Dynamic Rope--Jumping

[moray]

This is partly about gear, a lot about rigging, and all about fun. I am talking about intentionally jumping from height only to be caught by a dynamic rock climber's rope.

When I got my 60-meter Petzl Zephyr 10.3mm dry rope 3 weeks ago, the first thing I did was climb it using a pair of ascenders. It was immediately apparent that this was NOTHING like my arborist ropes. The rope went over a pulley 30 feet above me, and over to a tree about 60 feet away. It seemed like I was climbing for a minute and a half before I even left the ground! That stuff stretches!

Having developed a feel for the rope, it was time to rig it up for jumping. If you want a soft landing, you want a lot of rope to stretch. Using about 130 feet of the rope, I was able to rig it through two high-quality pulleys and anchor it at a Port-a-Wrap. The Porty would allow easy adjustment of the length and avoid the need to tie a knot in the middle of the rope. Three trees were involved: the jumping tree with the TIP pulley, the apple tree about 60 feet away with the second pulley, and the anchor tree with the Porty, about 50 feet from the apple.

When all was ready, I called my friend Jack, the local arborist, who is sometimes crazy enough to go along with my schemes, or narcissistic enough to want a copy of the video which I usually take. The photo shows him in the first moments of an eary jump.

But first, why am I doing this? The flip answer is "Cheap Thrills", but there is a deeper, personal reason. Half a lifetime ago I was practicing rock-climbing moves at a wonderful park in Berkeley, CA, called Indian Rock Park. On the day in question, some real rock climber (I was just a wannabe) was belaying people with a rope while they attempted the treacherous overhanging traverse that almost no one ever climbed. If you fell it was at least 15 feet to the hard ground below and you might well land flat on your back. I hung out with the belayer for awhile, asking lots of questions, and before long he was offering to belay me while I attempted the dreaded overhang. Well, I fell. And the feeling of being caught by the rope (deliverance!) has been a vivid memory ever since. Now I was about to experience it a second time...

 

[moray]

The first photo shows Jack in the middle of an early jump. The second shows the view from the jumping perch, almost exactly 20 feet high, looking down.

Now that we have over 20 jumps between us, I figured I know enough to file this report. First and foremost, jumping out of a tree is an absolute blast. The softness of the "catch" is indescribable. Second, you have to be very careful not to augur into the ground, and this is technically tricky. There is a mathematical connection between the length of rope, quality of the pulleys, inherent stretchiness of the rope, weight of jumper, length of freefall, and ultimate rope stretch for a particular jump. Even though I like the math, I don't try to figure this out beyond keeping a rough model in my mind.

The safe way to proceed (and the way we did it) is to do the first jumps with a nearly taut rope and plenty of height above the ground. With 130 feet of rope out, we ended up dropping about 10 feet, leaving a comfortable ground clearance of 10 feet. Now is the time to be careful. Do NOT give yourself 10 more feet of rope, thinking on the next jump your feet will just kiss the ground. No, give yourself about ONE more foot and see what happens. You'll probably drop about 3 extra feet. We lengthened the rope in small increments until our jumps were consistently taking us all the way to the ground. This is called getting your money's worth...

The rigging issues are very interesting and quite different from those that face an arborist. Here, you are concerned at every turn with stretch. Forget the jump--our weight alone will stretch my rope about 6%. With the 130 feet of rope we were using, that is almost 8 feet! You also care about pulley quality. Even with the low-friction Petzl Rescue pulleys I was using, the last stretch of rope at the Porty was seeing only about 85% of the tension of the part next to the jumper. In effect, then, its useful length is only 85% of its true length. In similar fashion, the middle rope leg needs to be derated to about 93% of its true length.

Our 20-foot jumps, given the amount of rope available to absorb the energy, are mild to the point of insignifcance from the rope's point of view. I roughly calculate that the maximum tension in the rope was about 300 pounds. For those rock climbers out there, I figure the fall factor at about .04--5 feet of freefall caught by 130 feet of rope. Chump change!

 

[MasterBlaster]

I fell straight down once, about ten feet on safety blue rope. I was facing the ground when the limb broke, and I was whipped around to a sitting position. Kinda cool, and I didn't even drop my saw.

 

[JonnyHart]

You crazy man.

 

[CurSedVoyce]

Not for me but I can see the attraction of the thrill... My thrill is NOT falling however... LMAO I work awful hard at it .... LOL

 

[NeTree]

Told ya us Maine-iacs is nutters.

 

[Hobby Climber]

Interesting saddle ya gots thar!

 

[Greenhorn]

Didnt Dan Osman invent this stuff?

