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Re: 3/32" Hammock Hanging Rope?

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  • Ralph Oborn
    To engineer the straps/ropes how big of a safety factor do you plan on? If I weigh 200 lbs. and hang at 40°. then my static load on each rope is 155 lbs. is a
    Message 1 of 22 , Aug 4, 2004
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      To engineer the straps/ropes how big of a safety factor do you plan
      on?
      If I weigh 200 lbs. and hang at 40°. then my static load on each
      rope is 155 lbs. is a rope with 5oo lbs. breaking strength enough?
      1000 lbs? 1500 lbs?




      --- In hammockcamping@yahoogroups.com, "Ray Garlington"
      <rgarling@y...> wrote:
      > --- In hammockcamping@yahoogroups.com, "Mirage" <mirage@p...>
      wrote:
      > This is what I have evolved to. I found the bulk and weight of the
      > 30 ft of webbing rather too much for my tastes. I used what I had
      > to make two 10' "tree huggers" (rather long, but some trees here in
      > the PNW really require it).
      >
      > One thing about ropes & trees. I've noticed that most of the
      > rubbing/friction is in the first 1/4 turn of the rope around the
      > tree. By the time you get to ropes about 5/16" diameter there is
      no
      > significant damage (but some slight cosmetic scraping). I made
      some
      > pads to protect this 1/4 turn, and a similar idea might work on
      the
      > thinner cords. You might try some thick wall tubing for that
      area
      > to act as a pad.
      >
      > Concerning breaking strength: I found the following rule of thumb
      > for nylon rope on the Internet. (I have observed that woven
      > polyester rope seems to have slightly higher breaking strength
      than
      > predicted by this formula.)
      >
      > breaking strength = <circumference of line in inches> x 2,400
      >
      > so
      > 1/8" cord - .3927" in circumference = 942 pounds breaking strength
      > 3/16" cord - .589" C = 1413
      > 1/4" rope - .75" C = 1809 pounds breaking strength
      > 5/16" rope - .98" C = 2356
      > 3/8" rope - 1.18" C = 2827 pounds breaking strength
    • Rick
      ... Hey Mirage, I was asleep at the wheel last month when y all were talking about knots for the hammock to rope junction. What is this whipping to 10 foot of
      Message 2 of 22 , Aug 4, 2004
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        Mirage wrote:

        >
        >I then whipped the hammock hanging lines on the end of the hammock,
        >leaving about 10' of line to hang from on either end.
        >
        >
        >
        Hey Mirage,

        I was asleep at the wheel last month when y'all were talking about knots
        for the hammock to rope junction. What is this whipping to 10 foot of
        line knot that you use?

        Rick
      • Rick
        ... Hi Jon, I would want the weight to be suspended from the webbing against the tree for two reasons: - eliminate roll down - spread weight across the full
        Message 3 of 22 , Aug 4, 2004
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          moneymakerjk1 wrote:

          >What about short sections of tubular nylon sling as a cover for the
          >line as it goes around the tree? A one or two foot length wont weigh
          >that much I suspect. I used to be a Ropes Course instructor, and the
          >stuff is pretty hardy.
          >
          >jon
          >
          >
          >
          Hi Jon,

          I would want the weight to be suspended from the webbing against the
          tree for two reasons:
          - eliminate roll down
          - spread weight across the full width of the webbing

          I have used the Hennessy Hammock style tree huggers and think they are a
          good solution. They are also easy to make at home. What this is, is a 2
          or three foot piece of webbing with the ends folded over and sewn into a
          loop. To tie the hammock up to the tree, the hugger is either wrapped
          around the back of the tree (big tree) or wrapped a couple times around
          a smaller tree, ending up with the two loops equidistant from the
          hammock. Then the rope is passed through the loops and tied with a
          hennessy hammock knot.

          I would not think that passing the rope through a piece of tubular
          webbing would do much to protect the tree from anything except abrasion
          (which is not the damage I am concerned about) or to reduce roll down.
          BTW, the damage I am concerned about is pressure damage to the live
          cambrium layer under the bark.

