Building a rappel anchor that will take the weight

The Anchor: Look before you leap

     All too often in descending accidents, failure of the rappel anchor is the main cause.  Remember, just because someone else previously used a given anchor is not an adequate reason for you to use the same anchor.  Pitons loosen, rock fractures, slings become frayed or a given anchor may have been woefully inadequate to start and someone before you was lucky- and you don't want to count on luck too often.

     When many of us started climbing in the early 80’s (and before- and since?), there was a strong ethic in the climbing community that discouraged leaving gear behind  and that only the absolute minimum equipment should be sacrificed in a descent.  It seemed strange to me then and now, that a person who would take great caution to set-up solid anchor systems on their ascent would risk it all on a sketchy rappel anchor (rappelling off of one nut or a loose block) just to save a few bucks. 

     The same rules that apply to climbing anchors should apply to rappel anchors:  Solid, Equalized, and Redundant.

                                                                                                                                                                                                 .

Solid: Un-questionable strength

     Rappel anchors need to hold significantly more than body weight. Each point of an anchor, be it one large tree or three pieces of gear needs to be individually solid. Check each component thoroughly.  Is the tree alive?  Does it move when you shake it? (bad sign) Are the wires connected to the nut? Are the pitons super rusty? The worst decision you can make while rappelling is to have blind faith in the anchor.     

An example of a 3-piece equalized rappel anchor that is redundant down to the metal ring which is rated to 20kn  (1 or 2 kn weaker than your rappelling carabiner).  All knots are an overhand follow-through.

A single-rated 9.3mm rope and a 7mm cord are tied together for a light-weight alpine rappel system (both are 60m long).  The knot is a flat overhand which binds well on the different diameter materials and there is another overhand with the cord around the rope.

     Be wary of fixed gear, test it before you dangle you life from it.  I’ve pulled out dozens of pitons with a firm outward yank, and removed countless old bolts with little more than a few tugs.  Pitons and old bolts rust with age and the freeze/thaw cycle which takes place in many environments can cause pitons to easily pull-out, sometimes in less than a few days after being placed. When in doubt, add more gear (nuts or hexes are cheapest).  Hitting pitons with a rock can give you an idea if they are solid or potentially you can knock it back in with the stone hammer. 

. 

Equalized:  Share the load equally

     Be warned: the " American Death Triangle"(ADT) is not an anchor that shares the load equally among all of it's components.  The self-equalizing (magic-x) method is best at equalizing the load, but suffers the fatal flaw of serious shock-loading potential should one piece of the system fail.  Pre-equalized (all points connecting to one master point via knots) is the most fail-safe anchor method available as it is relatively equalized without the shock-loading risks. 

The overhand follow-through is the easiest knot to connect cord or webbing to nuts, pins or bolts.  Once you've figured out where you want the knot, simply tie the first overhand, loop the tail through your anchor and retrace.  HInt-  pull in a few inches of slack when tying these knots so that when they tighten the length provides an equal load to all anchor points.

An overhand follow-through on both sides of the red cord connect it and equalize it with the rest of the anchor system.

I'm not sure that anyone has actually died from the ADT as they are as they are often between very solid bolts.   I do know that many climbers have died because their rappel anchor was not adequate for the load.

                               .

Redundant:  Don't depend on just one

     Multiple pieces of solid gear are the way to go, with each piece holding it’s equal share of the weight. The only time I rappel from one point is when it is a healthy living tree that is bigger than my fat uncle's thigh. 

                                                                                      .

Connecting the same pieces of gear together with less material (one 3' sling) using a method of tying knots to create redundancy down to the metal link.  This aluminum link is 20kn strong.  A carabiner is typically 23kn and a steel link 3/8" - 30kn.  All are sufficiently strong for rappelling. 

The top piece will have a couple of half-hitches connecting it to the sling-  like all knots and hitches it is important that they are completely tightened before use.  All of the other knots are either overhand on a bight or overhand follow-through.  Essentially the same knot tied differently.

                                               .

The Master Point: Your connection to this world

    The master point is what any anchor comes down to: make sure you are using the right materials and applying the same principles of Solid, Equalized and Redundant.  Metal links at the master point are always a better idea than relying on the nylon from cord or webbing.

     I have seen ropes of the same diameter burn through one inch webbing because they move through a rappel device at different rates. Aluminum rappel rings are the cheapest solution: remember these are hollow and unless brand new should be doubled up to assure adequate strength.  Steel links bought from a hardware store or climbing shop  (5/16” minimum) are the more modern solution for long-term anchors and their stamped strength is actually 1/3 of their full strength as they are manufactured for industrial use which has different rating guidelines - the strength should be printed on the side of the link. 

     Carabiners are another great alternative but be sure to leave a locker or tape shut the gate on the biner to keep it from opening as they are only 25-30% of their full strength when this occurs.  Of course when possible or necessary, redundancy with links or carabiners is more ideal.