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2889RE: Hammock Camping Re: Breaking Strength of support webbing/rope/cord

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  • Thomas Peltier
    Sep 16, 2003
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      This type of information is good.  When everyone talks about sag and how much sag having a degree of sag takes all the ambiguity out of it.  Now I know what sag you are talking about.  In my case I have to tighten things up, I tend to get to much sag.  As I think about it the 30 degree mark seems to be about were the hammock works best for me.  More sag than that and I start having trouble.  I don’t think I’ve ever been tighter than that; at least not by much.

       


      From: Dave Womble [mailto:dpwomble@...]
      Sent: Monday, September 15, 2003 7:23 PM
      To: hammockcamping@yahoogroups.com

       

      Scott,

      Ricks analysis is correct.  I know that it may not be intuitively
      obvious, but the rope angle does generate a horizontal force that is
      trying to pull the hammock supports together and that horizontal
      force is a function of the horizontal angle of the hammock straps. 
      The vertical force, the occupants weight, is constant.  However, the
      hammock straps experience the vector resultant of the horizontal
      force and the vertical force, just as Rick described.  What it
      amounts to for us is that the horizontal strap angle represents
      a 'force multiplier' that is sumarized for Rick's 200 lb load as
      follows:

      200 lbs at a 30.00 degree horizontal angle.
      300 lbs at a 19.47 degree horizontal angle.
      400 lbs at a 14.48 degree horizontal angle.
      500 lbs at a 11.54 degree horizontal angle.
      600 lbs at a 9.59 degree horizontal angle.
      700 lbs at a 8.21 degree horizontal angle.
      800 lbs at a 7.18 degree horizontal angle.
      900 lbs at a 6.38 degree horizontal angle.
      1000 lbs at a 5.74 degree horizontal angle.

      As you can see, a tight pitch is pretty stressful.  SAG IS GOOD!  You
      will sleep more comfortable and safer with sag.  I try to set up my
      homemade Speer hammock's consistantly for a 30 degree angle.

      If you like, I can describe a not to complicated experiment so you
      can see first hand how this works.  It is pretty eye-opening and will
      give you a first hand appreciation as to how this works.  Let me know
      if you are interested in a little physics experiment.

      Youngblood

      --- In hammockcamping@yahoogroups.com, "subypower" <a9144me@a...>
      wrote:
      > i would disagree with the thought of the weight effect vrs angle of
      > pull those numbers would work if the straps where made of something
      > ridged like steel and fixed at a parallel angle to gravity and you
      > where pulling perpendicular to gravity. But the strap is being
      pulled
      > straight and thats how it takes the load it does not matter if it
      is
      > down or side ways it carrys the same weight. there is no such thing
      a
      > torsional strength in a very flexible object.
      >
      > now there is some thing called bounce and the sretchiness of the
      > hammock and straps can very quickly cause a greater load than
      gravity
      > alone, take for instance you said you weigh about 200 lbs but if
      you
      > bounce from a height of 1 foot you would put the force of 200 lbs
      and
      > from 2 foot you put 400 lbs, from 3 feet it would be 800 lbs of
      > force, it is not a linear ratio of height to force it is closer to
      > squaring the force for doubling the distance.  which is why in
      > firearms a light bullet at a 10 % increase in speed puts out 20 %
      > more energy than a heavier bullet at the slower speed
      >
      > scott thacher
      > white knight



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