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  1. #121
    Frawg's Avatar
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    Quote Originally Posted by TeeDee View Post
    ... I have had a straight bury inch out under repeated load/unload cycles. So now I stitch the buried eye splice immediately.
    I'll add a second data point ... had exactly the same thing happen to me, so I also add the recommended stitching. Cheap insurance!
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  2. #122
    PuckerFactor's Avatar
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    Yeah, I may take them apart and do a straight bury if I get bored one day, but I kinda like the look of the locked brummel. Meh. I figure I have plenty of strength to play with.

    Acer

  3. #123
    Senior Member TeeDee's Avatar
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    Question

    Frawg - I have a question for you.

    I'm thinking of trying to reduce the amount of rope needed for the buries in the splices.

    The lower I can get the length of the splices means I can get the minimum tree span lower. For the Whoopie sling, I only have two splices and so the amount taken is the lowest I can get in that regard.

    I was looking again at your slipped eye splice. It appears that you only use 2" or 3" for the finished splice. Is that true? What is the finished length of the bury for your finished eye splice?

    Also, I'm not sure about what holds the toggle in the splice. When pulled tight under a weighted hammock, is the bury holding the weight by a gripping action of the constrictor or does the bury function more as a means of holding the two rope sections together to act as one rope? What I'm concerned about is the bury near the toggle pulling the strands of the constrictor apart and becoming a weak spot. It appears that the forces would tend to do that if the constrictor section isn't acting to grip the buried part, but only acting to form the loop. I haven't had the time to try one yet so thought I would ask.
    Those who sacrifice freedom for safety, have neither.

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  4. #124
    Frawg's Avatar
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    Quote Originally Posted by acercanto View Post
    Yeah, I may take them apart and do a straight bury if I get bored one day, but I kinda like the look of the locked brummel. Meh. I figure I have plenty of strength to play with.

    Acer
    FWIW, I've been doing locked brummels lately myself. I just add two sets of 3 loops of stitching at the end of the bury, forming a crosshairs pattern as viewed along the axis of the line.
    - Frawg

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  5. #125
    Frawg's Avatar
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    Quote Originally Posted by TeeDee View Post
    Frawg - I have a question for you.

    I'm thinking of trying to reduce the amount of rope needed for the buries in the splices.

    The lower I can get the length of the splices means I can get the minimum tree span lower. For the Whoopie sling, I only have two splices and so the amount taken is the lowest I can get in that regard.
    Yeah, I'm actually doing micro whoopies for really short spans. They're already part of my finished (hah! ) overall setup, anyway.

    I was looking again at your slipped eye splice. It appears that you only use 2" or 3" for the finished splice. Is that true? What is the finished length of the bury for your finished eye splice?
    Here's a picture of two iterations of work.

    The blue one is the most recent, and is at the end of a micro whoopie. As you can see, you don't need much bury at all.

    Also, I'm not sure about what holds the toggle in the splice. When pulled tight under a weighted hammock, is the bury holding the weight by a gripping action of the constrictor or does the bury function more as a means of holding the two rope sections together to act as one rope?
    The working part of the line (that passes through the bury) actually pulls the bury extremely tight. Tension is applied around the toggle to the part of the bury nearest to the toggle, decaying exponentially along the bury. If you look closely at the pic above, you can see how the compression in the bury gradually decreases as you move farther from the toggle. As best I can figure, it forms a Chinese finger puzzle with no room left to allow buried line to release, gripping the toggle very tightly. This kind of line gets stiff when placed under heavy tension because the free space in the braid gets squeezed out, leaving only the flexibility and compressibility of the base material -- i.e., there's no room left to release the 'puzzle'.

    What I'm concerned about is the bury near the toggle pulling the strands of the constrictor apart and becoming a weak spot. It appears that the forces would tend to do that if the constrictor section isn't acting to grip the buried part, but only acting to form the loop. I haven't had the time to try one yet so thought I would ask.
    I think you're spot on. Here's a pic to show the effect:


    IMO that's a valid and significant concern, and something I factored into my own thinking. Using a UCR or a slipped eye as I do, I'm certain that max loading is compromised to an extent that depends on how the total tension gets distributed among the individual strands. IAE, I derate my setup to 50% of the base line strength, which I suspect (but haven't researched) is somewhat conservative. That would leaves me 600 or 700 pounds to work with when using 7/64 line and I'm comfortable with that. I don't anticipate applying any significant dynamic forces in the hammock.
    Last edited by Frawg; 07-16-2009 at 21:07. Reason: too many actuallys, actually; also added a link
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  6. #126
    Senior Member TeeDee's Avatar
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    Frawg - Thanks for the pictures and thoughts on your slipped eye.

