How to Make a 3-Screw Anchor
Sometimes you want an extra screw for security. It could be because the ice itself is not that strong and you want another anchor point to add to the mix. It could also be that you only have shorter screws, which can sometimes leave you wanting another piece.
The process itself is quite similar to a 2-screw anchor. Place three screws in the ice, ideally about one foot away from the others. it is best to offset the screws a bit on both vertical and horizontal planes. Clip a carabiner to each screw, and clip in your anchor material. A triple-length sling or cordalette works really well with 3-screw anchors.
And then tie your figure-8 knot. Make sure to keep the cordalette's knot (the one shown in the upper left) away from the figure-8 knot:
And clip in your master 'biner (always a locker):
How to Make a V-thread and Screw Anchor
Sometimes you may want to add in a V-thread to your anchor. I use this especially in the summer on glaciers on Mt. Baker, where we toprope for hours in the hot July sun. Screws can melt out quite quickly in this case because they conduct heat. So I'll often make a V-thread to add to an anchor. Sometimes I'll even do an anchor with two V-threads, but I'll show just one V-thread and one ice screw:
To make this anchor, do a V-thread (see a following blog for how to make V-threads) and put in a screw. Again, make the screw up and to one side of the V-thread. Clip a carabiner to each piece. Clip in your anchor material (shown is a 48" runner). Tie your figure-8 knot to create a masterpoint and clip in your master locker. Voila! A similar setup can be used to backup a V-thread for rappels. Stay tuned to the blog for more info about how to do this.
--Mike Pond, instructor and guide.
5 comments:
What is the knot used to create the loop that forms the cordelette in the photos? Looks like an overhand w/ a fatter knot as the backup.
This is a double overhand flat bend, also known as a double Euro Death Knot. You essentially tie two overhands on top of each other.
Most guides use this to join the two ends of their cordelletes together.
--Jason Martin
Why not triple fisherman's?
The problem with the triple or double fisherman's is that you cannot untie the knot easily. A double overhand flat-bend allows you access to the entire cord instead of fixing it as a loop. In other words, the ability to open up the cord gives you the ability to use it like a webolette...
If you're going to fix the cord permanently as a loop, you're probably better off just purchasing a couple of triple slings. Triple slings are lighter and are more easily stowed than cordalettes.
--Jason
Regarding an untie-able cordelette: A zeppelin bend or alpine butterfly bend are easily tied and untied with gloves on, don't require back-ups, are adjustable once tied, and stronger than a flat overhand (which while fine for rappelling loads may not be the best choice in the leg of an anchor that may see a FF2 fall).
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