|
scm007
Jan 25, 2010, 6:56 AM
Post #1 of 39
(2297 views)
Shortcut
Registered: Apr 10, 2007
Posts: 44
|
Is the breaking strength the same whether or not the forces on either stand are in the same direction of pull or opposite directions?
|
|
|
|
|
Storjon
Jan 25, 2010, 10:36 AM
Post #2 of 39
(2250 views)
Shortcut
Registered: Jun 22, 2009
Posts: 38
|
No, if all forces are in the same direction the sling is accelerating and if this acceleration is big enough air friction could possibly melt the sling and thus reduce itīs strength.
A sling is either pulled or compressed. Compression loading a sling shouldnīt be a problem in a climbing situation.
Regarding pulling, how many ways can you pull a sling?
Think about this and the answer is obvious..
|
|
|
|
|
johnwesely
Jan 25, 2010, 2:09 PM
Post #4 of 39
(2208 views)
Shortcut
Registered: Jun 13, 2006
Posts: 5360
|
j_ung wrote: scm007 wrote: Is the breaking strength the same whether or not the forces on either stand are in the same direction of pull or opposite directions?
Smart man.
|
|
|
|
|
kachoong
Jan 25, 2010, 2:51 PM
Post #5 of 39
(2183 views)
Shortcut
Registered: Jan 23, 2004
Posts: 15304
|
Storjon wrote: No, if all forces are in the same direction the sling is accelerating and if this acceleration is big enough air friction could possibly melt the sling and thus reduce itīs strength. A sling is either pulled or compressed. Compression loading a sling shouldnīt be a problem in a climbing situation. Regarding pulling, how many ways can you pull a sling? Think about this and the answer is obvious..
Really? Air friction?
|
|
|
|
|
johnwesely
Jan 25, 2010, 3:14 PM
Post #6 of 39
(2168 views)
Shortcut
Registered: Jun 13, 2006
Posts: 5360
|
kachoong wrote: Storjon wrote: No, if all forces are in the same direction the sling is accelerating and if this acceleration is big enough air friction could possibly melt the sling and thus reduce itīs strength. A sling is either pulled or compressed. Compression loading a sling shouldnīt be a problem in a climbing situation. Regarding pulling, how many ways can you pull a sling? Think about this and the answer is obvious.. Really? Air friction?
It is the new micro fracture!
|
|
|
|
|
bill413
Jan 25, 2010, 4:04 PM
Post #7 of 39
(2136 views)
Shortcut
Registered: Oct 19, 2004
Posts: 5674
|
BTW - Yes, the direction of loading across a knot can make a difference in the load it can hold. Depends on the knot.
"A sling is either pulled or compressed." Yep - pulled while climbing, compressed to put in my pack. 
(This post was edited by bill413 on Jan 25, 2010, 4:04 PM)
|
|
|
|
|
shimanilami
Jan 25, 2010, 4:58 PM
Post #8 of 39
(2109 views)
Shortcut
Registered: Jul 24, 2006
Posts: 2043
|
johnwesely wrote: kachoong wrote: Storjon wrote: No, if all forces are in the same direction the sling is accelerating and if this acceleration is big enough air friction could possibly melt the sling and thus reduce itīs strength. A sling is either pulled or compressed. Compression loading a sling shouldnīt be a problem in a climbing situation. Regarding pulling, how many ways can you pull a sling? Think about this and the answer is obvious.. Really? Air friction? It is the new micro fracture!
Dudes. Meteors burn up all the time when they re-enter the atmosphere. If you were on the space shuttle and dropped a sling, it would probably almost certainly burn up before it reached the ground. And even if it didn't, would you still trust your life to it?
