by Anonymous_Coward » Mar 19, 2012 10:23 am
I think I can help with this one.
First of all, I am not some kind of expert canyoneer guy. I am just a caver that goes canyoneering quite a bit.
The answer is yes and no. Yes, it is standard practice to leave the rope unknotted. This is a safety consideration for rappelling into water. It avoids the dreaded "floating disconnect" which can and has been fatal, especially in whitewater. No knot also greatly increases efficiency on dry bottom rappels, especially with large groups. Pulling the rope through your rappel device (once on the ground) is faster than disconnecting for anyone, regardless of what device you use. Multiply that by 6-8 people, plus rigging, pull-down, and rope stuffing for each drop X 15 rappels + racing approaching T-storms and you start to get the idea.
However, we do not usually lower people with the method that you described seeing at the quarry. Our normal mode at the top of the drop is to first see if you can see the bottom.
If you can, you lower enough rope down to touch the bottom, (rock, sand, or water) and then run the rope back up about 3 feet to account for rope stretch. We then set a carabiner block at the anchor. If you do this right, when your feet touch bottom, the rope pulls right through your rappel device. In water, as soon as your body is in the water, the rope pulls through. If the pool has been safety checked for obstacles, then the rope can be set even higher for cannonball action, but I digress.
If you cannot see the bottom of the rappel, then someone must be lowered to set the rope length. This requires either a contingency eight block or a munter mule at the anchor. We attach the lower-ee directly to the bottom of the rope with a munter-mule hitch on their D-ring or carabiner. The brake end of this is held together against the rope by the lowered person. When you are lowered to within 5 feet of the bottom, you can pull the "rip cord" on the munter-mule, the munter starts moving, and you come right off the end of the rope with your feet on the ground or with you treading water. It is a pretty slick system when done correctly.
This all takes practice of course, and trust in your partners.
The way you saw demonstrated at the quarry we would only do if we THOUGHT we had the rope length set correctly, but then the first rappeller tells you that you were sadly mistaken. This guy would need to be lowered until the rope touches bottom, or if a carabiner (not able to lower) block was set, this guy would need to ascend back to the top. This is one reason why we always wear our up gear, even though many canyoneers out there do not.
Andy Armstrong
American Carbide Council