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I have a decent amount of FF jumps but only one static line from my FJC over a year ago. I like to test and research thoroughly before I do something. I tested a batch of break cord yesterday at work by tying a 65lb weight to a CWY and dropping it from the top of a weight machine. The cord broke. I test all a few different scenarios of 2 loops (different sizes for redundancy etc) using all the cord. I had another batch at home for the actual jump.

I was going to jump an A tonight that was tall enough so that even if the break cord failed prematurely the pc (48 inch) would still have time to do it's job. I have FF this particular A 2 times (good lz etc) I decided on a hunch to test the new break cord. I could not get it to break by attaching the CWY to a railing outside the loop on my bridle, holding my bridle in my hand pulling as hard as I could. So I figured what the crap. I went outside and tied the CWY around a tree branch and tied a rope to it. I stood on it (I weigh 200LBS) and it did not break. I ended up hopping up and down until it broke (effectively busting my ass). The cord did break, not at the knot etc.

I then thought maybe the branch was absorbing some of the shocK, so i attached the CWY to my neighbors balcony upstairs (metal railing in concrete). Got on the rope and swung. Long story short IT DID NOT BREAK (but I did get some sweet rope burn). WTF! I am paranoid as crap to get hung up on an Antenna. I do not have weights at home to test with, but I plan on doing the same test tomorrow at work as I did with the first batch. Am I thinking wrong, is my 200lbs body weight not greater than 80lbs of force? Maybe I should have paid attention in math class..

On a side note-
Thanks Green Machine for answering all my other SL/CWY questions!

maybe you should have paid more attention in science.

static forces versus dynamic...

reading this now
http://www.blincmagazine.com/forum/wiki/Carry-With-You_Static_Line_Evolution

i promise my SL i sent out to you today will work ;)

I have done similar tests myself.
Bryan and I have also tested one
of my CWY S/L in his garage.

Findings - toss a 20 pound weight
and the break cord will snap cause
the inertia applies dynamic loading.

Your body & gear will accelerate as
soon as you exit and once you get
to the end of the line the force will
be much higher than 200 pounds.

WTF I must be retarded.. I am going to read more so I understand, but the 65lb weight test revealed the same results with the new cord this am... Broke just fine..

What have I learned-
65lb falling maybe 12 inches > 200lb fat guy on a rope..

Wheres Yuri when you need him

Please crunch some numbers for us, with your scientific knowledge

stand up.
feel the weight in your feet. that is "Static Load."

step off of a chair and land on your feet. the weight you momentarily feel in your feet is the "Dynamic Load." the Dynamic Load is your weight, plus the force required to arrest your momentum.

now, I don't understand how 80lb break cord can support a 200lb person, unless it is looped. single strand, double strand, etc. of break cord is another discussion that pops up regularly and confuses folks.

I was using a loop! 160lbs not 80lbs..

I am an idiot, I just notice that the break cord in this image is not in a loop! A loop seemed logical...



So what is the standard procedure, using a "loop" or using the setup in this pic? Would the same knot procedure apply as with a loop? Surgeons knot then 2 regular knots..

setup like yours depends heavily on surface being flat/smooth. if you are attaching to rough surface, the dacron under a load will be held on to the object.

take your finger and run it down a smooth countertop, then use the same finger and the same force and run it down a piece of sandpaper.

I say it's possible to load the dacron side of the setup all the way from the object to the PC attachment point.

and what's the last few year's fetish with carry with ya setups ? I carry 1 foot of break cord with me, haven't run in a situation where a dacron would have been better...

Holy crap people put a lot of thought into this. It really isn't that complicated

True, in your neck of the woods you just need to decide what size zip tie to use!

We just use some (4) wraps of electrical tape, taped sticky side out so it falls off the object after it has done its job. NOTE: Electrical tape and cold weather don't mix well.

A better setup than the one you have pictured is to take a piece of dacron or webbing and attach a single strand of break cord to each end. Wrap the dacron around the object and attach the two single strands of break cord to a quick connect that is attached to your bridle. This way the only thing connecting you to the object is break cord, so if the dacron somehow gets hung up, both sides will break. Or you could just use a piece of break cord with a loop in each end, wrap around object and attach to quick connect.

WARNING: many would advise against using the second method when attaching to sharp edges, like all those super sharp handrails and sharpened steel angle found at many exit points.

John - gimme a shout bro!!

KC

has anyone strength-tested a wal-mart bag tied in a square knot?

fwiw...

the red dacron creates a loop, thus a pulley. that means a single strand will require 160lbs. a loop of break cord will require 320lbs to break.

all numbers will also be reduced (in theory) by rough surfaces, sharp edges, knots, and other stress concentrators.

not understanding how these forces accumulate can lead to ugliness. I think the CWY s/l setup creates confusion and thus can increase risk.

use electrical tape mate,three-four wraps just under the knot on your pc,breaks every time..

Yuri, outrager, static lined with a convenient mart plastic bag that was found under tiny piney. No problems. He wouldn't do it again, but only cuz he stated he hates static lining.