Chine development

Discussion in 'Boat Design' started by frank smith, Jul 27, 2011.

  1. MikeJohns
    Joined: Aug 2004
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    Location: Australia

    MikeJohns Senior Member

    Design for least drag at the chosen operational speed. You'll find that studies on chines don't support what you've suggested above. For example vessels with completely flat sections forward can have an advantage over a V'd foresection because of their high pitch damping, providing the flat is deep enough not to slam.

    Sweeping the chines up forward is nearly always detrimental to smooth water flow and trips the flow and produces a visible wave pattern at the chine waterplane intersect. The continuous longitudinal flow has far more effect on drag than periodic transient vertical turbulence.

    Experiments have clearly shown that carefully placed chines reduce the total resistance over even round bilge forms, but the rules are that you sweep the chines with the flow field at the design speed and keep the exit waterplane intersect chine angle shallow. Sweeping the chines up forward was always detrimental.

    A sailboat designer has to consider the heeled windward condition as well.

    But the usual proviso is that if you are designing a heavy boat that will operate at low Froude numbers then it's not going to make much noticeable difference in a seaway whatever you do;)
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