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  1. #31
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    Quote Originally Posted by leiavoia View Post
    Let me ask a few questions

    I am assuming that force per line approach body weight / 2 when the handle angle is straight up.

    On the other hand, force goes to infinity as the angle approaches zero. Intuitively, that doesnít sound right. I should be able to pull out whole trees by their roots just by putting my hammock up flat.

    What am I missing?
    The other thing, and Grizz alludes to this, is that you never get quite to infinity (as you stated "approaches zero") because the line WILL sag with weight on it. That little sag ends up being a far cry from infinity, although still a very large number. I guess if the trees are small enough, they'll just bend and lower you gently to terra firma. (Had to sneak in some Latin for credibility's sake...)
    Last edited by TominMN; 07-09-2018 at 11:36.

  2. #32
    Senior Member oldpappy's Avatar
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    A tear came to my eye as you explained why Shug's beloved 'Green Bean' ripped.

    Thank-you for the very informative video.
    Enjoying the simple things in life -
    Own less, live more.

  3. #33
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    Yeah, that was sad. But then, that hammock survived to a ripe old age and it had come down to just a matter of time. Might've even lived a couple of more years with extreme TLC.

  4. #34
    GrizzlyAdams's Avatar
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    Quote Originally Posted by HandyRandy View Post
    So here comes another question for Grizzly. Letís say you take a perfect and symmetrical hang in every way. Now all that you do is change the length of the suspension in equal, but opposite directions. You shorten the foot strap by X inches and lengthen the head strap by X inches. Have you increased the forces applied or simply shifted some of the forces from one tree to the other?
    Likewise, apply those same questions to the scenario where you take the perfect hang and raise the foot straps anchoring point without any change in the strap lengths.
    Did the math. Ain't pretty. I suspected, and this was borne out, that it's not a matter of shifting a fixed amount of tension from one side to another. 1/sine(theta) isn't linear. The angle gets a little shallower on one side, and a little deeper on the other. And even if they were the same amount (they aren't) it's not so simple as a shift.

    The important point is that with the lengths involved here (hammock length compared with change of maybe 1 ft) the changes in the angles aren't especially significant in normal operating ranges. Some minor changes in tension, but minor.
    Grizz
    (alias ProfessorHammock on youtube)

  5. #35
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    Quote Originally Posted by GrizzlyAdams View Post


    The important point is that with the lengths involved here (hammock length compared with change of maybe 1 ft) the changes in the angles aren't especially significant in normal operating ranges. Some minor changes in tension, but minor.

    Pretty much figured your answer would be something like this. The whole discussion has to account for reasonable limits. After all, gravity isn't exerting force on body (and hammock, etc.) weight at a single given point. All you have to do is switch positions in the hammock and you can see changes in the tension (or slackness) of the SRL.


    So "close" counts in hang angle, just as it does in horseshoes, ballroom dancing, and things that can't be mentioned in a forum such as this!

  6. #36

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    Hey Grizz, Shug made a point in one of his videos about how it is important to position a Dutch clip to the side of the tree so that the suspension comes straight out of the clip.
    https://youtu.be/gLrcm-bGTOM
    I have a few questions related to this topic. Is it also important to do as outlined above when routing the strap through itís own sewn end loop? About how much extra force is being applied to the sewn loop, Dutch Clip or biner in a mirror image configuration? How about when placed halfway between; about the center of the tree? Would a climbing rated biner be strong enough to make this no longer a concern? Additionally, is the fact that the strap is now bending around the biner going to weaken the strap itself too? Knots and bends degrade rope, so I imagine a bend in a strap under tension lowers itís rating too, right?

  7. #37
    GrizzlyAdams's Avatar
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    Quote Originally Posted by HandyRandy View Post
    Hey Grizz, Shug made a point in one of his videos about how it is important to position a Dutch clip to the side of the tree so that the suspension comes straight out of the clip.
    https://youtu.be/gLrcm-bGTOM
    I have a few questions related to this topic. Is it also important to do as outlined above when routing the strap through it’s own sewn end loop? About how much extra force is being applied to the sewn loop, Dutch Clip or biner in a mirror image configuration? How about when placed halfway between; about the center of the tree? Would a climbing rated biner be strong enough to make this no longer a concern? Additionally, is the fact that the strap is now bending around the biner going to weaken the strap itself too? Knots and bends degrade rope, so I imagine a bend in a strap under tension lowers it’s rating too, right?
    The principle is the same, angling forces is a multiplier. That said, a rigorous analysis of forces on webbing and biners/clips would need to account for effects due to the webbing on the tree, particularly if you can wrap the webbing around once before connection.
    Take-away message --- whatever the connection mechanism (pass through sewn loop, biner, clip) you'll have less force on that point by getting the webbing to come off the side. That said, I tend to carry longer straps (at least six feet) and can usually wrap, which means the force 'from the tree' to the sewn loop is pretty well eliminated and I tend not to worry about it and have it all centered.

    The webbing is likely to be the weakest link in this if you use a Dutch clip or climbing rated carabiner. Weakening of rope is pronounced on tight bends, you don't think of it as being degraded a lot going around something with a diameter significantly larger than the rope, so I would say whatever extra stress on the webbing there is would more likely be attributed to the angle-induced-force-multiplier than a knot-related weakening.

    just shooting from the hip here though. YMMV
    Grizz
    (alias ProfessorHammock on youtube)

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