Today we are going to be taking a look at highline anchors and some general principles to follow to build a safe highline anchor that takes various failure modes into consideration and mitigates them through various means. This guide is intended to educate you on a few general principles to follow for building highline anchors in hopes that it can be used as a base knowledge for a series of articles to come. I am hoping to explore several different types of highline anchors with pros, cons, and suggestions on how to make them better using this guide as a template.
Note: This guide is not meant to be comprehensive! There are a large number of variables to consider when building highline anchors (and rigging highlines in general) and a wrong move could end with a fatal accident! Please seek professional advice or rig with someone who has a good knowledge of highline rigging before doing so on your own!
Alright, highline anchors. This is typically the most important part of setting up a highline: finding and building your anchors. The integrity of your entire setup relies on your anchors being absolutely bomb-proof on every single level. In order to build a proper highline anchor, it's important to understand the following concepts that apply in any and all situations:
Strength - Highline anchors need to be STRONG! Much stronger than anything else in your entire setup. Remember that the anchor is what you are relying on for the integrity of your entire highline! A good rule of thumb is that your highline anchor should always have a strength in the range of 100 kN (22,480 lbf), or stronger than the sum of the strength of your mainline and backup line materials. Keep this in mind when choosing objects to anchor to. Don't choose the bush with a 3" diameter trunk or the boulder that you can move by pushing on it. An ideal highline anchor will have no movement even during a leash fall. In order to achieve that, you need to have strong anchor points.
No Abrasion - Abrasion is the most dangerous thing in highlining. If all other things are considered and you forget to protect against abrasion, your anchor can fail. Highlining is an extremely dynamic sport and so your anchor points are likely going to be moving. In addition to constant movement, the anchors are always going to be under tension. Tension plus abrasion can easily cut through even the strongest materials! So, you must protect against this with padding or other means! Any spot in your highline anchor (or any part of you highline) with the potential to rub on anything needs to have some sort of abrasion protection.
Redundant - Redundancy is king in highline rigging. Never, never, NEVER rely on a single piece of gear for your safety in a highline setup. Every single component within the rig (not just the anchor) needs to have some sort of backup system. When building your highline anchor, think about what would happen if each point were to fail. What is the effect of this failure? Will it cause your entire anchor to fail? Is there something in place to catch the system? If not, you need to rethink this part of the anchor.
Don't only think about the gear when analyzing your anchor for redundancy, also think about what you are anchoring to. If using bolts in the rock, what happens if one of the bolts fails? If using trees, is the tree bomb-proof? What happens if it isn't? If wrapping boulders or using natural protection, what happens if the boulder moves or one of the pieces pulls out? Will your anchor move around or completely fail? You need to protect against this! Not every spot has 4 perfectly placed glue-in bolts or massive trees right next to the edge, sometimes you have to be creative. This is when it's especially critical to check for redundancy.
Equalization - Share the load with every anchor point! Having a single point that is loaded more than others can be dangerous, especially if it's not as strong as some of the other anchor points. Take into consideration what the strength of each anchor point is and build your anchor such that stronger anchor points receive a higher percentage of the load. Avoid building anchors where there is a huge difference between the loaded points.
Small Angles - When the angles within your highline anchor start to become larger, this means exponential forces applied to each point! For example, if you are equalizing 2 points and there is an angle of 150 degrees between the 2 points, you can have nearly 100% of the load ON EACH POINT! That means each anchor point is taking the full force (or even more)! Avoid this like the plague! Make sure all the angles in your anchor are small to ensure you don't have multiplicative forces amongst your equalized anchor points.
No Extension - Extension is the enemy! Most of the time when building a highline anchor, multiple points will be used (as per the redundancy requirement above). If something happens to one of these anchor points and proper extension-proofing has not been established, the master-point can extend out towards the other anchor, causing shockloads to the remaining anchor points. These shockloads can cause failure of the other anchor points putting you at risk for complete anchor failure. This is very bad!
To prevent this sort of thing from happening, you need to build systems into your anchor that limit how much the master-point can move if any of the equalized points fails. There are a number of ways to do this, which we will explore when analyzing various highline anchors.
When you add all these things together, you get the following acronym:
This is similar to the climbing anchor acronym of SERENE-SA, with the addition of the "No Abrasion" criteria. This is an important acronym to remember when checking your own or other peoples highline anchors. Always run through the list and be sure the anchor meets every criteria before stepping foot on to a highline. Remember, every single one of these aspects is critical in the building of a solid highline anchor.