          Risk
        • Rick
          ... Thus far I have done well with straps with a breaking strength of 300-600 pounds. I figure that with a breaking strength of 950 pounds, the 3/32 T-100
          Message 4 of 22 , Aug 4, 2004
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            Ralph Oborn wrote:

            >To engineer the straps/ropes how big of a safety factor do you plan
            >on?
            >If I weigh 200 lbs. and hang at 40°. then my static load on each
            >rope is 155 lbs. is a rope with 5oo lbs. breaking strength enough?
            >1000 lbs? 1500 lbs?
            >
            >
            >
            Thus far I have done well with straps with a breaking strength of
            300-600 pounds. I "figure" that with a breaking strength of 950 pounds,
            the 3/32 T-100 cord is probably strong enough. All I know about stretch
            is that the line is said to stretch less than one percent at 95 pounds
            of tension.

            Another cord I might think about would be the 1/8 inch Pulse Line which
            is also about 900 pounds of strength.

            This is just an experiment for me. I will not guess any conclusion
            until I actually try it. I know that I will be *very* surprised if 3/32
            inch cord is sufficient. But if it is, this offers considerable space
            and weight savings, as well as a little cost savings.

            Risk
          • Mirage
            ... hammock, ... knots ... foot of ... Initially, I was using 1/8 polypro line to whip the folded ends (instead of knots) together, then using a larks head
            Message 5 of 22 , Aug 4, 2004
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              --- In hammockcamping@yahoogroups.com, Rick <ra1@i...> wrote:
              > Mirage wrote:
              >
              > >
              > >I then whipped the hammock hanging lines on the end of the
              hammock,
              > >leaving about 10' of line to hang from on either end.
              > >
              > >
              > >
              > Hey Mirage,
              >
              > I was asleep at the wheel last month when y'all were talking about
              knots
              > for the hammock to rope junction. What is this whipping to 10
              foot of
              > line knot that you use?
              >

              Initially, I was using 1/8" polypro line to whip the folded ends
              (instead of knots) together, then using a larks head from the straps
              or rope to hang the hammock.

              I just took it one step further, once I decided to go back to rope
              and tree huggers. Instead of whipping with 1/8" line first, I just
              use my 3/8 hang line and whipped it to the end, leaving the long end
              comming out the end of the folds.

              I'll post pics as soon I I get them back from my dads camera (I
              borrowed my sons, and forgot it only has 16Mb and the pics turned
              out poor as well).

              Shane "Mirage"...
            • Ray Garlington
              ... plan ... As a practical example: Hennessey uses line with a breaking strength from about 1600 to 1800 pounds depending on the model. If the webbing used
              Message 6 of 22 , Aug 5, 2004
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                --- In hammockcamping@yahoogroups.com, "Ralph Oborn"
                <polecatpop@y...> wrote:
                > To engineer the straps/ropes how big of a safety factor do you
                plan
                > on?

                As a practical example: Hennessey uses line with a breaking
                strength from about 1600 to 1800 pounds depending on the model. If
                the webbing used by the Speerians really is 800 pound breaking
                strength, and they are not reporting problems then you can see that
                Tom has built in a large safety factor.

                It will be interesting to see if Rick ends up risking the 3/32"
                which is typically used for working loads around 100 pounds. On a
                positive note, it seems like it should work if the webbing he's been
                using really only goes to 800 pounds.
              • Ray Garlington
                ... live ... Apx what pressure (in psi) will cause damage? We could calculate (or measure) the localized pressure being generated at the outside bark surface
                Message 7 of 22 , Aug 5, 2004
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                  --- In hammockcamping@yahoogroups.com, Rick <ra1@i...> wrote:
                  > BTW, the damage I am concerned about is pressure damage to the
                  live
                  > cambrium layer under the bark.


                  Apx what pressure (in psi) will cause damage? We could calculate
                  (or measure) the localized pressure being generated at the outside
                  bark surface and stay above that figure. The exterior bark would
                  also act as padding serving primarily as a safety factor.

