Downwind lift possible with a non-rotating freestanding mast?

Discussion in 'Sailboats' started by folotp, Dec 29, 2011.

  1. folotp
    Joined: Dec 2011
    Posts: 5
    Likes: 0, Points: 1, Legacy Rep: 10
    Location: Gatineau, Québec, Canada

    folotp Junior Member


    I am wondering if it is possible for the sails to generate lift when going downwind on a non-rotating freestanding mast. Like on a Freedom rig for example. Would the boom have to go too far forward?


  2. messabout
    Joined: Jan 2006
    Posts: 3,359
    Likes: 498, Points: 83, Legacy Rep: 1279
    Location: Lakeland Fl USA

    messabout Senior Member

    Pierre; When you say lift, are you referring to vertical lift? If so you will need to introduce a vertical component to the force of the sail. That implies that the mast is raked, as on a windsurfer. More rake means more vertical lift and diminished forward drive. Vector sums at work.
  3. Perm Stress
    Joined: Sep 2009
    Posts: 554
    Likes: 24, Points: 0, Legacy Rep: 323
    Location: Lithuania

    Perm Stress Senior Member

    Windsurfer style freedom rigs with wrap-around sails, certainly.
    If dead downwind, booms have to be about 30 or so degrees forward from abeam.
    The side effect is force component to "windward" -opposite side from the boom.

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

    tspeer Senior Member

    You need to reduce the angle of attack below the stall angle. The boom has to go well forward to accomplish this. It can't do that when there are shrouds, and the gooseneck is probably not going to have enough freedom of motion on a fixed mast.

    A fixed, cantilevered round mast could do it, with the sail and gooseneck rotating around the mast.
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.