Cargo Sailing Ship: a near future reality?

Discussion in 'Boat Design' started by Laurent, May 28, 2014.

  1. Rastapop
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    Rastapop Naval Architect

    hp is not thrust.

    A flettner rotor is large, heavy and relatively ineffective. It's success (or lack of it) has no relationship to sails whatsoever.

    The fact that flettner ships barely exist at all, while sailing vessels number in their tens or hundreds of thousands isn't a coincidence. Sails are proven, mature, effective technology. Comparing them to flettner rotors is a waste of time.
     
  2. rwatson
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    rwatson Senior Member

    The HP for forward power is created by thrust from the wind, and converted to the equivalent units for convenience,

    This statement demonstrates a lack of understanding. A Flettner rotor generates 10 times the equivalent power as the same size sail, from wind force.

    It also points higher into the wind than conventional sails, and requires no sail trimming to maintain optimum power.

    Flettner ships arrived as cheap coal made all forms of wind power un-economic. They outperformed conventional sails by a large factor, with a fraction of the manpower required.

    The ship I mentioned in my first post was only built a few years ago, so obviously the engineers didn't agree with you.


    View a sailing Flettner rotor ship here if you want to see it in action

    http://www.britishpathe.com/video/rotor-ship-extra
     

    Attached Files:

  3. Rastapop
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    Rastapop Naval Architect

    "270 hp of thrust" is nonsensical.

    So? What would anyone be doing with sails the same size as a flettner rotor? How about you compare sails the same weight, or same cost as the flettner rotors.
    I suggest you do some reading before you claim flettner rotors outperform a kite sail: https://www.escholar.manchester.ac....&datastreamId=POST-PEER-REVIEW-PUBLISHERS.PDF

    It also won't point downwind.

    Outperformed what conventional sail? One the same size as the rotor? Again, who cares.
    Modern sails can be controlled by computer and from the bridge - effectively no manpower requirements.

    This is just getting silly. Which statement of mine did they disagree with? Would you like to count the number of engineers who designed a sail boat since then?

    Have you forgotten why you mentioned flettner ships? It was to denigrate them (and all wind assistance by association), remember?

    Kite sails are lighter, smaller, cheaper, easier to retrofit, and far simpler.

    The failure of flettner ships to become popular doesn't reflect on the viability of sails in the slightest.
     
  4. rwatson
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    rwatson Senior Member

    No its not - the article you included shows the KW propulsive power - HP is just another measurement.



    sigh .... concentrate ... look at the profile of the rotors in the illustration. It will take sails of ten times that size to produce the same propulsive power.


    Oh yes, the article that says "the average power contribution from a Flettner rotor is higher than that from the kite on some routes" in the opening summary ?

    Oh yes it will. Check out the Polar diagram on page 367. It will point within 30 degrees of the wind, downwind and upwind.

    I notice that the Kite provides no forward power with the wind forward of 90 degrees - the Kite is the one that wont point.


    Yes, theoretically sails can, but not kites. Kites are problematic to control.

    The one where you said Flettner Rotors are "relatively ineffective"
    Have a look at the attached table from your publication - and see just how close the Rotor and Kite are in theoretical propulsion contributions

    Would you like to count the number of sail or kite assisted ships fully designed in the last two years ? Zero !

    Yes, it was. I have been following wind assisted commercial ship schemes for over 40 years, so I have a good basis for saying that its not going to happen for a long time.

    If a controllable rotor ship, proven in practical demonstrations over the years isnt commercially desirable, what hope does a theoretical sail or kite system have ?


    Only in your mind. In actual fact the deployment, control and retrieval of kite systems is very difficult in all but ideal conditions. Imagine sailing under the bridge like the Flettner ship does in the film with a Kite, let alone in a busy harbour.

    It is a direct indicator. If a proven, commercially built wind, efficient wind assist scheme like the rotor isn't viable - sails and kites are a long way from being common.





    Edit - finding from the paper for my future reference
    "The average power contribution from the Flettner rotor on the analysed routes ranges from 193 kW to 373 kW. On the route between Varberg and Gillingham, fitting three Flettner rotors on a typical 5500 dwt, slow-steaming general cargo carrier could provide more than half of the required main engine power. Such a market could be a natural starting point for more detailed studies to establish the case for the Flettner rotor.

    The average power contribution from the kite ranges from 127 kW to 461 kW; it is more volatile, both over time and geographic location, than that from a Flettner rotor and, in comparison, the transient power is lower than that from two or more Flettner rotors."
     

    Attached Files:

    Last edited: May 31, 2014
  5. DCockey
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    DCockey Senior Member

    Thrust is a force.

    Power is the time rate of energy (energy per unit time), and can equal a force multiplied by a speed.
     
  6. Rastapop
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    Rastapop Naval Architect

    I repeat: "270 hp of thrust" is nonsensical.

    First, that's of no concern: rotor cross sections are small compared to sails, a sail can easily be more than ten times larger.
    Second, if you'd bothered to read the paper I linked a 500m^2 kite on average produced up to 461 kW of propulsive power, while the 175 m^2 rotor produced up to 373 kW - your "10 times" claim is way off.

