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What is break cord made of? Does anyone know what the elongation or stretch percentage is?

thanks,
Chris

Don't have a percentage for you, but we experimented with break cord in a tensile tester and noticed it barely stretches and then just snaps suddenly. So whatever the percentage is, it's not going to be very high.

Not sure if that's useful, but there you have it anyway...

Shouldn’t we be asking you that question?

As the physics professor surely you have colleagues and/or acquaintances with access to a materials testing lab and it would be a 15 minute job to run 20 or so samples through a tensile strength tester.

I have no data to offer, but I do support the qualitative answer of: ‘not very much at all’ based on some uninstrumented testing I have done.

I hope somebody actually tests this and posts the answer, I’m curious now.

yes, I could repeat reinventing the wheel but their should be well measured spec's already.

May I ask why you are interested in this information?

I’m pretty sure that for a standard BASE static line breakcord loop set-up with a surgeon’s knot, you will see the loop length increase in size more due to the knot tightening up than due to the elongation of the cotton tape.

And by standard I guess I mean breakcord loop 1 to 3 inches in length between tie-off and link.

Because breakcords can be easily misused with potentially fatal results. I'm trying to come up with a recommended break cord strength versus length of fall before loading occurs. For example, if you take 10 feet of break cord and drop 10 pounds on the end of it, it will break. The 80lbs force to break is related to elongation and is a static force specification. The specs for using a break cord for providing a virtual PCA require the jumper to consider the length of the cord and where it's attached. I saw a photo recently of what appears to be a misuse.

You should ask the Apex folks what they learned when doing test drops for the SuperBowl demo.

Can you elaborate on this?

I've heard of people extending their static-lines by as much as twenty feet without problem. I can see how a longer delay will increase the snatch force and increase chances of a premature break though. Is that what you're getting at?

Every jumper I've ever talked to about breakcord recommends a surgeons knot... I'm curious as to why no one is using a water knot? Seems like a better choice, and it's the one I used, and continue to recommend. Criticism welcome..


-smd7

http://www.scoutingresources.org.uk/.../knots_waterknot.pdf

They suggest using a water knot for flat lines since I suppose they don't slip compared to round lines. How are you using a water knot since you are not joining to equally sized lines?

The water knot is used to join the break cord to itself.

because that's not the easiest knot to tie when it's dark ? Because what most people already do, works well, and complicating the system = asking for trouble.

Keep
It
Simple
Stupid

I used the water knot and tie it as a loop (just like 1" tubular for climbing), I make (made) two loops, one smaller than the other, both loops through the bridle & pilot chute and those are clipped with a locking crab to a supertape sling to whatever object we were jumping from.

that dosn't make a bit of sense... I'll try to get a pic.

-smd7

Ah, gotcha!

surgeon's knot is what is traditionally tought

the only reason I can think of why, is the security of the knot and the low reduction in strength due to the knot

water knot looks good too

I've done an overhand knot in some.

I even girth hitched the loops of breakcord directly to hole in a metal plate on the object and that worked too.

If anyone is exceedingly curious about some static line testing, I will be in the Twin from 21-29 April and one of the things I am going to do is play around with some static line techniques.

Let me know if there is any test jumps I could do that would be of interest you.

FWIW I have been using two different sized loops of breakcord on all my static line jumps from Oct 05 and have not noticed any ill effects.

The extra loop does give me that warm and fuzzy feeling when exiting, though.

 Check the poynters manual it may have more info.E

Chirs,

It's around 7.5%.

i would like to know the headding preformance on a SL jump were you do an arial.. like a front flip or standing floater way and do a reverse salto/gainer but jumping backwards

Let me know how it goes and please get some video

PS make sure to clear the bridel

dude

I was totally going to do that anyway!

Just ask anyone who has seen the ‘Ho-Bag’.

I will happily send experienced jumpers the footage, along with an essay on why it’s bad idea.

I won’t be the first person to have done static line aerials, though…

damnit hope you will ship to me aswell anyway

you´ll get pm in a sec or two

hey hey

I didn't get around to doing any straight static line aerials, but two new versions of the Ho-bag and I think they qualify.

one even used some breakcord...

see it here


cya

Ha Ha nice one,if posible i would like to buy a copy as the vid is done