November 2000 - Tech Tip Supplement
Important: This is not meant to replace hands-on
instruction, nor to replace the need for hands-on practice.
The pictures below illustrate a few alternate ways of equalizing
multiple anchor points, the advantages and disadvantages of
each are discussed in the actual newsletter. There are additional
ways of doing this as well, including some that are complicated
enough to be difficult to remember and easy to get wrong.
There are several ways to "equalize" multiple anchor points in a system.
The two most common ways are to use a cordelette tied off at the common
end with a figure 8 knot to create a clip-in and to use a long sling
or cordelette to loop between the tie-in point and each anchor point
(with a twist in each loop). This text note is not intended to instruct
how to do this. Books such as "Freedom of the Hills" and others should
have good illustrations, and if you've taken a basic mountaineering
class or a rock climbing class on leading and/or anchors you should
be familiar with these two methods.
The first method does not allow for "readjustment" and if the direction
of pull is off just a bit the forces will all be on one anchor. However,
there is no "extension" shock loading if the weighted anchor fails and
forces are transferred to another anchor in the system.
The second arrangement has the advantage of readjusting as the direction
of pull is changed so that forces are always spread out among multiple
anchor points. It is popular for this reason. The problem is that if
one anchor fails there will be a major self-adjustment of lengths (a
sudden extension) and the remaining anchor points will be shock loaded.
Climbers sometimes like to use this setup to avoid stressing anchor
points they don't like too much. To accept that one such point failing
will lead to shock loading on other such points is not a good idea.
The way to reduce this extension is to tie a knot in each anchor point
loop, as close as possible to the tie-in but allowing enough room for
self-adjustment within the range needed. (If using 2 anchor points there
is still full self-adjustment up to the knots. If using 3 points the
load will distribute across at least 2 anchor points. Try it out and
you'll see what I mean!)
Keep in mind that this is a technique note, not instruction on application.
Different configurations are all potentially useful and it is reasonable
to choose to apply different techniques in different situations.
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