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  1. #11
    Senior Member Cabmanhang's Avatar
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    Quote Originally Posted by BigE94 View Post
    Whats your weight using the 10' lengths?
    180lbs

    Quote Originally Posted by rodentface View Post
    My stand is 10' EMT.
    I weigh 190#.
    No problems.

    Sent from my Nexus 5X using Tapatalk
    Good to see others having success with ten foot lengths. Is it tall enough for you to have a tarp? How many times have you used it? I'm just getting started with it, but it seems plenty sturdy for my needs.

  2. #12
    Senior Member jeff-oh's Avatar
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    There are many factors that go into this. But as you lengthen the pole, and specifically where the hammock is attached, and shallow out the angle by increasing the distance between the apexes, or ground splay the moment in the pole increases and the closer you get to the failure load.

    Based on some assumptions as you do not give the full dimensions of your set up, it I calculate you Margin of Safety to be less than .5 for a centered-static load of 350lbs. This would be closer then I would like. But if you are substantially less than 350 then margin improves. Ideally you'd want the MS to be greater than 3

    If your willing to share load and the distance between the tips (both top and ground) the a MS could be calculated.

    At 180lbs and assuming the hole is drilled 1 1/2 from the end, the top is 144" long and the base 8' (96") wide the MS is ~1.85. Not too bad. You may notice that the poles will start to bend a little with use but should hold and feel steady unless the bow gets too pronounced.

    For comparison I designed mine for 8' pole, 120" length and 6' (72") base with a 350 lbs load and I am at a MS of 2.0. So we are taking about the same amount of risk for failure.
    Last edited by jeff-oh; 09-17-2019 at 15:51.

  3. #13
    Senior Member Cabmanhang's Avatar
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    Quote Originally Posted by jeff-oh View Post
    There are many factors that go into this. But as you lengthen the pole, and specifically where the hammock is attached, and shallow out the angle by increasing the distance between the apexes, or ground splay the moment in the pole increases and the closer you get to the failure load.

    Based on some assumptions as you do not give the full dimensions of your set up, it I calculate you Margin of Safety to be less than .5 for a centered-static load of 350lbs. This would be closer then I would like. But if you are substantially less than 350 then margin improves. Ideally you'd want the MS to be greater than 3

    If your willing to share load and the distance between the tips (both top and ground) the a MS could be calculated.

    At 180lbs and assuming the hole is drilled 1 1/2 from the end, the top is 144" long and the base 8' (96") wide the MS is ~1.85. Not too bad. You may notice that the poles will start to bend a little with use but should hold and feel steady unless the bow gets too pronounced.

    For comparison I designed mine for 8' pole, 120" length and 6' (72") base with a 350 lbs load and I am at a MS of 2.0. So we are taking about the same amount of risk for failure.
    What a breakdown!

    Some more details:

    The feet were spread 73inches. The top holes are drilled 3 inches from the end and the bottom holes at 1.5 from end. The temp ridgeline cable provides for a spread of 14'4" from side to side. It seems sturdy. I may not have the best MS, but it looks solid from the hammock.

  4. #14
    Senior Member jeff-oh's Avatar
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    Quote Originally Posted by Cabmanhang View Post
    What a breakdown!

    Some more details:

    The feet were spread 73inches. The top holes are drilled 3 inches from the end and the bottom holes at 1.5 from end. The temp ridgeline cable provides for a spread of 14'4" from side to side. It seems sturdy. I may not have the best MS, but it looks solid from the hammock.
    With the dimensions you are giving the MS is just shy of 1.6. This means the pipe would not be predicted to buckle unless the load increases by 160% (500lb total load). Be aware the calculations are based on a perfect system and nature is rarely perfect. Variation does affect the results.

    That all said. I would use it, I probably would not jump into the hammock, nor have multiple people in it. But yes it should feel solid when your in it --- a great build.

    For what it's worth if one of these EMT stands failed it would be by buckling one of the poles. The pole would bend out of shape. Because of the ductility of the soft steel, I would predict it would let you down gentler than the taco mode-ground stake trebuchet failure mode.

    Fun discussion.

  5. #15
    Senior Member Cabmanhang's Avatar
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    Quote Originally Posted by jeff-oh View Post
    With the dimensions you are giving the MS is just shy of 1.6. This means the pipe would not be predicted to buckle unless the load increases by 160% (500lb total load). Be aware the calculations are based on a perfect system and nature is rarely perfect. Variation does affect the results.

    That all said. I would use it, I probably would not jump into the hammock, nor have multiple people in it. But yes it should feel solid when your in it --- a great build.

    For what it's worth if one of these EMT stands failed it would be by buckling one of the poles. The pole would bend out of shape. Because of the ductility of the soft steel, I would predict it would let you down gentler than the taco mode-ground stake trebuchet failure mode.

    Fun discussion.
    Thanks for everything Jeff Oh. The thread on your initial build was very helpful. Thanks for all of the calculations and sharing your experience to make it easier on us non-scientific bunch.

