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  1. #11
    Senior Member Mouseskowitz's Avatar
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    With the lack of threads on Amsteel failure I already figured that I won't break it. But since we are using it in a manner other than seemingly intended (putting knots in it) I'm curious how close to the limits we are coming. There doesn't seem to be much research available since most groups that look at this data just say not to use the rope for climbing related applications. I've see the video of the destructive test of the woopie and am wondering if there is anyone out there that has the time, means and ability to do this for the other potential failure points of the system. Maybe I'm just too curious.
    northermark, I stand corrected. I see what you are talking about with the large radius while going around the cloth, but at the point where it crosses its self it looks like a 2:1 bend to me. Thus, in my mind a significant potential failure point.

  2. #12
    Senior Member angrysparrow's Avatar
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    I think this may simply be a case of overthinking it. Not to discredit the curiosity, but the fabric that is being attached to isn't nearly as strong as the amsteel suspension... That is the more logical point of failure in my mind.

    Regardless, there's really no knot. If the loop for the larks head is formed by a fixed eye splice, and the larks head is around the fabric (large radius), and the place where the cording passes through the eye is on the top of the fabric...there's no complete bend.

    While it's anecdotal evidence to be sure....there are literally thousands of hammocks equipped with amsteel suspensions now in this manner, used by a wide variety of occupants under wildly varying conditions. We're not hearing about failures from the cording...
    I think that when the lies are all told and forgot the truth will be there yet. It dont move about from place to place and it dont change from time to time. You cant corrupt it any more than you can salt salt. - Cormac McCarthy

  3. #13

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    I have tried both amsteel and paracord as structural ridgelines; both seem to work well enough. I ended up reclaiming the amsteel for another project. The paracord stretched the first couple of times and then seemed to settle. But then I went all "gram weenie" and went looking for something lighter.

    About that time, I happened to buy some mason line for another project and though "What the heck. I have 500' of the stuff ,and if it breaks, I'll know better". So, I made an adjustable ridgeline (static buried-line loop on one end and an adjustable loop on the other end, like a whoopie sling) and it held! It's still holding after using it every night for three weeks now(I sleep fulltime indoors in my hammock). No sign of stretching or fraying. I weigh 210 lbs and it weighs something less than 1/10 oz.

  4. #14
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    Remember that your working with loops and not single lines of Amsteel, essentially doubling the tensile strength. Testing would be interesting - I expect that the hammock fabric would fail before the larks head, and the weakest point in the Amsteel will still be the end of the bury.

    My own belief about where we push limits is all the rope on rope junctions and the low melting point of dyneema.

  5. #15
    Senior Member DemostiX's Avatar
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    Quote Originally Posted by Knotty View Post
    OK. That clarifies things Mousekowitz. Unfortunately there probably is no definitive answer to your concern about the small bending radius problem. All part of why I feel safest using at least 7/64" amsteel for suspension. The 1000# rated Dynaglide is just cutting it too close for too little gain IMHO. However, field experience of those using Dynaglide does not support my concerns.
    To the thread:

    Concern in safe design will never be supported when the advice to leave a minimum margin is followed. We can agree that engineering application is fun without finding it virtuous to convert what is a sedentary activity --resting, napping, or sleeping -- into an activity which has the risk of mountain climbing.

    There must be a good essay somewhere on the incredulity of fit recreational climbers, arborists or rescue team members being questioned about that heavy burden of rope they carry.... by a hammock camper.

    On one of OP's questions. Yes, theoretically a larks head through and around the end channel of a hammock is different than the larks head around another piece of thin cord, where the knot would be of minimal radius; or around a piece of thin polyester strap. Testing to failure would be the way to find out how much the larks head weakens the system on the one hand or tears apart the polyester strap on the other.

    In sewing, the most elementary books caution on use of thin strong non-elastic threads with weak thin fabrics. "When seams are stressed, polyester thread can tear delicate fabrics." It would seem to me good practice to expand the radius of knots, including larks heads, if possible. Unfortunately few of us using single braid Dyneema and similar have any nylon or polyester outer jacket to easily accomplish that, but jacketing to protect cord is standard practice elsewhere.

    If OP want to jacket the cord, the most durable stuff he can jacket with is another layer of Dyneema cord. The hassle is sealing the ends of the jacket. But nothing wrong with neat whipping to do that.

    By the way: If anyone does jacket or sleeve Dyneema, say with outer layer of Paracord, keep heat away from the Dyneema when sealing the ends of the jacket. Once heated above 300F, Dyneema is permanently weakened.
    Last edited by DemostiX; 03-28-2012 at 21:45.

  6. #16
    Senior Member Mouseskowitz's Avatar
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    I hadn't considered that much fabric as a fail point but that does make sense... The low melting point and heat caused by stress is something that had crossed my mind as well. I know my first set of tree straps were nylon. They stretched and heat welded themselves together to the point I had to cut them off the tree. I'm guessing that the lack of stretch with Amsteel lessons the likelihood of that some.
    Looks like I'm going to go with an adjustable structural ridge line and either whoopies or rings going to my tree straps.

  7. #17
    Senior Member Mouseskowitz's Avatar
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    When I go in to get my rope I'm going to see what they have to say about putting a jacket over the portion used to tie the larks head. I will try to remember to post how/if this works.

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