    Surely you can't be serious!!
    It says: "he average power contribution from a Flettner rotor is higher than that from the kite on some routes and lower on others."
    Are you deliberately being misleading or are you having trouble reading the paper?

    Exactly my point: it has a 60 deg downwind hole - a conventional sail doesn't, so your statement "It also points higher into the wind than conventional sails..." is meaningless.

    I don't disagree. I only mentioned pointing because your previous statement on it was misleading.

    Completely wrong, again.

    Relative to their size, weight, cost complexity, deck footprint? Yes, I stand by that statement 100%.

    What, dropping the "rotors provide ten times more" mantra? :D

    If you think a flettner ship being built reflects well on flettner rotors, what does the huge number of sailing ships being built say about sails?

    BS. What wind assistance was there 20 years ago?
    Waving your 40 years around here won't change the facts.

    A large, heavy, expensive complicated rotor system? It says nothing at all about kites.
    The kite system isn't theoretical, it's in use today (did you just ignore the pictures of it I posted?)

    No, in fact it's almost entirely controlled by computer or the bridge.
    Obviously a kite won't be suitable around bridges or busy harbours!

    See above.
    Who said anything about common in the short term? Don't put words into my mouth.

    So not lower than that from one rotor? ;) Seems some of your arguments are melting away...

    I see no problem here anyway. That's a comparison only of the sizes and quantities selected by the author.
    What's important is the power provided for each dollar spent. The size and complexity of flettner rotors take them out of that race before it starts.




    Anyway, back to the point: the failure of flettner rotors to become popular has no bearing on the viability of sail assistance. Flettner rotors are too expensive for the benefit they provide.
     
  7. whitepointer23

    whitepointer23 Previous Member

    nuclear power is the way of the future for ships I think. what else can provide so much power for so little fuel. I know there plenty of issues with it but it is still a new technology that keeps on improving. if nuclear propulsion was released to the commercial market the cost should reduce as the market becomes larger. I would also like to see Australia powered with nuclear power plants to but most people don't want it here. they don't mind us selling our uranium as long as we don't use it here or store waste here either. I know this topic has been discussed quite a bit but it is something that will receive a lot more attention as fuel costs get to high.
     
  8. Yobarnacle
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    Yobarnacle Senior Member holding true course

    New technologies develop. Change is constant. I'm amazed at how life has changed in MY 66 years.
    plan to be around another 100 years or so, just to see what developes! :p
     
  9. SamSam
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    SamSam Senior Member

    I imagine the kite tether is pretty stout stuff. If the wind shifted, the kite fell in the water, the ship ran it all over and got the tether all wound up in the propeller in the middle of the ocean, that would be sort of a cluster.
     
  10. Yobarnacle
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    Yobarnacle Senior Member holding true course

    Kite powered ships are by necessity jet propelled, just to keep the tether OUT OF THE WHEEL in such eventuality!
     
  11. rwatson
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    rwatson Senior Member

    Oh, and I suppose the KW on the diagrams in your reference is also nonsense ? The diagrams show a propulsive force up to 2000 KW for a rotor in some conditions, that's 2600 HP. The motor to drive that is only 200 HP. By any paper you can find, the ratio of power generated to power required is way more than my original quote.


    No, a sail cant be 'easily' larger. It needs 10 times more material, 10 times more supporting structure, 10 times more controls, 10 times less visibility, 10 times more deck clutter from the masts and stays etc

    Imagine unloading cargo from this one
    http://www.gizmag.com/b9-shipping-cargo-sailing-ships/23059/


    My claim was 10 times more than SAIL - not Kite ( see below) . But having said that - here is a rotor 2.3 times less than the size of the Kite, that actually outperforms the Kite in some situations.


    I dont know what you are concerned about - your own figures show that the Flettner Rotor can outperform a Kite in some conditions, and that is what the point was.


    "

    The diagrams in your reference are not accurate. Rather than nitpick them, I just had to presume that those polar sailing diagrams in your reference were for commercial hulls. They are certainly not as generous as actual sailing rotor results. The paper is understandably conservative. I attach more accurate sailing results below found at
    www.see.ed.ac.uk
    from a google search of "flettner sailing performance graphs"

    You will see that under real conditions, we get lift up to 20 degrees to windward, and the downwind performance is not zero as portrayed in your reference.


    A sailor knows what POINT means. It means being able to sail into the wind to a big degree due to the Lift function. Another reference

    "a rotor ship can sail within 25 degrees of the wind - while a conventional sailboat can only achieve 30 degrees"

    http://www.boatdesign.net/forums/at...ttner-rotor-ship-launched-flettnerboat003.jpg


    The Kite cannot point anywhere near as well as a fixed mechanism like a sail, wing or rotor. It has a 180 degree 'hole', if the wind isn't coming from the 180 degrees astern, it cant sail.

    Lets address the other BIG problem with a Kite while we are at it. It needs enough wind to launch and support the Kite.