Case closed.
|
|
|
|
|
happiegrrrl
Jan 25, 2010, 5:49 PM
Post #9 of 39
(2075 views)
Shortcut
Registered: Mar 25, 2004
Posts: 4660
|
I see we're off to just another day at the University of RC.n00b....
|
|
|
|
|
bill413
Jan 25, 2010, 6:03 PM
Post #10 of 39
(2065 views)
Shortcut
Registered: Oct 19, 2004
Posts: 5674
|
shimanilami wrote: johnwesely wrote: kachoong wrote: Storjon wrote: No, if all forces are in the same direction the sling is accelerating and if this acceleration is big enough air friction could possibly melt the sling and thus reduce itīs strength. A sling is either pulled or compressed. Compression loading a sling shouldnīt be a problem in a climbing situation. Regarding pulling, how many ways can you pull a sling? Think about this and the answer is obvious.. Really? Air friction? It is the new micro fracture! Dudes. Meteors burn up all the time when they re-enter the atmosphere. If you were on the space shuttle and dropped a sling, it would probably almost certainly burn up before it reached the ground. And even if it didn't, would you still trust your life to it? Case closed.
Depends. Did it land on a rock or something soft?
|
|
|
|
|
majid_sabet
Jan 25, 2010, 6:04 PM
Post #11 of 39
(2059 views)
Shortcut
Registered: Dec 13, 2002
Posts: 8390
|
happiegrrrl wrote: I see we're off to just another day at the University of RC.n00b....
Technically, most RC Grads should die with what they learn right off the university but, miraculously, they all survive and yet, they return back to RC to teach other Jr. n00bs on how to climb.
|
|
|
|
|
dugl33
Jan 25, 2010, 6:17 PM
Post #12 of 39
(2049 views)
Shortcut
Registered: Oct 6, 2009
Posts: 740
|
scm007 wrote: Is the breaking strength the same whether or not the forces on either stand are in the same direction of pull or opposite directions?
When two teams pull on a fat rope in opposite directions, its called "Tug of War". When the teams cooperate, and pull the rope in the same direction, it's called "Dragging a Fat Rope".
Does that help?
|
|
|
|
|
scm007
Jan 25, 2010, 6:21 PM
Post #13 of 39
(2038 views)
Shortcut
Registered: Apr 10, 2007
Posts: 44
|
So............ still haven't gotten a response.
Say I have a 50 foot sling, and I only need a 10 foot sling. Can I just grab a 10 foot bight of rope, figure 8 it, and use it like I would a regular 10 foot sewn runner? The direction of the forces on the knot are pretty funky...
|
|
|
|
|
dugl33
Jan 25, 2010, 6:35 PM
Post #14 of 39
(2026 views)
Shortcut
Registered: Oct 6, 2009
Posts: 740
|
scm007 wrote: So............ still haven't gotten a response. Say I have a 50 foot sling, and I only need a 10 foot sling. Can I just grab a 10 foot bight of rope, figure 8 it, and use it like I would a regular 10 foot sewn runner? The direction of the forces on the knot are pretty funky...
No one is responding because no one understands your question. So which is it a rope or a sling?
Why not quadruple it and tie an overhand knot?
|
|
|
|
|
scm007
Jan 25, 2010, 6:39 PM
Post #15 of 39
(2019 views)
Shortcut
Registered: Apr 10, 2007
Posts: 44
|
For my purpose it is a sling, but I was wondering more generally.
Say I have a 10000 foot sewn sling (ridiculous of course) and I need a 10 foot sling. What do you do? logBase2(10000)-uple it
|
|
|
|
|
happiegrrrl
Jan 25, 2010, 6:44 PM
Post #16 of 39
(2009 views)
Shortcut
Registered: Mar 25, 2004
Posts: 4660
|
Here it is, 4 years passed since your "Does Walmart carry hand anti=perspirant" thread (link below; I was wondering why someone reprised it) and you want to make another go at being a pissant with 10 mile long sling tak?
http://www.rockclimbing.com/...d;page=unread#unread
(This post was edited by happiegrrrl on Jan 25, 2010, 7:10 PM)
|
|
|
|
|
dugl33
Jan 25, 2010, 6:48 PM
Post #17 of 39
(2005 views)
Shortcut
Registered: Oct 6, 2009
Posts: 740
|
scm007 wrote: For my purpose it is a sling, but I was wondering more generally. Say I have a 10000 foot sewn sling (ridiculous of course) and I need a 10 foot sling. What do you do? logBase2(10000)-uple it
1.) Cut a 22 foot length with your pocket knife, and tie a water knot.
