Carry-With-You Static Line Evolution

[mknutson]

Preliminary Information

• The following slides contain numerous static line examples that have been posted on either BLiNC Magazine or bj.com over the years.
• These slides are roughly in sequential order of when they were posted. Over 20 threads were researched to create this presentation.
• Each slide title contains a direct link to the original post.
• Comments for each setup were taken off of the forums. Information contained in this document may not be accurate and in some cases be contradictory.
• Experimentation should be conducted on the ground before actually jumping any of these static line devices. The responsibility of your actions is solely on you. Stay Safe!

BASE 704

I personally use 80lb break cord, tied to a piece of dacron suspension line, which in turn i usually lark's head to the object. I connect the bridle to the break cord with a rapide link (canopy connector link) at the p/c end. The break cord is what it sounds like: a cord designed to break at a pre-determined point. In this case, 80lbs.

COMMENT – It is not wise to tie to the structure as the SL cord may be inadvertently “cut.”

DexterBase

• June 2003 – “I had an idea for a system that wouldn't leave anything behind at the anchor point.
• I thought of the snag possibilities when the sling whips around, but as long as there aren't any huge burrs on the beam or rail, it should be okay.”
• COMMENT – Use a Pilot Chute
• COMMENT – No breakaway capability or redundancy
• COMMENT – Force multiplier may cause center cell stripage

DexterBase v2

Hooknswoop

Based on Dexterbase’s design but using Dacron

COMMENT – Possibly not abrasion resistant enough. Try a 4 mm dyneema climbing rope? It's got a 750 kg - 1653 lb Break Load, and, more important than that, its sheath is made for resisting abrasion

nicknitro71

Improvements on Dexterbase’s setup to include full secondary breakaway and a quick connect

COMMENT – Not sure how the carabineer works…
COMMENT – Do not use junk biners.
COMMENT – Carabineers may inadvertently open and snag something.

base689

• Red and Blue lines on the sketch photo are breakcord
• The main break cord loop should be quite tight; perhaps 4 cm in diameter
• Secondary branch is 10-15cm in length.
• Use about 25 cm of break cord to create the main break cord loop. But this should be object dependent in the end.

Gus

Single sling setup similar to DexterBase’s initial CWSL concept.

COMMENT – No breakaway
COMMENT – No PC

NickNitro71

COMMENT – No Breakaway
COMMENT - Too high up on the bridle (snatch/dynamic force is higher)

-image-

COMMENT – No quick connect
COMMENT – A little too complex to setup on the object

DesxterBase v3

Tie the two ends of the dacron to the bridle with a single loop of 80 pound breakcord. When you tie the knot, take all the slack out of the loop of breakcord.

If you're doing a lower jump where you want redundancy you can add a longer loop routed through the same points, just make it long enough that the first loop must break before the backup loop can be loaded.

DexterBase’s Setup Procedure

1. 1. After the container is closed, pass a rubber band over the PC and slide it up the bridle to the container. You'll use this later. For best results, use the same rubber band you would use to close your tailgate (and not the black ones!!)
2. 2. Find a suitable place to anchor the static line to. Don't use a wimpy little strap of steel, find something that doesn't look like you will pull it off and find yourself doing a 2-way with the chunk of steel that used to be attached to the bridge. Most handrails are good. Give it a tug and make sure it's as solid as it looks.
3. 3. Take out your Dexterbase Rigging carry-on Static Line attachment and girth hitch the white loop to the bridle/PC junction. (You can also tie the attachment to the bridle with break cord.) Pass the red end (away from the white end) over the handrail so that the white line faces away from the object.
4. 4. Tie the two red ends to the bridle/PC junction with a surgeon's knot using a piece of 80lb break cord.
5. 5. Start s-folding the bridle at the SL attachment point and stop about 24" from the container. Use the rubberband from step 1 to contain the s-fold. Don't use a double wrap. This stow is not meant to hold anything. The only purpose is to keep the bridle neat and staged while you get into position and exit. The bridle should easily unfold as you fall away from the object.
6. 6. Ensure that the bridle runs straight from your container to the anchor without passing under or through anything that will prevent it from loading correctly.
7. 7. Climb into position so that you're standing next to the SL anchor. Try not to stand off to one side of the anchor, as this may lead to heading problems.
8. 8. Exit with some forward movement so that you clear the object, but don't huck out there. Minimal forward movement will create less of a pendulum effect on opening and you'll be able to control the canopy easier if you're close to the ground. Have fun and have someone check your rigging before you exit. Don't be afraid to do some test drops with a SL attachment. You can easily simulate a SL attachment setup on a balcony with a bridle and a weight. Be careful and think about your rigging! Be sure.

mr prick

COMMENT – No breakaway in case of a bridle hangup.

