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  1. #1
    Member
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    Hello and some technical info for you

    Hello Folks.
    I discovered your Forum via www.BushcraftUK.com and my new interest in Hammocks for winter use.
    It seems there is a Forum for everything on the www
    I am 47, from Germany, and sell outdoor- and mountaineering equipment since 21 years.
    And since I didnt want to make a too short entry here, the following is about the loads a Hammock has to withstand. A posting I had just made over at Bushcraft and which might be useful here:

    I got interested in Hammocks for using them in the woods next winter. Makes a bit of a difference from selling them to customers who wouldnt dream of doing so.
    So I thought I post some informations I gathered years ago to make live easier in the shop when Hammocks are concerned.
    My customers always think, when setting one up, that they can get away with the thinnest, cheapest, most fragile rope lying around. Not realising that this might be a bit dangerous, because the load on each end of a Hammock can far exceed the weight of the user.
    This is the case when the Hammock is not set up in the traditional curved way but stretched tight to achieve a flat position for the user.
    Digging a bit into long lost knowledge from school, I came up with this (, no scanner):





    Usually, its not possible to pitch a hammock and use it completely flat. The material will always sag a bit, so the angle will be greater than 10.
    But, as can be seen from the pics, the loads depend on this pitching-angle and may vary a bit from the users weight. Also one has to take into account, that a simple knot or a tight radius will reduce the loadbearing quality of any rope by 30-50%.
    For me, after 21 years working retail, there has also to be considered what I call the "DF-quotient", meaning how much of a dumb F**k the customer might be. Sounds harsh, but if something fails I am the one to be blamed, so I like to err on the cautious side.
    An example:
    Mayself and some equipment amount to ca 100kg. So the load on each rope can be easily 200kg.
    A standard static rope (called "Reepschnur") with a diameter of 5mm holds a STATIC!!!!!! load of ca 5,8kN.
    So for myself I would be on the safe side with this and if I were a weightweenie would even consider 4mm with 4,1KN.
    The customers get a recommendation of 6mm (9,7KN) or better 7-8mm (12,8-14,8KN).
    Long term use/abuse and substandard setup have to be considered and who knows how many children might try to climb into the Hammock and jump around etc?
    The good thing on the pics above is, that everyone can do as he likes, but with solid neutral information as Base

  2. #2
    oetzi, welcome to hf.

    you are right on about the forces. the more sag the less force. even with lots of sag, force is still substantially greater than the weight of the user.

    you must also factor in the force applied to the hammock fabric as well. the forces on it are the same as on the rope, and it would most likely be the point of failure, not the rope. that being said, many folks do use rope that is quite strong.

    have you looked at high tech polymer rope. the sailboat racing industry has iincorporated fibers such as spectra/dyneema and vectran and others to drastically reduce the weight/diameter of their many lines.

    i use 3mm vectrus 12 by yale. the 3mm is rated to almost 9kn/2000lbs. and weighs very little.

    check out http://www.apsltd.com/Tree/d3000/e826.asp ,or find a similar dealer in your neck of the woods.

    i like the uncovered lines the best, but they have the same high tech fibers with polyester covers as well. stay away from the 3mm yale crystaline (the cover is too big) the 2mm and 4mm however handle well, but i was able to break the 2mm at the knott, by bouncing hard in the hammock, and the 4mm seems like overkill, thats why i tried the uncovered 3mm (vecrtus 12) and i love it. uncovered spectra seems to work great too. in my opinion a cover does nothing for a hammock suspension rope, but add weight and reduce strength.(3mm covered has less core to make room for the weaker sheath, and is thus weaker and heavier for any given diameter than an uncovered single braid.

    also, the high tech polymers work great b/c they do not stretch. of the 3 "low tech" lines you might consider, polyester is the best, almost as strong as nylon, but with little stretch, polypropelyene doesn't stretch alot, but is quite weak, and nylon is sufficiently strong, but stretchs like a mofo.

    if you search this site, you may find loads of complicated mathamatical jargon related to hammocks, as several here are engineers, and like to use lots math.

    good luck, and happy hanging.


    Quote Originally Posted by oetzi View Post
    Hello Folks.
    I discovered your Forum via www.BushcraftUK.com and my new interest in Hammocks for winter use.
    It seems there is a Forum for everything on the www
    I am 47, from Germany, and sell outdoor- and mountaineering equipment since 21 years.
    And since I didnt want to make a too short entry here, the following is about the loads a Hammock has to withstand. A posting I had just made over at Bushcraft and which might be useful here:

    I got interested in Hammocks for using them in the woods next winter. Makes a bit of a difference from selling them to customers who wouldnt dream of doing so.
    So I thought I post some informations I gathered years ago to make live easier in the shop when Hammocks are concerned.
    My customers always think, when setting one up, that they can get away with the thinnest, cheapest, most fragile rope lying around. Not realising that this might be a bit dangerous, because the load on each end of a Hammock can far exceed the weight of the user.
    This is the case when the Hammock is not set up in the traditional curved way but stretched tight to achieve a flat position for the user.
    Digging a bit into long lost knowledge from school, I came up with this (, no scanner):