2.) Tie an overhand knot in one end, travel out 10ish feet, tie an overhand knot, travel back to the carabiner, tie one more overhand knot. Repeat if you want greater redundancy.
Getting to the nature of your question, knots are weaker than sewn slings. Wierdly loaded knots can be weaker than not-wierdly loaded knots. With large safety factors in strength, though, this doesn't always matter for practical purposes. Using a figure eight the way you describe would not be the best choice.
Edit to add: You could also start the water knot 20ish feet in on the 10k' long sling, and feed the end through this. Voila, water knot with a 6 inch tail on one side, 9,978 ft on the other.
(This post was edited by dugl33 on Jan 25, 2010, 6:55 PM)
|
|
|
|
|
scm007
Jan 25, 2010, 6:55 PM
Post #18 of 39
(1986 views)
Shortcut
Registered: Apr 10, 2007
Posts: 44
|
Cool thanks for the reply, in practice what I have is ~60 foot section of 1 inch webbing that I use for top-roping when I need to sling a tree that is a ways away from the lip. However it sure would be nice if I had a way to use this section to do whatever lip extension work I needed to for a TR.
I was faced with having a 2 bolt anchor and had a lip about 10 feet down. Simply pulling the strands down and tying a figure 8 or overhand would leave me with 30 feet too much slack, so I ask what is a better system? I'm not really understanding #2 and #1 isn't practical.
What I was thinking of doing was just essentially building two 10 foot slings out of this 60 footer by just grabbing any two random 10 feet sections on here and tying a figure 8 on a bight, creating 10 foot loops. But I have never loaded a figure 8 like that so I wasn't sure. My gut says that this is safe for TR'ing but I've never seen anybody do it like that.
EDIT: Yes I could untie the water knot before each use and retie the sling to the length I need, but I was hoping there was a better way.
(This post was edited by scm007 on Jan 25, 2010, 6:57 PM)
|
|
|
|
|
dugl33
Jan 25, 2010, 7:09 PM
Post #19 of 39
(1972 views)
Shortcut
Registered: Oct 6, 2009
Posts: 740
|
scm007 wrote: Cool thanks for the reply, in practice what I have is ~60 foot section of 1 inch webbing that I use for top-roping when I need to sling a tree that is a ways away from the lip. However it sure would be nice if I had a way to use this section to do whatever lip extension work I needed to for a TR. I was faced with having a 2 bolt anchor and had a lip about 10 feet down. Simply pulling the strands down and tying a figure 8 or overhand would leave me with 30 feet too much slack, so I ask what is a better system? I'm not really understanding #2 and #1 isn't practical. What I was thinking of doing was just essentially building two 10 foot slings out of this 60 footer by just grabbing any two random 10 feet sections on here and tying a figure 8 on a bight, creating 10 foot loops. But I have never loaded a figure 8 like that so I wasn't sure. My gut says that this is safe for TR'ing but I've never seen anybody do it like that. EDIT: Yes I could untie the water knot before each use and retie the sling to the length I need, but I was hoping there was a better way.
Well, this is ok, however, use overhand knots (with nylon webbing), not figure eights. The structure of an overhand knot is similar to a water knot. With the loading you're going to get, this will be similar to an EDK on webbing. Making two independent 10' loops would ease my mind 100% regarding strength and redundancy. Adjust lengths so loads are statically equalized on the bolts. Good luck.
Edit to add, one more time: EDK style loading on figure eights, whether tied in rope or webbing, has been shown to fail at low levels of loading. Figure eights loaded this way roll indefinitely. I think knot nerds call it "capsizing". This is the reason behind the concern and the recommendation of overhands, not figure eights. Water knot, overhand knot, or double fishermans... use one of those.
(This post was edited by dugl33 on Jan 25, 2010, 7:25 PM)
|
|
|
|
|
scm007
Jan 25, 2010, 7:18 PM
Post #20 of 39
(1959 views)
Shortcut
Registered: Apr 10, 2007
Posts: 44
|
Exactly! Thanks! I was thinking of using overhands actually but then it seemed just like a EDK. Out of curiousity how many KN would you reckon that a EDK in webbing breaks at?
|
|
|
|
|
dugl33
Jan 25, 2010, 7:31 PM
Post #21 of 39
(1949 views)
Shortcut
Registered: Oct 6, 2009
Posts: 740
|
scm007 wrote: Exactly! Thanks! I was thinking of using overhands actually but then it seemed just like a EDK. Out of curiousity how many KN would you reckon that a EDK in webbing breaks at?
