Canting keel lab experiments?

Discussion in 'Stability' started by gbr43926, Feb 12, 2007.

  1. gbr43926
    Joined: Feb 2007
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    Location: Portsmouth

    gbr43926 Junior Member

    Hello everyone,

    Since i first saw a canting keel and CBTF technology in action it has amazed and excited me...
    ~So much so that ive began a small investigation just for my own interest.

    Ive been looking at the existing mechanisms in place on such vessels as the VO60 and V070 (hydraulic systems) and comparing them to designs such as the Backman canting system (pulleys).

    I understand there have been Material issues with the hydraulic systems which ultimately caused failure> 2 ram rod failures and 1 ram end cap failure in the Volvo Ocean Race. Which has caused much debate in the technology. Was this simply wrong material selection? or was it down to faulty materials?

    Im interested in undertaking some simple experiments which would help me to understand the effects of using a canting keel compared to a fixed keel.
    I have thought of some simple moment calculations which would allow me to calculate the difference in displacement, righting arm etc.

    I want to be able to show what sort of performance increase a canting keel will provide.

    If anyone has some simple tests/ experiments or even just opinions then i would be most grateful to hear from you..
    Many thanks
     
  2. Doug Lord

    Doug Lord Guest

    Cbtf

    From some conversations I've had with couple of the CBTF guys they expect a 30-40% reduction in displacement for the same righting moment as compared to a fixed keel. Thats with a 55° canting keel. You might write to Bll Burns at CBTFco....
     
  3. gbr43926
    Joined: Feb 2007
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    gbr43926 Junior Member

    re:cbtf

    Wow thats am impressive reduction! looking at the backman 21 for example, which cants approx 43 degrees; the bulb weighs 225kg
    the total displacement of the vessel is only 520kg!

    so a reduction in bulb weight of about 40% would be quite a significant displacement reduction in this vessel, this boat must plane really easily!
     
  4. Guillermo
    Joined: Mar 2005
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    Location: Pontevedra, Spain

    Guillermo Ingeniero Naval

    Have a look at its stability implications in the attached document.
    Cheers.
     

    Attached Files:

  5. gbr43926
    Joined: Feb 2007
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    Location: Portsmouth

    gbr43926 Junior Member

    re:

    thanks! think ive looked at this document before, the righting arm curves look impressive! at 10 degrees heel, the righting arm for the canter is 3 times what it is for the fixed keel. i suppose this means it will hold 3 times the power? incredible!
    even at 30 degrees heel, the canter holds 60% more power than the fixed keel!

    thanks for the replies :)
     

  6. gbr43926
    Joined: Feb 2007
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    Location: Portsmouth

    gbr43926 Junior Member

    Righting arm experiment

    I have been advised to do an experiment which will help determine the righting arm achieved with different ballast systems.

    the idea is to build a scale model of a particular hull which is suspended along its COG
    > have the hull sprung so that it is at rest at an angle
    model keels can be attatched to the model to show the righting angle they achieve
    also the weight reduction for a canting keel can be calculated

    any thoughts?

    cheers
     
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