  6. #16
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    The guy That knows how to do all the calculations. If I use three-quarter inch EMT conduit and I weigh 240 pounds, would this work and if I cross them using lashings and hose clamps? No drilling would be ideal. I would do the thing where they crisscross at the end effectively only using 8 1/2 to 9 feet or so.

    If not, would 1 inch conduit work better?

    Thanks!

  7. #17
    Senior Member jeff-oh's Avatar
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    Quote Originally Posted by talon1974 View Post
    The guy That knows how to do all the calculations. If I use three-quarter inch EMT conduit and I weigh 240 pounds, would this work and if I cross them using lashings and hose clamps? No drilling would be ideal. I would do the thing where they crisscross at the end effectively only using 8 1/2 to 9 feet or so.

    If not, would 1 inch conduit work better?

    Thanks!
    You should be fine with 3/4 EMT as long as you suspend the hammock between the lashed poles. i.e. the suspension attachment to the stand is between the poles. That is why I used a spacer on the bolt.
    IMG_2082.jpg

  8. #18
    Quote Originally Posted by jeff-oh View Post
    There are many factors that go into this. But as you lengthen the pole, and specifically where the hammock is attached, and shallow out the angle by increasing the distance between the apexes, or ground splay the moment in the pole increases and the closer you get to the failure load.

    Based on some assumptions as you do not give the full dimensions of your set up, it I calculate you Margin of Safety to be less than .5 for a centered-static load of 350lbs. This would be closer then I would like. But if you are substantially less than 350 then margin improves. Ideally you'd want the MS to be greater than 3

    If your willing to share load and the distance between the tips (both top and ground) the a MS could be calculated.

    At 180lbs and assuming the hole is drilled 1 1/2 from the end, the top is 144" long and the base 8' (96") wide the MS is ~1.85. Not too bad. You may notice that the poles will start to bend a little with use but should hold and feel steady unless the bow gets too pronounced.

    For comparison I designed mine for 8' pole, 120" length and 6' (72") base with a 350 lbs load and I am at a MS of 2.0. So we are taking about the same amount of risk for failure.
    Jeff-oh
    Would you please Help me figure my setup safety factor? My pole length is 112 inches, 79 inch base, and a tip to tip length of 152 inches not counting the 2 inches past the point where the points come together, and 165 lbs weight. also at 30 degree hammock hang I end up only 2-3 inches from ground with a 11.5 ft. hammock. ( not far to fall) but would like to be higher how can I achieve a higher hang? and remain in a safe factor. I understand "safety factor, just not how to achieve it. want to add that my poles3/4 inch are total length of inch 40 inches with a 4 inch insert into a 1 inch centerpiece of 40 inches.
    Last edited by AlumaTurtle; 10-15-2019 at 10:43.

  9. #19
    Senior Member jeff-oh's Avatar
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    Quote Originally Posted by AlumaTurtle View Post
    Jeff-oh
    Would you please Help me figure my setup safety factor? My pole length is 112 inches, 79 inch base, and a tip to tip length of 152 inches not counting the 2 inches past the point where the points come together, and 165 lbs weight. also at 30 degree hammock hang I end up only 2-3 inches from ground with a 11.5 ft. hammock. ( not far to fall) but would like to be higher how can I achieve a higher hang? and remain in a safe factor. I understand "safety factor, just not how to achieve it. want to add that my poles3/4 inch are total length of inch 40 inches with a 4 inch insert into a 1 inch centerpiece of 40 inches.
    The calculations I am doing are based on a single pole. Jointed poles will add stress concentrations that will adversely affect strength. Based on the numbers provided I would not predict a bending failure in the middle piece. The 3/4's might have an issue at the joint. Though the simple column buckling calculation I am doing does not cover this. In general to increase SF's steeper angles are positive. For example in your case the 152" tip to tip length is longer than may be needed. Bringing them closer together and shortening the suspension will raise the hammock higher than the 2-3 inches off the ground.

    Hope that helps some.

  10. #20
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    DIY Tensahedron -- 3/4" emt conduit longest length?

    Thanks. Any thoughts on using these lashing only? I donít want to buy a drill, a bit, and I live in a tiny condo with nowhere to work. I saw somewhere else that a guy used hose clamps to prevent the lashings from sliding. I was going to wrap each cross of the poles with 6-7 feet of paracord in between the hose clamps. I was going to cross the poles with about a foot left over at the top and 4-5 inches at the bottom. This would make the effective portion of the pole Iím using being 8 1/2 feet or so.

    So If I have it lashed, I was picturing draping the hammock suspension over one pole, using the opposite pole for each end. The suspension would be stopped by the lashings and would approximately be placing the downward force in the center (I think?).

    Iím not going to split the poles.


    Thanks for clarification man!


    Appreciate what you are doing.



    Quote Originally Posted by jeff-oh View Post
    You should be fine with 3/4 EMT as long as you suspend the hammock between the lashed poles. i.e. the suspension attachment to the stand is between the poles. That is why I used a spacer on the bolt.
    IMG_2082.jpg

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