Try a search in "the Lab" forum on this. I think its been tested. I'd be a little nervous using this with a single loop, but would personally be ok with using it with two completely independent loops. Also, try tying the water knot a ways into the webbing a time or two. Measure out arm lengths for location. Its not too bad.
|
|
|
|
|
johnwesely
Jan 25, 2010, 7:48 PM
Post #22 of 39
(1934 views)
Shortcut
Registered: Jun 13, 2006
Posts: 5360
|
shimanilami wrote: johnwesely wrote: kachoong wrote: Storjon wrote: No, if all forces are in the same direction the sling is accelerating and if this acceleration is big enough air friction could possibly melt the sling and thus reduce itīs strength. A sling is either pulled or compressed. Compression loading a sling shouldnīt be a problem in a climbing situation. Regarding pulling, how many ways can you pull a sling? Think about this and the answer is obvious.. Really? Air friction? It is the new micro fracture! Dudes. Meteors burn up all the time when they re-enter the atmosphere. If you were on the space shuttle and dropped a sling, it would probably almost certainly burn up before it reached the ground. And even if it didn't, would you still trust your life to it? Case closed.
I will keep that in mind when commercial space flight becomes available, and I become a millionaire.
|
|
|
|
|
scm007
Jan 25, 2010, 7:53 PM
Post #23 of 39
(1926 views)
Shortcut
Registered: Apr 10, 2007
Posts: 44
|
Thanks I'll keep that it mind.
|
|
|
|
|
bigjonnyc
Jan 25, 2010, 8:42 PM
Post #24 of 39
(1900 views)
Shortcut
Registered: Dec 17, 2004
Posts: 369
|
johnwesely wrote: shimanilami wrote: johnwesely wrote: kachoong wrote: Storjon wrote: No, if all forces are in the same direction the sling is accelerating and if this acceleration is big enough air friction could possibly melt the sling and thus reduce itīs strength. A sling is either pulled or compressed. Compression loading a sling shouldnīt be a problem in a climbing situation. Regarding pulling, how many ways can you pull a sling? Think about this and the answer is obvious.. Really? Air friction? It is the new micro fracture! Dudes. Meteors burn up all the time when they re-enter the atmosphere. If you were on the space shuttle and dropped a sling, it would probably almost certainly burn up before it reached the ground. And even if it didn't, would you still trust your life to it? Case closed. I will keep that in mind when commercial space flight becomes available, and I become a millionaire.
Even then I'm pretty sure they wouldn't have windows for passengers to casually open and toss slings out of on commercial space flights.
|
|
|
|
|
johnwesely
Jan 25, 2010, 8:48 PM
Post #25 of 39
(1891 views)
Shortcut
Registered: Jun 13, 2006
Posts: 5360
|
bigjonnyc wrote: johnwesely wrote: shimanilami wrote: johnwesely wrote: kachoong wrote: Storjon wrote: No, if all forces are in the same direction the sling is accelerating and if this acceleration is big enough air friction could possibly melt the sling and thus reduce itīs strength. A sling is either pulled or compressed. Compression loading a sling shouldnīt be a problem in a climbing situation. Regarding pulling, how many ways can you pull a sling? Think about this and the answer is obvious.. Really? Air friction? It is the new micro fracture! Dudes. Meteors burn up all the time when they re-enter the atmosphere. If you were on the space shuttle and dropped a sling, it would probably almost certainly burn up before it reached the ground. And even if it didn't, would you still trust your life to it? Case closed. I will keep that in mind when commercial space flight becomes available, and I become a millionaire. Even then I'm pretty sure they wouldn't have windows for passengers to casually open and toss slings out of on commercial space flights.
Well, never mind then.
|
|
|
|
|
|
|
|
|
1
