View Full Version : Breaking strength for hammock line
What type of breaking strength does a line to support a hammock need to have?
3/32 Spectra has 950lbs, that seems pretty good. Anybody ever try it?
Would you have to use this line together with a piece of webbing around the tree, or could you wrap Spectra around the tree directly?
Here's a link to the product:
http://www.westmarine.com/webapp/wcs/stores/servlet/product/10001/-1/10001/118240/10001/666/490/800
titanium_hiker
02-18-2006, 00:40
use webbing on trees! do NOT put narrow line/rope on trees, you will cut into them and damage their health!
sorry for the excess !exclamation! marks! it's just something that I feel deeply about. Don't hurt trees ok?
TH
Rain Man
02-18-2006, 01:01
When thinking of a safe strength rating for lines (ropes), you cannot just take the manufacturer's stated rating, for several reasons.
One is that knots can halve a line's breaking strength. Bad knots that is. Good wrapping methods and knots can give you almost (but still not fully) the stated strength of the line. So, BEWARE knots and sharp angles of any kind.
Angles can do the same! Rated breaking strength is usually with the line hanging straight down and the dead weight at the end. Hammock lines do NOT hang down, but go horizontal. That doesn't reduce the breaking strength of the line, but can DRAMATICALLY increase the effective weight of anything hanging from the middle of the line. A 200 lb man can become a 400 lb (or more!) effective weight, easily.
Also, rated breaking strength is with a static weight. Since no hiker is a static weight in a hammock, but is a moving "dynamic" weight, that also can DRAMATICALLY increase his effective weight when reaching the bottom of a "bounce."
So, take a 1,000 lb line, throw the wrong knot at each end, and you now have a 500 lb line. Stretch the line horizontally, and now the 200 lb hiker is effectively 400 lbs. Then get him bouncing around as he straightens his sleeping pad and sleeping bag, or just rolls over in his sleep, and ........ "DANGER, WILL ROBINSON, DANGER!"
Maybe Hennessey will tell you what their line is rated? I know they recommend a really good knot and weights only up to 200 lbs.
Rain:sunMan
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johnthebaton
02-18-2006, 20:37
Hennessy's website says he uses 1400lb breaking strength for hammocks with a 200lb weight limit and 1650lb for hammocks with a 250lb weight limit (it's under their comparison chart, in the lower section I believe). I would stick with these ratings.
Backpackinglight.com' strongest rope--AirCore Pro Dyneema--has a 1450lb breaking strength, but unlike Hennessy's rope, it is quite slick. Not sure how that would impact the holding power of the knot. I use the rope for bear bagging in wet, soft trees to prevent the rope from digging into the limb and it looks like the same diameter as Hennessy's rope.
johnthebaton
02-18-2006, 20:40
er... that is, food bag hanging, not bear bagging. I don't actually go hanging bears up in trees. :-?
Anyone know where the 'edit' button is?
A thread on hammocks open for 24 hours and no Neo??? What's up with that? Is the question too technical Neo? :D
er... that is, food bag hanging, not bear bagging. I don't actually go hanging bears up in trees. :-?
Anyone know where the 'edit' button is?
That's good, but I wouldn't mind hanging some mice who ran away with my gorp one night. The edit button seems to come and go, so when I think I might cause I ruckus I like to use the edit button so that I can make sure it is a good ruckus. :D
I replaced the broken multiple strand line on my cheap Byer hammock with 6mm accessory cord (have no idea of breaking strength). I'm 220 lbs. It stretched quite a bit at first, but seems to have stabilized.
The cordage on my HH Ultralight Backpacker A-sym needs to be replaced due to the sheath fraying in half (after 2 years of use, the last one I've been over the 200 lb. weight limit. I'm sending it to Hennessy, where they'll replace it with the rope used on the models rated for users over 200 lbs.
Spectra does not hold an easily untied not well. I use it on my tarps and tent lines.
A thread on hammocks open for 24 hours and no Neo??? What's up with that? Is the question too technical Neo? :D
Please do not encourage him.
Lumberjack
02-19-2006, 08:32
as a rough figure divide static breaking strength by 6. You can use the dynamic breaking strength pretty much as is. I would go up one size on the spectra, 950 static is a bit light and will likely break after a few uses.
Billygoatbritt
02-19-2006, 08:50
I purchased a HH Ultralite Backpacker Asym designed for those under 200 lbs. After talking with them about my 230 lbs, they said they could use the heavier rope. It's been 3 years and everything is in good shape. The couple of ounces you gain by the bigger rope will be small compared to wasted time, energy, or possible injury if it fails.
OK, it looks like the 1/8" Spectra with an 1800lb breaking strength should work for hanging the hammock. I figure 12 feet on each side should be enough.
For the tree wrap, a 6' length of 1" poly webbing, with some loops tied in the ends.
Can anyone give me a suggestion for a good knot in spectra to tie the hammock lines to the tree wrapper?
Goals:
easy to undo with cold hands in the morning
easy to adjust
secure, I don't want to fall
A thread on hammocks open for 24 hours and no Neo??? What's up with that? Is the question too technical Neo? :D
i'll bet he went hiking this weekend, for the holiday...