    Sails and Rotors can ghost along in very low winds, that would not support a kite.


    As SAILS - as per my previous comments. Its not my mantra, I point you to the reference.
    "“The outstanding fact is that rotating cylinders produce about ten times the propulsive force as canvas sails of the same area and that the actual results obtained in the trial trips of the Buckau confirmed the laboratory results with remarkable exactness. "
    http://www.oldsaltblog.com/2010/08/e-ship-1-has-the-flettner-rotor-ship-finally-arrived/


    Of course - but you missed the big point, its a COMMERCIAL CARGO ship. How many commercial cargo ship of a similar size with sail assist ? Its not a "huge number"


    The arrogance of youth. Do you even remember the oil shock of the 60's ?

    Here's a link to one of my hero's. Lloyd Bergeson. You wouldn't have heard of him, but he was until quite recently, one of the leading sail assist NA's of all time.
    http://news.google.com/newspapers?n...BMhAAAAIBAJ&sjid=QXUFAAAAIBAJ&pg=3763,1654741

    He was instrumental in getting the Minilace sail assisted cargo ship into operation in 1981, as well as a Flettner Rotor ship 'Tracker'
    http://www.boatdesign.net/forums/at...ettner-rotor-ship-launched-flettnerboat00.jpg

    The search for sail assistance for powered craft has been going on since the late 50's, but you wouldn't know about any of that.



    I post a picture of some lightweight Flettner Rotor yachts. In these days of reinforced fibre construction, they dont need to be as heavy as the originals. The mechanism is not at all complicated
    http://www.boatdesign.net/forums/at...ttner-rotor-ship-launched-flettnerboat002.jpg


    Yes, lots of pictures of TRIALS of Kites. Feel free to publish the names and details of any actual current commercial craft using them regularly. I note that the prime contender MV Beluga ( featured several times in your photos) has very little info online since it got chartered by the US navy in 2008. I cant find it at
    http://www.marinetraffic.com/en/ais/index/search/keyword:mv beluga

    There was one reference at http://www.reddit.com/r/Infrastruct...mv_beluga_skysails_transporting_wind_turbine/ but i cant see how recent that was.


    Almost ! Oh, apart from the two guys on deck to launch, retrieve, pack and stow of course. I bet they love that in really heavy weather. I cant locate the photo I remember of that event, but launching and retrieval need guys on deck. Lets not imagine the hassle of a gust smashing the kite against the ships superstructure.

    ..... or close to other Kite powered ships, even Supertankers, yachts or any other tall boat. That cuts out 80% of the busy shipping lanes of the world.


    Then thats agreed.



    I totally missed any cost analysis. Which page is that on ? I bet that sails and kites aren't that much cheaper.

    The sails on the Mini lace
    http://www.boatdesign.net/forums/at...ttner-rotor-ship-launched-flettnerboat003.jpg

    cost $250k, hardly cheap.


    It has EVERY bearing. For commercial ships, Rotors are as likely to be used as sail or Kites. You have no cost figures on building rotors to make the assertion that they are excessively costly. Also, once a technology becomes more common, the price drops significantly.


    Rotors are every bit as valid for wind assisted cargo ships as Kites and Sails, as well as having some major benefits.



    Personal Link for future ref:
    http://www.see.ed.ac.uk/~shs/Climate change/Flettner ship/Popular Science 1925.htm
     
  12. rwatson
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    rwatson Senior Member

    yeah, but not when maintenance and decommissioning are included.

    The US Navy figures show nuclear vessels have a lifetime cost of over 30% more than conventional ships.
     
  13. whitepointer23

    whitepointer23 Previous Member

    true , but you would expect these costs to come down as time goes on. can you think of any real alternative to nuc, coal , gas and oil are a finite resource. how many billion liters of oil get burn't everyday, its a wonder we haven't run out already. bio fuels are great can enough be made to replace diesel and petrol. sorry to go off topic op.
     
  14. rwatson
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    rwatson Senior Member

    Actually, the costs wont decrease much over time, as the complexity of controlling nuclear increases.

    Its like the space program, the more you know, the risk amelioration gets so expensive its prohibitive.

    Bio fuels have to be the answer, and oils from algae would be where I would put my money if I had to.

    This little discussion is probably quite pertinent to sail assist. Its not just the cost of oil that might pressure shipping companies, but the health issue from burning ship oil.

    ".....15 of the world's biggest ships may now emit as much pollution as all the world's 760m cars. ......
    US academic research which showed that pollution from the world's 90,000 cargo ships leads to 60,000 deaths a year in the US alone and costs up to $330bn per year in health costs from lung and heart diseases. ....."

    http://www.theguardian.com/environment/2009/apr/09/shipping-pollution
     

  15. whitepointer23

    whitepointer23 Previous Member

    I would love to make biofuel at home. I spend $1000 to $3000 a fortnight on fuel in my truck depending on what runs I do. even 150 lt a week could save me a lot of money over a year. I watched a program on algae fuels last week and it does look promising . the volume will be the big question.
     
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