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  1. #11
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    Hammock physics

    This shows the effect of hang angle on line tension.
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  2. #12
    REV's Avatar
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    ok, i think theres some things that need to be clarified

    first, the SRL should NOT be tight when there is no load in the hammock. it should only gain tension when weight is added. so DO NOT hang the hammock tight. always strive for that magical 30*.

    yes, the 83% is the "starting point" for most hammocks, not the rule. hang the hammock as youre supposed to and measure between the ends of the hammock

    If im right in thinking, the SBP has a ton of lines on each end that connect to the hammock body. you need to include those when measuring.

    an SRL is only supposed to help keep the 30* sleeping angle when trees arent at the ideal distance. it is NOT supposed to be a substitute for improper hanging and you run the risk of putting too much stress on other parts of the hammock, which runs the risk of gear damage and injury if something lets go
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  3. #13
    MDSH's Avatar
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    Quote Originally Posted by ibgary View Post
    83% of hammock leangth is ~ 99" on a 10' hammock, ~107" for 11' ext.

    Structural ridge line tension is effected by the suspension length and angle, right?
    So if the trees are 40' apart and the angle is 5-10 deg, there will.be a lot of tension when you weight the hammock. What's wrong with having a lot of tension on the Srl? After all is is structural and it, the suspension and the anchors/trees are taking the load, not the hammock, right?
    What's wrong, Gary, is that sometimes the SRL is not strong enough for the angles employed.

    Therefore, I have split my gear between conventional hanging and SLS.

    Be that as it may, if the SRL truly becomes "structural," as you have rightly noted, then it needs to be stronger than those utilized in conventional hangs (or sold on line).

    A man can reach only so far up a tree in the field. And he has less control over how far apart are the trees or where their branches might be positioned relative to the ideal elevation. Therefore, he is advised to have a stronger SRL than commonly put into service (or sold on line).

    It's just a matter of math, really.

    Mike

  4. #14
    MDSH's Avatar
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    Quote Originally Posted by REV View Post
    ok, i think theres some things that need to be clarified

    first, the SRL should NOT be tight when there is no load in the hammock. it should only gain tension when weight is added. so DO NOT hang the hammock tight. always strive for that magical 30*.

    yes, the 83% is the "starting point" for most hammocks, not the rule. hang the hammock as youre supposed to and measure between the ends of the hammock

    If im right in thinking, the SBP has a ton of lines on each end that connect to the hammock body. you need to include those when measuring.

    an SRL is only supposed to help keep the 30* sleeping angle when trees arent at the ideal distance. it is NOT supposed to be a substitute for improper hanging and you run the risk of putting too much stress on other parts of the hammock, which runs the risk of gear damage and injury if something lets go
    There should be no such thing as "improper hanging" or "striving" for the ideal 30* angle, REV.

    The simpler solution, according to Ockham, is a stronger SRL.

    Mike

  5. #15
    REV's Avatar
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    Quote Originally Posted by MDSH View Post
    There should be no such thing as "improper hanging" or "striving" for the ideal 30* angle, REV.

    The simpler solution, according to Ockham, is a stronger SRL.

    Mike
    we may have to disagree there, but the logic is that no matter what the 30* angle puts the least amount of stress on all things, including the tree. the tighter the hammock & lower the angle, the more force is put on all things in line of the suspension. we are not talking about an SLS suspension in this matter. when things vary from 30* (again, give or take a few degrees) the stresses involved multiply and cause undue wear on parts and in some cases can cause failure of parts.
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  6. #16
    MDSH's Avatar
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    Quote Originally Posted by REV View Post
    we may have to disagree there, but the logic is that no matter what the 30* angle puts the least amount of stress on all things, including the tree. the tighter the hammock & lower the angle, the more force is put on all things in line of the suspension. we are not talking about an SLS suspension in this matter. when things vary from 30* (again, give or take a few degrees) the stresses involved multiply and cause undue wear on parts and in some cases can cause failure of parts.
    Duly noted and appreciated, REV, but I live in a part of the world where we do not have trees conveniently placed every 15 feet. Plus, it's axiomatic that the larger the trees the further apart they are found.

    Therefore, my point is that for the simple fact of a stronger SRL the hang angle is not so critical. That's all ... just a stronger SRL.

    Mike

  7. #17
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    Quote Originally Posted by MDSH View Post
    Duly noted and appreciated, REV, but I live in a part of the world where we do not have trees conveniently placed every 15 feet. Plus, it's axiomatic that the larger the trees the further apart they are found.

    Therefore, my point is that for the simple fact of a stronger SRL the hang angle is not so critical. That's all ... just a stronger SRL.

    Mike
    i also agree that the SRL should be strong enough to handle loads, which is why i have an amsteel ASRL and not a dyneema. will dyna hold me? probably, but its that "probably" that worries me, and its not worth the weight "savings" to use it and not have the peace of mind.

    i just dont agree that the SRL should be relied upon to get the perfect hang. not saying that every situation should will be 30, but if you can get it as close as possible to that then youll be better off all around.
    Give a man fire and he's warm for the night.
    Set a man on fire and he's warm for the rest of his life. Dante

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  8. #18
    Senior Member DemostiX's Avatar
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    Scare oneself as one might, if the cord is strong enough, then all is good, and the chart can be put away. At any hang angle for the hmmk of more than 20 degrees, the fabric is fine. It is difficult to hang with the suspension at less than 15 -20 degrees due to stretch in the fabric and suspension. At flat angles, small amounts of stretch result in great increases in that hang angle, toward 30 degrees, so the tension is somewhat self-adjusting. Very self-adjusting with nylon cord. <smile>* In practice, it is hard to multiply the tension on the tree or the SRL by more than 3 times the minimum achievable on the suspension, no matter that this chart includes a multiplier of 5.

    Per MDSH, one adapts to environments. I'd sooner hang beneath far-spaced railroad ties of an abandoned trestle in a culvert than hike more than 100 yards in search of a pair of trees 15-20 feet apart. Where most trees are big and all of them spaced far apart, the cost to hang is just longer tree straps and maybe a few more ounces in longer and stronger suspension. So, an SRL might be of 7/64" Amsteel (tm) instead of smaller, with a weight penalty over 15 feet of just 1/2 oz.

    --------
    There is, for a few, an issue of comfort associated with any SRL. But, I have not read an engineering explanation of that discomfort in any thread that has reported it.

    * Think of a right triangle with one very acute angle and therefore one long adjacent side . Tnink of that angle as being the difference from 0 degrees, and the adjacent side as being a horizon line, or the SRL. Notice that the hypotenuse of the right triangle grows longer very slowly as the angle opens. That growth in the hypotenuse is the stretch in the suspension and hammock bed. A little stretch goes a long way to opening the angle.
    Last edited by DemostiX; 11-09-2012 at 18:52.

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