COMMENT – “ie the two looped ends (of the pieces that go around the object) to the pc attachment loop on the bridle with a primary and secondary break cord loop (these things sometimes fail prematurely, so if you staticline low objects it's worth the backup) tie the loop of the long strand of dacron to the pc loop on the bridle with a single piece of break cord (this is your take-with-you lanyard now)

COMMENT – you still only have to loop your loose ends around the object and rapide link them together, but you now have a back-up break cord loop and in case your system gets snagged somehow, you have a piece of break cord acting as a seperable link, that will allow the system to detach from your bridle in case of a snag (after your primary and secondary break cord loops are broken)” -- 980

livenletfly

COMMENTS – Metal on metal is bad
The connector link type used could pop open

blitzkrieg

Pretty good setup used by a number of jumpers:

• Pidge
• Blitzkrieg
• Mfob
• JamMasterJay
• Tom A

[table="head;class=head;cellpadding=4;cellspacing=2;border =1"]CON's
No quick connect setup
[/table]

fastpete

Very good setup incorporating a number of key concepts:

• Cary with you design
• Quick setup connector link
• “160lb” break cord loops
• Bridle failsafe breakaway
• Mid-bridle hookup to reduce snatch force

pidge

basenut

[table="head;class=head;cellpadding=4;cellspacing=2;border =1"]CON's
If the dacron line snags you can damage your canopy due to larks head and no breakaway.
Knot in the middle of your bridle
Needs 160lbs on the bridle to break the breakcord
[/table]

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.

mynamebedan

[table="head;class=head;cellpadding=4;cellspacing=2;border =1"]CON's
If the dacron line snags you can damage your canopy due to larks head and no breakaway.
Knot in the middle of your bridle
[/table]

GreenMachine v1

“I use my normal bridle, place a knot in the middle, clip the spring link to the knot, and wrap the long part of the Y in the photo around a strong point and close the circle with the quick link.”


[table="head;class=head;cellpadding=4;cellspacing=2;border =1"]CON's
No Weak Point
Don’t use a loop of break cord
Tying a knot in the bridle might weaken it
Needs “320lbs” of force to break it
[/table]

GreenMachine v2

2 new features:

• Single strand of break cord to reduce the force required to break it
• Uses only 1 piece of metal, my idea is to larks head the thing onto my bridle at the end.

[table="head;class=head;cellpadding=4;cellspacing=2;border =1"]CON's
No Weak Point if using a larks head to the bridle
No backup on the primary break cord.
Single strand of break cord, but it will not break until there is 160lbs on the bridle.
[/table]

Nocturnal59

Pretty good setup used by but needs to have the break cord set differently.

[table="head;class=head;cellpadding=4;cellspacing=2;border =1"]CON's
It is only using a single strand of breakcord (“80lbs”), which is not how it is intended or designed to be used (should be a “160lb” loop)
If you form one leg of the loop with part of your static line, then only does it make sense to use a single strand.
[/table]

GreenMachine v3

1 new feature:

• Weak link (double wrap)

Wrench = bridle just below PC
Gaff Tape = object


[table="head;class=head;cellpadding=4;cellspacing=2;border =1"]CON's
No weaklink at the bridle connection
You are loading both of the breakcords when you jump.
You are attaching the rapid link straight to the breakcord. You should rig so that the rapid link never touches the break cord and the break cord is tied between dacron loops.
[/table]

Sum1Sneaky

-image here-

Notes, Dynamic Force Testing, Setup Procedures & Knots

Notes

• Finger trap 10x the diameter of the line
• Use 750 Dacron around the object
• I also don't like systems where the rapide link around the break cord - I believe there is a chance that the link's threads could abrade the break cord, it can be pinched when it is closed in a hurry.
• Use a 46 or 48” PC as a backup
• bridle attachment point on canopy is supposed to break away at 400 pounds of force. - marty
• Stow excess bridle (between attachment point and PC) in “s-folds” with a band.
• "short tie" your bridle or plain use a shorter bridle. With a longer static line there is more chance you will have it break by dynamic vs static force.

