Bungee Cords

I learned on a mil. spec. system. In pirate jumping it has a number of advantages. You have a set of 5 individual cords that you group together in a set of 3,4,or5. So you can jump from 100-250lbs with one set of cords. They are covered in Nylon (or Cotton) sheaths that protect them from dirt when you lay them down. Also, the redundancy of multiple cords, as well as the sheaths which act as a static back up in the case of over elongation, provide (I believe) a greater degree of safety. Traditional mil. spec. cords have an elongation of about 110%. By the way, in the “bungy or bungee” page a common mistake is made about this word. Elongation refers to the change in length of the cord, not the ultimate loaded length. So 110% elongation in a 100 foot long cord is 110 feet for a total stretched length of 210 feet, or 2.1 times it’s original length. Since mil. spec. cord stretches less, a longer length is often used, resulting in more initial free fall.

After the 1995 X-games I realized that, because of the bigger rebounds, more acrobatic stunts were possible on all rubber cord. So I set about learning how to build that type of cord. New Zealand style cord is built with a ribbon, about 3 inches wide, composed of a number of stands of rubber. This is wrapped around teflon spools, tied together, stretched to it’s ultimate elongation and wrapped down it’s length, with the same type of rubber, to hold it all together.

The actual building of an all rubber cord, or tying loops on the ends of mil. spec. cord is not something that can be learned through words only. You need to learn first hand from someone who knows what they are doing. So you can watch them and they can check your work. The same goes for the bungee system, whether it’s a lowering system, a man basket on a winch, or a raising system, you either need to learn it first hand or start from scratch with the engineering done on all the materials, and many practice “jumps” done with sandbags.

New Zealand specification cord has an elongation of 200-300%, i.e. it will stretch to 3-4 times it’s original length. I believe the Kocklemans came up with the idea of building a length of webbing into all rubber cord. This back up is the length of the ultimate elongation of the cord. This gives it the redundancy that I like. The Kocklemans build their cords thicker than New Zealand specs. This gives the cord a long life (over 1000 jumps) but results in higher G-forces, and less ability to do rebound tricks. I believe their elongation is 150-200%.

It is difficult to determine actual elongation because many people will tell you the length of the all rubber cord before it is stretched out and tied down it’s length. This makes the cord a little longer (about 5-10%) than when the ribbon is first layed around the spools. For example, for a 100 foot jump you would first lay the rubber out at 22.5 feet, which would need to stretch to 4.5 times it’s original length to get to 100 feet. But once the cord is stretched and tied it would be about 25 feet long. So then it would need to stretch to 4 times it’s length to reach 100 feet.

Well, I’m starting to ramble so that’s all I have to say about that. Here’s some info for your bungee sites list. Total Rebound and Yesh in California are friends of mine that are no longer in the business. My company will be active again in Northern California in December 1996. I’ll update you later. The sites at Raging Waters and Big Bear were both temporary stops for Thrill Sport Productions, who produces our show in Taiwan. They will have arches at state fairs this summer in Wisconsin, Michigan, Ohio, and other places. Their Corporate office is 88 A Elm St. Hopkington MA 01748 Tel.(508)435-0420 Fax(508)435-6594. Total Hard Core Gear, in Redding California, makes what I think are the best harnesses. They make both ankle harnesses and chest and waist harnesses. They are fleece covered, well padded, and use self locking parachute buckles, which are easy to use and secure. Sorry, I don’t have their address or phone number. I used the N.Z. Bungy Knot ankle binding at the 95 X-games and didn’t like it. Like you said, you feel trapped. Also, the force is transferred to your legs with a 1 inch strap, which, even though padded, digs in after a while. The worst thing though is that when it tightens there is a 2 foot strap of webbing hanging off which can wrap around your calf on a rebound and then your are hanging from an unpadded 1 inch strap which really abrades the skin and can cause hematomas. This happened to three of my friends at the ’95 Extreme Games.

