Review: Slackers 90' Zipline Eagle Series w/ Spring Brake Kit

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To pass time during the COVID-19 crisis, one of our kids came up with the genius idea of setting up a zipline in the backyard of our vacation home in Murphys, CA. We have several large trees as well as a 100 ft. creek bed, making it the perfect spot to set one up. I immediately started researching ziplines and after reading numerous online reviews, I settled on the Slackers 90' Zipline Eagle Series w/ Spring Brake Kit. I chose Slackers because it appeared to be the most established business for online zipline kits. While there were several cheaper brands on Amazon, they didn’t have as many reviews and I felt it was worth paying a little extra for what appeared to be better quality and the potential for better customer service should I need it.

Finding the Right Kit

At the time of this writing, Slackers sells kits on Amazon that are 100 ft. long, 90 ft. long, 70 ft. long, and 40 ft. long. The 100 ft. “Night Riderz” Kit comes with a light-up seat that would be pretty cool if you plan on doing any night-time riding. We don’t plan on riding at night and didn’t need 100 ft., so we saved ourselves $20 and went with the 90 ft. kit. To decide what length kit you need, you basically just measure the distance between two trees that will form the path of your zipline course. Our kit came with a few extra feet of cable to take into account wrapping the line around the trees. In other words, if the distance between your two trees is exactly 90 ft., you should be fine with a 90 ft. kit given the extra few feet of cable. If there’s any doubt, go with the longer kit as you can always wind up the extra cable.

Whether you go with Slackers or another brand, one thing you’ll want to make sure your kit comes with is a spring brake. Some of the reviews on the Slackers kits noted that older models came with a different braking mechanism. Every review says to avoid those, as spring brakes are much safer. I can’t disagree, as the spring brake in our kit does a great job of stopping riders at the end of the zipline. A spring brake is basically a long coil spring that is installed at the end of the zipline. As shown below, as the trolley (the handlebar unit your kid holds on to) approaches the end of the zipline, the spring will compress and slow down the trolley.

Installation

In our setup, we found two solid trees on opposite ends of the creek bed. The ground on one side is slightly higher, creating a nice slope for our course. Slackers recommends a 6% maximum slope when using a spring brake, which means that the line drops a maximum 6 feet per 100 feet. We couldn’t think of a way to precisely measure slope without some sort of sophisticated tool, so we just eyeballed it. It took us three tries to find the right slope. The first try wasn’t sloped enough and the kids wanted to go faster. The second try was too fast, which as you can imagine, is not safe. The third try was Goldilocks—just right. Adjusting the slope was just a matter of wrapping the zipline higher or lower around the trees on either end of your course. You don’t want the zipline too low to the ground or the rider’s feet will drag.

BEWARE: the instructions manual is garbage. It gives you a general sense of what you need to accomplish but fails to provide clear instructions. For example, the manual tells you to refer to Figure 2 on how to thread the cable through the trolley, but… there is no Figure 2. Luckily, threading the cable through the trolley is pretty straightforward. Other steps weren’t as straightforward however. Below is a list of things you’ll want to know before you begin your installation.

• Install the spring brake before you tie off the zipline. The instructions tell you to tie off the zipline and complete installation. Then, in an afterthought, the instructions say that if your kit came with a spring brake, you should have installed it before you tied off the zipline. Nice. Luckily, I had read the instructions all the way through and noticed this before beginning the installation.
• The instructions say nothing about installing the turnbuckle. The turnbuckle is pictured below and you can read about turnbuckles in general on Wikipedia. The turnbuckle in the Slackers kit allows you to tighten the zipline after installation by about four inches or so to make up for slack. The problem is, the instructions tell you to tie the end of the zipline to the second tree without mentioning anything about the turnbuckle. After much contemplation, I decided that the turnbuckle should be installed as follows (no guarantees this is right, but it works for us). The kit comes with a short cable with two loops at the end. I wrapped this short cable around the tree at the end of the course and connected both loops to the bolt at the end of the turnbuckle. Then I attached the zipline cable to the other end of the turnbuckle using three supplied U-bolts.

• The instructions claim that two adults can tighten the cable using gloves and manpower. I’m a pretty strong guy (my wife might disagree) and I commissioned the help of my father-in-law, who is probably stronger than I am (don’t tell him I said that). We pulled as hard as we could and couldn’t tighten the cable anywhere close to what we wanted. I could see a situation where your starting point is very high off the ground (perhaps you have a treehouse or have constructed some other raised platform) and having slack would be a good thing. But that wasn’t us. We wanted a tight zipline. Luckily, my father-in-law (a jack of all trades) had a ratcheting cable power puller (also known as a “come along”). You can buy one from Amazon for 25 bucks. After attaching the end of the zipline to the turnbuckle, create a small loop at the end of the zipline with one of the supplied U-bolts (our kit came with three extra) and connect the loop to one end of the power puller. Connect the other end of the power puller to a nearby tree using another piece of cable or rope. You can also use a cable grip attached to the zipline itself, which is what we did—yes my father-in-law had one—but cable grips are expensive. Once both ends of the power puller are secure, ratchet away until tight and then clamp the zipline down using three of the supplied U-bolts. The instructions say to space the U-bolts three inches apart.

  

  I read in some online reviews that people had success tightening their ziplines by using a winch on a truck. Others were able to tighten their ziplines using a ride-on lawnmower or ATV. I would have loved to try these methods but couldn’t get any of these vehicles into the creek bed. If you’re installing in open space, these methods might work.

At the end of the day, installation wasn’t that bad… if you have a cable power puller or some other way of tightening the zipline. Tightening the zipline was the hardest part and took up the most time. As mentioned above, we installed our line three times to find the right slope. The first time it took a couple of hours, including planning time. The third time, which involved undoing, repositioning, and tightening the zipline with our power puller, we were done within half an hour.

Overall Impressions

At the time of purchase, I was hesitant to drop $180. And when I got the kit, I wondered whether I should return it and buy all the pieces at my local hardware store to save some money. I decided not to for convenience; the savings wasn’t worth the hassle and the trolley and spring brake would have needed to be ordered online. At the end of the day, the kids LOVE this thing and it’s been a huge hit during the COVID-19 crisis. I would buy again. As long as you’re a little handy, installation should be OK. It’s a little disappointing Slackers didn’t put more thought into the instructions manual considering how expensive the kit is. Nonetheless, block out the better part of a day, take your time, follow the words of wisdom above, and you should be fine.