Round Bilge vs hard chine

Discussion in 'Multihulls' started by nickvonw, Apr 11, 2011.

  1. rattus
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    rattus SeƱor Member

    I beg to differ ;-)

    [​IMG]

    Yellow Box Fish

    Mike
     
  2. Ad Hoc
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    Ad Hoc Naval Architect

  3. upchurchmr
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    upchurchmr Senior Member

    Thanks for the reference, thats why I only asked for a couple. Don't know when I will really get into this, but I appreciate the help.

     
  4. OldYachtie
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    OldYachtie Junior Member

    I'm surprised no one recommended looking at a diagonal where it crosses the chine in a hard chine hull. In a recent v bottomed design of mine in which the chine is mostly submerged below the DWL, you cannot see any unfairness at all in the diagonal that crosses the chine. I believe that it was Douglas Phillips Birt that said that the diagonals are the lines which best represent the movement of the water past the boat hull.
     
  5. Ad Hoc
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    Ad Hoc Naval Architect

    Diagonals are merely construction lines to establish the 'fairness' of the hull surface; like watelines and buttocks etc. Nothing else.
     
  6. Richard Woods
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    Richard Woods Woods Designs

    I suspect Birt was talking about wide beamed traditional long keeled monohulls that heel. Not so relevant to a narrow non heeling multihull

    RW
     
  7. OldYachtie
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    OldYachtie Junior Member

    I think he was indeed talking about long keeled monohulls that heel, but I don't think that this limits the idea. I still think the diagonals are the lines that best reflect how water moves past a hull (the converse, really, but the principle is the same.)
     
  8. OldYachtie
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    OldYachtie Junior Member

    Alas, that a human heart should be so numb

    Really? I see a world of information when I look at a lines drawing of a hull. I feel narrow waterlines slicing through water smoothly with little effort, and water being pushed out and then recovering and rushing back in as it passes diagonals. I see wide, deep boats pushing up huge waves that are high at the bow and stern, and low amidships. I feel sharp bows smoothly parting waves that blunt bows smack harshly. It's all quite visceral to me. When a sailboat is in the groove, I feel it dancing with the sea, with a light rhythm, like the lilt of a pretty girl with a lovely accent.
     
  9. Ad Hoc
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    Ad Hoc Naval Architect

    Exactly. All subjective to you and you alone.

    It is only for the purpose of establishing if the line is a smooth and thus a faired curve on the hull's bilge radius or other more curved parts of the hull, that's all.

    To 'YOU' yes, but not to the scientific independent objective world.

    Naval architecture is about engineering based not faith based design.
     
  10. OldYachtie
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    OldYachtie Junior Member

    Spock speaks. Numbness, friend, is a failure of nerve function, not improved nerve functioning.
     
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  11. upchurchmr
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    upchurchmr Senior Member

    What the heck did that mean? "Spock speaks....."

    Of course you are welcomed to build your boat any way you feel.

    It's just not good to lead others down a non engineering path - if they think they are hearing gospel.
     
  12. OldYachtie
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    OldYachtie Junior Member

    Spock was a character in Star Trek, in both the television series, and in several movies. He eschewed emotion, and glorified logic at its expense. If you remove the poetic license from my comments, you will find a list of truisms that almost no one would disagree with.
     
  13. upchurchmr
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    upchurchmr Senior Member

    Emotion has its place.

    And yes I know Spock.

    But you are not talking about the small changes that result in more efficient sailing. Everything you said would apply to a cat boat as well as a trimaran.

    No help in choosing a 20' Tri.
     
  14. OldYachtie
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    OldYachtie Junior Member

    Actually, I suggested making sure that a diagonal that bisects the DWL is fair. Of course, you have to have access to the lines drawing to check that.
     

  15. MikeJohns
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    MikeJohns Senior Member


    For a chined hull the angle of the waterlines at the chine intersects in plan view is more useful but diagonals could be quite misleading. Flow lines don't look much like diagonals either but that will depend on the volume distribution .
     
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