"Reverse" keel design??

Discussion in 'Sailboats' started by SeaJay, Sep 11, 2007.

  1. SeaJay
    Joined: Jun 2007
    Posts: 211
    Likes: 5, Points: 0, Legacy Rep: 112
    Location: Sacramento

    SeaJay Senior Member

  2. tspeer
    Joined: Feb 2002
    Posts: 2,319
    Likes: 303, Points: 83, Legacy Rep: 1673
    Location: Port Gamble, Washington, USA

    tspeer Senior Member

    Don't believe everything you read on the internet.
     
  3. SeaJay
    Joined: Jun 2007
    Posts: 211
    Likes: 5, Points: 0, Legacy Rep: 112
    Location: Sacramento

    SeaJay Senior Member

    Tom - I'm highly skeptical of this claim but was wondering if there was any hydrodynamic principal to support it...something that I was unaware of. (me and apparently everybody else in the world)

    Regards,

    Doug
     

  4. jehardiman
    Joined: Aug 2004
    Posts: 3,762
    Likes: 1,152, Points: 113, Legacy Rep: 2040
    Location: Port Orchard, Washington, USA

    jehardiman Senior Member

    In one sense, yes, there is less pressure drag by having a smaller entry half angle for a 2D foil and placing the point of maximum section well aft. It is a well know fact that NACA 00XX shapes have less hydrodynamic drag towed "backwards" than "forwards" at operational Reynolds numbers. But this is for locked, fixed zero AOA, straight line, ONLY.

    Otherwise, lift/drag and stall performance are poorer than a more "conventional" foil shape. Extreme sweep effects will tend to smear the data when different shapes are compared (due to the sweep making the apparent t/c << 0.1 which effectively makes all shapes flat plates from a hydro point of view), but data shows the advantage is still with a more conventional shape. See PNA Chpt. IX, FDD Chpt.6, and FDL Chpt 8.
     
    Last edited: Sep 12, 2007
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.