In an effort to help remember how to properly set anchors, many people use the acronym "SERENE".
SERENE
- S - Strong (or Solid) - The stronger the better
- E - Equalized - Anchors should be constructed so that each component of the anchor carries an equal amount of the load
- R - Redundant - Anchors should consist of multiple components in case one or more components fail
- E - Efficient - Anchors should be as simple and timely as possible without giving up any of the other SERENE qualities
- NE - No Extension - Anchors should be built so that if one or more of the components fail the remaining components won't be shock loaded
1. Two Solid Bolts Evenly Spaced: This bolted setup is one of the simplest to build and is quite common at most crags. All you need is two equal length slings and 4 carabiners. At least 2 of them should be "lockers". At the very least, be sure there is at least one locker on the master point (the point where the rope goes through).
2 - Two Solid Bolts Slightly Offset: If the bolts are slightly off-set you can add an overhand knot or a figure 8 knot into the longer sling. This should equalize the anchor point so the weight is evenly distributed on both slings.
3 - Two Solid Bolts Slightly Offset: If the offset is only minor, you can add a couple wraps on the carabiner to the longer sling. Make the wraps on the locker if you have a choice.
4 - Two old bolts & 1 new bolt: This scenario tends to occur in back country settings where the bolts have to be hand drilled. Rather than pull the two old bolts and replace them, the bolt replacer has chosen to simply add a single new bolt. You could simply clip only 2 bolts (the new one and the best looking of the old ones) but it's better to add both old bolts into the system and having them equalized. This rigging uses a single length runner on the old bolts with an overhand knot in the middle of it. In order to be redundant on the old bolts, be sure to clip into both loops so if either old bolt pulls out, there will be no "Extension". This rigging uses 4 carabiners, 1 shoulder length sling and one double length sling. Pretty efficient and most climbers have at least one double and one shoulder length sling. Take your time adjusting the knots so that everything is equalized. This setup could be slightly better by extending the left leg of the blue sling so that more of the weight is taken up by the new bolt.
5 - Two old bolts and 1 new bolt: This is the same bolt arrangement as above but rigged with a 20' cordellete instead. Note that this rigging uses one less carabiner (but you have to remember to bring a cordellete). Weight the system with body weight then make any final adjustments before you use it. Some people worry about whether they should clip the bolts or the chain or chain links attached to the bolts. The answer is that it usually doesn't matter. Most of the metal hardware you run into at the crags is stronger than the rope or sling that's attached to it. If you have any doubts, then just clip the bolts. WARNING - Sometimes rap anchors are extended with "fixed slings". Never trust fixed slings for an anchor and always clip the bolts. Better yet, bring a knife and cut the old fixed slings off and replace them with chain.
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7 - Two Solid Bolts, set way back from the edge: Sometimes you need even more length. With a 20' cordelette, you can untie it and extend it quite a distance. The bolt ends have Figure 8 Knots in them. Be sure to use 8 millimeter nylon cord since you have only 1 strand going to each bolt. At the master point, you'll need to tie a BHK, or Big Honkin' Knot. This is simply an overhand knot with one side folded back. Google "BHK Climbing Knot" and you'll find info. on how to tie these.
8 - Two Solid Bolts: This is the same bolt arrangement as before but the BHK has been moved up to bring the master point closer to the bolts. Using the BHK you can quickly move the master point further or closer to the anchor. The BHK results in an extra "leftover" loop. If it's short leave it hanging free. If it's long, you can bring it up and clip it to one of the carabiners on the bolts or tie it in an overhand knot on one of the other cords.
In terms of setups 1 - 3, I think it's important to note that those systems are only equalized if the load is in just the right direction so that both slings are equally extended. As soon as the load changes direction slighty, the entire load will be on one bolt. Obviously there will be situations in which it will be hard to build the "perfect" SEREN anchor, but if you have two slings, and barring the bolts arn't too far apart, why not clip both bolts with each sling, make two sliding x's and clip both lockers through both master point's? Now you're redundant, and equalized no matter which direction the load. I think it would also be good to mention that the systems using the cordellete need to be pulled in the direction of "expected" loading before you tie the over-hand or figure-eight to create the master point. This is especially important for trad anchors to make sure every piece is as close to equally loaded as possible.
ReplyDeleteAdam, good comments. I did not mention that the sliding X (or Magic X) is often used for setting anchors on 2 bolts. It can also be used to equalize two pieces of pro that might not be quite as strong. For example, if you have 2 old 1/4" bolts and one new 1/2" bolt you might equalize the 2 old bolts with the sliding X.
ReplyDeleteThe advantage of the sliding X is that it's quick, requires minimal gear, and self equalizes. However, there are some significant disadvantages of the sliding X.
1. It's not redundant - if the sling is cut, you loose the whole anchor.
2. Shock Loading - if one side blows, the other side gets shock loaded as the sling extends (possibly causing that side to fail). If the anchor is set far back from the edge, the extension could be enough to drop your climber onto a ledge or onto the ground.
3. Wear - the sliding X has value because it's constantly moving and equalizing. The disadvantage of movement is that it creates wear on the slings and sometime locking biners unlock themselves as they roll.
If you really like the sliding X and want to use it, add 2 slings for redundancy (as suggested by Adam) or tie "load limiting" knots in the slings to minimize shock loading if one side fails. Also, protect the slings so that any movement doesn't run the slings over sharp edges. When I get a chance, I'll add in some sliding X pics to demonstrate what Adam & I are talking about.
My preference is to simply "pre-equalize" your anchor by determining the direction of pull and tying an overhand (or Figure 8) knot in it.
As you mentioned, a sliding X with an overhand knot between the carabiner and each anchor addresses 1, 2, and 3, plus, is equalized over the two anchors.
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