Clove hitches on traverse lines

[mikem]

What shape of karabiners were you using?

Mike

 

[damian]

Also FYI karabiners have a breaking load stamped on them eg. 24kn <> this means the krab will break at 24kn on its major axis. A "working load" is not given on karabiners but is stamped on maillons eg. 20kn <> this means the maillon can take a force of up to 20k "comfortably".

Hrock's already said this, but just to clarify: the Safe Working Load of both krabs AND maillons is 1/5 of their rated breaking load. That means standard krabs and 7mm maillons are both around 6Kn (but I'm not sure that is very relevant to this discussion anyway to be honest).

Personally, I find the krab twisting argument pretty compelling and a good reason to stick to looser knots like butterflies. I also think teaching people to sometimes use clove hitches, will lead to an increased tendency for people to rig directly from bolt to bolt regardless of the bolt's position in relation to the rest of the traverse line, rather than rigging a "line of best fit" by lengthening some butterflies on the travers line. That way, traverse lines are much more likely to be rigged in zig-zags up and down, with increased forces should one of the upper bolts pop out. Perhaps more concerningly still, though, this willl make it harder for following cavers to move along an aid traverse, and therefore, make it more likely that human error will occur ... in my view usually more of a problem than equipment failure these days.

 

[paull]

hms , oval & d-gate , same result on all 3

the only way to stop it would be to put one krab through the p-hangers and then put anther krab through that krab, that way it would not put the hanger under sideways strain

 

[hrock]

if you use spoon hangers for the traverse then there is no twisting action on the krab as it is already originated with its spine to the wall. like i said every thing has it place asses the situation and use what is best.

 

[Bob Mehew]

Also FYI karabiners have a breaking load stamped on them eg. 24kn <> this means the krab will break at 24kn on its major axis. A "working load" is not given on karabiners but is stamped on maillons eg. 20kn <> this means the maillon can take a force of up to 20k "comfortably".

Hrock's already said this, but just to clarify: the Safe Working Load of both krabs AND maillons is 1/5 of their rated breaking load. That means standard krabs and 7mm maillons are both around 6Kn (but I'm not sure that is very relevant to this discussion anyway to be honest).

I am a bit suspicious of the rule of thumb of a factor of five, but the multiplier value is around there.  For what it is worth, I see ropes break at between 10 and 18kN, so I don't see the crab breaking before the rope unless it has a serious defect.  But could one see the clove hitch slip around onto the gate area?  Or is that a really stupid thought?

 

[damian]

But could one see the clove hitch slip around onto the gate area?  Or is that a really stupid thought?

I think it's much less likely to move than a knot with a loose loop, like a butterfly. That's another (small) reason why I prefer rigging with maillons.

 

[Bob Mehew]

But could one see the clove hitch slip around onto the gate area?  Or is that a really stupid thought?

I think it's much less likely to move than a knot with a loose loop, like a butterfly. That's another (small) reason why I prefer rigging with maillons.

My thought was that if the clove hitch formed on the gate (is there enough room to do so without overlapping?) and then a load was placed on the rope from the critical direction, the gate could open assuming it was not screw gated.  But I accept I am stretching things a bit.  I accept the point about maillons.

 

[damian]

Hrock's already said this, but just to clarify: the Safe Working Load of both krabs AND maillons is 1/5 of their rated breaking load. That means standard krabs and 7mm maillons are both around 6Kn (but I'm not sure that is very relevant to this discussion anyway to be honest).

Oops ... my maths! That should read 5Kn of course