DIY Tensahedron -- 3/4" emt conduit longest length?

Does anyone have experience with maxing out the length of their diy tensa poles?

Anybody experience failure on 3/4 emt at any particular length.

I may be asking a question that has already been answered, but in my searching I haven't found it.

I see the results vary from under 8ft to 9ft 6inch.

Is there any reason I can't leave mine a full ten feet?

Any help is greatly appreciated and kudos to all of the great threads that have been created showing how to diy a tensa.

Latherdome, you are awesome for supporting the diy aspect of your clever product!

I could be all wet here but recall that with trees, the further apart the trees, the higher the suspension has to be in order to maintain the best angle. So longer poles could just make the setup more complicated. One goal is to use the minimum amount of material that will do the job. It seems there is a "balancing act" going on in setting up the stand - setting it and the best angle, with the base the required distance apart and hammock positioned so the support poles are being hit, etc. Once that golden setup is achieved, you could look at what is excess and remove it.

So you could leave yours at 10 ft, but you might find yourself crossing them at a point shorter than at the ends. So for storage and carry weight, you might cut off the excess.

Longer poles means more bending moment, with the peak stress at the center of the pole. You didn't mention your weight, and I don't have any empirical numbers to list anyway, but if you're reasonably lightweight, you could probably use 3/4 EMT at the full 10' length. I'd recommend you don't segment the poles if you want them to be that long, but if you do segment, I'd break them into thirds rather than in half, so the center of the assembled pole is solid, not a joint. While you're still building confidence, it would be wise to hang over some padded material and avoid having the hammock too high above ground.

Before the commercial Tensa4 was released, I played with 3/4 EMT and didn't want to cut them, preserving their versatility for use on future projects. However, I also didn't suspend the hammock from the very ends of the poles. The poles crossed at the apex probably a foot or more from the ends of the poles, so effectively I was only using 8.5' - 9' poles even though they were uncut 10' lengths. I didn't drill any holes either - I used lashings, and tightened hose clamps onto the EMT to keep the lashings from sliding up or down the conduit.

Using 10' poles would give you some potential advantages, like being able to easily set up a 12' tarp, if that's what you have. With the commercial version, using a tarp longer than 11' requires either some compromise, creative rigging, or the addition of the tarp extension poles.

With longer poles, you can still achieve the desired 30ish degree hang angle and an appropriate sit height above ground. It just involves tinkering with things like your hammock suspension lengths, stand ridgeline length (if you use a ridgeline on the stand), and stand baseline length.

Quote:

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Originally Posted by cougarmeat

I could be all wet here but recall that with trees, the further apart the trees, the higher the suspension has to be in order to maintain the best angle. So longer poles could just make the setup more complicated. One goal is to use the minimum amount of material that will do the job. It seems there is a "balancing act" going on in setting up the stand - setting it and the best angle, with the base the required distance apart and hammock positioned so the support poles are being hit, etc. Once that golden setup is achieved, you could look at what is excess and remove it.

So you could leave yours at 10 ft, but you might find yourself crossing them at a point shorter than at the ends. So for storage and carry weight, you might cut off the excess.

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Excellent thing to consider about the height complicating matters. Only one way to find out..:scared:

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Originally Posted by cmc4free

Longer poles means more bending moment, with the peak stress at the center of the pole. You didn't mention your weight, and I don't have any empirical numbers to list anyway, but if you're reasonably lightweight, you could probably use 3/4 EMT at the full 10' length. I'd recommend you don't segment the poles if you want them to be that long, but if you do segment, I'd break them into thirds rather than in half, so the center of the assembled pole is solid, not a joint. While you're still building confidence, it would be wise to hang over some padded material and avoid having the hammock too high above ground.