    I think I'll make a few and load them and see how the constrictor is affected and if it is enough to worry me.

    Quote Originally Posted by Frawg View Post
    ............

    This kind of line gets stiff when placed under heavy tension because the free space in the braid gets squeezed out, leaving only the flexibility and compressibility of the base material -- i.e., there's no room left to release the 'puzzle'.

    ...............
    Yes - That is one of the properties of Amsteel and Amsteel Blue that I don't like.

    I thought for a long time that it was merely the forces pulling the braid tight as you say.

    But then I got some AS-78. Same braid, different dyneema, SK-78 instead of the SK-75 used in the Amsteel and Amsteel Blue. The AS-78 has the same Samthane coating as the Amsteel.

    I have found that it pulls tight also and the rope gets a little less flexible, but not nearly as bad as the Amsteel. Also, the AS-78 returns to a very soft state when the load is removed and the rope flexed slightly which loosens up the braid. The Amsteel that I have stays pretty rigid when the load is removed and takes a LOT of work to loosen up. The Amsteel Blue isn't as bad as the plain Amsteel, but neither return to the soft flexible state.

    So I think that it is more a property of the SK-75 Dyneema used in the Amsteel and Amsteel Blue.

    This is the most frustrating when trying to undo a knot that has been pulled tight under a heavy load or when removing the Whoopie Sling loop from the hugger Marlin Spike. The stiffness of the Amsteel can make undoing tight knots a real challenge and the stiffness can interfere with removing the loop from the Marlin Spike.

    I haven't experienced this problem with the AS-78.
    Those who sacrifice freedom for safety, have neither.

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  7. #127
    Frawg's Avatar
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    Quote Originally Posted by TeeDee View Post
    Frawg - Thanks for the pictures and thoughts on your slipped eye.
    Glad it helped, TeeDee. Good hunting with your experiments.

    ...I have found that it pulls tight also and the rope gets a little less flexible, but not nearly as bad as the Amsteel. Also, the AS-78 returns to a very soft state when the load is removed and the rope flexed slightly which loosens up the braid. The Amsteel that I have stays pretty rigid when the load is removed and takes a LOT of work to loosen up. The Amsteel Blue isn't as bad as the plain Amsteel, but neither return to the soft flexible state.
    Yeah, I believe "fiber set" is the operative term used to describe that rigidity. From what I've read, the elasticity of the fiber material is what determines a line's characteristics once fiber set has occurred.

    This is the most frustrating when trying to undo a knot that has been pulled tight under a heavy load or when removing the Whoopie Sling loop from the hugger Marlin Spike. The stiffness of the Amsteel can make undoing tight knots a real challenge and the stiffness can interfere with removing the loop from the Marlin Spike.
    I feel your pain. (had the same issues.)

    I haven't experienced this problem with the AS-78.
    I need to give that a try, I guess. Problem is, I'm a cheapskate and that's really why I went with the 7/64 AmSteel Blue in the first place... it was a cheap entry into what I'd read about rope suspension systems here. Before that I was into strap suspensions.

    Samson makes some HMPE line with a high coefficient of friction (Quantum 8, Quantum 12) but the smallest line I saw was 1 inch diameter. It would have been interesting to see how that would have worked in smaller diameters with friction knots.

    BTW, the strand separation I'm getting is probably exaggerated by the small diameter of my toggles. I think it'd be less of a problem with larger toggles like you've mentioned. IIRC, the recommended bend radius for these ropes is something like 3 or 4 times the rope radius, to mitigate weakness from unequal distribution of the load among the strands.

    Anyway, good luck with your testing. I look forward to your next round of reports.
    - Frawg

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  8. #128
    GrizzlyAdams's Avatar
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    Quote Originally Posted by TeeDee View Post
    ....
    Yes - That is one of the properties of Amsteel and Amsteel Blue that I don't like.

    I thought for a long time that it was merely the forces pulling the braid tight as you say.