Dynamic Force Testing #1

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.

-- Tom A.

Dynamic Force Testing #2

From an individual who took a BR FJC –

“Tie a 5lb weight to 80lb break cord and drop the weight from the height of a table, the 80lb break cord will break… The cord breaks because of dynamic force that is created from the acceleration of the 5lb weight. So it may only be 5 lbs but with acceleration it excerpts more pull force than 80lbs. Same thing when you are doing a static line jump. In a perfects scenario it may only take 20-30lbs to extract the parachute, but how much pull force are you really putting on that 80lb break cord on every jump?”

Dynamic Forces #3

When they were doing the demo jump at the Superbowl, Apex had to do a bunch of drop tests to satisfy the various powers that were involved in the event. They found that tying break cord at the end of the bridle had a noticeable rate of premature breakage (if I recall correctly, Jimmy told me it was 1 in 20 or something), but that tying the cord halfway down the bridle reduced the premature breakages to the point that they were unable to create any with repeated test drops. They created bridles with sewn in loops to static line from, about halfway down, just for that demo.

An easy way to tie in partway down is to put an overhand loop in your bridle and tie to that.

Dynamic Force Experiment –

Conduct a simple experiment to demonstrate this dynamic force. Attach a 9 foot bridle to a fixed point (the ceiling). At the bottom, attach a 5lb packing weight. The two are attached by a 80lb break cord. The 5lb weight is dropped from the ceiling and allow to freefall 9ft. The 5lb weight will generate enough dynamic force to break the 80lb break cord.

From 9 ft it should take about 0.75 sec to fall, reaching 24 ft/s velocity with a momentum of 120 lb ft/s. Because it's decelerated quickly over a very short amount of time) it generates more force on the cord (more than 160 lbs) than just it's momentum.

Let's make it clear once for all. A 80 lb - 36 kg break cord will break at 80 lb - 36 kg when "deployed" in a "perfect" environment such a laboratory with one single strand of break cord in the "jaws" of a dynamometer.

When we use break cord we are NOT in a laboratory and so we use it in a loop configuration, which loop configuration is going to break at 160 lb - 72 kg, again when measured in a laboratory environment, i.e., with a long loop with terminal ends sewn together in a long seam and same loop placed in the proper fitting of same dynamometer.


When we SL BASE jump, we do NOT have such a proper fitting, moreover we don't have up there a sewing machine, so, in the end, we do a surgeon knot in order to be able to close the loop and "surgeon knot" in order to minimize the "knot degradation factor".


Any cord/rope/whatever is going to have its own BL (Break Load) diminished every time a knot is done on it.

According to various books/text (Dan Poynter manual included), we can expect to have the BL diminished of 40% when a knot is done (or, new BL is 60% of theoretical BL).


So, given for granted the theoretical break load of our break cord is 160 lb - 72 kg (we are using it only in a loop configuration), in the end we come up with an actual BL of 0.6 x (160lb-72kg) = 96 lb - 43 kg. To make short a long story:
when we use a 80 lb - 36 kg of break cord in our SL BAS Ejump, we can expect that we break the loop of same break cord at 96 lb - 43 kg.


Or, said in another way, closing the loop with a knot "deteriorates" the break cord BL in a way that in the end we have a real BL which is nearly the same as the theoretical single strand BL (it should be double but returns to the "original" value because of the knot).

Dynamic Forces #4

Flex is the key! NO flex => infinite force!

Dynamic energy, aka Kinetic energy: => Ek = 0.5*m*v^2
v^2 = 2gs (for a falling object, ignoring air resist)
Ek = mgs, g=gravity's acceleration

150 lb, 25 feet => 68 kg, 7.6 m:=> Ek = 68*9.8*7.6 = 5064 Joule
10 lb, 9 feet => 4.5 kg, 2.7 m:=> Ek = 4.5*9.8*2.7 = 119 Joule
10 lb, 4 feet => 4.5 kg, 1.2 m:=> Ek = 4.5*9.8*1.2 = 53 Joule
If this energy is transferred to the bridle over a short period of time => large force.

If this energy is transferred to the bridle over a longer period of time => smaller force.



I mean, think of a bungee jump: the reason your legs don't snap off is because the bungee gives in and absorbs the kinetic energy over some time!!!!


So, let's assume your SL/bridle/folded canopy can stretch/flex/give in 5 cm when reaching bridle-stretch.

In order for the break cord not to break, it would have to withstand a force of approx:F = Ek/d, F= force, d= distance
This gives these shocking numbers:

10 lb, 9 feet => 4.5 kg, 2.7 m: => F = 119 J / 0.05m = 2380N
= 242 kg
= 535 lb

10 lb, 4 feet => 4.5 kg, 1.2 m: => F = 53 J / 0.05m = 1060N
= 108 kg
= 238 lb

And at line stretch: If the lines also stretch with 5 cm, then:

150 lb, 25 feet => 68 kg, 7.6 m: => F = 5064 J / 0.10m = 50640N
= 5167 kg
= 11392 lb

These numbers assume a solid mass, which the folded canopy is not... which probably contributes to load the cord in 3 stages => so can divide the numbers above with 3 ?? If so the numbers make more sense.

Dynamic Forces #5a

You're basically right about the force required to stop something from falling. After an object with mass m has fallen a distance h, it has energy E = m g h, where g is the acceleration due to gravity (9.8 m/s^2). To stop it, you need to do work equal to that energy. We can use the equation W = f d, where f is the applied force and d is the distance over which it's applied, to figure out how much force needs to applied over some distance to do that work. If the distance was zero, the required force would be infinite.

To get an idea what the real forces look like, I cooked up the attached graph of force vs. distance for a hypothetical jump, with the following assumptions:

• The length of bridle from the anchor point to the pins is about 2 m; to the canopy is 2.5 m. From the anchor to the jumper is 10 m.
• I assume a 2 kg (19.6 N) pin tension.
• The canopy is lifted over its own height, about 1 m. I assume the canopy weighs about 5 kg, so it has about 122.5 J of kinetic energy when it begins deceleration.
• Finally, it takes about 80 lb to break the break cord, or about 356 N.

There are (as anybody who's done PCA's has experienced) three points at which a falling jumper applies force to a static line system...

1. A small tug as the pins are pulled out of the container.
2. A bigger tug as the pack job is pulled to a stop, and extracted from the container.
3. A final, potentially huge, yank as the jumper hits line extension.

Ideally, a static line setup would mimic a skilled PCA, holding through the first two and breaking just as the third comes into play (or even just before it). When the static line breaks before (1), somebody's towing their pilot chute, maybe for a while. When it breaks before (2), somebody's getting a little freefall on their S/L jump. When it fails to break early enough on (3), somebody's replacing their bridle and/or canopy.

--force distance image here--

Dynamic Forces #5b

The jump is made up of three events:

• Event 1: The pin is extracted. This event is dominated by pin tension, since the energy required to decelerate the pin is quite small. The force continues to build until this threshold is reached, and then the pin is freed and the event is complete.
• Event 2: The canopy is lifted. This event is dominated by the energy of the falling canopy, since the canopy needs to be completely stopped. The canopy is stopped over its own height, assumed to be about 1 m. At the time it is lifted, the canopy has about 122.5 J of kinetic energy. Since the canopy is a pretty homogeneous thing, I figure the force is evenly distributed over the height of the canopy. Using the equation W = f d, we get about 122.5 N of force over 1 m.
• Event 3: Line stretch is reached, and the jumper is decelerated. The applied force increases until the break cord breaks. Thus, the jumper's vertical motion may not be completely stopped by the break cord. Indeed, if it were, the jumper would be hanging off the object.

Looking at the graph for the hypothetical jump, there are a couple of things that catch my eye:

First, the key point as far as the break cord is concerned is that it should break at a force higher than the maximum force in Event 2, but as low as possible otherwise. Any additional force is just contributing to wear and tear on the gear, and also shocking the canopy (which results in some altitude loss). Now, we don't know exactly what force it will take to lift the canopy, and we don't know exactly what force the break cord will break at, so we build in a bit of a safety margin. In this case, 80 lb break cord seems just about ideal.

Second, I wonder how a bungee cord would affect this graph. Event 3 would be mostly unchanged, since the peak force still needs to reach 80 lb if we are using the same break cord. Event 1 would likewise be unchanged, since the threshold force must still be reached. Event 2, however, might be smoothed out a bit, so that the peak is lowered and the bump becomes a bit broader.

For the benefit of those who are not familiar with calculus: When we look at an equation like W = f d, what we're really saying is that work is the area under the curve, when force is plotted against distance. That means we can do the same work with a short, broad bump, or with a very high, narrow peak. When we add the bungee to the system, we increase the distance over which the canopy is decelerated, which means we can apply a little less force, and get the same work.

So, a bungee might bring the Event 2 peak down a little bit. However, unless we change to a weaker break cord, the peak forces are unchanged, since these occur in Event 3.

Sum1sneaky’s testing

1. = Broke at 105lbs – deemed the most reliable method.
2. = Broke at 98lbs
3. Bad idea since the two ends would still have a loop on them once the single strand breaks.

Believe it or not, I just tied 12 feet of 6mm climbing rope to a 4 pound rock and dropped if off my balcony (a fall of 12 feet), it broke 80lb break cord tied in a loop (same knot as in test 1)


MIL-T-5661 Type I Plain Weave cord is designed to have a breaking strength of 80 lbs (minimum). That breaking strength is measured with one piece of material pulled in a straight line. Breaking strength will be reduced by any bends or knots used. The knots you have in Test 1 and 2 use a "loop" of the material, that is, two pieces. In theory, that would take the breaking strength to 160 lbs. As you found in your tests, the material's strength is reduced (and is weakest) at the knot, so that is where it broke (your test2_break.jpg). A 97lb breaking strength indicates the knot reduced the strength by 63 lbs or about 39%. That's par... Poynter's Manual, Vol 1, Section 8.6 indicates a 40% reduction can be expected with a bowline knot. I'd go with Method 1 as well - It keeps the whole sling from sliding around. And as you mentioned, I'd avoid method 3 like the plague...
- riggersam (mark)

SBCmac Procedure

The one thing that the diagram doesn’t demonstrate is how you manage your bridle when standing at exit point. I personally “S” fold the bridle and use a rubber band to manage the access that is left over. Again be careful how you manage your bridle; there are many things that can go wrong with just your bridle… Again, get advice from others that have lots of experience on how they manage their bridle….

gweeks Procedure

1. Tie your bridle into a small loop about 2-3 feet from your pins or shrivel flap -- far enough away so you can still climb out. Taking a bite of bridle and tying an overhand knot should work.
2. Tie this loop to the attachment point with a small loop of break cord and a large loop of break cord.
3. S-fold the excess bridle and stow it loosely with a rubber band.
4. Tie the pilot chute attachment loop to the attachment point with another loop of break cord. (not sure how this will work though)

Ten48 Procedure

When I static line I like to attach the SL as close to the shrivel flap/pins as possible while still allowing me to stand-up at the exit point. In fact, I'll bring several different lengths of static line to still allow me to attach close to the pins and still stand up. (ie - If I'm standing on a platform and tying off to the platform the SL needs to be longer than if I'm tying off to a rail that's right behind my back.)

What to do with the extra bridle? The same thing I do on a hand held jump. I s-fold the bridle up to the pilot chute in my hand and execute a throw-and-go on exit. I pitch up and out to keep the bridle and PC away from the object yet ready to inflate if the break cord breaks prematurely.

Why do this? The shorter the static line, the lower the shock-loading applied to it at SL stretch. It probably means more with a shrivel flap than pins, but at heights lower than 150 ft, anything I can do to avoid a premature breakage of the break cord, I'll do. Also, pitching the PC up and out puts it above and away from the object.

I have video of this technique and the PC is inflated VERY quickly after the break cord breaks. Of course, canopy is inflating at the same time, but it sure looks like that PC is ready to do its job. (This was a 143 ft B with a 50 ft palm tree directly below and a 90 right required for landing.)

Alpine Butterfly

Water Knot

Surgeon’s Knot

4:1 Frictionless Pulley Theory

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