Before the commercial Tensa4 was released, I played with 3/4 EMT and didn't want to cut them, preserving their versatility for use on future projects. However, I also didn't suspend the hammock from the very ends of the poles. The poles crossed at the apex probably a foot or more from the ends of the poles, so effectively I was only using 8.5' - 9' poles even though they were uncut 10' lengths. I didn't drill any holes either - I used lashings, and tightened hose clamps onto the EMT to keep the lashings from sliding up or down the conduit.

Using 10' poles would give you some potential advantages, like being able to easily set up a 12' tarp, if that's what you have. With the commercial version, using a tarp longer than 11' requires either some compromise, creative rigging, or the addition of the tarp extension poles.

With longer poles, you can still achieve the desired 30ish degree hang angle and an appropriate sit height above ground. It just involves tinkering with things like your hammock suspension lengths, stand ridgeline length (if you use a ridgeline on the stand), and stand baseline length.

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Sound logic. Thanks for the feedback. I do want to accommodate a 12ft tarp. I think I will just go full length and take my chances. I can always work it down in length and just redrill the top holes. In Carpentry we say "they don't make board stretchers, so ease up on the cut."

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Originally Posted by Cabmanhang

Sound logic. Thanks for the feedback. I do want to accommodate a 12ft tarp. I think I will just go full length and take my chances. I can always work it down in length and just redrill the top holes. In Carpentry we say "they don't make board stretchers, so ease up on the cut."

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Exactly right - you can always make them shorter, but....

For reference, the commercial version has poles that are just about 8'6" long and the holes are drilled less than 2" from the ends. A 12' tarp will not fit on that setup unless you really compromise the hammock sit height and the height of the tarp ridgeline above the ground by splaying the ends of the stand far apart. Well, actually a 12' tarp can fit, but you have to do something more creative like pull one corner of the tarp past the apex of the stand and stake it to the ground, sort of like this photo from Crazytown3.

https://www.hammockforums.net/forum/...3&d=1535384561

Attachment 177024

Full ten foot lengths work fine. Fits a 12ft tarp nicely.

A bit of an aside, but are you using regular pegs for holding down the end. I couldn't tell. The big plastic ground screw looks like an ideal thing to get. Tough but easy in.

Regular aluminum + stakes. Holding fine. I would recommend a stronger stake though. Just in case. I also have a guy line on the head end to keep me from collapsing the tensa on myself.

The tarp is also tied to stakes in the ground. Probably best for the tarp to have it's own stakes, but at the foot end I have it coupled to the same stake. Just testing the minimums, but this is working in my sandy soil.

Quote:

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Originally Posted by Cabmanhang

Attachment 177024

Full ten foot lengths work fine. Fits a 12ft tarp nicely.

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Whats your weight using the 10' lengths?

My stand is 10' EMT.
I weigh 190#.
No problems.

Sent from my Nexus 5X using Tapatalk

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Originally Posted by BigE94

Whats your weight using the 10' lengths?

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180lbs

Quote:

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Originally Posted by rodentface

My stand is 10' EMT.
I weigh 190#.
No problems.

Sent from my Nexus 5X using Tapatalk

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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.

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.

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Originally Posted by jeff-oh

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.

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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.

Quote:

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Originally Posted by Cabmanhang

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.

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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.

Quote:

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Originally Posted by jeff-oh

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.

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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. :)

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!

Quote:

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Originally Posted by talon1974

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!

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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.
Attachment 177609

Quote:

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Originally Posted by jeff-oh

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.

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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.

Quote:

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Originally Posted by AlumaTurtle

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.

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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.

Thanks. Any thoughts on using these lashing only? I don’t 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 I’m 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?).

I’m not going to split the poles.


Thanks for clarification man!


Appreciate what you are doing.

Quote:

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Originally Posted by jeff-oh

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.
Attachment 177609

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Quote:

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Originally Posted by jeff-oh

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.

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I have used the stand with the mentioned measurements and have had no signs of problems so I am going to try bringing the hang higher like you said will do it a little at a time and see if i can raise it higher and get it up to a sitting height, without other problems, maybe i can get it there. will report findings.