bow entry angle

Discussion in 'Hydrodynamics and Aerodynamics' started by cristianon, Sep 17, 2015.

  1. cristianon
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    cristianon Junior Member

    is there anyone who can help me to explain how to determine the good angle of bow entry for optimazimation seakeeping analysis?
    thanks...
     
  2. gonzo
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    gonzo Senior Member

    The first step is to determine the operating conditions, size of the vessel and intended use. Everything else will be determined by those basic restrictions.
     
  3. TANSL
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    TANSL Senior Member

    Inconsistent advice. I imagine that if the OP is in the design phase to make a "seakeeping analysis" it is because he already knows many other things about his boat.
    In any case, cristianon, if you give more details, it is possible for someone to help.
     
  4. rasorinc
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    rasorinc Senior Member

    Need length of boat
    need width (beam) of boat
    need usage of boat such as fishing or inter island delivery's
     
  5. cristianon
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    cristianon Junior Member

    here's the details:
    Lwl: 50m
    Lpp:48.5m
    Boa: 21.25m
    B1: 6.25m
    T:2.5m
    Cb: 0.386
    separation ration Ratio: 0.3
    Type: ferry catamaran
    operation: rough water with wave height up to 4m
    thank you...
     
  6. cristianon
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    cristianon Junior Member

    sorry i've forgot about the speed
    max speed: 25knot
    separation ratio: 0.3
     
  7. Mr Efficiency
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    Mr Efficiency Senior Member

    Take a look at comparable existing vessels of much the same proportions, see what the range of entry angles is for them. It is unlikely they have all chosen an angle that gives unfavourable sea-keeping characteristics.
     
  8. rasorinc
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    rasorinc Senior Member

    I'm out of my league here and maybe should not post but looking at pics of 90' cats the angle of the bow appears to be 70* off vertical. However maybe you should consider in 12' to 14' seas a Bulbous Forefoot. I hope that is the correct term for a extension of the 2 bows under water. Just an idea with no knowledge backing it up. However. I see it done on larger boats that travel in HARD water.
     
  9. PAR
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    PAR Yacht Designer/Builder

    Stan, I think this poster is looking for an optimum "entry half angle", which is dependant on several factors. The simple answer is there's no generic angle that is ideal, because of the multiple concerns that might affect it. This said, there are averages that can be used comparatively, to see if what you have is in the range with others of similar configuration.
     
  10. Ad Hoc
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    Ad Hoc Naval Architect

    With such a prescriptive set of principal data, it matters not what the angle of entrance is or shall be. The above principal dimensions shall dictate the motion response in a given seaway already. It is cart before the horse!!
     
  11. Mr Efficiency
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    Mr Efficiency Senior Member

    I think I mentioned somewhere a fast commercial cat that I went for a day trip on, that seemed unusually full at the waterline forward, and the designer came on here and said it was to provide more room for people in an underwater viewing area(s) up forward. It seemed to have little effect on performance, so obviously a degree or two would be inconsequential.
     
  12. cristianon
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    cristianon Junior Member

    thank's for all of your answer, maybe i'll change the question.
    if i've to change the angle of entrance which parametric i could keep or change.
    or is there any limit to change the angle?
     
  13. gonzo
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    gonzo Senior Member

    The angle in which plane? For example, you can have a fuller entry on the horizontal plane with a shallower vertical plane, or vice-versa. The flare will also influence seakeeping characteristics. Basically, each time you change one parameter, all others have to be checked out again.
     
  14. Mr Efficiency
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    Mr Efficiency Senior Member

    I imagined he was talking about waterline half angle at the bow.
     

  15. cristianon
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    cristianon Junior Member

    thank you for your answer i'll try lackenby method to change the angle
     
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