force of sail

Discussion in 'Boat Design' started by sailcat, Feb 5, 2011.

  1. sailcat
    Joined: Dec 2010
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    Location: canada

    sailcat Junior Member

    Hi
    vertical rope between points A and B ( as a rope mast)
    with triangle sail : P= AB = 50 ft E= 15 ft
    how may I calculate force of the sail on the rope for wind v= 50 ft/s
    same as beam? max load in A or B?
    I am looking for rope dimension

    thank you for help
     
  2. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    Part of the force will be the tension on the halyard. Stretchy halyards may need more tension. Roller furlers and foils can bet away with less. I assume you are asking about a sail set flying.
     
  3. sailcat
    Joined: Dec 2010
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    sailcat Junior Member

    sail is working as the main in A shape mast
    I think in project Amazon(?) with A shape mast. They had this system with the rope for the main sail.
    I am trying to fin forces from sail on this rope.
     
  4. Tim B
    Joined: Jan 2003
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    Tim B Senior Member

    You'll find by inspection that the rope will sag to leeward. This is not good for performance, and is the reason that most people use a single mast. Beyond working out the overall lift and drag forces of the sail, how these forces transfer to the structure is impossible to say without a pressure distribution and an FEA solution. Not simple, and not for the faint hearted.

    Tim B.
     
  5. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    This is an old problem, with wire being much better then a length of line, even if it is spectra. Next, up the food chain would be rod, though the typical aluminum extrusions used in masts will have less drag then your two stick and line/wire/rod leading edge treatment. At least this has been the case with all the attempts, at cleaning up the leading edge by using a bi pod mast arrangement.
     

  6. Perm Stress
    Joined: Sep 2009
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    Perm Stress Senior Member

    Take a look at any Class Society Rules on Large Yacht Rigs. They give calculation method for headsail on a stay, in principle similar to your problem. Of course, Class load estimation always err on the high side.
     
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