Sail trim, where to bend the wind?

Discussion in 'Boat Design' started by lunatic, Mar 15, 2009.

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

    lunatic Senior Member

    Where to bend the wind? maximum bend perpendicular to course, see drawings. A is not perpendicular but bend facing forward, typically achieved with full battens. B is possible with partial battens. C is possible with no battens, but at what point is this a hooked leech? What are the limits in off wind sailing of the exit angle, pressure recovery or dumping velocity at trailing edge? Or does it matter with sail distorted up against stays and spreaders. With free standing Laser rig, one technique running down wind is with rig to leeward, drawing D. This puts sail's driving force closer to center line for better directional stability and reduces sail distortion in a stayed rig.

    This backward approach bends a battened sail in the right place, but has sharp leading edge and the mast as a trailing edge. The Laser has a relatively clean sleeve luff compared to separate sail-mast configuration. Even if attached flow could be maintained, where is the trade off between lift and drag generated drive force in off wind sailing?

    Chafe reduction sailing with main to leeward might even appeal to cruising sailors but for the risk of jibing, yet it is a counter intuitive solution for the Laser. Nice in diagrams but any practical application of this?

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