View Full Version : Hammock Physics 101
mr. dribbles
03-05-2006, 08:33
First, let me thank everyone for turning me onto hammock hanging. I've learned so much from all of your posts and can never go back to the ground sleeping rotisserie.
Here's my question. How much weight is transmitted through each support line? Today I tried an experiment in the basement. With one end of a rope tied to a support post and the other connected to a small universal gym (with weights that are connected to one pulley), I had my 60 lb daughter sit on the middle of the rope. It took over 110 lbs to support her just on one side. I predicted the weight would be half of her weight on each side.
Would a ridge line make a difference- the line on my Hennessy asym ultralight is much thinner than the support lines.
For my homemade hammocks, the working strength of all parts would have to be 2 or 3 times body weight and gear...
Can anyone explain? ('counting on you Neo...) Thanks.
luckliver
03-05-2006, 09:39
I'd check out this page (http://hikinghq.net/hammock/hammock2.html) (http://hikinghq.net/hammock/hammock2.html for those with older browsers)
It's on SGTRock's site, very informative
MacGyver2005
03-05-2006, 10:03
I'd check out this page (http://hikinghq.net/hammock/hammock2.html) (http://hikinghq.net/hammock/hammock2.html for those with older browsers)
It's on SGTRock's site, very informative
Man, that made my life easy! I was trying to figure out the best way to desribe what happens with this stress, and that site has it pegged. Great link.
Regards,
-MacGyver
GA-->ME
mr. dribbles
03-05-2006, 10:06
Thanks. That's a good explanation.
The reason behind my experiment came from the tips page on the Hennessy site http://www.hennessyhammock.com/tips-from-users.htm. One hammock hanger said he started using a carabiner for easy setups. But the cheap, lightweight 'biners are rated to about 150 lbs so he might be dramatically exceeding the load rating. Seems to me that a real climbing 'biner would be just excess weight if you know how to tie knots.
Anyone else use carabiners?
First, let me thank everyone for turning me onto hammock hanging. I've learned so much from all of your posts and can never go back to the ground sleeping rotisserie.
Here's my question. How much weight is transmitted through each support line? Today I tried an experiment in the basement. With one end of a rope tied to a support post and the other connected to a small universal gym (with weights that are connected to one pulley), I had my 60 lb daughter sit on the middle of the rope. It took over 110 lbs to support her just on one side. I predicted the weight would be half of her weight on each side.
Would a ridge line make a difference- the line on my Hennessy asym ultralight is much thinner than the support lines.
For my homemade hammocks, the working strength of all parts would have to be 2 or 3 times body weight and gear...
Can anyone explain? ('counting on you Neo...) Thanks.
not sure,but welcome to the wonderful world of hammocking:cool: neo
Just Jeff
03-05-2006, 13:16
I've used climbing biners before. Clip it to the huggers, and a double slipknot secures the spectra to the biner. Just pull the free end to undo. I don't carry them hiking, though.
I've used climbing biners before. Clip it to the huggers, and a double slipknot secures the spectra to the biner. Just pull the free end to undo. I don't carry them hiking, though.
i like the idea of the sling shot tensioners on your website,will 550 olivedrab para cord work with the rubber sling tube:cool: neo
One hammock hanger said he started using a carabiner for easy setups. But the cheap, lightweight 'biners are rated to about 150 lbs so he might be dramatically exceeding the load rating. Seems to me that a real climbing 'biner would be just excess weight if you know how to tie knots.
Anyone else use carabiners?
yeah, that was me... they're rated 150lbs each... i weigh 180... have no idea why it works... but no accidents so far...
Just Jeff
03-05-2006, 15:33
Maybe. It'll work if you can secure it well enough to the slingshot. It might be too big to stay snug to the v1, and might not fit inside the contracted tube for the v2. Using bigger tubing might make it work, though.
