C.W.Y. (carry-with-you) SL setup

[BASE_689]

Carrying on here a discussion that started and currently ongoing on Dropzone.
To Gus: don't use the setup of your second photo!!! In that way, to break the break cord loop (that needs in absolute a force of 96 lb - 44 kg), you need to apply 96 lb - 44 kg to that branch containing the break cord loop: to do that, you need to apply 192 lb - 87 kg to your bridle. Doing like your setup, your body-your harness-your risers-your lines-your parachute-your bridle need to apply a force of 192 lb - 87 kg to break the break cord loop: TOO MUCH!!!!!!!
To nicknitro71: Your simple setup is just like mine (see my photos) with the difference that in the loop of your break cord, beyond the two loops of your C.W.Y. (Carry With You), you must include also the loop in your bridle (where PC is attached), otherwise, doing like in your photo, you end up needing 192 lb - 87 kg to your bridle to break the loop: TOO MUCH!!!!!
To K - K763: Yes, I saw the bridle extension and relevant setup as per Apex's website. Very mice and smart way of doing a SL jump. But. Your setup would leave EVERYTHING (Static Line + Carabiner) onto the handrail/object, thing that: 1) either you don't bother to loose and to be noticed by guards/general public/whatever; 2) or you must go up to exit point again to recover everything.
Nothing against the above, but my CWY (Carry With You) setup was born with something different in mind: NOT TO LEAVE ANY TRACE BEHIND AFTER THE SL JUMP!!!!!!!!!!!!
My setup was born after few discussions with Dexter, and then I received a very precious hint by CRWPER, who suggested me to tie my C.W.Y. to my (special) bridle with a break cord loop (instead of larksheadknotting it onto my bridle as I thought of doing firstly): in case of a (possible) hangup of my C.W.Y. on structure, C.W.Y. itself would be released breaking the break cord loop.
Comprising with break cord loop n° 3 loops (n° 2 loops belonging to C.W.Y. and n° 1 loop to bridle) you end up needing the "standard" 96 lb - 44 kg of force for breaking the break cord loop.
The "explanation" of the 96 lb - 44 kg is the following: we are using a calibrated 80 lb - 36 kg break cord, it means that in a laboratory if you put a single line of break cord in the "jaws" of a dynamometer, you end breaking it at 80 lb - 36 kg (plus minus a natural tolerance). If you do a loop with above break cord, now you need (theoretically) 160 lb - 72 kg to break such a loop (the loop contains two branches of break cord, each needing a force of 80 lb - 36 kg to break). But you do not "close" your loop with sewing or other very smart method, you "close" your loop with a knot.
ANY knot weakens the cord itself (=failure of cord would happen in correspondence of knot).
Doing the surgeon knot we all do to close the brak cord loop weakens of 40% the break force of cord itself (Dan Poynter manual, I have been told), so we are left with 60% of breaking force: our break cord loop would break at 0.6 x 160 lb = 96 lb - 44 kg. A good value for our SL jumps: high enough to withstand with opening forces required by container/velcro/pin/whatever, accelerations/whatever, low enough not to cause problems to the opening of parachute/integrity of bridle/harness/whatever.
So, to make short a long story: Apex method is fantastic, but my CWY SL setup is aimed basically (and only) to not leave any evidence on exit point, in rder to have NO NEED of returning to exit point to pick stuff left behind.
A word about the photos I posted here: it cannot be seen, but my setup includes LEAVING THE PC ONTO THE (special) BRIDLE, where bridle loop (with PC attachment) is something like 1 ft - 30 cm beyond that knot you can see (knot been passed through by break cord loop), so there are still 9 ft - 2.74 m between PC attachment and pin (or shrivel flap).
Just my 0.02.

[Faber]

Andrea,how much does your bridel weigh?(thinking of the chance of poping the pins..

which kind of rubberband do you use to hold the bridel?

[BASE_689]

> how much does your bridel weigh?(thinking of the chance of poping the pins..
I really don't know, but once I return home, I can put it onto my electronic scale and I will let you know, but definitely there is NO CHANCE that with its proper weight (dynamical weight, if you like) it can possibly open the pin up...

> which kind of rubberband do you use to hold the bridle?
I use the very thin rubber bands you can buy in supermarkets in boxes of 100 (or in boxes of 50 g). When I was a kid (more than 40 years ago ), those very thin rubber band came only in yellow colour, now they come in boxes where there are several colours.
I pass my PC and (special) bridle THROUGH the above very thin rubber band, then, once ready to jump, I do 8 folds to my (special) bridle (and I leave only the necessary slack in (special) bridle itself) and I do few wraps with such very thin rubber band, such wraps are needed to just barely hold that amount of bridle there, in position, not to hang down. Few wraps of very thin rubber band require very low force (few 10's of g or perhaps a couple of 100's of g) to be released, so that there is no way that the 8 folded bridle and rubber band can ever open up prematurely my pin (and container).
Passing my PC and (special) bridle THROUGH the above very thin rubber band has the effect of carrying with me ALSO the very thin rubber band and not leaving it on the scene of action.
In fact, most of times, such a very thin rubber band doesn't break and I find it again around my bridle when I return home, so there is another piece of equipment (very thin rubber band) that is NOT left on site but taken with me.
I do not know if this story of "carrying with me anything possible" is manily due to the fact of not leaving evidence behind, or rather it is due to myself being joyfully mean and so saving money for buying SL pieces and rubber bands and other stuff (yes, the grandma of my grandma was Scottish ).

