Accident Report - Rigging Failure During a Rappel

[canyoncaver]

Double strands help move large groups thru a canyon, especially Youth Groups. If the anchor is bomber you can have two Youth rappeling at the same time. If one Youth is extremely slow several other Youth may descend the other strand while the other Youth is still on Rappel. When the group is big and the anchor can support it, it is the only way to fly.

Sorry if I wasn't clear, but yeah, I know all that. I make it a point to not canyon with large groups, especially Youth Groups. That is why none of those "advantages" really add up to much for us, as I said in my earlier post. We consider six persons to be a "large" group, for wilderness and safety reasons.

Tom was asking why folks set up contingency anchors instead of Stone knots in non-class C canyons so I responded with the reasons that we sometimes do.

We like to keep the bag at the top, for rope management and rescue reasons. Your "drop the bag and biner block it" method is messier than our current setup. But thanks anyway.

[ratagonia]

OK, I'll bite. Sometimes in class A and B canyons, you can't see the bottom of the rappel. In this situation, we often use a contingency 8 to lower the first person down in order to set rope length. Or, if we "think" we have the rope on the bottom, but aren't quite sure, we will go ahead and rig the 8 block so that the first person doesn't have to ascend back up when the rope is actually not on the ground.

Yeah, I sometimes do this, not often. Faster, more reliable to Block and Drop, then reset.

We rarely lower from the get-go, more often set up for a lower if needed.

Do you lower from the get-go? (Hard on the rope, tends to put grooves in the rock).

Tom

[ratagonia]

Sorry if I wasn't clear, but yeah, I know all that. I make it a point to not canyon with large groups, especially Youth Groups. That is why none of those "advantages" really add up to much for us, as I said in my earlier post. We consider six persons to be a "large" group, for wilderness and safety reasons.

Tom was asking why folks set up contingency anchors instead of Stone knots in non-class C canyons so I responded with the reasons that we sometimes do.

We like to keep the bag at the top, for rope management and rescue reasons. Your "drop the bag and biner block it" method is messier than our current setup. But thanks anyway.

Different strokes for different folks...

C'mon, we been playing nice - let's not get snippy!

Tom

[Mountaineer]

I'm reading through these threads and learning from the experienced folks... I've done shy of a hundred canyons now (still a beginner among giants), and have never had to lower anyone in an emergency yet (doesn't mean it will not happen). It seems that with 3-4+ people, the efficiency gained with a stone knot method outweighs the figure eight block "ready to lower" method. As long as you are proficient, confident, and safe at converting the stone to a lower method.

[canyoncaver]

Different strokes for different folks...

C'mon, we been playing nice - let's not get snippy!

Tom

Thanks for the admonishment Mr. Pot. I will try to behave myself better in the future.

-Mr. Kettle.

[ratagonia]

2) The figure 8 block's locking mechanism is squeezing a lower-tension strand between the quick link and figure 8"

Well, I suppose, if you use the NON-LOCKING FIGURE-8-BLOCK, then the only locking mechanism is that. However, why would you use that? With a simple half-twist, you can make a LOCKING FIGURE-8-BLOCK, which seems to have all the bene's of the non-locking version, plus the benefit that it locks, no matter what the cord size.

EXCEPT, as Benjamin has pointed out in a separate conversation, it is no longer a contingency anchor because it does not release!

Tom

[bjp]

EXCEPT, as Benjamin has pointed out in a separate conversation, it is no longer a contingency anchor because it does not release!

That is indeed my view of the locking modification (half twist of the second bight that captures a low-tension strand under a high-tension strand), though to be fair, I think it is contingency-releasable sometimes and secure always. In some circumstances, that may be more desirable than contingency-releasable always and secure sometimes. A different way I'm using now that I haven't seen anyone else use is to add an extra half-wrap around the stem just before feeding the second bight back through the big hole. In my limited testing, that seems to be contingency-releasable always and secure almost-always -- a slight but noticeable improvement over the non-wrap versions (both the non-locking half-twist and the no-twist for the second bight). More info here, and I hope to keep updating it:
http://ropewiki.com/index.php/Figure_8_block