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  1. #11
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    From what I've read on this forum, Hancock's ripstop nylon is usually 1.9 oz.

    Someone correct me if I'm wrong.

  2. #12
    Senior Member DemostiX's Avatar
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    In post 4 of this thread, I miscalculated the estimated tensile strength of a hammock, relied on to to swing from, as I did from a bedsheet to get out of jail time before last.

    I tacked on this correction.

    Error in original. I forgot that the hammock is not 1 yard wide. Typically it is, say 1.5 yards wide --about 54 inches -- so you'll be swinging from 50% more fabric and tensile strength than in the calcualations above. Now you can send your 110 lb bride safely across.

  3. #13
    Quote Originally Posted by DemostiX View Post
    In post 4 of this thread, I miscalculated the estimated tensile strength of a hammock, relied on to to swing from, as I did from a bedsheet to get out of jail time before last.

    I tacked on this correction.

    Error in original. I forgot that the hammock is not 1 yard wide. Typically it is, say 1.5 yards wide --about 54 inches -- so you'll be swinging from 50% more fabric and tensile strength than in the calcualations above. Now you can send your 110 lb bride safely across.


    actually it would not matter the width of the fabric the hammock is made from, but rather only the portion that supports your weight. for instance if laying straight down the middle, that would put more weight on the threads than if your weight was spread out over the diagonal (more width), and you also have to consider how is the force distributed when you first sit down (more concentrated width-wise compared to laying down diagonally for sure)

    i think you're right about the threads running the other direction, they don't contribute to the strength really, only threads in one direction are loaded, but the breakdown of warp/fill threads is not usually 50/50 so technically speaking you can't simply divide the weight by 2.

    also, there is not just one major factor determining strength, but rather 2.

    for an end gathered hammock, there is of course the strength of the fabric, but also how the suspension is attached. this is a very big factor, because when a hammock is loaded to failure, it will fail at the point where hammock meets suspension (the weakest link) so how the 2 are attached together makes a huge difference.

    there are only 2 main ways that suspensions are attached to end gathered hammocks:

    one is by sewing an end channel and running the suspension through that. the weight is transferred from hammock fabric onto the stitches of that seam, and then to the suspension.

    the other method is the one i use, where an end mass is created and the suspension is hitched on, the end mass not being able to slide through the hitch keeps it on there. with that method, force is transferred directly from fabric to the suspension without applying force the stitches/seam.

    there is a big difference in strength between these 2 methods without even talking about fabric.

  4. #14
    Senior Member SC_Dave's Avatar
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    Quote Originally Posted by warbonnetguy View Post
    actually it would not matter the width of the fabric the hammock is made from, but rather only the portion that supports your weight. for instance if laying straight down the middle, that would put more weight on the threads than if your weight was spread out over the diagonal (more width), and you also have to consider how is the force distributed when you first sit down (more concentrated width-wise compared to laying down diagonally for sure)

    i think you're right about the threads running the other direction, they don't contribute to the strength really, only threads in one direction are loaded, but the breakdown of warp/fill threads is not usually 50/50 so technically speaking you can't simply divide the weight by 2.

    also, there is not just one major factor determining strength, but rather 2.

    for an end gathered hammock, there is of course the strength of the fabric, but also how the suspension is attached. this is a very big factor, because when a hammock is loaded to failure, it will fail at the point where hammock meets suspension (the weakest link) so how the 2 are attached together makes a huge difference.

    there are only 2 main ways that suspensions are attached to end gathered hammocks:

    one is by sewing an end channel and running the suspension through that. the weight is transferred from hammock fabric onto the stitches of that seam, and then to the suspension.

    the other method is the one i use, where an end mass is created and the suspension is hitched on, the end mass not being able to slide through the hitch keeps it on there. with that method, force is transferred directly from fabric to the suspension without applying force the stitches/seam.

    there is a big difference in strength between these 2 methods without even talking about fabric.
    Thanks very much for the useful information! Good stuff!
    David

  5. #15
    Senior Member hippofeet's Avatar
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    Did this chair get made? Are there pics? Sc Dave, did you get the numbers you wanted?
    An emergency of my own making...is still an emergency.

  6. #16
    Senior Member SC_Dave's Avatar
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    Quote Originally Posted by hippofeet View Post
    Did this chair get made? Are there pics? Sc Dave, did you get the numbers you wanted?
    Thanks hippofeet, I did make it. I'll try to get some pics up. I used the rip-stop from Hancocks that I think is 1.9. Made a gathered end chair, whoopie slings from 1/8 Amsteel and attached them using a larkshead, made tree slings from some webbing I had. Also made some toggles from 5/8 dowel rod. Anyway, I set it up and loaded it slowly. As I gained a little confidence in the material and my workmanship I could sit and relax. I think it's going to work just fine. I may make a few changes but nothing major. I appreciate all the help.
    David

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