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  1. #11
    Senior Member swoody126's Avatar
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    here's a link to a post i made, that may help you w/ your weight capacity issue:

    https://www.hammockforums.net/forum/...674#post990674

    where i was playing w/ a scrap of AMSTEEL 7/64

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  2. #12
    Knotty's Avatar
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    Here's the info Samson Rope provided about how much a whoopie derates a rope.

    https://www.hammockforums.net/forum/...ad.php?t=12319
    Knotty
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  3. #13
    Senior Member TheIrishmanHangeth's Avatar
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    Quote Originally Posted by GrizzlyAdams View Post
    The fundamental issue is the strength of the cord, not the "whoopie sling" part of it. And the strength of the cord is gauged from the diameter.

    There are three commonly discussed cords here, so-called 'dynaglide', whose diameter is 2mm, "7/64" and "1/8" Amsteel, where the numbers describe the diameters.

    For you, don't even think about dynaglide.

    The listed breaking strength of 7/64" Amsteel is about 1600 lbs,
    for 1/8" Amsteel, 2500 lbs.

    These sound like big numbers, but you have to be aware that the tension on the whoopie sling is larger than half your weight, owing to geometry (the angle of the line from hammock to tree), and dynamic forces (when you drop into the hammock). Furthermore, any knot or slice will lower the average breaking strength.

    The good news is that splices and whoopie slings lower the breaking strength the least among any possibilities of connecting hammock to tree with cord, lets say,
    to 80%. So for 7/64" Amsteel you're looking at maybe 1280 lbs, and for 1/8" Amsteel, maybe 2000 lbs.

    Then to account for dynamic forces and variation in manufactoring it is typical to say the "safe working strength" is some fraction of those numbers, conservatively from 1/10 to 1/5, so a range of 128 to 256 lbs for 7/64" Amsteel,
    and 200 - 400 lbs for 1/8".

    The recommended angle of the cord from hammock to tree is 30 degrees, which
    means the static (non-dynamic) load on whoopie sling set-up is your body weight.

    executive summary : To support a 400 lb occupant I'd go with 1/8" Amsteel.
    I've always been curious about by how much dynamic forces increase the weight put on suspensions. Here's a thread I posted showing some hardcore numbers about what it would actually take to break the weight threshold of dynaglide-https://www.hammockforums.net/forum/...ad.php?t=73701- are dynamic forces really enough to bump the forces up past failure under normal hammock? Even someone who weighs 300 lbs is well below the 900 lbs limit of dynaglide under static hanging.

  4. #14
    pgibson's Avatar
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    Quote Originally Posted by TheIrishmanHangeth View Post
    are dynamic forces really enough to bump the forces up past failure under normal hammock? Even someone who weighs 300 lbs is well below the 900 lbs limit of dynaglide under static hanging.
    Here is a simple experiment to show a very simple dynamic load. Find an old analog scale...the kind with a dial that when you step on it goes back and forth for a second before settling down. Step on and let it settle. Now without letting your feet leave contact with the scale flex your legs down and spring up. What happens to your weight? Now your weight never left contact with the scale...you did not change weights momentarily...and yet the Load on the scale changed...even just for a few seconds. As you came back down onto the scale for just a second your weight pressed down with more force than you actually weigh.

    I think you would be shocked at how much potential there is for Dynamic forces to shock load a system. Ever stumble a little when going to sit down? Toss and turn through the night? Have a small kid get excited and come run and jump in at you? There are many folks here that have tried 550 paracord to hang with a 1:2 or even 1:3 margin of safety and had it snap on them. Math alone does not always keep your tail bone off the ground.

    There are all sorts of things that can load a suspension system in ways we don't expect or plan for. Hence the prevailing train of thought is to have a safety margin in your suspensions capabilities. What margin YOU need is up to YOU and what YOU are comfortable with. Some folks are comfortable with a 1:2 margin and others prefer a 1:10 and still others want 1:???

