Mainsheet Systems

Discussion in 'Sailboats' started by BRZ Designs, Dec 30, 2011.

  1. messabout
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    messabout Senior Member

    You guys must be getting really old. How could you be focusing exclusively on mainsheet arrangement and ignore the pretty lady on the next boat?:)
     
  2. BRZ Designs
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    BRZ Designs Junior Member

    Uh Oh, I see now the differences on the mainsheets :D The nice lady was throwing me off... hehehe.... Nice catch Messabout!

    PAR, I should mention also that I am originally from Brazil, so here is my next question: What does SOR mean?

    Cheers
     
  3. PAR
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    PAR Yacht Designer/Builder

    She wasn't all that Messabout, a bit scrawny if you ask me.

    SOR is Statement Of Requirements, which is a list of all the goals, needs and desires for the design.
     
  4. ancient kayaker
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    ancient kayaker aka Terry Haines

    I wasn't gonna ask you; I can form my own opinions about that stuff. Weren't you complaining about your spouse's butt in another thread Par, or was that a figment of my imagination? Sounds like she found your post and sorted you out . . .

    The bending strain on the boom changes direction as the sheet location moves from the end to the center of the boom, so there is probably an optimum location in between, at least from an engineering point of view. However that's starting to get a bit persnickety even for me.
     
  5. jamesgyore
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    jamesgyore Senior Member

    Thanks for the reference Michael,

    It looks to be a rather elegant and tidy system.
     
  6. PAR
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    PAR Yacht Designer/Builder

    That was my ex-wife's butt Terry, which is completely different then the current version.

    End of boom sheeting is preferred usually, though I often spread the loads along the last 1/5th of the boom, just to handle some common sense issues.
     
  7. BRZ Designs
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    BRZ Designs Junior Member

    Before I start, Happy New Year, May you all have a great 2012!!

    PAR would you by any chance have an SOR you can send me so I see can a real one?

    Thank you



     
  8. michael pierzga
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    michael pierzga Senior Member

    If possible look at the deck layout design work of Luca Brenta or Judel Vrolick. Very fine sailing yachts
     

  9. tspeer
    Joined: Feb 2002
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    tspeer Senior Member

    The mainsheet meets the hull at two points. The boom will move along an ellipse, with the foci of the ellipse being the two attachment points. It's the same principle as drawing an ellipse by dropping a loop of string over two pins and running a pencil around the loop.

    You might think of this as being equivalent to a traveler approximately as long as the distance between the two blocks.

    The mainsheet shown is simple, and lighter than a traveler. However, it does not have any ability to move the boom to or above centerline. I suspect twist control on this boat is primarily through the vang, rather than the traveler.

    It all depends on what you want to have happen when you vary the mainsheet. Sheet tension will typically move the boom in and out, controlling the angle of attack of the mainsail, and it will vary the leech tension, controlling the twist. The traveler is used to adjust the proportion of the sheet tension that goes to twist vs angle of attack.

    To some extent, a traveler and a vang are redundant. I once owned a Merlin Rocket dinghy in which the mainsheet was mounted to a hoop so the sheet came off horizontally to the boom. The mainsheet made zero contribution to twist, controlling only angle of attack, and leech tension/twist was controlled 100% through the kicking strap. On a multihull, you can have a very wide traveler and not need a vang. In that case, the traveler controls angle of attack and the sheet controls twist.
     
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