Zipline Site Selection and Take Measurements for a Zip Line Project
Zip Line Site Selection
Selecting a location for your zip line is typically the first step in the planning process.
The four most important factors to consider are 1) What anchors are available, 2) How riders will get on and off the ride, 3) The elevation path, or profile, the zip line will take during the ride, and 4) What hazards along the pathway may need to be removed or accounted for during installation.
Let’s jump into each of these in more detail.
Anchor Points - A sturdy anchor point will be needed at each end of the zip line, with a clear path between them. If suitable trees are unavailable or not ideally positioned, installing posts or creating a custom structure is an alternative.
For more information on assessing the suitability of anchors, refer to our instruction manual on Anchor Selection of all versions of ziplines. The short version is that you’re looking for a live tree at least 12” in diameter at the attachment point, or a post/structure capable of significant horizontal loading.
A typical backyard zip line can load its anchors with anywhere from 800 lbs of tension on the low end to 3,000 lbs on the high end.
- Launch and Landing Locations Before beginning the installation process, identify suitable starting and ending points. The terrain often dictates these locations and can influence the overall setup of the zip line. In some situations, the dismount location is at the end of the zip line, not necessarily at the cable's lowest point. Depending on the layout, a platform might be necessary for easy access at one or both ends of the zip line. Check out our instruvtions on Zip Line Types to see a few of the options available.
- Zip Line Profile The profile of a zip line is defined by its slope and sag. The slope, or grade, should generally fall between 3 to 6% over the zip line's length, promoting a gradual descent. The sag of the cable should be a minimum of 2% of the zip line's total length, to prevent over-tensioning. For a more in-depth understanding check out our Zip Line Slope and Sag article.
- Clearance Clearance for a zip line refers to the area clear of obstructions below and on either side of the zip line. There should be a minimum of 7 feet of clearance below and 5 feet on either side of the zip line cable (when loaded) to avoid potential hazards, including large rocks, logs, branches, and sharp objects.
In all situations, safety riding gear is crucial wherever a fall could lead to injury, regardless of the height or terrain of the zip line.
The site selection process should always be conducted by an adult who has thoroughly reviewed and understood all instructional material.
Now you’ve evaluated your site and have a plan for your zip line, it’s time to pick out your gear.
Next Topic：What are the tools and methods for taking measurements for my zip line?
In planning out your zip line installation, you will need to take a few measurements in order to determine how much cable you will need and where the anchor points will be.
Here are a couple tools and methods that might save you some time: Tape Measures: A standard tape measure is great for measuring vertical distances, and can be indexed over a long distance to determine the total length of your zip line.
Most hardware stores also carry extra long tape measures up to 300’, as well as measuring wheels that can be rolled along the ground to get an approximate distance.
Pacing: Use a tape measure to figure out the length of your pace. For example, if 10 steps gets you a distance of 27’, then each of your steps is about 2.7’. You can then pace out your zip line run, multiplying your steps by 2.7 to get the approximate total length of the run.
Sight Levels: Sight levels are used to establish a reference point at both ends of your zip line that are at the same elevation.
For detailed instructions, check out our video guide on Using a Sight Level. A standard construction level can also be used, simply by looking along the edge of the level from one end of the span and finding a visual reference point on the opposite end at the same height.
If you really want to get fancy making your own sight level, attach a scope to a construction level and use the crosshairs to pinpoint the reference.
Google Earth, GPS devices, or GPS apps on a smartphone can also be used to approximate the distances and elevation changes.
GPS will typically give you a sea level reading at each end, subtracting the higher elevation from the lower will give you the elevation change over your zip line span.
Watch our Google Earth Video Guide for more information.
Keep in mind that all measurements and calculations are for planning purposes, and should only be used as a starting point during the installation process. Every zip line must be tested and adjusted as needed to ensure safe operation before anyone is allowed on the ride.
Understanding Zip Line Slope and Sag
Whether you're a DIY enthusiast looking to install your own zip line or a professional in the recreational industry, understanding zip line slope and sag requirements is crucial for safety and effective operation. These two components determine the profile your zip line needs to follow to ensure an exciting, yet safe, ride from start to finish.
Disclaimer: The content provided in this article is designed for informational purposes only and is intended for use in backyard zip line installations under 500 feet in length. While we have made an effort to provide accurate information, some of the concepts have been approximated for the sake of simplicity and understanding. This guide does not replace the expertise of an engineer or an industry professional. If you are planning to install a zip line, it is strongly recommended to consult with such a professional to verify your plans and ensure the safety and integrity of your installation. Always remember, safety should always be your primary consideration in any recreational activity.
Defining Zip Line Slope
The slope of a zip line refers to the amount of drop the cable has from the upper anchor to the lower anchor. Ideally, the slope should be between 3% and 6% - this means that for every 100 feet of horizontal distance, the cable should drop 3 to 6 feet in elevation. For an in-depth review of how to calculate your anchor heights.
When the slope is at 3% or less, riders are likely to lose momentum before reaching the end of the zip line, an effect we sometimes refer to as a "gravity brake". If the slope is closer to 6%, riders are likely to maintain high speeds all the way to the end, necessitating some form of Braking System.
Zip Line Sag Explained
The sag of a zip line (a measurement of how tight the cable is), refers to how much the cable dips when bearing its maximum intended load. A good rule of thumb is to aim for a sag of 2% or more of the total zip line length. For instance, a 100-foot zip line should sag at least 2 feet at its lowest point when loaded with the maximum intended weight.
To check the sag, measure the cable's height at the lowest point without any load, and again with the maximum intended load. If the difference between these two heights is less than 2% of the zip line's length, the cable is too tight and you risk loading your hardware beyond the recommended limits.
Importance of Clearance and Elevation Change
Remember to maintain at least 7 feet clearance over the entire zip line avenue when supporting the heaviest riders. This ensures safety for riders and protects the integrity of your zip line.
Moreover, consider any elevation change from the starting point to the ending point. Using tools such as a site level or GPS, this measurement will need to be accounted for when calculating anchor heights.
Helpful Hint for Installation
When choosing a location for your zip line, finding a landscape with a natural slope of 3% to 6% will make installation much easier. Also, if you plan to build launch or landing platforms, construct them approximately 5 to 6 feet lower than where the cable is anchored. Ideally, install the zip line and test it before building the platforms. It’s much easier to make adjustments to the zip line cable than to your platform.
A Final Word of Caution
Before letting anyone ride, always perform a weight and speed test. There are many factors that impact a rider’s speed, and these guidelines should be thought of as a starting point for planning purposes, not as a guarantee for safe performance. The maximum allowable slope without a professionally engineered braking system is 3%. Any slope over this and up to 6% should never be attempted without appropriate braking measures. A high-speed collision with the endpoint can cause serious injury or even be fatal.
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