    This is one of the great parts about hammocks, you can customize a system that works for you.
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  5. #15
    Senior Member TheIrishmanHangeth's Avatar
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    Quote Originally Posted by aboyd View Post
    I am 295 lbs, and I use 1/8" whoopies. I have used 7/64" without concern, but decided to try so 1/8" just for a little added security. I have not hit the ground as of yet.
    Quote Originally Posted by pgibson View Post
    Here is a simple experiment to show a very simple dynamic load. Find an old analog scale...the kind with a dial that when you step on it goes back and forth for a second before settling down. Step on and let it settle. Now without letting your feet leave contact with the scale flex your legs down and spring up. What happens to your weight? Now your weight never left contact with the scale...you did not change weights momentarily...and yet the Load on the scale changed...even just for a few seconds. As you came back down onto the scale for just a second your weight pressed down with more force than you actually weigh.

    I think you would be shocked at how much potential there is for Dynamic forces to shock load a system. Ever stumble a little when going to sit down? Toss and turn through the night? Have a small kid get excited and come run and jump in at you? There are many folks here that have tried 550 paracord to hang with a 1:2 or even 1:3 margin of safety and had it snap on them. Math alone does not always keep your tail bone off the ground.

    There are all sorts of things that can load a suspension system in ways we don't expect or plan for. Hence the prevailing train of thought is to have a safety margin in your suspensions capabilities. What margin YOU need is up to YOU and what YOU are comfortable with. Some folks are comfortable with a 1:2 margin and others prefer a 1:10 and still others want 1:???

    This is one of the great parts about hammocks, you can customize a system that works for you.
    Indeed, I was definitely not trying to force dynaglide on anyone. To each their own. Merely showing some figures and letting folks make up their own minds.

  6. #16
    jons4real's Avatar
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    I'm 290lbs (ISH) and I rock out the 7/64 . No issues once so ever.
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  7. #17
    Senior Member Captain Smiley's Avatar
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    Okay, I'll simplify it further. I'm 430 pounds in a Hammock Bliss No See Um No More with 7/64 amsteel whoopies and seatbelt tree straps. Been using that setup for 2 years. Works fine.
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  8. #18

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    Quote Originally Posted by Captain Smiley View Post
    Okay, I'll simplify it further. I'm 430 pounds in a Hammock Bliss No See Um No More with 7/64 amsteel whoopies and seatbelt tree straps. Been using that setup for 2 years. Works fine.
    And I weigh a bit more than half of what you do so I did 1/8 in whoopies and have zero interest in 7/64. ;-) It's all a matter of how willing one is to hit the ground combined with one's propensity to screw up if possible...

    ;-)
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  9. #19
    A tad under 300 and the only issue I had with 7/64 Amsteel is that I managed to have my loops slip down and hang on the toggles I had in my tree straps. They held though, just slipped 3-4 inches over the night (the toggles in the marlin spike hitches that is).

  10. #20
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    Re: Whoopie sling weight limit

    Quote Originally Posted by nothermark View Post
    And I weigh a bit more than half of what you do so I did 1/8 in whoopies and have zero interest in 7/64. ;-) It's all a matter of how willing one is to hit the ground combined with one's propensity to screw up if possible...

    ;-)
    This.

    Numbers and strengths used here are VERY conservative.
    This is good for general people, so that things are safe even when they do dumb things or act with out thinking and use them for years with out really inspecting things.

    Suspention angles can do a lot of things... but break out the trig and your pretty much putting your own body weight on each end.

    As others have said.... dynamic forces change things.
    As one poster said stand on your scale and lunge upward and you can see how much weight you can add... On the other hand, when was the last time you squatted in a deep bend in hour hammock, then tried to exlode out? Do you want to plan your hammocks durability around this activity?
    Now again, do the scale exercise... can you double your own weight? Can hou quadrupal your weight? Because that is what the level of abuse they are talking about with the factor of 4....

    So what am I saying? What is safe vs what is overkill is highly dependant on how you use, how often you use, how observant you are, how often you inspect and the conditions you use it in.
    With that in mind its hard to responsibly reccoment how low of a factor of safety can be used to strangers... so error is most often on the side of caution, because a few grams is simply not worth having to be fully on top of your material selection for most people.

    The bounce on your scale test is probably a good one. I am betting most peolle are seeing closer to 50 to 100lbs variance there, in MOST cases most here could significantly reduce ratings of suspension but 7/64ths is so small there is no need to push it, especially when you account for wear and tear and the occational manufacuring defect...

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