Keel Design

Discussion in 'All Things Boats & Boating' started by Lyle Creffield, Dec 21, 2006.

  1. Lyle Creffield
    Joined: Jun 2006
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    Location: Sunshine Coast Australia Lat 27S

    Lyle Creffield Junior Member


    My question relates to reducing a 1.8 m draft, 3m toe, 3.3 mean keel length, cord of 300mm attached to a 14.2m LWL crusing sloop

    By reducing the draft to 1.5 yet maintaining the ballast C of G the same

    Wings - not new

    simply a wing of 900mm total width, same cord, same length, same ballast C of G

    Provided the vertical keel area and sufficient for direction stability

    why not?
  2. MikeJohns
    Joined: Aug 2004
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    Location: Australia

    MikeJohns Senior Member


    Reduced performance to windward with more leeway. Problems getting hooked under coral at times and makes brute force towing off much harder.

    The wings will add an end plate which can compensate to some extent for the loss of keel depth (but not that much). Usually when retrofitted they often add a lot of turbulance (drag) unless very carefully designed and that means tank testing.

    I'd stick with the 6 foot draft on a 45 footer if you are planning for blue water .
  3. Tim B
    Joined: Jan 2003
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    Location: Southern England

    Tim B Senior Member

    Except that you can't see the Reynolds number effects in a tank-test, and therefore you're getting bogus data. Wind-tunnel tests or CFD are your best options for optimisation. Niether are cheap.

    There is a lot of information about reducing the draught of a yacht on this forum, I suggest you have a search around. I have expressed my opinions on the matter several times. In short, "It will cause a lot of problems. Do you really need to do it?"

    Tim B.
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