Small Boat Drag Question....help!

Discussion in 'Boat Design' started by Biomechanist, Oct 30, 2004.

  1. Biomechanist
    Joined: Oct 2004
    Posts: 4
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Olympi, WA

    Biomechanist New Member

    A quick question about small boat drag. We are using Reynolds Number vs. Froude Number graph to get a drag coefficient to plug into our main equation and find out the actual drang of our boat.
    The problem is that the graph we are using is for huge ships...and so we are getting wrong numbers. We were wondering if someone could get us a graph or a site online that has a graph for Froude Number vs Reynolds Number for smaller boats like kayaks ets.
    We would really appreciate that.
    Thanks
    BioMechanist
     
    Biomechanist, Oct 30, 2004
    #1
  2. tspeer
    Joined: Feb 2002
    Posts: 2,319
    Likes: 305, Points: 83, Legacy Rep: 1673
    Location: Port Gamble, Washington, USA

    tspeer Senior Member

    You don't say what kind of boat you're interested in. Re vs Fr is an interesting approach, but would be highly dependent on the wetted area for the displacement, etc.

    For sailboats, take a look at
    http://www.rina.org.uk/rfiles/HISWA/1996/The bare hull resistance.pdf
    http://www.curtin.edu.au/curtin/centre/amecrc/papers/ame98/bmcrae1.html
    http://www.curtin.edu.au/curtin/centre/amecrc/papers/ame98/bmcrae2.html
    http://www.curtin.edu.au/curtin/centre/cmst/publicat/rinamodernyacht98.pdf

    For slender hulls, see
    http://www.cyberiad.net/michlet.htm
     
    tspeer, Oct 31, 2004
    #2
  3. jehardiman
    Joined: Aug 2004
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    Location: Port Orchard, Washington, USA

    jehardiman Senior Member

    If you are after Cf, why not just calculate it directly with the ITTC line. Or are you trying to use some of Froude's "circle" factors for a given "shipshape" hull? Better to use Taylor's data from a modern re-analysis or one of the standard boat hull series out there if you are doing something small.
     
    jehardiman, Oct 31, 2004
    #3
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