Originally Posted by Rain Man
That's how I understand it too. The brummel or locked brummel is what derates the rope so much. A simple buried eye, like we all use, doesn't do that. I think our Whoopie Slings and UCR's remain at about 90% or thereabouts.
Jerry
The "Search" function is your friend!
I brought this up in another thread but it's applicable here as well.
A standard eye splice has a taper in the bury. The taper prevents a sudden transition, which is where lines generally fail.
With a whoopie sling a taper in the bury of the adjustable loop isn't possible. My theory is that the weak link in a whoopie is where the tail exits the bury. I also believe that's why Samson uses a locked brummel in the fixed eye, because it is stable with just a short bury and may not be the weak link. A chain, or whoopie, is only as strong as the weakest link.
Also gotta agree with Rain Man. Where life safety is involved a 10:1 safety margin makes sense and I think we are too often well below that. Maybe because a fall would just be a foot or so we don't have to go with a full 10:1 but it's something to think about.
Knotty
"Don't speak unless it improves the silence." -proverb
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Knotty, then wouldnt the entrance of the dead eye bury fall under that same derate?
Maybe, but the load is distributed between the two lines which come together so maybe no.
Disclaimer: I'm not an expert on lines and knots, I just play one on the internet.
Knotty
"Don't speak unless it improves the silence." -proverb
DIY Gathered End Hammock
DIY Stretch-Side Hammock
Stretch-Side "Knotty Mod"
DIY Bugnet
Valid points to consider, but with the high tensile strength of the Amsteel Blue I can't imagine one of these failing.
I'm sure there could be an exception, but it would almost have to be some type of neglect like abraded or nicked rope. I'll definitely treat these like all of my equipment, with some amount of care. And everything gets inspected regularly.
Jerry
The "Search" function is your friend!
Agreed... I think with the loads hammockers put on the line... Its a non issue.
I also puzzled over the coolness of eyesplices vs the length they consume.
I compared my three hammock lines: (That is an 18" ruler, by the way)
The first is my old line which is just tied together - nice and short
The second is eyespliced on both ends - too long! Arrrrrgh!
The third is me messing around and is not too clear - I made an eyesplice in each end of the line, both around the same ring. I treat the line as a loop and feed the loop through the sewn channel of the hammock, then dropped the loop over the ring. Ta Da!
-Liz -
Here's a chart for determining just how much load hammockers put on lines. I forget where I stole this from. Sorry. And keep in mind, this is static weight. True real-life weight is dynamic.
You can see on the far left side of the chart that if the two hammock lines were hanging straight down (hmmmm.... mountain climbing rigging for a night on El Capitan maybe?), each line carries half the total weight, which makes sense, with no multiplier for an off-vertical angle. As the hammock lines get more and more taunt (closer to horizontal), the effective weight can go way up (to infinity, in theory).
I just don't get guys who put 200lbs into a hammock and then publicize that a 1,000lb-rated line (expressly intended for non-human-safety applications) is good enough. All to save an ounce. Not in my book. YMMV and HYOH, though.
Part of my problem is that I'm an ex-caver, where rigging forces really were "life and death." Even though that's not normally the case in hammocking, I still don't rig my hammock over rocks I wouldn't want my backbone to do any destructive testing on! But that's just me. I'm such an amateur knuckle-head, that I want a generous margin of error when it comes to my spine relying on my DIY. LOL
Enjoy!
Rain Man
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Last edited by Rain Man; 11-25-2009 at 11:52.
Great point Rain Man ....
Dynamic loads can be tricky .... I mean, how many times do you turn over in your hammock per night? Each time will see a spike in the loading on the line .... 10 times factor of safety is a good place to be, however, I think it important to realize that a 220 lb man would most likely be fine with 1800 lb rated line
As one of my old engineering professors would say ... be careful with your factors of safety for the ground is hard and gravity unforgiving ....
Many a good hanging prevents a bad marriage
William Shakespeare
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It's from Youngblood's stuff on the yahoo hammock group.
- Frawg
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