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Re: support line strength

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  • Dave Womble
    ... a ... Jeff, I think you re asking about the rope breaking... I think the first think I would worry about with a prussik knot under that kind of load is if
    Message 1 of 5 , Nov 2, 2005
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      --- In hammockcamping@yahoogroups.com, "jwj32542" <jwj32542@y...> wrote:
      >
      > Hrm...600 lbs is a good strength for hammock supports. But knots can
      > reduce the working load considerably.
      >
      > So lets say I'm putting a prussik knot in Air Core cord rated at
      > 1100lbs...would that type of knot still be safe on that cord to hang
      a
      > hammock with?
      >
      > Jeff
      >
      Jeff,

      I think you're asking about the rope breaking... I think the first
      think I would worry about with a prussik knot under that kind of load
      is if it has enough friction to hold, will you still be able to slide
      it when you want to.

      Dave
    • jwj32542
      ... load ... slide ... You re right. I tried putting a prussik with 550 cord on my homemade spectra supports. I had to fidget with it a bit, but it held.
      Message 2 of 5 , Nov 2, 2005
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        --- In hammockcamping@yahoogroups.com, "Dave Womble" <dpwomble@y...>
        wrote:
        > I think you're asking about the rope breaking... I think the first
        > think I would worry about with a prussik knot under that kind of
        load
        > is if it has enough friction to hold, will you still be able to
        slide
        > it when you want to.

        You're right. I tried putting a prussik with 550 cord on my homemade
        spectra supports. I had to fidget with it a bit, but it held. Making
        it slip afterwards was a little tough, but I found a very easy way to
        fix that - one small loop attached to the "wrap-around" part of the
        prussik. Immeasurable weight (on my 2g scale, anyway) and not any
        appreciable added complexity.

        But the HH spectra is a bit thinner than my other spectra, and the
        prussik line needs to be thinner than the support line. It wouldn't
        hold.

        So I looked up the Air Core on BPL and it looks like it'll work, but
        I'm concerned that if I put that much force on it, I'll be too close
        to its working load.

        What do you think?
      • Dave Womble
        ... Jeff, I m not sure how you are using it. 1100 lbs wouldn t worry me too much for your weight if you are using a hammock without a structural ridgeline and
        Message 3 of 5 , Nov 3, 2005
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          --- In hammockcamping@yahoogroups.com, "jwj32542" <jwj32542@y...> wrote:
          >
          > So I looked up the Air Core on BPL and it looks like it'll work, but
          > I'm concerned that if I put that much force on it, I'll be too close
          > to its working load.
          >
          > What do you think?
          >

          Jeff,

          I'm not sure how you are using it. 1100 lbs wouldn't worry me too much
          for your weight if you are using a hammock without a structural
          ridgeline and are setting the hammock sag around 30 degrees. In that
          case the static load on each suspension line is pretty close to your
          body weight. However, if you are using the 'initially pull everything
          taut' technique that some folks are using, particularly hammocks with a
          structural ridgeline like Hennessy uses, then I would be a little
          worried because you might be putting several times your body weight on
          each suspension line.

          Again, I'm not sure how you are using it but the bowline with a quick
          release is very easy to tie/untie and holds very well with slippery
          rope. With not so slippery rope, it is not that easy to pull the quick
          release free-- I had trouble getting my Hennessy to slip from the quick
          release a time or two. I had the nylon webbing on a twin-layer hammock
          actually melt from the tension/stretching at the knot and had to
          literally cut it off of the tree. It is important to not use the wrong
          knot for the type hammock suspension line you use... not only does it
          have to hold under pretty high loading, you also want it to
          untie/release in the morning! That bowline with a quick release is
          what I have been using for my rather slippery poly rope and it is what
          the Clark Hammocks use for there poly rope. I suspect that it is
          easier to use than many of the 'easy' attachment schemes that I have
          seen for hammock suspension lines. If you are not familar with bowline
          with a quick release, there is an excellent illustration on Clark's web
          site in his online manual.

          Dave
        • dlfrost_1
          ... wrote: [...] ... close ... [...] ... it ... what ... have ... I think the problem he s going to have is that the Prusik will shred the spectra line s
          Message 4 of 5 , Nov 4, 2005
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            --- In hammockcamping@yahoogroups.com, "Dave Womble" <dpwomble@y...>
            wrote:
            > --- In hammockcamping@yahoogroups.com, "jwj32542" <jwj32542@y...>
            wrote:
            [...]
            > > I'm concerned that if I put that much force on it, I'll be too
            close
            > > to its working load.
            [...]
            > It is important to not use the wrong
            > knot for the type hammock suspension line you use... not only does
            it
            > have to hold under pretty high loading, you also want it to
            > untie/release in the morning! That bowline with a quick release is
            > what I have been using for my rather slippery poly rope and it is
            what
            > the Clark Hammocks use for there poly rope. I suspect that it is
            > easier to use than many of the 'easy' attachment schemes that I
            have
            > seen for hammock suspension lines.

            I think the problem he's going to have is that the Prusik will shred
            the spectra line's braided nylon sheath in fairly short order. As
            slippery as spectra is the sheath will eventually just separate and
            slide along, slowly lowering the hammock to the ground. It's just
            not meant to hold that kind of weight in that fashion.

            For webbing on a 'biner (winter setup) I've gravitated towards using
            the figure-8 wrap used with the HH line. Solid and secure, easy to
            handle--even with gloves, or if it gets rained on and freezes. (Take
            the hammock off the 'biner and thaw out the rigging later on. No
            holdup getting on the trail.)

            Folks here were praising the Ossel Hitch for webbing a while back.
            One of its virtues is easy adjustability. I wonder how many are
            still using that?

            Doug Frost
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