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Safe knot?

Posted: Thu May 10, 2012 12:06 pm
by Justin
What is your opinion on the stance setup below (with emphasis to the blue cam being clipped into the inside of Fig of 8 knot)?

Re: Safe knot?

Posted: Thu May 10, 2012 12:20 pm
by shorti
Bad idea if you ask me. I assume you were tied in to the end going straight down on the photo. Your own weight would stop the knot from pulling apart and obviously you'd do well to pull yourself through the knot. The other end (going to your partner I assume) would have been really bad. Just use the other rope when you want to tie into two pieces. Or clove hitch, back to yourself and then clove hitch the second piece. Or extent the top piece to equalise. Or use a sling to equalise. But you know all this. Why did you do that? :?

Re: Safe knot?

Posted: Thu May 10, 2012 12:27 pm
by emile
shorti wrote:Why did you do that?
Perhaps he's tired of growing old ? :pirat: :wink:

Re: Safe knot?

Posted: Thu May 10, 2012 1:07 pm
by Justin
shorti wrote:Why did you do that?
I was setting up a safety rope for walkers and it just happened to be a convenient way to equalise the two anchors.

If this stance did take a heavy fall from a climber, I would be fearful that the biner inside the knot with mess with the integrity of the knot.
Be interesting to see what happened in a lab!?

I would not use this setup/technique for climbing.

Re: Safe knot?

Posted: Thu May 10, 2012 1:19 pm
by shorti
In the mean time I noticed you clipped both loops. So you will basically have to pull someone through the knot. The advantage is that you won't struggle to undo the knot :cyclops:

The entire reason for the backup is for in case the first anchor fails. If the top anchor fails you are now basically just pulling the knot apart. In other words the knot will be undone when the top anchor fails, so it is not a backup at all. Think about it, how do you untie a fig8. You pull exactly where you clipped the biner of the second anchor. So unless something stops the loop from pulling through the knot, I'd say you're a gonner.

Re: Safe knot?

Posted: Thu May 10, 2012 1:36 pm
by Justin
Agree 100%

Re: Safe knot?

Posted: Thu May 10, 2012 1:45 pm
by Hann
shorti wrote:If the top anchor fails you are now basically just pulling the knot apart
Not being a member of Mensa I may miss something, but.....

Looking at the knot and biner placement I'm not convinced that it would pull apart.

Weigh the rope in your minds-eye, and see what moves.

Re: Safe knot?

Posted: Thu May 10, 2012 1:56 pm
by Justin
Perhaps but it would change the shape of the knot (which would not be a good thing). Maybe I'll set this up and see what happens when the top anchor is pulled out.

Again and for the record I have never seen this technique recommended for rock climbing - so don't do it.

The image below is the only reference I could find for clipping into the inside of the fig of 8 (used by cavers):
Image
In this photo, a carabiner has been inserted through the figure eight knot and into the bight. It is there to make the knot easier to untie once you retrieve your rope.
Image via: canyoneering.net

Re: Safe knot?

Posted: Thu May 10, 2012 2:08 pm
by Justin
An Equalizing Figure of 8 Knot would do the job.

Re: Safe knot?

Posted: Thu May 10, 2012 2:13 pm
by Rocky
Personally I think in that situation a double loop figure 8 would have been a good option. The double loop can be adjusted to allow for a longer and shorter loop, this can also fairly easily be equalised. :)

Re: Safe knot?

Posted: Thu May 10, 2012 2:34 pm
by shorti
Oi Justin, easy on the birthday cake lad, that thing looks even worse to me :mrgreen: If the one end fails the loop will pull through the knot and simply fall off the second anchor. If the other anchor fails you don't have a knot any more. Maybe I'm not MENSA material either, but Rocky's knot is good.

Re: Safe knot?

Posted: Thu May 10, 2012 2:56 pm
by Justin
Nomnomomnom (down goes the cake) Yes, for bolted belays and still not good if you have a failure :oops:
Rocky's solution will probably be best.

Re: Safe knot?

Posted: Thu May 10, 2012 3:21 pm
by thomsonza
I'm definitely with the double loop figure eight...

http://www.animatedknots.com/fig8loopdouble/index.php

The equalizing figure 8 looks scary :shock: ... am I missing something? If either side fails you are untied. Which effectively doubles your chances?!

Re: Safe knot?

Posted: Thu May 10, 2012 3:48 pm
by DiabolicDassie
I would rather use a double-loop figure 8 there, solves equilising problem. Other option is a figure 8 on first anchor and a alpine butterfly on second,which you can also adjust easily to equilise.

Re: Safe knot?

Posted: Thu May 10, 2012 6:18 pm
by Nic Le Maitre
@Justin: Don't really like your equalizing 8, looks like it only works if both points are intact. If the point on the left goes you aren't tied in at all and if the right hand point goes then you may or may not be tied in, depends what is down rope from the knot.

Double loop 8 or BFK would be better options

Re: Safe knot?

Posted: Fri May 11, 2012 10:57 am
by Chris F
I'd whack a bolt in :wink:

Re: Safe knot?

Posted: Fri May 11, 2012 11:00 am
by Justin
Maybe two or three :mrgreen:

Re: Safe knot?

Posted: Fri May 11, 2012 3:41 pm
by fivesix
Not the Safest... as mentioned before.

Real quick though if you had of tied a single overhand to one piece then left say 2m between the pieces, then tied a single overhand to the second piece, you could have each climber tied in directly to each piece. Then with the 2m that you left in the middle, tie an equalized figure 8. Now you have each climber tied in individually(as a back up) and you can connect them to the equalized 8 in the middle as your main point of anchoring.
In this case you would use maybe 2m more rope than what is pictured, but it would be safer. You could climb on the equalized 8 if you wanted to.
The overhands could be upgraded to figure 8s if you want more robust knots, but they take up more rope and if your not climbing on them overhands are weighted well beyond your body weight. Or you could use clove hitches to save rope.

This all depends on your situation. Use all the knowledge you have to make the best outcome for you and your partner under your circumstances :mrgreen: