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Just curious what some of you are doing with your S/l set ups; if any one is replacing the bridle with a shorter piece of cord, if so, how long and why?

Thanks

I tie an overhand loop in the bridle where ever I want it, object depending. I use my 48 pc as a back up in case both my break tapes break pre-mature, atleast there's still a chance my 48 will tow it out for me. Can't doe that if you take your bridle off.

same setup as SBCDave

I'm using the rig in the picture that I was shown to me by Tom A. A mate recently came back from Tom's course and was shown a totally different way, not sure why.. Maybe Tom has changed his methods for some reason. Tom?

Personally would never take the pilot chute or bridle off and use something else. No need, or if there is a need then maybe the jump isn't worth it.

If you run the single line to the shorter length on that s/l setup, you can still use break cord on the longer one to the bridle and it's a carry away that will break away if it hangs up on anything.

Edited
I learned a lot and will be trying some new things.


Please Note

At 79 BASE jumps I am still a newbie, all of the
above WAS simply things I learned from Tom A.,
Robert, 2nd hand by DW & my own practices.

I would NOT jump your static line device.

where is the weak point? what happens if the longer hunk of red line gets hung up? something will give!

also, you probably should NOT be using a loop of s/l with that setup. you may have a 4x system there. (I thought previously you mentioned conducting test. I could be wrong.)

where is the weak point?
The metal pieces are rated for less than my body weight.

you probably should NOT be using a loop of s/l with that setup
What?

you may have a 4x system there
Please explain.

thought previously you mentioned conducting test
Yes, I have done tests, both in my backyard and
a dozen jumps from antennas between 190 & 315.
Myself and a few friends have all had good jumps
and no problems using this kit.

However, please show me what you use so maybe
I can avoid some possible future problems, thanks.

Yep. I've changed my method several times. I'm a firm believe in continuously thinking about and improving anything I'm trusting my physical well being to.

The specific set up you've got there I stopped using after we tore a bridle in half during a course. We then got a nice lecture from some engineers about how to rig things differently.

I"ll try to either take some pictures or draw some diagrams and of the method I'm currently teaching, and post them.

The system you are using multiplies the force necessary to break the break cord by a factor of 4. Meaning that if you are using 80 pound break cord, the actual breaking force is 4x80, or 320 pounds.

To reduce your system to a 2x system, simply change the loop of break cord into a single strand (tie one end to each side, leaving just a single line between them to break).

Note that the dynamic force of your body freefalling to line stretch is going to produce _a lot_ more than 320 pounds, so the worry is not that you will end up hanging on the end of the system. Rather, the problem is that you're unnecessarily stressing your bridle (and other components). As I noted in the last post, we discovered this when an old bridle, tied in a knot halfway (which weakens the bridle) broke using this style of system.

The weak point, in theory, is the screw link, which is rated at 220 pounds.

In actual practice, the thing that I've seen fail is the bridle, which is rated, when new, to around 1000 pounds.

A manufacturer once told me that the attachment of the bridle to the canopy is rated at less than the strength of the bridle, and that he considered that to be the "fail safe" point in case of a bridle entanglement.

Body weight isn't really terribly relevant. When you hit line stretch, you've fallen something like 20 feet. The dynamic forces involved create a huge amount of force, even with a relatively light load. Remember Force = Mass x Acceleration? Dropping a 40 pound weight 20 feet onto that link would break it. Any jumpers body weight, after that fall, is going to be more than enough to break the link (or in the event of some entanglment, the dacron line itself, or the bridle).

Shortening the bridle (or using an intermediate tie off point) is not about getting open higher. It's about avoiding a premature breakage.

If you drop a 10 pound weight 9 feet onto your break cord, it's probably enough to break it. Guess what weighs about 10 pounds? Your BASE canopy (the force needed to open a velcro rig is also usually above 10 pounds). Shortening the bridle reduces the distance fallen prior to loading the break cord. This greatly reduces the dynamic force that loads the break cord when the canopy (or shrivel flap) is first felt, reducing the chance of a premature breakage by a noticeable amount.


The best way to test this is to tie a 10 pound weight onto the end of your bridle, and then tie up some break cord on the other end, attached to some sort of anchor.
Drop the 10 pound weight.
Does it break the cord?

Now shorten the bridle to 4 feet and try it again.
Does it break the cord?

Repeat these drop tests as many times as necessary to prove that it really won't break, not even one time in 100 (or however many static line jumps you expect to make in your BASE career).



You want to make sure that the cord doesn't break when you load it with that first 10 pounds, every single time, because that's your canopy, which is not yet at line stretch. If it breaks there, you're in free fall with an open container and the canopy sitting in the pack tray (pin rig) or worse, a closed container (velcro rig). The way to fix this is to shorten the distance fallen prior to the initial loading.

