Knotty, not to argue, but Samson's site says 60%.
"AmSteel® and AmSteel®-Blue Whoopie Slings have a break strength of 60% of the published average ROPE break strength."
For what it's worth.
Rain Man
.
Knotty, not to argue, but Samson's site says 60%.
"AmSteel® and AmSteel®-Blue Whoopie Slings have a break strength of 60% of the published average ROPE break strength."
For what it's worth.
Rain Man
.
"You can stand tall without standing on someone. You can be a victor without having victims." --Harriet Woods
http://www.MeetUp.com/NashvilleBackpacker
.
Not argumentative at all my friend. A while back I contacted Samson to ask them about whoopie slings and this is what they said.
http://www.hammockforums.net/forum/s...ad.php?t=12319
Knotty
"Don't speak unless it improves the silence." -proverb
DIY Gathered End Hammock
DIY Stretch-Side Hammock
Stretch-Side "Knotty Mod"
DIY Bugnet
So...with a "working load" of 20% (per Samson's site), we have 1600 x 0.8 x 0.2 = 256 lbs rating. Not quite the 1600 lbs commonly referred to.
It still works for me.
Last edited by gmcttr; 04-20-2011 at 11:58.
I thought that using 20% of static rating to come up with a safe working load (SWL) took into account using knots. A quick look at that bulletin reveals a typical 50% reduction due to knots is likely used to come up with the 20% derating factor. So wouldn't replacing a knot with a whoopie sling increase the SWL?
Youngblood AT2000
Always important to understand safe working load. Too many people think that all they need is a line that's rated for the static load. That leaves no margin of error for wear, shock load, point load, etc.
I don't know the official way to calculate SWL with rope but my goal is to have a 5:1 safety factor after accounting for knots and splices. So stealing gmcttr's equation, 1600 x 0.8 x 0.2 = 256, tells me 7/64" amsteel is good for most people.
People have had good success with Dynaglide (1000#?) but for me there's just not enough safety factor there.
Knotty
"Don't speak unless it improves the silence." -proverb
DIY Gathered End Hammock
DIY Stretch-Side Hammock
Stretch-Side "Knotty Mod"
DIY Bugnet
I would like to know if that "working load" is for lifting "stuff" only, or if it also applies where human safety is involved. Often (I think), those are different and not interchangeable. In skimming the article, I didn't see yet which that rating applied to. (NOTE: Found it... see bottom below.)
I did note something else interesting and applicable, however:
"When given a choice between ropes, select the strongest of any
given size. A load of 200 pounds represents 2% of the strength
of a rope with a breaking strength of 10,000 pounds. The same
load represents 4% of the strength of a rope that has a breaking
strength of 5,000 pounds. The weaker rope will have to work
harder and as a result will have to be retired sooner."
Anyone retire their whoopie slings sooner when lower rated Amsteel is used? Otherwise, we are cherry picking the bits and pieces of data we want, or so it seems to me.
I do note something else very interesting in that article:
"Our published strengths and test results reflect as accurately
as possible the conditions under which they are to be used.
Because all ropes are terminated with a splice, all published
strengths herein are spliced strengths."
That means we don't have to take into account how much a splice reduces the strength of Samson Amsteel, because they have already done that?
I think I found the answer to my question about whether Samson's ratings are good for human safety. Apparently not:
"Working loads are the loads that a rope is subjected to in
everyday activity. For rope in good condition with appropriate
splices, in noncritical applications and under normal service
conditions, working loads are based on a percentage of the
approximate breaking strength of new and unused rope of
current manufacture. For the products depicted in this catalog,
and when used under normal conditions, the working load
percentage is 20% of published strengths."
Their ratings are good for "noncritical applications," which means they can not be used for determining safety in hammock hanging, as I see it.
Rain Man
.
Last edited by Rain Man; 04-20-2011 at 22:54.
"You can stand tall without standing on someone. You can be a victor without having victims." --Harriet Woods
http://www.MeetUp.com/NashvilleBackpacker
.
Rain Man - I believe the standard for life safety is a 10:1 margin. For hanging a hammock 5:1 seems reasonable. If you want to play it extra safe consider using 1/8" instead of 7/64". Still not 10:1 but moving in that direction.
PS - DawgU, sorry if we've strayed too far off topic.
Knotty
"Don't speak unless it improves the silence." -proverb
DIY Gathered End Hammock
DIY Stretch-Side Hammock
Stretch-Side "Knotty Mod"
DIY Bugnet
Knotty, I recall that the packaging that came with rope I bought in the past said the SWL was between 8% and 20% of the breaking strength, depending on application... but if it was for life support that you want to further derate it.
I figure that we give our hammock suspension lines a lot of inspections, pretty much every time we hang them and take them down, so I feel okay with the 20%. When I first started hammocking I used 3 strand, twisted polypropylene rope because that is what I thought I saw on a Clark Hammock but changed to braided rope after I saw one of the 3 strands kink where the slippery bowline had been tied because that meant only 2 of the strands were supporting the load. You have to keep your eyes open when you go light weight.
This dyneema cordage is some amazing stuff. I found this bulletin the other day that has info about tension fatigue http://www.samsonrope.com/site_files...tic_Ropes_.pdf
Youngblood AT2000
Bookmarks