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Re: To Cat or not to Cat, was re:Tyvek

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  • Dave Womble
    ... ridgeline ... Bill, What you are trying to do is to keep the tarp material taut and this is not always easy or even possible with some tarp designs by just
    Message 1 of 32 , Jan 4, 2005
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      --- In hammockcamping@yahoogroups.com, "zippydooda" <zippydooda@y...>
      wrote:
      > Anyone who has an opinion, please weigh in. Is a catenary
      ridgeline
      > better on a hammocking tarp? How much drop would you want?
      >
      > Bill in Houston

      Bill,

      What you are trying to do is to keep the tarp material taut and this
      is not always easy or even possible with some tarp designs by just
      pulling hard enough on the tieouts to stretch the material so that it
      is taut. This has to do with the stretch characteristics of the
      fabric... it stretches differently along each orthogonal weave of the
      fabric and it stretches very much differently along the bias. So, on
      tarp designs were you can pull hard enough to take out any looseness
      you can get a taut tarp. With a catenary ridgeline you don't have to
      pull as hard to achieve tautness because you have essentially removed
      the loose fabric in the manufacturing. (Think of it as just
      gathering up the loose material at the center of the tarp.) So it
      that sense a catenary ridgeline works different, maybe better, maybe
      not.

      My experience with large 8'x10' tarps (or bigger) in an A-frame pitch
      is that the catenary ridgeline works better. This advantage will
      diminish with smaller tarps or maybe even with tarps that are not
      rectangular. A catenary ridgeline is not without tradeoffs. It is
      more difficult to cut, much more difficult to sew and is not
      necessarily as flexible as a flat tarp (which hasn't been as issue
      for me). I've made two different size catenary tarps, the largest
      one I use for winter hammock camping. I posted a few photos of them
      under this folder, http://tinyurl.com/6s3qz . I used the same
      characteristic curve for the ridgeline and the sides, with the curve
      being defined as having a 5" drop over 10'... this gives it a 6" drop
      over 11' and a 1.8" drop over 6'. I used a cardboard sewing board(?)
      that had 1" grids to make my templetes and cut the material with a
      soldering iron using those templetes.

      Youngblood
    • Admin
      Well, I actually find the hanging method to be quite easy. I use rolled kraft paper for my patterns and a lightweight metal decorative chain purchased at a
      Message 32 of 32 , Jan 20, 2005
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        Well, I actually find the hanging method to be quite easy. I use rolled kraft paper for my
        patterns and a lightweight metal decorative chain purchased at a home improvement
        warehouse. Instead of relying on a wall that's as long as I need for the curve, I have a 1" x
        12" x 10' board that I use to put everything on (I store it against the wall behind the couch
        in the living room so it's out of the way and out of sight when not in use). I cut the paper
        into strips 10 inches wide (the paper comes in 30" width), and use 2 spring-loaded clamps
        ($3 each) to hold the paper to the board. Then I measure the center point, how far down I
        want the curve to go, and mark where I want the chain to hang. Open one clamp slightly
        and slide one end of the chain under it. Pull the chain until it is as taut as it needs to be
        for the curve, stick it under the other clamp, and trace the line. Setup time is about 5
        minutes and drawing the curve takes another minute. It's also very easy to adjust the
        chain.

        Not knocking the templates. I just wanted to share that it can be done easily with the
        right supplies.

        -howie

        --- In hammockcamping@yahoogroups.com, "zippydooda" <zippydooda@y...> wrote:
        >
        > Having finally done this last night, I gotta say that the templates,
        > or at least the X-Y coordinates, are the way to go. Being one who
        > did not like the template idea, I hung the fabric on the wall, spent
        > quite a while trying to get it level and straight and keep it from
        > sagging too much between the support points, and all that, and then
        > trying to dangle a rope, figuring out it was too heavy, and then
        > dangling a thread so I could mark out some points and play connect
        > the dots.
        >
        > It would have been MUCH easier to use the spreadsheet and then mark
        > out several dots, and then connect them with the ruler.
        >
        > Gravity is NOT your friend - once you get the material off the floor,
        > bad stuff starts to happen. In a fitting bit of irony, you get
        > little catenary curves between your support points that cause
        > headaches when you are trying to make your nice big cat curve.
        >
        > Now to sew along the line...
        >
        > Bill in Houston
        >
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