UKC

http://s21.postimg.org/w6it7u6vb/IMG_20150510_125355.jpg

Please look at the picture. Does anyone know how strong an inline figure of 8 is?

In reply to zimpara:

It's a flemish bend knot (aka figure 8 bend) which scores 81% strength ratio vs 79% double fisherman's ( http://www.bethandevans.com/pdf/8_strength.pdf ).

In reply to PPP:
Thanks. Found plenty on Flemish bend now.

One last thing. Once it is cranked up tight (welded after hanging on the rope.) It stays welded right?
I'd prefer this for prusiks in that case as the exit points are less cinched and more flexible compared to a DF's that holds the exit rope solid and straight an inch out of the knot (making wrapping prusik around ab line more fiddly than need be on a short loop.)

In reply to zimpara:

Just don't mix it up with a figure of 8 tied together with both strands like showed here: http://www.needlesports.com/catalogue/content.aspx?con_id=75b7be92-45dd-474...

It is especially weak knot which flips at low forces. Some sources, including the link above, says that it flips even under a body weight.

In reply to PPP:


If thats the case (im not saying it is or isn't) then why do we belay off it. Would that not the potential to put the same sort of forces on the knot?

In reply to andy.smythe:

i know everyone in the uk ties there prusik loops with a double fishermans, but i have started to use an inline overhand (rethreaded overhand). This is perfectly strong enough to prusik on but has the big advantage its much easier to get undone if you need to use the tat for another purpose

In reply to zimpara:

death on a rope. Anything less than a dbl fisherman's is just foolish :p

In reply to andy.smythe:

It seems to be more an issue while joining the ropes for an abseil rather than belaying. I honestly have no idea why is that. It must to do something with static load (abseiling) and impact (belaying). It doesn't look like there's much research done on either.

However, I never understood why people want to belay from the rope loop. I am just one of the punters, so I'd rather just post Andy Kirkpatrick's blog post about it: http://andy-kirkpatrick.com/cragmanship/view/rope_loop_belaying .

On the other hand, other side of the camp says that you'd rather belay off the rope loop: http://www.ukclimbing.com/articles/page.php?id=1129

... while the third group of people belay directly off the anchor while bringing up the second. Do what you prefer the most. It's one of the debates similar to "gates in or gates out" while racking the gear on the harness.

In reply to andy.smythe:

Not necessarily as belaying off the loop (fig8) doesn't pull the knot apart as it does when abseiling - the pull of each strand is 90 deg to the knot.

In reply to PPP:


My understanding was that you need to repeatedly load/unload the fig 8 crossways to start it rolling. If you flip it once, it forms another stable knot (assuming you have left tails) which then would need to go through repeated loading to roll again. Not a problem with a knot that's in front of your eyes, but could be when out of sight and you're bouncing around on an abseil.

In reply to higherclimbingwales:

This is what you use then? Flem

In reply to zimpara: basically the fig of eight, when you belay doesn't have two loose ends and the rolling effect doesn't occur. It's only when you have tied it for an abseil and you have two loose, unloaded ends which can flip over and over that it becomes a problem. Its the same with the overhand which when used for abseiling should be well dressed, well cinched and have nice long tails and/or a second overhand knot tied tight up behind the first to prevent and make absolutely sure it won't roll. If its done right, there is nothing wrong with an overhand. But the fig eight really does roll at quite low loads. If you decide to use a flemish bend or a ring bend for your prussicks, use a little bit of electrical tape to help prevent the knot from loosening. Nothing wrong with them, you just need to be a little more vigilent...

In reply to beardy mike:


which begs the question 'why use it?'. I can tie a dbl fishermans, load it once and pretty much know it's not going to come undone.

In reply to PPP:

I belay off the anchor, but clip my belay loop into it as well and sit so that I take the weight of the second before the anchor does. Means I don't have to escape the system, yet I can feel what's going on.

In reply to higherclimbingwales:

I was advcating using it, just suggesting the way to use it safely if you're going to use it. As someone pointed out above, they like to be able to use them as abseil tat in a pinch, which is fair enough. Once you've loaded a double fishermans, its not going anywhere, ever, so that is not an option. So I can sort of semi understand it. I'd still rather just have a cord for a chalkbag belt...

In reply to Ciro:

The figure 8 belay loop also has an added advantage in that _if_ it rolls once or twice (from absorbing a big whipper) it has absorbed a lot of energy - whereas if you had belayed the whipper straight onto your abseil loop, there's no absorption of energy, and more goes onto the anchor.

In reply to PPP:
Just don't mix it up with a figure of 8 tied together with both strands like showed here: http://www.needlesports.com/catalogue/content.aspx?con_id=75b7be92-45dd-474...

Around 1990 years ago the Figure of Eight Knot method appeared.

-probably time for a rethink then

In reply to SenzuBean:


If a fig8 rolls twice it will pull about 2ft of rope through the knot, and I don't think you would then still be tied on.

In reply to David Coley:


Are you sure?
This is a video of a fig8 rolling, and as you can see - it rolls about 10 times before even a foot of rope is taken in (no stopper knot as well, which would further decrease slippage):
vimeo.com/40767916

In reply to zimpara:


Plenty strong enough.
jk

In reply to zimpara:



I'm not sure why so many of the replies start talking about cross loading FO8 when you appear to be asking if the pictured knot or an in line FO8 are strong enough to secure the loop of a prusik. The answer is yes.

In reply to SenzuBean:




The pure fig8 doesn't seem to roll even once in the video. The fig8 with with a yosimite finish rolls twice, and fails because it rolls of the end. This is why we leave long tails when tying ropes together with an overhand when abseiling - rolling eats rope.

In reply to DubyaJamesDubya:

No idea!
I just get my answers and leave: whilst everyone else jukes it out over (belay loop vs knot loop.)

In reply to David Coley:


After looking into it - it seems I should've originally used the term slip instead of roll; I didn't know that 'roll' is synonymous with 'capsize'. Back to my original point - if the fig8 in the belay loop _slips_, it will have absorbed a lot of energy. I have never heard of properly tied belay loops slipping all the way through, but I have heard of a few complete anchor failures.

In reply to SenzuBean:


I haven't either.