The Euro Cord

The European/New Zealand cords described above look like this

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Steve who wrote that section above believes that the US mil spec system is safer because of the extra redundancy, but the Euro cords do have the advantage that they can be inspected after each jump for signs of rubber failure or possible problems. The sheath on Mil spec cords prevents this. Some Euro cords have an extra static line built into the core to prevent over stretch and provide extra backup. The term Euro cord is a little misleading – this cord is used and made in many countries.

Mil Spec Cord

Mil Spec cord is cord that is made to US military specifications, these specifications were designed to hold down tanks on boats and in planes rather than to suspend adrenaline junkies jumping off bridges. As it turns out they work rather well for both!.

Picture of Mil Spec Cord

Here is some mil. spec cord made by Glenn from Bungee Experience. The pink/white stuff is the cord, the blue webbing is attached in a very special way to the ends of the cords so that carrabiners can be attached to each end. The way the end of the cord is connected with a piece of webbing is called termination. The Red Tape is part of the special way the cords are terminated.

Specs

Lots + lots of people have asked me for bungee cords specs and I just got emailed this from J Kockelman (cheers!)

Most Bungee Jumping Cord is made from “natural rubber” whose physical constants are in most college libraries. The most common bungee cords stretch 2 to 4 times the original length and the jumper feels 2.5 to 3.5 G’s.

I found a page on bungee.com (link expired) which had a technical paper on Bungee jumping.

Butterflies When Skydiving? Here’s Why You Don’t Feel Them

Anyone who’s ever fallen off a chair, been surprised by a bump in the road, or rode a crazy rollercoaster knows the feeling.

That sudden drop in your stomach – paired with a little burst of adrenaline as your body tries to figure out what the heck is going on!

One of the biggest fears with skydiving is getting that butterfly feeling. And not just for a few seconds, but for a minute straight.

Thankfully, you don’t get that ‘dropping feeling’ when skydiving. Since you’re jumping from a plane in flight, you’re already travelling at speed. The butterflies are caused by a sudden acceleration, which in this case is only a change in direction (travelling down, instead of along).

That’s the quick answer, but there’s much more to it than that.

As a skydiver who was once terrified of this feeling, I’ve fully researched why it does (and doesn’t) happen. Interested? Then let’s dive in.

What Causes That ‘Dropping Feeling’?

The usually explanation people have for the sudden butterflies when going over a road bump is the sudden ‘jump’ downwards.

This is only half-right.

The way to think of this is that it happens when you move faster than your stomach. Let me explain.

When you suddenly plummet in a rollercoaster, or fall from a chair, your body is rapidly accelerating downward from a static position. This happens so fast that everything inside you gets lets behind for a second.

It’s not that your stomach ‘drops’, is that the your body does – and your insides take a quick second to catch up!

This is similar to what is known as “negative g-forces” in physics.

Rollercoasters give you butterflies due to negative g-forces. Photo courtesy of NBC News

Normal g-force is when you’re pressed into your seat – like in an accelerating or hard-turning car/rollercoaster. It’s the feeling of suddenly weighing 2-3x more than you usually do.

The butterfly feeling comes with negative g-forces. It’s the opposite to being pressed into your seat.

Right now if your chair was to suddenly rocket upwards –you’d be pushed down into it.

Instead, if it was to suddenly rocket downwards, you’d be left floating for a tiny moment, before following gravity’s call. That little bit of lag time from being static to accelerating downwards is what causes this feeling.

It’s almost like you’re entering zero-gravity for a second.

Especially in cases where you’re travelling upwards, like on a small road bump, and then the car suddenly goes downwards. You’re left in mid-air for a quick second. That tiny moment where you’re not being pulled by gravity is what causes this feeling.

Note – this same shift in momentum is also how they do zero-gravity flights.

Why Don’t We Get This Feeling While Skydiving?

So, bearing in mind that it’s the sudden acceleration downwards from a static position that causes it, why doesn’t it happen in a skydive?

We’re jumping straight down from a plane that’s flying horizontally, aren’t we?

Correct. However, it’s that momentum from already travelling forwards that counteracts this.

