Drag reduction for low aspect sweptback rigs?

Discussion in 'Sailboats' started by lunatic, Mar 19, 2010.

  1. lunatic
    Joined: Jan 2008
    Posts: 111
    Likes: 1, Points: 18, Legacy Rep: 28
    Location: nyc,ny

    lunatic Senior Member

    The "crab claw" or, at least the leading edge vortex rigs I have sailed, seem to have good offwind potential at the cost of upwind performance with lift on aft facing surface FIG 1A. FIG 1C shows reduced heel and upwind potential, though somewhat negated by sweepback angle. Experimenting with planforms, subsequent prototypes got ever smaller ending with FIG 2 which surfed a Sunfish hull in 15-20 Kts wind with a sail area that would be disappointing even on a short sail board. FIG 3 is rig's leading edge detail; the sail was taut with no perceptible camber and easily outsailed a similar rigid wing with theoretically better sharp leading edge, even offwind.
    Speculating on what might be the best leading edge and possible forward facing working surface led to http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19860017728_1986017728.pdf.
    Is there any precedent or potential for this counter-intuitive forward facing flap in sailing?
    I have been using a sweptback wind vane for a self-steering system FIG 4. Very light weight, low profile yet good torque, nice twist-off when overloaded and application requires no upwind performance.
     

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  2. Pauls
    Joined: Jul 2010
    Posts: 11
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: USA

    Pauls Junior Member

    This is a very interesting post! Have you done more experimenting since you wrote it? I'd be very interested in what you've found.

    Thanks,

    Paul
     
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