Before reading this article, make sure you understand pulley systems and the alternative rigging techniques we’ve described previously. These are the common systems used when tensioning highlines. Many say tensioning a highline is not much different than tensioning any other slackline. But often the circumstances of hanging in a harness or sitting on the edge of a cliff make it a little more tricky and precarious. In this article we are going to review the alternative tensioning methods as applied to highline rigging as well as discuss main and backup line tensioning practices. Furthermore, we strongly advise against using ratchets on highlines, as they can fail and release under the shockloads experienced during leashfalls and catches.
Pulley systems are the most common tool for tensioning highlines. Smaller more specialized pulley combinations exist that are light and efficient for putting in your pack and taking up the crag. Most pulley systems used in park settings are heavy and bulky. Pulleys offer the advantage of being able to easily manipulate tension of the slackline. Some like it loose, some like it tight. Using a small block and tackle pulley system like the Rock Exotica Aztek pulleys (pictured below) in combination with a linegrip give you a high degree of versatility while minimizing weight and bulk in the pack. If put together correctly, the pulley system weighs about 3.5 lbs.
Highlines are commonly softpointed to streamline the derigging process. A soft release (red webbing pictured above) is wrapped a minimum of 5 times around the RamLock and rigging masterpoint. This keep you from having to put the LineGrip back on the highline when detensioning. Putting on the LineGrip and detensioning with pulleys can often prove difficult to accomplish due to the location of the rig and how far out the linegrip must extend to release the webbing from each anchor. It can be precarious to say the least. Always remember to be connected to the anchor with a safety lanyard when dangling off cliff edges. More accidents happen from scrambling around at the anchor than on the highline.
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These systems are a great way to tension highlines when you’re not trying to achieve high amounts of tension. The benefit to these systems being minimal gear and you there’s generally no limit on sag (minus obstacles). These methods are great when low tension is the perfect tension.
These systems are lighter, require less hardware and are easier to detension than using a pulley system. The Genesis rigging plate and Ramlock webbing anchor work well together for these tensioning methods. It’s worth repeating that you should not use carabiners in embedded highline systems. It doesn’t matter if they are steel or aluminum.
The Buckingham Method is an ideal method to use for rigging low tensions highlines because most highliners bring a hangover or highslide/webbing pulley and carabiner with them anyway. This means you don't have to carry an additional pulley system. Another benefit is that you do not need to reach way out and extend the LineGrip far out beyond the weblock. This is because there’s no bulky pulley system in the way and the system is really easy to reset when adding tension. The technique also creates a very low profile. The one drawback is that it does require a soft release or pulley system to let out tension when derigging because the webbing is locked in the weblock. And be careful with hand tension; webbing can and will slip through the weblock so be sure it’s tied off tight.
Mainline tension has the greatest effect on shockload transfer to the anchor and its gear. When someone takes a leashfall, energy is absorbed by the webbing but the anchors still experience a significant shockload. A big leashfall or whip close to the anchor generates the largest anchor shockloading of any condition while highlining. As ironic as it seems, some webbing actually requires a certain amount of tension to actually stretch. A short highline with no tension and semi-static webbing can result in a very violent experience. This is because the webbing is unable to stretch and absorb the energy created, so the majority of the load transfers to the anchors and body.
Selecting tension comes down to safety, then your personal preference. Additionally, there are some considerations to be aware of on short lines up to around 100ft. When determining your tension, you must be aware of the terrain, conditions and fall zones. It’s also common to put some tension on the webbing to ‘activate’ the stretch but remember it is a slackline, not a tightrope. Most highlines these days are rigged at 900 lbf standing tension or under. It should be noted that low-stretch polyester and high tech webbing should probably not be used in a highline under 150ft due to the low stretch and lack of energy absorbing capabilities. Static line catches and whips are not fun with this type of webbing and you will get scratched and cut by it.
Large amounts of tension are not necessary for the backup webbing, but you always want to be aware of the terrain conditions. If anything, large amounts of tension makes the slackline harder to walk and decreases the safety factor of the backup system. You certainly should not put as much tension on the backup as you put on the mainline. Backups can be either webbing, static rope or in some situations dyneema rope. Dynamic rope can work, but if you do experience a mainline failure you’ll be going for quite the ride due to all the stretch. Be sure to only use this as a backup if you have a huge amount of air underneath you. You can leave the backup taped to the mainline with small loops visible, those will act as wind dampeners and slow down the lines movement while you're slacklining by acting as a counterweight to your inputs. This can be done by taping the backup to the mainline at about every armspan or 2 or 3. Larger loops tend to have a greater dampening effect but can get wrapped around the mainline during falls and general line movement, which can result in a potential safety issue. Tapes should be made in a way that allows one side to stick onto the webbing and one side to slide along it. We call this style of tape, slider tapes. Allowing the mainline and backup to slide independent from each other decreases their interaction with each other.
REPEAT: You need to take into account stretch of the backup and terrain. If you were to take a ride on the backup, you want to make sure that you’re not going to hit any terrain or feature on the way down. You’d be surprised by how much stretch can take place even on a static rope when the backup is fully engaged.
Tensioning a highline is not much different than tensioning a longline besides it being a more challenging environment to rig in. Be sure to select the appropriate tensioning system for the scenario and desires. Remember that rigging at height will always take more time than on the ground. Make sure to be tied into the anchor when scrambling around in precarious places. Play around with the backup tension and see what will keep you safe and what tension you prefer. Keep in mind that it’s good practice to softpoint highlines as opposed to leave the pulleys in the system because it removes links in the “failure mode” chain. It also keeps the pulley system from getting in the way of mounting the highline.