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When the plane cuts the engine to allow you to jump, it’ll be flying at around 80-100mph. When you jump from the plane, you’ll rapidly decelerate horizontally while accelerating vertically. This roughly balances itself out.

If, instead, the plane was to quickly jump up then down, you’d get the feeling because the momentum suddenly shifts in opposite directions. Like when we go through a huge hit of turbulence in a standard passenger flight.

But because you’re transitioning from flying 100mph forward, to flying 100mph downward, that momentum is simply changing direction. You aren’t hit with a negative g-force which comes from a sudden shift.

What Does Cause You To Feel Butterflies?

As well as skydiving, I’ve also done a fair few bungee jumps.

And let me tell you, you seriously feel it when on a bungee jump!

Just like when you fall off a chair, you’re going from standing still to rapidly accelerating downward. This is as big of a butterfly feeling I’ve ever had.

I actually found bungee jumping way more scary because of this feeling. While skydiving felt relaxed and free (once over the fear), bungee jumping came with that terrifying feeling of falling. (That said, I’d still do it again!)

Any situation where you’re suddenly going from zero to full acceleration is when you’ll get that dropping feeling.

For example, skydiving from a static object will make you feel this like nothing else.

Jumping from a hot air balloon or a hovering helicopter comes with the full ‘oh my god I’m falling!’ package. Same goes for basejumping, or even high diving into a pool.

So What Does Skydiving Feel Like?

Ask any skydiver this question, and you’ll get the same response.

It’s hard to put into words.

I really let loose on this topic in my post about how it feels to go skydiving for the first time.

Skydiving feels like freedom. A very scary, windy, adrenaline-filled freedom. It feels less like you’re falling, and more like you’re flying.

There’s no butterflies in your stomach, no real sensation other than that of 120mph of wind hitting your whole body. To imagine what that feels like, picture sticking your head out the window on a motorway. Now double that, and put it over your whole body.

Once you get over the adrenaline and fear of skydiving, it really does feel so freeing. There’s no butterflies, and no feeling of falling. You’re just there, in the sky, with the whole world below you.

It’s a beautiful thing, which can feel like anything from a high-adrenaline buzz with friends to a serene, soul-cleansing experience which gives you so much appreciation for the world. It all depends on you, the skydiver!

Conclusion

Skydiving isn’t exactly a common thing to do, so there’s still a lot of vague-ness about different aspects of it.

In particular, the fear of that falling feeling can be a major stickler for why people are hesitant to sign up.

I hope this article – and my poor attempts at explaining physics – have helped explain why this sinking feeling doesn’t happen in a traditional skydive.

If this content’s helped you, please consider checking out the related articles below!

Bungee Cords

I learned on a mil. spec. system. In pirate jumping it has a number of advantages. You have a set of 5 individual cords that you group together in a set of 3,4,or5. So you can jump from 100-250lbs with one set of cords. They are covered in Nylon (or Cotton) sheaths that protect them from dirt when you lay them down. Also, the redundancy of multiple cords, as well as the sheaths which act as a static back up in the case of over elongation, provide (I believe) a greater degree of safety. Traditional mil. spec. cords have an elongation of about 110%. By the way, in the “bungy or bungee” page a common mistake is made about this word. Elongation refers to the change in length of the cord, not the ultimate loaded length. So 110% elongation in a 100 foot long cord is 110 feet for a total stretched length of 210 feet, or 2.1 times it’s original length. Since mil. spec. cord stretches less, a longer length is often used, resulting in more initial free fall.

After the 1995 X-games I realized that, because of the bigger rebounds, more acrobatic stunts were possible on all rubber cord. So I set about learning how to build that type of cord. New Zealand style cord is built with a ribbon, about 3 inches wide, composed of a number of stands of rubber. This is wrapped around teflon spools, tied together, stretched to it’s ultimate elongation and wrapped down it’s length, with the same type of rubber, to hold it all together.

The actual building of an all rubber cord, or tying loops on the ends of mil. spec. cord is not something that can be learned through words only. You need to learn first hand from someone who knows what they are doing. So you can watch them and they can check your work. The same goes for the bungee system, whether it’s a lowering system, a man basket on a winch, or a raising system, you either need to learn it first hand or start from scratch with the engineering done on all the materials, and many practice “jumps” done with sandbags.