 

[Stumper]

Ah, Greenhorn beat me to it. Moray if you don't know about Osman then you should read up. Stuff like 900 foot free falls.......ultimately to his death.

 

[No_Bivy]

Didnt Dan Osman invent this stuff?

and he died......rope was cut by his retrieval pulley after jumping almost 1200'

 

[No_Bivy]

if you want to use to rope...go climbing. Jumping out of a tree is sorta goofy

 

[Newfie]

Fook that crazy shit.

 

[rbtree]

It's not all that crazy. Dynamic rope is designed to handle multiple leader falls, which can be a fall factor of up to 2 ( defined as a 10 meter fall from 5 meters above an anchor point, I think) Stretch of a full dyno rope is up to 70% at break.....never applying more than a few times bodyweight force to the climber/jumper (faller?!)

 

[Newfie]

I understand the physics behind the practice Roger. I'm a loggerist. You won't catch me climbing UP a rope into a tree, never mind jumping out of a tree.

 

[OTGBOSTON]

I'd do it, then again, I'm kinda goofy myself

 

[moray]

Interesting saddle ya gots thar!

Not my saddle--I use a Glide. I have used Jack's saddle a couple of times and have to say it is mighty comfortable. It is a homemade rig, about 30 years old, that I consider quite unsafe. Reason 1: there are no side dees. Reason 2: it is a 2-part system using a fat leather (!) belt. Reason 3: there are no leg loops to keep the seat in place. Reason 4: the 3-strand line that supports the seat, while well constructed, is 30 years old and looking hard and ratty.

Jack's an old guy, set in his ways, and he loves his saddle. I did manage to get him to replace his disgusting 30-yr-old 3-strand climbing line with a modern 16-strand. I keep pushing him to at least re-rope his saddle, but it is like rolling a rock uphill.

 

[rbtree]

Tell him you'll not help dig his grave.....


insist that he lose that old thing...or at least restring it...


failing that....cut it up when he ain't lookin', mebbe get him good and juiced first.

 

[Bounce]

Looks like fun to me! Just don't forget that dynamic lines are only good for a certain # of falls. Each fall breaks a few of the load bearing fibers, which gradually reduces the strength.

 

[NickfromWI]

... Each fall breaks a few of the load bearing fibers, which gradually reduces the strength.

I'm not sure about this one.

I used to work on a ropes course where we used a dynamic rope for one particular element where the folks would climb a pole, stand on top, then jump off in an attempt to grab a nearby trapeze bar. The ropes were retired after 250 jumps.

Taking the ropes apart never revealed busted strands/fibers inside the rope. Things did feel much, much stiffer than a new rope, though...

love
nick

 

[woodworkingboy]

After his name was mentioned, I've looked at some of the Dan Osman videos at youtube. Pretty amazing rock climber for sure, but the free climbing he did without ropes, and the jumping, man it looks crazy to the uninitiated.

 

[Stumper]

After his name was mentioned, I've looked at some of the Dan Osman videos at youtube. Pretty amazing rock climber for sure, but the free climbing he did without ropes, and the jumping, man it looks crazy to the uninitiated.

Jay, That qualifier at the end is superfluous and overly restrictive. The guy was nuts.

 

[sotc]

Jay, That qualifier at the end is superfluous and overly restrictive. The guy was nuts.

and had a big pair!

 

[pantheraba]

Jay, That qualifier at the end is superfluous and overly restrictive. The guy was nuts.

And selfish, too...he had a daughter...who now has no father. The guy was terminally selfish, feeding his own ego. He should have put those kind of behaviors behind him when he became responsible for a family.

YOu can argue that a lot of us that correspond here also do extreme things by using chainsaws in trees...but we have much more safety built into our techniques and procedures than he did.

 

[woodworkingboy]

In one of the videos it said he was going to stop his activities, at least for awhile. I think he may have gone back up his fatal last time to retrieve his ropes, but decided to jump again. Some confusion about what really happened, one said that ropes crossed and melted. His free climbs look like madness, excluding the jumps.

 

[Bounce]

Each fall breaks a few of the load bearing fibers, which gradually reduces the strength.

I'm not sure about this one.

I am fairly certain of this Nick. This is the reason why UIAA approved dynamic rock climbing lines are only rated for a certain # of falls. If falling on a rope didn't damage it in any way, then a rope could potentially last forever (assuming you could prevent abrasion and UV degradation), which is of course not true. The place where the fibers break is not all in the same place either, so if you were to cut open the cover and look at the core, you would see apparently intact fibers. What you would not see is the microscopic break or tear in 1 out of 3000 fibers at some random point in the line.