How to equalize crevasse rescue anchors
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Anchors for crevasse rescue work under the same basic principles as any other type of anchor. However, when it comes to equalizing a placement that’s loaded, there are a few changes in methods that may be helpful.
If you’re building a two piece snow anchor and want to equalize / share the load between them, you can treat it pretty much like a rock anchor. Place your two pickets, deadman, buried skis, whatever you‘re using, connect the protection with a cordelette, long sling, or your rigging of choice to make a master point, and there you go.
However, in crevasse rescue, this is often not the best approach. The above method can take a lot of time, digging, and packing down of snow. This is all happening while your unfortunate partner is in the hole, and hopefully your other teammate(s) on the rope are trying to keep them from slipping down any further.
So, for crevasse rescue, the typical approach is:
Get one anchor in fairly quickly. (If the snow is reasonably dense, this can be a vertical picket.)
Transfer the load to that, ideally with one team member sitting in the snow behind it to back it up.
Then, if you think it’s needed, a second anchor can be made and equalized with the first one.
Here's the tricky part: because there's already a load on anchor #1, it can be difficult to get the length of the sling or cord from anchor #2 JUST right to have proper load equalization / sharing.
Here are a few ways to fine-tune the connection between the anchors so you can get a decent load distribution.
In these examples, I'm using what I call a “crevasse cord”. It's basically a mini cordelette made from ultra-strong cord. My preference is about 10 feet / 3.5 m of Sterling VT-X cord. It's 5.4 mm, rated to 15 kN, and has a Dyneema core with a polyester sheath.
This is carried “open”, or untied, not tied into a semi-permanent loop.
Because this cord is so strong, you can rig it “bunny ears” style, with a small overhand figure eight on a bight loop in one (or both) end(s). Rigged like this it’s still probably good for 8+ kN, which is a much higher load than you should ever experience in a crevasse rescue scenario.
The standard cordelette you might use for climbing, which is about 6 meters of 7 mm cord still works fine for crevasse rescue. But I find it heavy, bulky, and usually too long; I prefer a smaller length of the Sterling VT-X.
Method #1 & 2: Clove hitch or trucker’s hitch
Clove hitch: This is probably the easiest method and uses a knot you already know. Tie a bight knot in one end of your crevasse cord. Clip that knot to the carabiner on anchor #2. Tie a clove hitch and clip it to anchor #1. Feed cord through the clove to remove as much slack as you can in your crevasse cord.
Trucker’s hitch: The trucker’s hitch isn’t used very often in climbing, but it's a super handy knot to know for lots of other life applications. This also does a little better job than the clove hitch to actually share the load between the anchors. Just like above, tie a bight knot in one end of your crevasse cord, and clip that knot to the carabiner on anchor #2. Pass the other end of your cord through the carabiner on anchor one. Tie a trucker’s hitch to put tension on the crevasse cord.
Here's a video showing the trucker’s hitch method. It starts about 11:30.