We had a rather heated discussion about that topic 1 year ago. Some stubborn mules still have not grasped it (greetings to SE Asia), but claim to know their job´s.

    Go here for some more info on the topic, but take care, half of the bigmouthes there just drivel:
    http://www.boatdesign.net/forums/di...re-come-up-cold-start-28541-6.html#post292179

    The Gentlemans yacht at 25 meter will be about 150 tonnes I guess.
    No, 800 hp are not necessary, 500 - 600 should be enough, even uphill in force ten.

    Regards
    Richard
     
  7. Submarine Tom

    Submarine Tom Previous Member

    Shouldn't we really be taking about torque at rated RPM here?

    Horse power is so RPM dependant and we certainly aren't talking big rev's.

    -Tom
     
  8. dskira

    dskira Previous Member

    Yes, it is about torque. Large displacement, slow speed means tremendous torque.
    For exemple a 400 hp at 600 rpm give almost 3500 Ft/Lbs
    To sustain that kind of power, they have to be built very strong, thus the weight.
    As an example of a brand in the lower power, an ABC 120 hp three cylinders weight 6 tons and deliver 1575 Ft/Lbs at 400 rpm.

    Daniel
     
  9. DennisRB
    Joined: Sep 2004
    Posts: 1,270
    Likes: 27, Points: 48, Legacy Rep: 228
    Location: Brisbane

    DennisRB Senior Member

    When you mention torque and RPM in the same sentence you are talking power anyway. Once you know 2 figures out of the 3, torque, power and RPM the other can be calculated.

    An engine that makes 400hp at 7000rpm will still make that torque after you gear down ignoring gear losses.

    Thats a bit chicken or egg argument as small engine cant make that torque anyway, and a large engine will not be able to rev. Piston velocity is limited by stroke. You will find the larger engine is making much less specific power than the small one hence it is loaded far less. Thats why it lasts forever.
     
  10. dskira

    dskira Previous Member

    Fantastic

    Daniel
     
  11. WestVanHan
    Joined: Aug 2009
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    Location: Vancouver

    WestVanHan Not a Senior Member

    Efficiencies are also gained by turning a huge prop at a slower speed.

    How about that Callesen I posted?

    585 hp @ 425 rpm = 7250 lb ft
     
  12. dskira

    dskira Previous Member

    Unfortunately they do not manufacture it since last year.
    Richard reported that when he investigated an engine of this class.

    Daniel
     
  13. Submarine Tom

    Submarine Tom Previous Member

    So, all stating the obvious and bolstering my question, thank you.

    Why are we talking Hp on this thread when torque at rated RPM is much more relevant?

    This question was really directed to Richard (I should have indicated so) I certainly didn't mean for the whole thing to go off track on a hijack trajectory. Nor did I mean to open the can of worms about Hp vs. torque, I am fully aware of the difference and hence, my question.

    Richard?
     
  14. apex1

    apex1 Guest

    We are talking EXAMPLE engines for a range of characteristics, as mentioned already in the opening post.

    The hp/rpm numbers are easy to understand by everybody who likes to vote here. Not all our visitors here are experts on marine Diesels! But maybe they are prospective buyers of such craft. I therefore kept it simple.

    When we are going deeper into the propulsion properties we will see, that in fact power is not the value we need. We need high torque at low rpm to turn a large wheel in a fuel efficient load condition, hence the CPP.

    But that would have been a bit too specific for a poll, I think. Though discussing it, is of course very welcome!

    It is all about showing the interested buyer, dreamer, tinkerer, builder or designer, what our members prefer, when it comes to the "ideal" Passagemaker of the given sizes.
    I just narrowed the range down to make sure we can build it according to the finally found "optimum", and that it is possible to be sold at a adequate price.
    For the same reason I boiled down the range of engines to the most sensible examples for the given requirements.

    The Grenaa is a 6cyl. of 81 Ltr. swept volume, producing 600hp at 600rpm.
    (anyone puts the torque # in?)

    It has a piston speed of just 5ms and a TBO of 45000hrs ! It runs happily on 5 or less cylinders in case you have a clogged injector or something like that. You can even repair one cyl. while the others bring you home.
    Try that with a "contemporary" engine.

    The better efficiency is directly related to displacement. The most efficient IC engines on the market are the biggest ships engines at almost 50% yield of the heat content in the fuel.

    Going light is a sensible way, no doubt about that. Going reliable, long living and sturdy is another way.
    Now please don´t tell us, the 4,5Ltr Deere (Windhorse),is as reliable or rugged as a 81Ltr. Grenaa.
    On coastal cruises I would tend to say, the former (lighter) is the better way.
    Ocean cruising for years and years, read: passagemaking, calls for the latter in my opinion.


    Han,


    the Callesen (6cyl.) was a nice engine, but does not exist any longer. As mute to discuss as the formerly mentioned Gardner (which was too weak anyway).

    Regards
    Richard
     

  15. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    You can even repair one cyl. while the others bring you home.
    Try that with a "contemporary" engine.

    I wonder how the cooling water and lube oil supply is handeled if a cylinder head is lifted with an operating engine?

    Next item on the MUST list is self maintaining fuel tanks.

    Sure the centrifugal filters are great , but there a pain to clean.

    A cleanable fuel tank , man sized inspection ports , bottom 5% of tank capacity for sump and gravity low point drain.

    FF
     
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