Extreme sports are interesting and exciting because they consist of doing dangerous activities. However, because they are sports activities, they need to provide enough sense of danger to satisfy our need for adrenaline but also be completely safe to prevent any serious injury or death.
Bungee jumping is one the most fun extreme sports you can do, and it is becoming more and more popular over the years. And it is not reserved for adrenaline junkies either. But, how can we know it is completely 100% safe? Well, it mostly depends on bungee jumping cords and what they’re made from.
Bungee jumping cords are supposed to protect us from hitting the ground so it’s completely normal we want them to be as tough as possible. Nothing spells tough like the material that literally stops bullets – kevlar. However, bungee jumping cords are not made from kevlar, and there are a couple of reasons why.
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Properties of Kevlar
Since bungee jumping cords take on a lot of stress in their lifespan, it is no wonder most people believe that they’re made from something as tough as Kevlar. However, bungee lines and kevlar have two completely different ways of achieving the same thing – stopping the momentum.
While kevlar can withstand a lot of pressure and stress, it does so with its toughness, heat resistance, but mostly its rigidity. Apart from its small weight, it is the unyielding nature of kevlar that makes it so resistant to every damage, be it fire, slashing, or impact.
It was designed to stop momentum as soon as it hits the material, which is why kevlar has been used in the production of body armor, cut-resistant materials, firefighting apparel, and race car tires.
Even though it has a lot of applications in modern society and industry, kevlar is not used for the production of bungee cords.
What Are Bungee Jumping Cords Made From?
Bungee cords are made of natural or synthetic elastic materials with an outer cover.
The materials that will be used can vary depending on the weight the cord is designed to withstand. Naturally, the more weight it is supposed to carry, the more inner strands of elastic material there will be.
The inner part is made from natural or synthetic rubber. For some time, shock cords were made from latex, but the material proved to be too susceptible to weather damage to be considered reliable for the manufacture of bungee jumping cords.
The outer layer is made from nylon or cotton and serves a double purpose – to provide additional support and protect the elastic strands. Apart from these, the outer layer is used to customize the appearance of the cord, giving it a customizable look.
Additionally, some companies use color-coding to denote the year and month of manufacture of their cords, which should let everyone know when it was made and for how long it has been used.
Why Aren’t Bungee Jumping Cords Made of Kevlar?
While also having the purpose to stop the momentum, bungee jumping cords do it in a way that’s very different from kevlar.
Kevlar has no natural elasticity and doesn’t stretch even a little bit. This means that while kevlar could stop your fall when jumping off the platform, it will not allow you to walk away from the jump.
Namely, the point is not to just stop the downward movement instantly but to slowly bring it to a halt.
Do you know how, when you’re on the bus or in a car and your body continues to move even after the vehicle stops? Now, with bungee jumping, the force and the speed are much greater and there are no seat belts to slow you down.
By stopping your fall instantly, all the water in your body would transfer the energy and all the liquid in your body, as well as your internal organs, would continue the downward momentum following Newton’s First Law of Motion, and you would not have a good time.
That’s why all shock cords are made from materials that have:
- Good elongation rate
- Exceptional tensile strength
- Resilience
- Flawless design
- Great connectors
Bungee Cord’s Elongation Rate
This represents the amount a certain material can expand before it snaps. This is the property that prevents damage whether you’re bungee jumping with your dog or alone.
This rate is expressed in the percentage compared to the original length. Thus, a cord expanding to half its original length has an elongation rate of 50%, while a bungee cord expanding to double its length has an elongation rate of 100%.
The elongation rate of most bungee jumping cords is 110%, but it can range from 100% to 160%.
Generic Kevlar (K29) has an elongation rate of less than 1% which is definitely not enough to qualify as a material for bungee cords.
Tensile Strength of Bungee Jumping Cords
Ultimate tensile strength or just tensile strength is the amount of stress a material can take before breaking, snapping, or suffering other types of cross-sectional damage.
The tensile strength of your average shock cord will depend on its thickness. A 1/8 inch cord will have a tensile strength of 100 pounds while 1/2 inch bungee cord will have a tensile strength of 450 pounds.
While Kevlar has a tensile strength eight times higher than titanium, this isn’t the determining factor for the bungee cords. While it is very important to have strong cords that can withstand stress without breaking, it is not necessary for shock cords to be that strong.
The Resilience of the Shock Cord
This is the material’s ability to absorb energy, whether through elasticity or by redistributing it in some way and return to its original shape. It is defined by the amount of energy the material can withstand before not being able to come back to its shape.
Bungee cords use their elasticity to absorb the energy and transfer it along the cord, thus preventing your body from taking the most of it, which would be pretty damaging.
Shock Cords Are Designed Flawlessly
The inner layer is made by heating then cooling rubber, in order to increase its elasticity and resilience, as well as shape it correctly. After being heated, the material is compressed into straps so that it can be woven together to increase its durability, or it can be used as a single line, depending on what kind of bungee cord it’s meant for.
The most common type of shock cord has three woven rubber lines in its core.
The outer layer is made from cotton or nylon string. As the outer, nylon string is braided around the inner, rubber one, the rubber is stretched and squeezed together to ensure it’s properly coiled inside its protective sleeve.
Bungee Connectors Are Made to Last
Finally, a chain is as strong as its weakest link, and in order to make bungee jumping cords completely safe, we can’t allow the parts that anchor the cord and connect it to the jumper to be any weaker than the rest of the cord.
Bungee jumping cords are usually anchored using carabiners, hooks, or metal joints. They also come in the non-abrasive variants which prevent the metal from being worn down with overuse.
When choosing the connector, make sure you inform the bungee service provider about your exact weight and height. In addition to this, the height you’re jumping from will also determine what connectors will be required to ensure safety.
How Can We Know Bungee Jumping Cords Are Safe?
The last thing we want to think about when preparing for the jump is what will happen if the cord gives out. Safety should be the primary concern of all people attempting extreme sports, whether they’re bungee jumping or learning parkour.
You don’t have to worry, though. The safety precautions require the cords to be checked daily and if there’s even the slightest notion that something is wrong, the cords are replaced.
Apart from this, each cord has an allowed number of jumps it can take before it snaps. Mandatory replacement is required long before this limit is reached.
Finally, bungee cord technology has been around since the late 70s, and it has been substantially improved since that time. Bungee jumping is much safer today than it once was.
That being said, if you’re planning to go bungee jumping, you should only go to a certified and thoroughly vetted provider. This will ensure that every safety protocol has been followed through and that there’s no reason to worry.
To Sum it Up
Even though Kevlar is not used for manufacturing bungee jumping cords, it still has a lot of applications in our industry and technology. Also, the fact that it isn’t used in the production of shock cords doesn’t mean that there is something wrong with the material, just that it serves a different purpose.
Likewise, the fact that bungee jumping cords have enough tensile strength and elongation to prevent you from getting hurt when bungee jumping doesn’t mean that they’re a good all-round type of cordage – just that they serve the purpose that they were created for.
