Thought some of you backpackers might be interested in my one-tree backpack-able stand. The extra equipment --- items needed in addition to normal hiking-hammock gear --- I use to make this stand includes:
1. Aluminum tube 44 in length cut in two pieces (with 8 wooden 1.125 dowel rod, two PVC end pieces, one PVC coupling). Note that the aluminum tube comes from a telescoping pole used to clean pools. I believe the dimensions are 1.5OD x 1.43ID with .035 wall.
2. Polyester strap about 21 with a loop on one end (loop used as Larks head to attach strap to hammock whipping).
3. Two aluminum rings.
4. Four 7 aluminum tri-stakes.
5. Two 12 aluminum tri-stakes (I have ordered these, for this demonstration I used two 12 nails).
6. Three lengths of para-cord each about 10. One for pole lashing, two to create picket hold-fasts.
The aluminum pole with dowel rod and PVC fittings weighs 13 oz. The remaining items weigh about 14oz (including an estimated 5oz for the 12 aluminum stakes I have on order). In total the extra equipment weighs about ~27oz.
Other items needed to make this stand include:
1. Hammock with tree huggers.
2. Sturdy walking staff; I use 48 bamboo when I hike. Normal trekking poles are unlikely to be sufficient to carry the load for this hammock stand. My bamboo poles typically weigh 8oz to 11oz.
Image 1: This image shows the extra equipment. (Note 12 nails will be replaced with 12 tri-stakes from Campmor.com = http://www.campmor.com/outdoor/gear/Product___21105 )
Image 2: The aluminum pole and my bamboo staff lashed with para-cord to form bi-pod.
Image 3: The picket hold-fasts created with four 7 stakes, two 12 stakes, and para-cord binding them.
Image 4: The anchor system using picket holdfasts, tree hugger that I normally use around trees, and two aluminum rings to which I will attach the strap that supports the hammock.
Image 5: System hung. Note use of strap that is attached to hammock temporarily over the whoopie sling by use of Larks head. When not using the portable hammock stand, I remove the strap. One could use amsteel instead of the strap to reduce weight by about 3oz, but I am concerned amsteel would create too much concentrated force on bamboo and aluminum tube and crack one or the other.
Image 6: Hammock with me inside. Hammock is about 6 above ground here. One will need hammock and suspension that produces little stretch (Hammock Bliss types wont work here). My hammock is 1.5oz ripstop nylon from http://backwoodsdaydreamer.webs.com and it seems to have little stretch for me (I weight 200 lbs). Also note the hammock attachment height on tree -- extra height here helps prevent hammock from touching ground.
Image 7: Tarp attached to tree, cord run between poles and tied to picket holdfast.
Image 8: Me inside hammock with tarp attached. Note very little sag with this system. Despite the fact that the lashed poles are drawn toward the hammock by an inch or two when weight is placed in hammock, the tarp remains taut because the tarp is not tied to the bi-pod.
Images 9 and 10: These images show the strap wrapped about the bi-pod and also the tarp guy line passing through bi-pod.
Image 11: Parting image of me in hammock enjoying the absolutely beautiful weather we are experiencing in Georgia this 2 September 2010.
Some additional notes:
1. I considered a uni-pod (one pole) design, but in addition to the anchor point for the suspension, I would also want to have at least two guy lines for lateral support and these would increase items (rope/straps + stakes) and weight over the bi-pod configuration. Also, the bi-pod is very stable -- I can swing in my hammock with little evidence of collapse.
2. When initially hanging this system it is important to make the strap from hammock to anchor point very taut otherwise the hammock will likely hit ground once weight is added.
3. Distance from bi-pod to stakes should be at least twice the height of the bi-pod; such a distance provides about a 30 degree angle and reduces the force applied to the stakes. The shorter the distance from bi-pod to stakes, the greater will be the load on stakes, so better to make distance from bi-pod to anchor point longer.
4. I am not an engineer so the figures I provide below may be incorrect. If there are any engineers reading this, please provide feedback!
To determine what size aluminum tube to use for the bi-pod, I downloaded a spreadsheet that calculates theoretical buckling limits on columns. Image 12 shows results. Since the bi-pod will generally divide in half the weight placed on the support system, I figured an upper limit of 250 lbs per pole would be reasonable. I decided to select a pole of length 44 (which produces a hammock starting height of about 39 once lashed and bi-pod is spread). I also specified a safety factor of 3. For the aluminum I used only 6061-T6 specifications and round tube.
Spreadsheet column labels:
OD = outer diameter
ID = inner diameter
Wall = wall thickness
Total weight at 44 = estimated weight of tube in lbs
OZ - estimated weight of tube in oz
SF = estimated safety factor given CF
CF = critical force -- I think this is the theoretical limit in pounds when buckling will occur. Im sure this is optimistic hence the safety factor I used.
OD of inner sleeve = the outer diameter of aluminum tube that will slide within the given tube -- useful for those who want to telescope tubes or use a smaller tube as an inner sleeve
Again, let me emphasize that I am not sure the calculations above are correct, so use these figures at your own risk. The row in blue represents the tubing I am using (I think - not certain since I dont know wall thickness or grade of aluminum used in pool cleaning poles). If one wished to use a wooden pole, a thickness of about 1.38 is needed for most wood I examined to provide a safety factor of 3 (theoretical buckling limit of 750+ lbs).
Bryan
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Originally Posted by miisterwright
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