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womble
Jan 3, 2003, 5:29 PM
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As far as I know:
1) a properly tied figure 8 (including tail length) does not slip
2) it is incredibly easy to tell when the 8 has been mistied by looking at it
Given these two things, is there any compelling reason for backing them up? I only back them up when I have too much excess tail, to get it out of the way but some climbers insist on them. Is there any _good_ reason for this- ie documented instances of an 8 failing?
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data118
Jan 3, 2003, 5:37 PM
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Backup up everything!
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mountainmonkey
Jan 3, 2003, 5:41 PM
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the backup is good for two reasons:
1) It makes sure you have enough tail that won't slide into the knot. The knot does slip until it is set; you have to have enough tail to make sure it doesn't slip into the knot. This is why you have to keep a neat knot and have it firmly set.
2) It prevents the knot from loosening while climbing (prevents situation above)
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mattiem
Jan 3, 2003, 6:14 PM
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As discussed in this thread http://rockclimbing.com/forums/viewtopic.php?topic=15646&forum=23 the backup knot on a figure 8 is important, VERY important.
to quote the most relavent part
"Fig 8 (with backup knot ) Results: loads up and stretches. At 1500 lbs, the
knot inverts, and the load drops to about 1000 lbs. Reloads slowly, but it
creeps along the free ends at a load of about 1000 lbs until it hits the
backup knot. Then it loads fairly evenly to 4509 lbs where one side of the
sheath breaks. Max load was 4509 lbs."
So the knot under a high constant load slips and would have failed at about 1000 pounds instead of 4509 thats a 3509 pound strength difference. So tie the backup knot and stop being lazy.
matt
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saagax
Jan 3, 2003, 6:23 PM
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I usually backup figure 8 knot just to get rid of the tail, but anyway I never tight the knot, because I've read that if it's tight the rope lose resistence, therway the knot will absobrb some energy while it tights.
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hyhuu
Jan 3, 2003, 6:34 PM
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Wrong application and interpretation of the test, but right message: always be safe!
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mountainmonkey
Jan 3, 2003, 6:36 PM
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mattiem you should have looked carefully on that thread on what is being discussed in that quote or else you will missquote what was actually said. Look at karlbaba's post.
The test was conducted to test the loop strenght, not the strenght of the knot for normal climbing circumstances. The purpose of the test was to see if the knot was stong enough for using the loop of the knot as a belay loop.
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flynnypek
Jan 3, 2003, 6:46 PM
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You are right... only with the 8 knot is good enough... but then a question comes to me...
We are supposed to use the rope just as a back-up. It is not to inteded to be used for rock climbing, otherwise we would be doing artificial climbing... so we might as well stop using the rope...
See my point?
Seriously, all the gear we use is just for our safety. One extra knot on the rope for safety when possible won't hurt. Don't you agree?
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rideandclimbkid
Jan 3, 2003, 7:17 PM
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haha yeah...i think it only takes maybe 5 or 6 seconds to tie a safety and tighten it...i spend more time hangdoggin on the first hold of a .10 than tieing[sp?] a safety.
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flynnypek
Jan 3, 2003, 8:16 PM
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Rideandclimbkid:
... only if you are that anxious and your life does not worth 5 or 6 more seconds before rock-climbing.
If those 5 or 6 seconds make the difference between having a nice experience or a broken-leg (at least) my choice would be use a safety knot.
If you are in a hurry to climb and that time makes a difference to you, then go to the gym instead, drive faster, wake-up earlier, don't have breakfast or don't brush your teeth before going anywhere.
Don't get me wrong but I think safety should be the most important thing to take into account, specially in our sport. I don't think some extra time to be secure would make a difference.
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womble
Jan 4, 2003, 3:31 PM
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Thanks to everyone for their comments, especially the link and references to the previous thread. There is some interesting stuff there which I'll have to mull over.
Yes, I realise that backing up an 8 is very quick and easy. I was trying to get away from the off-the-cuff 'back up everything' mantras and figure out what the actual basis for backing up this knot is.
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wv5ten
Jan 4, 2003, 5:10 PM
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the basis is the same basis for the "back everything up" mantra.
SAFETY
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number7
Jan 4, 2003, 5:25 PM
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Yes, but how many times does the knot get in the way while on lead? I know I'm not the only one with this problem.
And why is it that most pro climbers (when pictured) don't have back-ups?
I'm not disclaiming the safety factor. In fact, I tie back-ups myself. I'm just wondering if we are being over-paranoid gumbies?
M
[ This Message was edited by: number7 on 2003-01-04 09:33 ]
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eshi-1
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Jan 4, 2003, 8:44 PM
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Figure 8.
When TIED CORRECTLY and have a long enough tail (min 4 fingers) DOES NOT NEED A BACKUP.
There was never an event of tails slippinng or knot getting loose with figure 8's that where tied correctly.
By the nature of a figure 8 knot, it can not happen if you tied it well - No crossings (knot well dressed) / Long enough tail / tightening of the knot.
AND:
Even if by some kind of miracle or bad spell the tail slipped back through the knot - You still have a well known and used safe knot : An in-line figure of 8.
Check this link out.
http://www.iland.net/~jbritton/inlinefigure8loop.htm
Safety and backup are very important to all, but you have to put the line somwhere.
You also have to know your tools and what they are capable of. For that meter - A Bowline must have a backup, A Figure 8 don't.
B U T :
If what gives you personaly a safer feeling and a happier climbing experience - by all means - backup as much as you feel necessery.
Hope that helps,
Esh
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womble
Jan 5, 2003, 2:38 AM
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Thanks Esh, I just had a look at the in-line figure 8- note that if the tail slips through one further segment of the knot, the whole thing comes loose, so the tail length would be a critical part of a correctly tied 8.
________
"the basis is the same basis for the "back everything up" mantra.
SAFETY"
________
I'm sorry, but this is the kind of answer I am trying to get _away_ from. 'Back up everything' literally means that we would always climb on half or twin ropes and abseil with two screwgates holding our ATCs. Also if safety is the ulimate goal of climbing, we would not be climbing at all as there are risks which simply cannot be eliminated (eg large chunks of falling rock). For me, an important aspect of climbing safety is to question why things are done a certain way. I think this thread has finally laid to rest a question that's been niggling me for quite some time now. Thanks everyone!
I agree completely with Esh- if it makes a climber feel safer, then fine. I admit to not using a bow-line when I'm climbing at my limit even though I _know_ it's safe as I'm simply less used to it.
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scubaboy26
Jan 5, 2003, 4:35 AM
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try a prussik.
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rprp
Jan 5, 2003, 4:54 AM
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Instead of tieing the tail around the rope, I poke the tail back down through the knot. This does three things. First, it gets it out of the way. Second, it solves the above problem of tail getting sucked back through a loose knot and failing. And third, it makes the knot easier to untie after a fall. You pull the tail out of the knot and that gives you some slack inside the knot to use to untie it. Most of my friends who do not use a bowline use a figure eight this way.
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