    But then I got some AS-78. Same braid, different dyneema, SK-78 instead of the SK-75 used in the Amsteel and Amsteel Blue. The AS-78 has the same Samthane coating as the Amsteel.

    I have found that it pulls tight also and the rope gets a little less flexible, but not nearly as bad as the Amsteel. Also, the AS-78 returns to a very soft state when the load is removed and the rope flexed slightly which loosens up the braid. The Amsteel that I have stays pretty rigid when the load is removed and takes a LOT of work to loosen up. The Amsteel Blue isn't as bad as the plain Amsteel, but neither return to the soft flexible state.

    So I think that it is more a property of the SK-75 Dyneema used in the Amsteel and Amsteel Blue.

    This is the most frustrating when trying to undo a knot that has been pulled tight under a heavy load or when removing the Whoopie Sling loop from the hugger Marlin Spike. The stiffness of the Amsteel can make undoing tight knots a real challenge and the stiffness can interfere with removing the loop from the Marlin Spike.

    I haven't experienced this problem with the AS-78.
    Found this really interesting. I've been using a UCR made of Vectrus (which evidently is not spectra at all). To loosen the UCR all I need to do is push up on the unloaded end and it fairly easily loosens up and lets go of the bury. The UCR comes together like an accordian as pretty as you please. (In fact, one of the things I need to test yet is if some sort of jostling of the hammock when under load is enough to shake the UCR grip loose....) But undoing a knot made in this same Vectrus cord after it has been under load can sometimes be problematic, even when it's a knot like the bowline which is supposed to be easy to undo after loading.

    I've made a couple of whoopie slings from Amsteel and gonna give them a try this weekend and see if I see what you all are describing.

    Grizz

  9. #129
    Frawg's Avatar
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    Quote Originally Posted by GrizzlyAdams View Post
    Found this really interesting. I've been using a UCR made of Vectrus (which evidently is not spectra at all). To loosen the UCR all I need to do is push up on the unloaded end and it fairly easily loosens up and lets go of the bury. The UCR comes together like an accordian as pretty as you please.
    I found the same thing -- in a short hang, I need to be careful pulling back the snake skins. An inadvertent touch on the unloaded end puts my hammock on the ground.

    BTW, here's this biologist's report I'd mentioned in another post: The importance of frictional interactions in maintaining the stability of the twining habit -- Silk and Holbrook 92 -- American Journal of Botany Gotta be pretty motivated to read it all, but there are some nuggets of insight that apply to what we're doing.

    (In fact, one of the things I need to test yet is if some sort of jostling of the hammock when under load is enough to shake the UCR grip loose....)
    Grizz, I did encounter that problem when I made the bury a couple inches short. Good news was that it was a gentle, controlled glide to ground. I've pretty much concluded that I'll always secure the unloaded as an insurance policy, either by a knot of some kind, or by a bit of gear hanging from it. Doesn't take much force, but it does take some to hold the load.

    I've made a couple of whoopie slings from Amsteel and gonna give them a try this weekend and see if I see what you all are describing.

    Grizz
    Cool! Looking forward to your insights.
    - Frawg

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  10. #130
    Senior Member TeeDee's Avatar
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    Quote Originally Posted by GrizzlyAdams View Post
    Found this really interesting. I've been using a UCR made of Vectrus (which evidently is not spectra at all). To loosen the UCR all I need to do is push up on the unloaded end and it fairly easily loosens up and lets go of the bury. The UCR comes together like an accordian as pretty as you please. (In fact, one of the things I need to test yet is if some sort of jostling of the hammock when under load is enough to shake the UCR grip loose....) But undoing a knot made in this same Vectrus cord after it has been under load can sometimes be problematic, even when it's a knot like the bowline which is supposed to be easy to undo after loading.
    Yes, my experience with the UCR using the Amsteel, Amsteel Blue and AS-78 is the same as yours with the Vectrus. As difficult as a tight knot is to undo in the Amsteel and Amsteel Blue, the constrictor section comes loose very easily in either.

    A UCR constrictor section can be easily and quickly loosened by simply pushing towards the load. Not too sure if jostling of the hammock would be sufficient, but our tests found that even under a heavy load, the UCR constrictor section is super easy to push and loosen. Of course, that's one of the things that Frawg has engineered away.
    Those who sacrifice freedom for safety, have neither.

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