Also, it's probably overkill for using on a tarp. Heavy, bulky, and tangles easier than some other cords. The biggest downside I see is that because 550 is so strong, in very heavy winds the tarp will fail before the cord. Repairing a snapped cord is as simple as a knot, but field repairing a ripped tarp in a storm could mean trouble.
I always have some 550 cord with me, but I don't use it for tarps.
Maybe. It'll work if you can secure it well enough to the slingshot. It might be too big to stay snug to the v1, and might not fit inside the contracted tube for the v2. Using bigger tubing might make it work, though.
Also, it's probably overkill for using on a tarp. Heavy, bulky, and tangles easier than some other cords. The biggest downside I see is that because 550 is so strong, in very heavy winds the tarp will fail before the cord. Repairing a snapped cord is as simple as a knot, but field repairing a ripped tarp in a storm could mean trouble.
I always have some 550 cord with me, but I don't use it for tarps.
your hammock site is kick but,excellent links pics and everything
what year is your jeep wrangler,here is a pic of mine:cool: neo
http://www.whiteblaze.net/forum/vbg/showimage.php?i=10166&catid=member&imageuser=3462
http://www.whiteblaze.net/forum/vbg/showimage.php?i=7571&catid=member&imageuser=3462
http://www.whiteblaze.net/forum/vbg/showimage.php?i=8293&catid=member&imageuser=3462
http://www.whiteblaze.net/forum/vbg/showimage.php?i=6994&catid=member&imageuser=3462
http://www.whiteblaze.net/forum/vbg/showimage.php?i=6987&catid=member&imageuser=3462
http://www.whiteblaze.net/forum/vbg/showimage.php?i=7918&c=665&userid=5949
Consider using toggles instead of a carabiner: a 3/4" stick does the work of an expensive piece of equipment.
http://www.cruisenews.net/backpacking/HammockatHome.html
Just Jeff
03-05-2006, 20:56
It's an '02. Most of the Jeep trails around here are groomed, gated or private, so I haven't been stuck in a while. :p Guess I need to find a good place to get real dirty.
mr. dribbles
03-05-2006, 21:05
Great pics.
The tubing I tried for tensioners was too stiff to be effective (it is surgical rubber, but thicker than my old sling shot black rubber tubing). I am trying this arrangement for simplicity- a knock off on the original sling shot tensioner by Just Jeff et al.
http://www.sultzmd.com/Backpacking.html
Life's too short to make all my own mistakes so I welcome your comments.
Just Jeff
03-05-2006, 21:12
The tensioners I use expand from ~6" to ~12" (IIRC), so they can each take up ~6" of tension. Not sure if those grocery bands will contract enough to keep the tarp taut all night. Give it a try...if it doesn't work, you can always put 2-3 bands on each one.
Jonas4321
03-06-2006, 10:16
I use heavier climbing biners to make tying to my home-brew tree huggers easier. If I was concerned with weight, I'd abandon the biners and tie directly to the 2" webbing of the tree huggers, NOT get lighter biners. My biners have a gate with a notch, and I have not noticed any change in their shape or the fit/operation of the gate.
Skylark, I see your toggles being convenient when you have a fixed-distance, repeatable hanging place like your bedroom (I am jealous of course...), but in the woods, I rarely (never, actually) find two trees the same distance apart as last time, so I still need to adjust, and the toggles seem to just add to the complexity. Neat idea though.
Seems to me that a real climbing 'biner would be just excess weight if you know how to tie knots.
Anyone else use carabiners?
I use Black Diamond Neutrinos for my winter setup and also with my hanging-in-the-back-yard hammock. This is a offset "D" shaped wire-gate aluminum 'biner that weighs about 3 ounces per pair.
Webbing tie-off is faster and easier with 'biners. For winter use, you can tie-off to a one with gloved hands. If the tied-on webbing gets wet and freezes overnight it's easier to manage. (You can take the hammock off and pack up without delay, dealing with the freeze-up seperately or later on.)
Other carabiners of note are the Camp Nano Wire, the Trango Superfly and the Omega Pacific Doval.
Doug Frost