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5892Re: Polytarp sail design

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  • C. O'Donnell
    Jul 6, 2000
      --- In bolger@egroups.com, "Peter Vanderwaart" <pvanderw@o...> wrote:
      >
      > I am trying to get my thinking together to help Leander build
      > polytarp sails.

      > Finally, my thinking is that it is better to err on the side of a
      > sail that is too flat than one that is too full.

      Too much draft is probably a better error, because you can always cut
      draft out of a sail.

      > How stretchy is the polytarp sailcloth? Any comments would be welcome.

      Fairly stretchy.


      I'm not exactly sure what Greg was trying to convey. Let's all run out
      and buy $1000 worth of sails? Let's face it, it's hard to beat a well
      cut sail made of modern materials, but not everyone is in it for that.

      I say go for it. If it's a lugsail, make sure you can keep the luff
      tight as a drum. Use prestretch dacron boltrope, and prestretch or even
      Spectra for halyard and downhaul. Use a 3:1 purchase on the downhaul.
      (Michalak says 2:1, I don't think that's enough).

      Here are some thoughts:

      1. Sails even 100 years ago on small sailing boats were nothing special
      and they would have been happy to have poltarp.

      2. Boltroping helps.

      3. Read Michalak's web efforts, and read if you can "The Sailmaker's
      Apprentice"

      4. If you're making small-boat batwing sails or junk sails, polytarp
      works fine. These are essentially cut flat. See Robert Laine's SAILCUT
      programs for one which will give you cambered panel shapes for junk or
      junklike battened sails.

      5. You will learn a lot making a polytarp sail. You won't win any
      races. You will be on the water for not much money. It will give you a
      point of comparison if you obtain a professionally made sail.

      6. Quite large cutters and schooners in Indonesia, even today, use
      polytarps, double-layered, cut dead flat, as sail materials.

      7. Many photos exist of Chinese sampans and such with various things
      like rice-bags semn together to make small sails.

      8. There's a fair amount of tarp sail info on my Cheap Pages. I am not
      as methodical, however, as Dave Gray who offers the kit materials on
      the web and in Messing About in Boats.

      9. A professionally made sail is going to be better.

      10. The lugsail which is sold with the Chesapeake Light Craft "Eastport
      Pram Sailing Option" is made by UK-Allan in Annapolis, it's about 40 sq
      ft, and it's *really* *really* well-cut - it is something to consider
      for small boats or sailing canoes which take a standing lug or balanced
      lug. I've sailed that pram a lot; I'm trying to get info on what the
      sail alone will cost from UK-Allan. (The "sailing option" from CLC is
      sail, rudder, tiller, daggerboard, mast, and spar materials, cleats,
      etc. and more stuff than someone making a Bolger boat will need).
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