[Faber]

"stowing" a regular bridel the correct way will bring home your tailgate rubberband(as im using normal bridel) whith you home(try experiment this,how to end the folds,you´ll find the way were you´ll keep the rubberband for EACH jump.. leaving less evidense(you´ll always leave 1-2 peices of breakcord and 1 tailgate rubberband from your tailgate..).

[sabre210]

Andrea

I'm not entirely sure i agree with you on your assessment of Gus' static line diagrams. His diagram clearly shows that although there are 2 loops of breakcord, each is an individual loop made from a section of breakcord of different diameters.One being a short loop and the other a longer (backup)one. In sequence the short loop will be loaded first and according to your calculations will break at approximately 96lbs.Prior to this loading , no force AT ALL has been applied to the long (backup) loop. It's just hanging there flapping in the breeze. Once the first loop fails and the slack is taken up, the second loop will be loaded and will fail as per the first. That's 2 autonomous loops, breaking sequentially one after the other (albeit within a split second) at 96lbs.

If Gus had used just one piece of breakcord and looped it twice then yes, i would agree that the load required to make it fail would be too much, but he hasn't. He's used 2 seperate pieces of cord. One has no bearing on the other and as they are of different lengths, their loading and failure will happen at different times.

Take another look and let me know if i'm wrong


ian

Ps. Faber, i hope you're not larksheading the tailgate bungee in order to keep it, as that can apparently cause a hangup.

[Gus937]

Cool, thanks Andrea. FWIW I think you're right. To apply 96 lbs to the break cord you'd have to apply twice that to the whole system - because the sling would take half the strain.

The design you're using is very neat.

Gus

[BASE_689]

To Ian:
> Take another look and let me know if i'm wrong
Sorry, you are wrong. I know that one break cord loop is longer than the other, but the issue here is that 96 lb - 44 kg are needed to break the break cord loop, and provided that in that configuration the break cord loop(s) is (are) in one of the (two) branches of the system, you need to apply 192 lb - 87 kg to the whole system in order to make the break cord loop break.

To Gus:
> To apply 96 lb to the break cord you'd have to apply twice that to the whole system - because the sling would take half the strain.
Correct.

To Faber:
> How much does your bridle weigh?
Standard bridle: 58 g
Special bridle (with C.W.Y.): 105 g
Yes, special bridle weighs slightly less tnah twicw the weight of a standard bridle, but being the overall weights "not excessive", I think the fact that (my) special bridle weighs 105 g is not an issue with respect to its dynamical weight being capable of (prematurely) opening up the pin/container.
Granted that I use my special bridle ONLY for SL jumps.

[sabre210]

Andrea

I see exactly what you are saying. My apologies, i was wrong Could you repost a pic of your setup please or preferably a diagram like gus'.

Respect

ian

ps Andrea. Have we met. Are you Winnie's good friend??? Was it you who had the 180 after the static line jump in the UK???

[BASE_689]

> Could you repost a pic of your setup please or preferably a diagram like gus
Here we are. First, my apologies for second pcture, but: 1) I am not very good in doing drwaings with computer; 2) I used Paint that possibly is not the best program to do drawings.
First pictures, even if NOT perfectly seeable in all its details, gives perfectly the idea of how the whole setup is made up.
Second picture is a drawings of my C.W.Y. setup.
In reality my C.W.Y. is made by two branches and three loops.
Each of the 3 loops is 2.5 cm long.
Measured from tip of loop to tip of loop, the main branch is 44 cm long.
The secondary branch (responsible for carrying with you the whole SL) is 25 cm long and is inserted/sewn 5 cm below/before the beginning of one loop of the main branch.
The above measurements are obviously NEITHER perfect NOR mandatory, they come simply from few good and sound reasonements about the average size/diameter of fixed part of structures to which we bind to, thought to be nicely working in 95% of situations.
In the drawing what is bridle and its loop is quite obvious (even if not very nice looking), what is PC is again quite obvious. Drawing is NOT in scale but break cord loops have been done bigger for explanation/instruction purposes.
Thick horizontal line is the handrail (or "anchor point") of structure/object.
Blue loop is the break cord loop necessary to connect C.W.Y. with bridle (in case of (possible) hang up of C.W.Y. with structure it would break and release everything).
Red loop is the break cord loop that is going actually to break at 96 lb - 44 kg (in reality is much tighter than drawing, so the slack of secondary branch is way longer), so when the system in under strain, it happens that the break cord loop breaks (secondary branch having much greater length and so it is NOT under any strain at all at the moment of break of break cord loop).
After break cord loop breaks, the bridle (through secondary branch) pulls and carries with itself the C.W.Y., LEAVING NO EVIDENCE AT EXIT POINT.
Yes, there will be a broken break cord left somewhere (nothing can be done about that, I am fraid), but it is more likely that such a piece of broken break cord lays somewhere down the vertical of exit point rather than on exit point itself.
Hope drawing and explanation are quite clear.