                  My experience with trees has been that they can survive quite well
                  even if cut through to the wood so long as decay does not start at
                  the injury site. You have to ring a tree most of the way around
                  (cut through the bark) to kill it.
                • Dave Womble
                  ... Ray, you overlooked something in your comparison. The Hennessy, with its intergal ridgeline, generally puts more tension on the hammock support
                  Message 8 of 22 , Aug 5, 2004
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                    --- In hammockcamping@yahoogroups.com, "Ray Garlington"
                    <rgarling@y...> wrote:
                    > --- In hammockcamping@yahoogroups.com, "Ralph Oborn"
                    > <polecatpop@y...> wrote:
                    > > To engineer the straps/ropes how big of a safety factor do you
                    > plan
                    > > on?
                    >
                    > As a practical example: Hennessey uses line with a breaking
                    > strength from about 1600 to 1800 pounds depending on the model. If
                    > the webbing used by the Speerians really is 800 pound breaking
                    > strength, and they are not reporting problems then you can see that
                    > Tom has built in a large safety factor.
                    >

                    Ray, you overlooked something in your comparison. The Hennessy, with
                    its intergal ridgeline, generally puts more tension on the hammock
                    support ropes/straps because it typically is hung so that the hammock
                    support ropes/straps are more horizontally than a Speer hammock.
                    Sometimes, this difference in tension is quite severe and it is not
                    obvious that Hennessy is using a greater safety margin. This extra
                    tension would also carry over to the other discussion concerning tree
                    damage. (While the internal ridgeline does help in getting a
                    consistant 'hang', it is not without its drawbacks.)

                    Youngblood
                  • navjohn@aol.com
                    ... Yes, but our goal should be leave no trace -- and this means no visible damage to trees. Many public (and some private) campgrounds already have
                    Message 9 of 22 , Aug 5, 2004
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                      In a message dated 8/5/04 10:35:38 AM, rgarling@... writes:


                      My experience with trees has been that they can survive quite well
                      even if cut through to the wood so long as decay does not start at
                      the injury site.   You have to ring a tree most of the way around
                      (cut through the bark) to kill it.


                      Yes, but our goal should be leave no trace -- and this means no visible damage to trees.  Many public (and some private) campgrounds already have restrictions against tying anything to trees because of damage caused by careless campers.   Any scarring or bark loss, even if it causes no long-term damage to the tree, should be considered unacceptable to an ethical hammocker.
                      John Wilson
                    • ra1@imrisk.com
                      ... John, I agree that my concern is at a higher level than killing the tree - and I know Ray s is as well. I am concerned about scars from damage to any
                      Message 10 of 22 , Aug 5, 2004
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                        Quoting navjohn@...:

                        >
                        > In a message dated 8/5/04 10:35:38 AM, rgarling@... writes:
                        >
                        >
                        > > My experience with trees has been that they can survive quite well
                        > > even if cut through to the wood so long as decay does not start at
                        > > the injury site. You have to ring a tree most of the way around
                        > > (cut through the bark) to kill it.
                        > >
                        >
                        > Yes, but our goal should be leave no trace -- and this means no visible
                        > damage to trees. Many public (and some private) campgrounds already have
                        > restrictions against tying anything to trees because of damage caused by
                        > careless
                        > campers. Any scarring or bark loss, even if it causes no long-term damage
                        > to
                        > the tree, should be considered unacceptable to an ethical hammocker.
                        > John Wilson

                        John,

                        I agree that my concern is at a higher level than killing the tree - and I know
                        Ray's is as well. I am concerned about scars from damage to any portion of the
                        tree's live portion - under the bark.

                        I am a little less worried about a little surface scrape of the outer bark,
                        which is only some friction against the dead outer layer of the bark. But this
                        is because I usually am using a tree that will seldom/never have another hammock
                        hung from it.

                        I guess it is not truely leave no trace, in the same way that stepping on grass
                        is not actually leave no trace.
                        >

                        Rick
                      • zippydooda
                        Hey Risk, as far as stretch, the amount of stretch per unit of load should be higher for the first unit of load than for subsequent units. Sorry, which means
                        Message 11 of 22 , Aug 5, 2004
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                          Hey Risk, as far as stretch, the amount of stretch per unit of load
                          should be higher for the first unit of load than for subsequent
                          units. Sorry, which means that if you get 1% stretch with the first
                          95 lbs, that the next 95 pounds should be less than 1% stretch. So
                          for 450 lbs, you are looking at maybe 4% stretch or less.

