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September 27, 2008

Mid-Clip Snow Anchor

27 September, 2008

The Vertical Mid-Clip Snow Picket .
This snow anchor was developed in New Zealand after an accident in 2003 which claimed the lives of several experienced mountain guides on Mt. Tasman. The investigating coroner asked the NZ Mountain Guides Association and the NZ Mountain Safety Council to look into whether industry standard snow anchors currently in use were adequate. The fact that the Tasman accident claimed the lives of two of the most highly regarded mountain guides in NZ suggested that they were not. After a great deal of research and testing, the kiwis came up with the vertical mid-clip picket. This anchor is now the standard in New Zealand, having gained favor over North American type anchors like the top-clip picket and t-slot.
The mid-clip is basically a vertical deadman. Imagine a snowstake with a clip-in cable swaged to the middle. The piece is placed 30 degrees back from perpendicular to the surface and a thin slot cut for the cable. The cable makes a 90 degree angle with the picket and should emerge from the snow just at its end.
When placed properly, the mid-clip is the strongest and fastest snow anchor for a maritime snowpack like the Cascades or the Southern Alps. I was skeptical at first, but ultimately blown away by its ease of placement and strength. This is the snow anchor currently carried by the Joint US/NZ Antarctic SAR Team.

Testing data from the Search and Rescue Institute of New Zealand (www.sarinz.co.nz) in strong snow (best case scenario):

Mid-clip picket (placed 30 degrees back from perpendicular): 10kn
T-slot (deadman): 7kn
Top clip picket: 5kn
Mid clip (placed at 45 degrees): 4.5kn

Note: 1kn approximates 220lbs of force.

To fully geek-out on the mid clip, follow this link to Don Bogie’s testing report: http://alpineclub.org.nz/documents/activities/instruction/Snow%20Anchor%20Report.pdf

Conclusion: In summer cascades-style snow the mid-clip is about as fast to place as a top clip picket while being stronger than the more time consuming t-slot anchor. They are stronger than they look, but require care in angle of placement.

Available at: http://www.aspiring.co.nz/ (I have no affiliation with Aspiring Enterprises, Inc.)

Be on the lookout for an SMC version available in the US soon??

1 comment:

Deling Ren said...

The report has been moved to https://alpineclub.org.nz/system/files/Snow_Anchor_Report_2005.pdf