> Have we met. Are you Winnie's good friend??? Was it you who had the 180 after the static line jump in the UK???
No, I am afraid I have been several times in UK but never when I was already a BASE jumper Anyway, I promised BASE #813 to get in touch with all you guys in case I came to UK to flick off something.

[Gus937]

In Andrea's 2nd picture, does anyone have an opinion on using 2 bits of 'red' break cord instead of 1? One short and one long. I suppose the break cord is less likely to break prematurely since it's no longer in contact with the structure but even so, I like having that backup.

Gus

[sabre210]

Thanks Andrea

Makes perfect sense. This is the exact same design i have had made up by a rigger. I got it made after the first discussion between you and dexter at least 18months ago. If i recall someone joked about the chair being part of the setup in the photo. I've only ever used it once to test it and it was fine. Other static lines i've done, i've been fortunate and have tied off directly to the round rail as per Gus' diagram 1, with 2 loops of breakcord of different lengths.

Alternatively, i have another setup for CWY static lines which is the same principle but instead of the third branch on the sling, i have a longer single strand of breakcord which will drag the sling with you but in the event of a snag will also break.

Just as an aside, doing a normal static line without a CWY setup,if i were to use a single strand of breakcord attached to the rail and the bridle using surgeons knots, this would fail at approximately 48lbs. (80lbs x 0.6) Correct???? At what stage in the deployment do you think this force would be achieved, shrivel flap peel, lifting the canopy out or all the way to line stretch. I have no intention of doing this (as i've already tried it and had a pretty bad experience) but am still curious to estimate how far down the deployment sequence you would get with a single strand before failure. I realise there are many variables (canopy size/weight, snatch force variables, knots etc) but am curious just the same.

ian

[BASE_689]

To Gus:
> does anyone have an opinion on using 2 bits of 'red' break cord instead of 1?
Personally, I have never done that, but I don't see any problem in tieing 2 'red' loops of break cord, the second being longer.

To Ian:
> if I were to use a single strand of breakcord attached to the rail and the bridle using surgeons knots, this would fail at approximately 48lbs. (80lbs x 0.6) Correct????
Yes, it will break at 48 lb - 22 kg. You would have to make two knots, though. Knots that are NOT a surgeon knot (with a surgeon knot you can tie the ends of a strand (forming a loop); to close a strand on itself, you do a knot that is not any more a surgeon knot, possibly lowering the 60% value).

> At what stage in the deployment do you think this force would be achieved, shrivel flap peel, lifting the canopy out or all the way to line stretch
This is a question which is impossible to give a single and definite answer to.
The only sure thing is that the single strand of break cord would break at 48 lb - 22 kg.
Different conditions in different jumps would make each component and/or stage of deployment to exert a force on what is "above" (bridle/break cord/anchor point) that can vary from case to case.
Read in the above: angle of launch you exit with, amount of push you give to your launch.
Just keeping into account the two above issues, each part of the system can exert a different force from time to time, from jump to jump.
To have a setup that breaks at 96 lb - 44 kg gives you the confidence that even if some parts exerts in a certain jump a force that is higher than it would have in "standard" conditions, still such a "higher" force is below 96 lb - 44 kg, so your SL system breaks the break cord when (and only when) you have reached line stretch.
The break cord departs whichever part of the system exerts 96 lb - 44 kg as first, could be shrivel flap/pin (if launched with a certain angle or if it exists a "strange" angle of routing of your bridle or whatever), could be the weight of your canopy that suddenly exerts its weight onto the bridle/break cord/anchor point system, could your own weight once you reached line stretch.
If your setup is good and you have double checked that there are NO strange angles or strange routings to your bridle (from anchor point to container), you are sure (...well... we are still BASE jumping... ...) that your break cord loop breaks only when you reached line stretch.
From the experience of all world BASE jumpers out there, in decades of SL BASE jumping, a value of 96 lb - 44 kg for breaking the break cord at line stretch seems to be a good and sound value. And, in that case out of 100 where your break cord loop breaks prematurely (=before line stretch), well, that's why we all keep that good 48" ZP PC as a backup
I didn't reinvent the wheel, I simply kept and transferred those values into a system that doesn't leave evidence that you have jumped off there.
Just my 0.02€

[sabre210]

Good stuff. Very valuable

thanks

ian

[Faber]

Originally Posted by Gus937

In Andrea's 2nd picture, does anyone have an opinion on using 2 bits of 'red' break cord instead of 1? One short and one long. I suppose the break cord is less likely to break prematurely since it's no longer in contact with the structure but even so, I like having that backup.

Gus

The way you describe it is the way i use it

no after a heavily debate whith Mac i never larksheadded anything on my gear..
same principe as you see this magic guy putting on a ring on a string...

cant rember how to do it right now,but will get back to you...

you could put on a rubberband to the bridel(bridel through it,before you s fold the bridel),i just tryed to find the way backwards as i tryed to regain the way to do it.it takes not alot force to let go of the bridel anyway...