New Zealand specification cord has an elongation of 200-300%, i.e. it will stretch to 3-4 times it’s original length. I believe the Kocklemans came up with the idea of building a length of webbing into all rubber cord. This back up is the length of the ultimate elongation of the cord. This gives it the redundancy that I like. The Kocklemans build their cords thicker than New Zealand specs. This gives the cord a long life (over 1000 jumps) but results in higher G-forces, and less ability to do rebound tricks. I believe their elongation is 150-200%.

It is difficult to determine actual elongation because many people will tell you the length of the all rubber cord before it is stretched out and tied down it’s length. This makes the cord a little longer (about 5-10%) than when the ribbon is first layed around the spools. For example, for a 100 foot jump you would first lay the rubber out at 22.5 feet, which would need to stretch to 4.5 times it’s original length to get to 100 feet. But once the cord is stretched and tied it would be about 25 feet long. So then it would need to stretch to 4 times it’s length to reach 100 feet.

Well, I’m starting to ramble so that’s all I have to say about that. Here’s some info for your bungee sites list. Total Rebound and Yesh in California are friends of mine that are no longer in the business. My company will be active again in Northern California in December 1996. I’ll update you later. The sites at Raging Waters and Big Bear were both temporary stops for Thrill Sport Productions, who produces our show in Taiwan. They will have arches at state fairs this summer in Wisconsin, Michigan, Ohio, and other places. Their Corporate office is 88 A Elm St. Hopkington MA 01748 Tel.(508)435-0420 Fax(508)435-6594. Total Hard Core Gear, in Redding California, makes what I think are the best harnesses. They make both ankle harnesses and chest and waist harnesses. They are fleece covered, well padded, and use self locking parachute buckles, which are easy to use and secure. Sorry, I don’t have their address or phone number. I used the N.Z. Bungy Knot ankle binding at the 95 X-games and didn’t like it. Like you said, you feel trapped. Also, the force is transferred to your legs with a 1 inch strap, which, even though padded, digs in after a while. The worst thing though is that when it tightens there is a 2 foot strap of webbing hanging off which can wrap around your calf on a rebound and then your are hanging from an unpadded 1 inch strap which really abrades the skin and can cause hematomas. This happened to three of my friends at the ’95 Extreme Games.

The Euro Cord

The European/New Zealand cords described above look like this

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Steve who wrote that section above believes that the US mil spec system is safer because of the extra redundancy, but the Euro cords do have the advantage that they can be inspected after each jump for signs of rubber failure or possible problems. The sheath on Mil spec cords prevents this. Some Euro cords have an extra static line built into the core to prevent over stretch and provide extra backup. The term Euro cord is a little misleading – this cord is used and made in many countries.

Mil Spec Cord

Mil Spec cord is cord that is made to US military specifications, these specifications were designed to hold down tanks on boats and in planes rather than to suspend adrenaline junkies jumping off bridges. As it turns out they work rather well for both!.

Picture of Mil Spec Cord

Here is some mil. spec cord made by Glenn from Bungee Experience. The pink/white stuff is the cord, the blue webbing is attached in a very special way to the ends of the cords so that carrabiners can be attached to each end. The way the end of the cord is connected with a piece of webbing is called termination. The Red Tape is part of the special way the cords are terminated.

Specs

Lots + lots of people have asked me for bungee cords specs and I just got emailed this from J Kockelman (cheers!)

Most Bungee Jumping Cord is made from “natural rubber” whose physical constants are in most college libraries. The most common bungee cords stretch 2 to 4 times the original length and the jumper feels 2.5 to 3.5 G’s.

I found a page on bungee.com (link expired) which had a technical paper on Bungee jumping.

Source https://www.bungeezone.com/equip/cord

Source https://friendlyskydiver.com/butterflies-when-skydiving/

Source https://www.bungeezone.com/equip/cord

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