                          Good luck with the experiment, and thanks for posting your ideas.
                          Hopefully the knots you use won't reduce the ultimate tensile
                          strength too much. Maybe put a big mattress under you when you do
                          the testing ;-)

                          Bill in Houston

                          --- In hammockcamping@yahoogroups.com, Rick <ra1@i...> wrote:
                          > Ralph Oborn wrote:
                          >
                          > >To engineer the straps/ropes how big of a safety factor do you
                          plan
                          > >on?
                          > >If I weigh 200 lbs. and hang at 40°. then my static load on each
                          > >rope is 155 lbs. is a rope with 5oo lbs. breaking strength enough?
                          > >1000 lbs? 1500 lbs?
                          > >
                          > >
                          > >
                          > Thus far I have done well with straps with a breaking strength of
                          > 300-600 pounds. I "figure" that with a breaking strength of 950
                          pounds,
                          > the 3/32 T-100 cord is probably strong enough. All I know about
                          stretch
                          > is that the line is said to stretch less than one percent at 95
                          pounds
                          > of tension.
                          >
                          > Another cord I might think about would be the 1/8 inch Pulse Line
                          which
                          > is also about 900 pounds of strength.
                          >
                          > This is just an experiment for me. I will not guess any conclusion
                          > until I actually try it. I know that I will be *very* surprised if
                          3/32
                          > inch cord is sufficient. But if it is, this offers considerable
                          space
                          > and weight savings, as well as a little cost savings.
                          >
                          > Risk
                        • Thomas Peltier@Goldenautomotive.com
                          Hey Risk, as far as stretch, the amount of stretch per unit of load should be higher for the first unit of load than for subsequent units. Sorry, which means
                          Message 12 of 22 , Aug 5, 2004
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                            Hey Risk, as far as stretch, the amount of stretch per unit of load
                            should be higher for the first unit of load than for subsequent
                            units. Sorry, which means that if you get 1% stretch with the first
                            95 lbs, that the next 95 pounds should be less than 1% stretch. So
                            for 450 lbs, you are looking at maybe 4% stretch or less.

                            Good luck with the experiment, and thanks for posting your ideas.
                            Hopefully the knots you use won't reduce the ultimate tensile
                            strength too much. Maybe put a big mattress under you when you do
                            the testing ;-)

                            Bill in Houston


                            Now I know that my climbing rope stretches much farther relatively on a
                            long fall than a short one.

                            Oh and I use a bouldering crash pad when I'm experimenting. Fortunately
                            I have yet to need it.

                            Tom

                            P.s. Now were is that piece of wood... Ah yes,, knock knock
                          • zippydooda
                            Yeah, I was afraid I wasn t making sense. The rope will stretch more as the load increases, you are right. It s just that in the first 95 pounds (or
                            Message 13 of 22 , Aug 5, 2004
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                              Yeah, I was afraid I wasn't making sense. The rope will stretch more
                              as the load increases, you are right. It's just that in the first 95
                              pounds (or whatever) the rope will stretch more, as the individual
                              fibers and strands shift against each other and lay down flat against
                              each other. One the rope is taut and all the strands are compacted
                              against each other, it will be relatively more difficult to stretch.

                              Bill in Houston

                              --- In hammockcamping@yahoogroups.com, "Thomas Peltier@G..."
                              <Thomas@G...> wrote:
                              > Hey Risk, as far as stretch, the amount of stretch per unit of load
                              > should be higher for the first unit of load than for subsequent
                              > units. Sorry, which means that if you get 1% stretch with the first
                              > 95 lbs, that the next 95 pounds should be less than 1% stretch. So
                              > for 450 lbs, you are looking at maybe 4% stretch or less.
                              >
                              > Good luck with the experiment, and thanks for posting your ideas.
                              > Hopefully the knots you use won't reduce the ultimate tensile
                              > strength too much. Maybe put a big mattress under you when you do
                              > the testing ;-)
                              >
                              > Bill in Houston
                              >
                              >
                              > Now I know that my climbing rope stretches much farther relatively
                              on a
                              > long fall than a short one.
                              >
                              > Oh and I use a bouldering crash pad when I'm experimenting.
                              Fortunately
                              > I have yet to need it.
                              >
                              > Tom
                              >
                              > P.s. Now were is that piece of wood... Ah yes,, knock knock
                            • Thomas Peltier@Goldenautomotive.com
                              as the individual fibers and strands shift against each other and lay down flat against each other. _________________________ Which would explain why short
                              Message 14 of 22 , Aug 6, 2004
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                                as the individual
                                fibers and strands shift against each other and lay down flat against
                                each other.
                                _________________________