HERE is a fairly recent discussion on this topic that has some decent information in it.

The diagram posted by BASEknut in post #6 of that thread is pretty much the system that I'm teaching now.

I don't like that set up, what happens if that Dacron line snags on something? You've then got a solid link from you to the tower (or whatever).

I think Blitzkriegs setup, in the post above that, is the way to go. If something does snag or hang up, you've got additional break cord points to give way.

If the dacron snags, generally the bridle will break. Depending on where and how the snag occurs, you may find that the dacron breaks. You're never going to end up hanging from the object.

If you're not comfortable with that, it's simple enough to tie two tight loops of break cord between the dacron and the bridle. That makes it 4 times as strong as the single piece of break cord that's intended to break, so it shouldn't break if all goes well. If somehow the dacron gets snagged, the break cord loops will break before the bridle (or the dacron).


The reason that I switched away from the 'Y' shaped piece of cord that Blitzkrieg uses is that I felt the 'Y' formation had more chance of snagging than a simple line. You can still use the "in case of snag break point" with my system, too. You just don't need the 'Y' shape.

In a pinch, you can even tie two loops in the bridle and use it as the static line attachment (wrapping it around the object). I taught this method for a while too, but I think it puts undue wear on the bridle.

I would agree with that.

believe me, the upper skin of the parachute can tear apart as well.

I strongly suggest a designed weak link if someone uses a carry on s/l device.

Sure. But in any case you're not hanging from the object.

when air is rushing up into the lower vents and OUT the new upper vent, it creates a virtual free-fall affect. I really recommend avoiding it.

I once landed an old PD-210 uneventfully
after a skydive with a couple very large
holes in the topskin.

Everyone at the DZ said "fucking stupid".
Of course they were totally right

I tie an overhand knot in each end of a piece of break chord, attach one end to a carabiner wrap the other end around the object and attach it back to the carabiner. If it's low, I use two pieces, one smaller than the other.

It's simple and the break chord goes with me.

If you wrap the break cord around a sharp edge, it can greatly reduce it's strength. That's why I like using the dacron around the actual object--you can never guarantee that there will be an anchor with no sharp parts unless you've jumped the object before.

I've though of that, and when I am doing a new object I carry some electric tape with me. I'll use a few wraps around the break chord to protect it from being cut if I have to attach to a sharp point.

i would still use the "Y" shaped version in that picture without hesitation...

but i too, have a newer version that allows me to pre-tie all the knots/break-cord and has no "Y" but adds an additional french link to the system.

i think Matt F may have showed me the original concept, but i don't have one with me now or a picture and i will be out of the country until bridge day.

anyway... i really prefer to just tie to the object directly, so long as it permits. (and i also just tie a loop in my bridle for the benefits described by Tom A.)

That's the idea.

Can you explain more about how this setup would cause enough force to break a bridle? The only possible way I can think of is if you tie the two loops the same length. Even then I believe you would only double it, therefore, not enough force to break a bridle as you stated in a later post. Cheers

Any static line system should be built such that the only thing you need to do at the exit point is wrap something around an object/anchor and screw (or snap) a single link closed.

First, remember that the bridle was fairly old (thus much weaker) with a knot tied in it (further weakening it).

When you create the wrap around the object, you've effectively doubled the force.

Using a loop (rather than a single strand) of break cord doubles the force again, for a total multiplier of 4x.

I've got a diagram somewhere that grayhgghost drew when we were discussing this via email. I'll see if I can dig it up and post it in this thread.

did any hole run fully across the center cell?
was any hole adjacent to the attachment point? or was it near the less important trailing edge?
did the center six attachment points (out of 32 total) separate from the canopy, or did it hold it's shape?

look at the image. I've heard that the canopy can NOT fail as it did.

The lines all stated attached.

The holes were near the center.

Your photo looks scary, yikes.

Im really just wanting to replace my bridle, save it for less "violent" openings, so to speak. I was just wondering if anyone is doing anything different.

Im still using my PC. I was going to replace my bridle with a "length" of nylon webbing attached to the shrivel flap with a rapid link, and thread the PC into a loop on the end(no larks head) and tie the break cord loops through the loop and connect it to a biner clipped into a loop of webbing tied to a beam coming off of the cat walk. I can walk out the beam, bend down, clip it, jump.

Im trying to avoid what is in the second picture.

Thanks

I've attached a hyper-simplified and kindergarten-quality drawing of where forces get distributed in this situation. This assumes, as has been mentioned, that all surfaces and cords/webbing are frictionless (which is not the case in practice).

I know several people who've replaced the bridle with 1" tubular webbing on static lines, without issues.

pm sent

 I'd like some feedback on my current system. It's a little outside the BOX.... but , it's worked for me so far.

that's black death, no, pink death.
crotchless is the only way to go

I would NOT jump your set up(sotospeak) because the pink die has been known to cause pre-mature release. I would jump your set up if the break thong was black or blue.