    Usually, its not possible to pitch a hammock and use it completely flat. The material will always sag a bit, so the angle will be greater than 10°.
    But, as can be seen from the pics, the loads depend on this pitching-angle and may vary a bit from the users weight. Also one has to take into account, that a simple knot or a tight radius will reduce the loadbearing quality of any rope by 30-50%.
    For me, after 21 years working retail, there has also to be considered what I call the "DF-quotient", meaning how much of a dumb F**k the customer might be. Sounds harsh, but if something fails I am the one to be blamed, so I like to err on the cautious side.
    An example:
    Mayself and some equipment amount to ca 100kg. So the load on each rope can be easily 200kg.
    A standard static rope (called "Reepschnur") with a diameter of 5mm holds a STATIC!!!!!! load of ca 5,8kN.
    So for myself I would be on the safe side with this and if I were a weightweenie would even consider 4mm with 4,1KN.
    The customers get a recommendation of 6mm (9,7KN) or better 7-8mm (12,8-14,8KN).
    Long term use/abuse and substandard setup have to be considered and who knows how many children might try to climb into the Hammock and jump around etc?
    The good thing on the pics above is, that everyone can do as he likes, but with solid neutral information as Base
    Last edited by warbonnetguy; 08-24-2007 at 13:36.

  3. #3
    you may be aware of this, but hanging the hammock in the traditional way(lots of sag) will allow a flatter lay than stretching the hammock out. when there is plenty of sag, and the hammock is at least 4.5 to 5 feet wide, you can lay quite diagonal to the suspension axis. this diagonal position gives the flattest lay for this type of hammock. much flatter than hanging the same hammock very tightly.


    Quote Originally Posted by oetzi View Post
    This is the case when the Hammock is not set up in the traditional curved way but stretched tight to achieve a flat position for the user.

  4. #4
    hey, just curious, what is the 1st #, the one that comes before the kn#?

    ?,#kn


    Quote Originally Posted by oetzi View Post
    A standard static rope (called "Reepschnur") with a diameter of 5mm holds a STATIC!!!!!! load of ca 5,8kN.
    So for myself I would be on the safe side with this and if I were a weightweenie would even consider 4mm with 4,1KN.
    The customers get a recommendation of 6mm (9,7KN) or better 7-8mm (12,8-14,8KN).
    Long term use/abuse and substandard setup have to be considered and who knows how many children might try to climb into the Hammock and jump around etc?
    The good thing on the pics above is, that everyone can do as he likes, but with solid neutral information as Base

  5. #5
    Peter_pan's Avatar
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    Oetzi,

    Welcome to the hanging gang.

    Pan
    Ounces to Grams.

    www.jacksrbetter.com ... Largest supplier of camping quilts and under quilts...Home of the Original Nest Under Quilt, and Bear Mountain Bridge Hammock. 800 595 0413

  6. #6
    Senior Member sk8rs_dad's Avatar
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    Quote Originally Posted by warbonnetguy View Post
    hey, just curious, what is the 1st #, the one that comes before the kn#?

    ?,#kn
    Europeans use a comma instead of a period to represent the decimal point.

  7. #7
    Senior Member lvleph's Avatar
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    Quote Originally Posted by sk8rs_dad View Post
    Europeans use a comma instead of a period to represent the decimal point.
    And spaces in place of a comma to separate every third digit.

  8. #8
    slowhike's Avatar
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    welcome to hammock forums oetzi.
    i understand & agree w/ what warbonnet said about hanging the hammock w/ more sag & laying across the diagonal to lay flat. it works great w/ a wide hammock.
    but i (at least for now) choose to go a different route. i use a more narrow hammock (maybe 48- 50") & hang it tightly. i also use an insulated air mat that's only partly inflated, so i lay fairly close to flat.
    one advantage i see to this way is less hammock material & less area to insulate on the bottom.
    but the wider hammock may be easier to get comfortable in w/o an air mat. ...tim
    don`t leave the CREATOR out of the creation!

  9. #9
    i've never seen strengths listed in kn or any other tensile strength measurement where they used ratings with decimal places, it's always whole numbers. 9kn or 2000#. i think rather it is another measurement, like the safe working load or something.

    Quote Originally Posted by sk8rs_dad View Post
    Europeans use a comma instead of a period to represent the decimal point.

  10. #10
    hey slowhike,
    do you find the air mat to be more comfy in a tight and narrow hammock than a loose wide one, or about the same in both?


    Quote Originally Posted by slowhike View Post
    welcome to hammock forums oetzi.
    i understand & agree w/ what warbonnet said about hanging the hammock w/ more sag & laying across the diagonal to lay flat. it works great w/ a wide hammock.
    but i (at least for now) choose to go a different route. i use a more narrow hammock (maybe 48- 50") & hang it tightly. i also use an insulated air mat that's only partly inflated, so i lay fairly close to flat.
    one advantage i see to this way is less hammock material & less area to insulate on the bottom.
    but the wider hammock may be easier to get comfortable in w/o an air mat. ...tim

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