                                Which would explain why short falls tend to be harder on ropes than long
                                falls.

                                Tom
                              • rambler4466
                                ... BTW Recently purchased 30 of 1 polypro. heavy link webbing. It weighs 5.5oz.
                                Message 15 of 22 , Aug 7, 2004
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                                  --- In hammockcamping@yahoogroups.com, "Thomas Peltier@G..."

                                  BTW Recently purchased 30' of 1" polypro. "heavy link" webbing. It
                                  weighs 5.5oz.
                                  >
                                • Dave Womble
                                  ... If ... that ... with ... hammock ... tree ... Since this comes up from time to time, I decided to upload a MSExcel spreadsheet of mine that shows the
                                  Message 16 of 22 , Aug 20, 2004
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                                    --- In hammockcamping@yahoogroups.com, "Dave Womble" <dpwomble@y...>
                                    wrote:
                                    > --- In hammockcamping@yahoogroups.com, "Ray Garlington"
                                    > <rgarling@y...> wrote:
                                    > > --- In hammockcamping@yahoogroups.com, "Ralph Oborn"
                                    > > <polecatpop@y...> wrote:
                                    > > > To engineer the straps/ropes how big of a safety factor do you
                                    > > plan
                                    > > > on?
                                    > >
                                    > > As a practical example: Hennessey uses line with a breaking
                                    > > strength from about 1600 to 1800 pounds depending on the model.
                                    If
                                    > > the webbing used by the Speerians really is 800 pound breaking
                                    > > strength, and they are not reporting problems then you can see
                                    that
                                    > > Tom has built in a large safety factor.
                                    > >
                                    >
                                    > Ray, you overlooked something in your comparison. The Hennessy,
                                    with
                                    > its intergal ridgeline, generally puts more tension on the hammock
                                    > support ropes/straps because it typically is hung so that the
                                    hammock
                                    > support ropes/straps are more horizontally than a Speer hammock.
                                    > Sometimes, this difference in tension is quite severe and it is not
                                    > obvious that Hennessy is using a greater safety margin. This extra
                                    > tension would also carry over to the other discussion concerning
                                    tree
                                    > damage. (While the internal ridgeline does help in getting a
                                    > consistant 'hang', it is not without its drawbacks.)
                                    >
                                    > Youngblood

                                    Since this comes up from time to time, I decided to upload a MSExcel
                                    spreadsheet of mine that shows the results of the analysis I did of
                                    the forces associated with using an integral ridgeline. I hope it
                                    will clear up the point I was trying to make. Basically without an
                                    integral (or tensioned) ridgeline the forces are just Force 1... I
                                    try to hang my homemade versions of the Speer Hammock such that Angle
                                    1 is at 30 degrees or so. With the Hennessy Hammocks, Angle 1 is
                                    typically less (my guess is somewhere around 15 to 30 degrees?)...
                                    depending on how taut you tie the hammock. This means that Force 1
                                    might be higher when using hammocks with an intergral ridgeline and
                                    that the tension on that ridgeline can sometimes exceed the tension
                                    on the hammock ropes (ie, Force 3 exceeds Force 1 on my
                                    spreadsheet). My thinking is that the ridgeline cord may be the
                                    first thing to fail if a hammock with an intergral ridgeline is
                                    overstressed due to hanging it too taut, and I say this because my
                                    observation with the HH that I had was that the ridgeline cord was
                                    not as thick (and therefore not as strong) as the hammock ropes while
                                    my analysis (which hasn't been scrutinized) suggests that maybe it
                                    should be. The spreadsheet is in the Files section under my folder.

                                    Youngblood
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