Shouldnt that be OVER the box?

So you have this problem often eh?

No, I use two break thongs, one about a size 7 and a smaller one about size 4!

Thank you for this impotent information. I am now in search of crotchless panties.... does anyone have sangi's contact info???

Just start a new thread (on any subject) he will chime in at some point.

 

Here is my latest, just tested it
in my backyard and hopefully I
will try it out this weekend.

2 new features: single strand of
break cord to reduce the force
required to break it and this one
uses only 1 piece of metal, my
idea is to larks head the thing
onto my bridle at the end.

Input, opinions, flames?

Glad to see all the latest tech. jumpers have come up with. Props to all. Honestly, If I have to get off an object so fast that a system like this is needed, I wouldn't jump cuz I'd hate to die on a fucking static line jump for chrissakes. Also , here where I live, if I left a small piece of webbing on a rail that I've tied off with with break cord , I doubt these mentals would think much about it.! Don't get me wrong, yallz some smart and gifted folks out there in the think tank...Keep it up.

I created a setup I thought was pretty cool for a high profile 145ft bridge. It was for a Tuesday night 3AM, but this bridge still had a high chance for traffic, so we needed to be quick. I've never been a fan of having a biner or rapid link adding weight and drag to my shit while flying, so I came up with larksheading myself to it. Made a loop with 3ft diameter in an 8mm kernmantle sheath rope that is probably good for 2000 lbs. The loop had about a 3 inch tail with a small loop at the end of it. The big loop stretched from end to end instead of laid out in a circle was about 5ft long, and the thing I was larkheading around was a 4inch pipe (railing), so I made the loop in my bridle about 2ft from the pin, and then attached the bridle loop to the small loop with a small and a big break cord loop with surgeons knots. Everything pre-rigged, all I had to do was put the big loop around the pipe and then step through it and pull it up over myself and it was larksheaded to the pipe. Stepped up, stepped off, and my buddy grabbed the rope and bailed. I still had my 46 attached to the end of the bridle, just as a precaution, even though I would prefer to not have the extra drag. It was over water but about 40 ft from a parking lot, I landed about 80ft from the water in the center of the parking lot, about 7-8 second canopy flight.

It seems very similar to your old set up, Just elimenated one quick link and tied a straight piece instead of a loop, solving 4x issue. You still have no fail safe, weak point, in case the dacron hangs on something, unless I am missing something.

I still can't see how using a loop will double the force. If there is only one break in the loop, to me that means the loop failed at 80ish pounds.... If the two loops where the same length, sure, that would double the force.

The amount of force required to break a loop can be 2x the normal break force because it acts like a pulley.

See Diagram #1 here.

The break cord IS the red line. The applied force (F) must equal 160 (2x) to achieve 80 lbs in the break cord.

If the carry-with you s/l device wraps around the object and then attaches to a loop, you have created a more complicated pulley. The dacron of the s/l device will carry 1/2 the load. The break cord loop will also carry 1/2 the load. A loop of break cord then further divides the load in two. Thus each side of the break cord loop carries F/4.

(Note: pulleys require a relatively large radius to do their magic. A tight radius, such as a connector link or a sharp edge, tends to concentrate stresses and thus lessen the force required to break the cord.)

Set it up and test it with weights.

Not quite break cord but these tables shows how certain bends, kinks etc weaken fiber slings used for lifting or increase lift capacity depending on how you rig them.
Seeing as break cord is ultimately a fiber sling the effects should be similar.
Also worth thinking about your SL if you choke/larkshead it.

Julian

I edited to add that I that it finally clicked in my head but somehow fucked it up.

So what we need is breakcord that breaks at a lower tension yeah?

 

So what we need is breakcord that breaks at a lower tension yeah?

It seems to me if we are shortening the bridle to avoid premature seperation of the break cord, a cord with lower tension not the answer.

I think we are pretty much using the same setup now. I got rid of the Y as well and now just use 2 separate pieces of dacron, one short, one long and attached by a quick link.

From there, I tie a primary and backup break cord thru both ends of the dacron line and the bridle, then I attach a third, and much longer piece of break cord to the bridle to the shorter length of dacron. This allows the rest of the carryaway to be dragged away with me unless it happens to snag

It would probably make more sense with pictures but basically it allows me to quickly attach the setup to the object. I just wrap the longer length of dacron around the object then connect the two pieces of dacron with the quick link. All of the knots are already made beforehand.

I've tested this system a few times and I have even had it snag on an exit. It did exactly what it was supposed to do as I later found it hanging off of the object.

There is no way in hell I would jump a carry-away that is solidly attached to my bridle.

There's 101 different good ways to rig a s/l setup. Pretty soon we'll all probably say it's object specific.