Ok, so I'm spending a lot of time sitting since my knee is injured. As such I've been finding lots of good videos online that I feel like linking here. Here's a great one showing a pull test of a 6mm prussik cord wrapped into an 8mm static rope. It breaks at nearly 2000lbs--which makes the prussik more than strong enough for all of the common uses we have for it.
Keys to good ice screw placement:
1. Find solid ice. Chop or clear out any rotten or sunbaked ice (usually white or gray in color).
2. Find (or chop out) a flat or concave spot. Make sure it is about 8" in diameter so the screw handle turns freely around its full radius.
3. Use a negative angle. Drill the screw upwards at about 10 degrees into the ice.
4. Ensure that the screw is fully in the ice. If not (e.g. bottomed out on rock), use a shorter screw for the strongest placement.
5. Clip into the hanger. Tying off screws dramatically reduces their strength. Chop away any ice that may cause the carabiner gate to open, reducing its strength.
Nuances for glacier ice:
1. glacial ice is softer/weaker than waterfall ice due to the way it forms.
2. Using a positive angle, positioning the hanger of the screw 10 degrees away from the potential forces (up if you're leading).
3. Screws melt out really fast in the sun, consider using a v-thread for anchors since they melt out a lot slower.
There are, however, two problems with the video. The first safety issue comes from the section that details how to lower a climber while the device is in autoblocking ("Guide") mode. I'll detail a safer method below:
1. Clip the brake strand of the rope through a new carabiner attached to the "shelf" of the anchor.
2. Attach a friction hitch (autoblock, prussik, kleimheist) to the brake strand
3. Thread a skinny sling through the small hole on the ATC-Guide, as shown in the video.
4. Hold onto the brake strand.
5. Pull down on the skinny sling, releasing the device. This is easiest if the sling is clipped into your harness and you lean back, thus allowing you to have both hands free to control the brake strand.
6. Lower your partner.
The other issue I have with the video is that it doesn't address what to do when you have two climbers following the pitch at the same time (i.e. you have two ropes in the device, each going to a different climber). The easiest way to prevent dropping both of the climbers simultaneously is to tie a "catastrophe knot" in the brake strand of the climber you are not going to lower. Tie the knot as close to the device as you can, then have that climber hang on the rope. This will prevent them from being dropped when you unlock the ATC-Guide to lower the other person.
Coming Soon: the danger of using an ATC-Guide (or Reverso) on traversing pitches...
I work as a climbing guide and instructor throughout North America and am pursuing IFMGA/UIAGM certification as an international mountain guide.
Contact me at kurt.hicks@gmail.com for information about climbing instruction or guided ascents.
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