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  1. #1
    Senior Member TheIrishmanHangeth's Avatar
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    The truth about dynaglide and safety...

    Now keep in mind this is based off of a limited test based on simple number crunching, I have no real world experience with dynaglide(or whoopies slings for that matter, although I will eventually). This is also basing a weight rating from the understanding that splicing degrades the rope by no more than 10%. If there is new information out there debunking that, please feel free to let me know. Alright, enough disclaimer and "I didn't tell you to use dynaglide" Mumbo jumbo and onto the numbers.

    I did some playing around with the ultimate hang calculator app on my phone just to get some hard numbers regarding hang angles, weight forces, and what not. I changed the hammock length, ridgeline, and tree spacing around at a given weight and angle and none of the forces changed so I didn't bother with doing that for the actual number testing.

    What I came up with was this:

    At a 20 degree angle with 600 lbs there is 877.1 lbs of force coming through the suspension

    At a 5 degree angle with 200 lbs there is 1147 lbs of force coming through the suspension

    At a 10 degree angle with 200 lbs there is 575.9 lbs of force coming through the suspension

    At a 10 degree angle with 300 lbs there is 863.8 lbs of force coming through the suspension

    Now assuming the whole 10% degradation principle for splicing that brings dynaglide down to a 900 lb breaking strength. Well, utilizing the numbers I provided even a 600 pound person could hang at a 20 degree angle(not bad, but still less than the ideal 30 degrees) and not break dynaglide. It would take a 200-300 pound person hanging at either 5 or 10 degrees respectively to come close or surpass the 900 pounds in the case of a 5 degree angle. I don't know about you but that a very minimal angle! You would have to hang your hammock guitar string tight to even achieve that angle when the hammock is loaded.

    I realize this is speculation based on numbers but the numbers are pretty definitive. I also realize that these are based off of static and not dynamic forces but in all honesty, unless you'e Shug practicing your next act of acrobatics, the dynamic forces from getting in and out of a hammock should not even come close to bring these numbers to a failure point. Now I am certainly not trying to force the idea of using dynaglide on anybody, if you don't feel safe using it then definitely don't use it. I was just putting this out there for the folks that were maybe undecided about it and could use some more info in order to make an informed decision. As always, HYOH and Happy Hangin folks!

  2. #2
    Trail Runner's Avatar
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    Quote Originally Posted by TheIrishmanHangeth View Post
    This is also basing a weight rating from the understanding that splicing degrades the rope by no more than 10%.
    This is what I was taught in the service & I've read the same in different knot publications. Splicing is definitely the best way to preserve the strength of a line. All knots reduce the strength of a line by at least 40% ex: a square knot reduces the strength by 60%.

    Cool post, thanks.

  3. #3
    MAD777's Avatar
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    The numbers don't lie..... However, dynaglide, or any other rope, going around something small, creating a very small radius can simulate a lot of what makes a knot degrade the strength of the line. For instance, dynaglide threaded through a Dutch whoopie hook.

    So, I guess it's a good thing that there is strength to spare because dynaglide and whoopie hooks is exactly what I've been hanging from for over a year. For reference, I'm a 200 pounder but always maintain a 30 degree angle on my suspension.
    Mike
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  4. #4
    Senior Member WV's Avatar
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    I have pulled structural ridgelines as tight as I could get them (spanning about 20', as I recall), and when I attached my hammock, my weight pulled the ridgeline angle down to about 15, so I figure whatever line I use needs to hold about twice my weight. That lets me use dynaglide with at least a 3:1 safety factor.

  5. #5
    Senior Member TheIrishmanHangeth's Avatar
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    Quote Originally Posted by WV View Post
    I have pulled structural ridgelines as tight as I could get them (spanning about 20', as I recall), and when I attached my hammock, my weight pulled the ridgeline angle down to about 15, so I figure whatever line I use needs to hold about twice my weight. That lets me use dynaglide with at least a 3:1 safety factor.
    You pull the ridgeline or suspension as tight as you can. I ask because you could have a guitar string tight and still have a 30 degree hang angle.

  6. #6
    Senior Member TheIrishmanHangeth's Avatar
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    Quote Originally Posted by MAD777 View Post
    The numbers don't lie..... However, dynaglide, or any other rope, going around something small, creating a very small radius can simulate a lot of what makes a knot degrade the strength of the line. For instance, dynaglide threaded through a Dutch whoopie hook.

    So, I guess it's a good thing that there is strength to spare because dynaglide and whoopie hooks is exactly what I've been hanging from for over a year. For reference, I'm a 200 pounder but always maintain a 30 degree angle on my suspension.
    And that's kind of my point. Under normal hanging circumstances there should be no reason why even someone who weighs 400-500 pounds( well above the weight of the "average" hanger) can't hang with dynaglide and feel safe and secure doing so.

  7. #7
    Senior Member Likeapuma's Avatar
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    Re: The truth about dynaglide and safety...

    This is interesting. I'm way too ignorant in the "ways of rope" to add anything to this discussion, but as a 300+ pounder, it opens the opportunity for whoopie slings! I'm still learning my webbing straps, but now I know there's other options!

  8. #8
    Senior Member TheIrishmanHangeth's Avatar
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    Quote Originally Posted by Likeapuma View Post
    This is interesting. I'm way too ignorant in the "ways of rope" to add anything to this discussion, but as a 300+ pounder, it opens the opportunity for whoopie slings! I'm still learning my webbing straps, but now I know there's other options!
    Even according to "conventional" safety standards you should be able to use 1/8 whoopies and have a very wide safety margin. Even 7/64 would still be perfectly safe by typical standards.

  9. #9
    pgibson's Avatar
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    Quote Originally Posted by Likeapuma View Post
    This is interesting. I'm way too ignorant in the "ways of rope" to add anything to this discussion, but as a 300+ pounder, it opens the opportunity for whoopie slings! I'm still learning my webbing straps, but now I know there's other options!
    The load forces put on a suspension are the same regardless of the material the suspension is made from.

    Most straps are made by the cottage vendors from webbing rated from 1000-1500 pounds.

    Far more critical than the type of suspension is that it is hung correctly. In testing I have broken 1500 straps in the shop. Don't kid yourself that just cause math says it's OK that it actually is OK. Ropes and webbings degrade, they are damaged by UV and abrasion. Check it often and replace any components that may have worn to the point of needing to be retired.


    As well a suspension that is pulled very tight and then sags to 30 degrees when loaded is not the same as a suspension that is hung with a 30 degree sag. It will be under extreme loads with the tension that will be put on the system. The math used in the calculator at The Ultimate Hang is functioning on the premiss that your measuring the angle of an unloaded/unweighted hammocks suspension.
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  10. #10
    Senior Member pizza's Avatar
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    The truth about dynaglide and safety...

    Quote Originally Posted by pgibson View Post
    Ropes and webbings degrade, they are damaged by UV and abrasion. Check it often and replace any components that may have worn to the point of needing to be retired.
    Good point. I've worn out tree straps after a year finding stitching for loops starting to degrade and pull out. Also, Amstel fixed loops wearing out from repeated creasing in high stress contact with Dutchware such as Dutch Biners or Whoopie Hooks. Nothing to be real concerned with as it takes a LOT of use to wear the stuff out but it does eventually happen.

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