bag dump/bag strip and why it might happen

[sundevil777 93]

I realize a lot of people say "line dump" when they really mean "bag strip", but I wonder if bag strip really isn't a whole lot more common than we realize, but for a different reason than we realize.

Normal rubber bands break often, right? I think it might be that they are breaking during the acceleration of the bag out of the container, and that during that extra stress might be when a lot of the bands are actually breaking. That would mean bag strip at some point during the deployment, maybe late in the process (not so much impact on the deployment), maybe early (more impact).

This leads back to a strong preference I have for locking stows that don't break easily. I don't like the idea of rubber bands breaking when I wouldn't want them to break. A lot of times it seems like a regular rubber band is impossible to use even one time without it showing some tearing. That just isn't good enough for me, not for the locking stows.

I should also mention that I have been around guys that freepacked their mains. I never would, but I've seen it, so maybe I worry too much about locking stows breaking, but I hate hard openings and malfunctions.

People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am

[riggerrob 558]

MIL SPEC rubber bands break at 40 pounds.

Most line dumps/bag strip are caused by sloppy packing. Sometimes the problem is too little suspension line hanging outboard of the rubber bands (un-balanced line stows), but more often the root of the problem is rubber bands (or Tube Stows or Silli Bands, etc.) being too large to hold the lines tight enough.

[sundevil777 93]

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MIL SPEC rubber bands break at 40 pounds.

Most line dumps/bag strip are caused by sloppy packing. Sometimes the problem is too little suspension line hanging outboard of the rubber bands (un-balanced line stows), but more often the root of the problem is rubber bands (or Tube Stows or Silli Bands, etc.) being too large to hold the lines tight enough.

Sure, 40 pounds is right, but only in new condition, without tears.

Haven't we all seen pre-torn locking stows used. Haven't we all had a band break while we were trying to use it while packing? That means we had intended to use the band as is, but we were lucky to have it break while closing the bag instead of when the bag was being lifted off our back.

To me, the 40 pound spec has almost no meaning, unless the band is in new condition all the way until when it is used. From my experience, rubber bands get tears in them extremely easily - it is hard to use one on a locking stow without tearing it. They often get torn just from installing it (new) on the d-bag. A more useful measure of strength would be after a couple jumps, with a typical set of little tears already started, the type of tears that most jumpers accept without much thought to the possible result.

People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am

[andreeb77 0]

Might be a dumb question but what exactly is the difference between a line dump and a bag strip?

[LongWayToFall 0]

Well, the way I see it is that the band isn't going to break until it is the next one to release lines, so all you get is reduced tension. Isn't the major downside to stronger stows like tube stows, is they cause bag locks? Breaking can be a good thing.

[Rover 9]

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Well, the way I see it is that the band isn't going to break until it is the next one to release lines, so all you get is reduced tension. Isn't the major downside to stronger stows like tube stows, is they cause bag locks? Breaking can be a good thing.

I've only ever seen 1 baglock. She bounced though

2 wrongs don't make a right - but 3 lefts do.

[sundevil777 93]

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Well, the way I see it is that the band isn't going to break until it is the next one to release lines, so all you get is reduced tension.

Bands get extra tension (they get additional stress) as a result of the acceleration of the bag off the container, long before a particular stow gets the chance to be the next to release. When one of the locking stows breaks, the remaining locking stow(s) are stressed even more. For many d-bags, the loss of just one locking stow can allow the canopy to fall out during the acceleration.

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Isn't the major downside to stronger stows like tube stows, is they cause bag locks? Breaking can be a good thing.

That is the myth. I think it is just a myth. Even so, your reserve is packed with a stow that will not break from the force of the pilot chute pulling on it. Others on this forum have seen bag locks happen despite the use of regular rubber bands.

I will take the chance that a locking stow won't break when I would want it to vs the near certainty (I feel) that a locking stow will break when I don't want it to.

People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am

[Cueb 0]

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Isn't the major downside to stronger stows like tube stows, is they cause bag locks?

They don't cause bag locks, if you packed a bag lock it is less likely to clear itself by breaking the stow. Haven't seen single baglock at my small dropzone and majority of people use tubes.

[rushmc 18]

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Well, the way I see it is that the band isn't going to break until it is the next one to release lines, so all you get is reduced tension. Isn't the major downside to stronger stows like tube stows, is they cause bag locks? Breaking can be a good thing.

I used Super Banz because they would not break. Because they would not break and sloppy line stows (I crossed one) I had my one and only reserve ride
Took them all out and went back to rubber. I would rather deal with lines coming out too early than not at all............ever again

"America will never be destroyed from the outside,
if we falter and lose our freedoms,
it will be because we destroyed ourselves."
Abraham Lincoln

[rushmc 18]

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Well, the way I see it is that the band isn't going to break until it is the next one to release lines, so all you get is reduced tension.

Bands get extra tension (they get additional stress) as a result of the acceleration of the bag off the container, long before a particular stow gets the chance to be the next to release. When one of the locking stows breaks, the remaining locking stow(s) are stressed even more. For many d-bags, the loss of just one locking stow can allow the canopy to fall out during the acceleration.

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Isn't the major downside to stronger stows like tube stows, is they cause bag locks? Breaking can be a good thing.

That is the myth. I think it is just a myth. Even so, your reserve is packed with a stow that will not break from the force of the pilot chute pulling on it. Others on this forum have seen bag locks happen despite the use of regular rubber bands.

I will take the chance that a locking stow won't break when I would want it to vs the near certainty (I feel) that a locking stow will break when I don't want it to.

Not a myth

If you cross one line from the stow it is supposed to be in to another one you can make a very effective friction type knot. It was quite clear once my d bag was found with the main still in it

Again, I was using those super banz. I loved them and they lasted forever but, they will not break when you need them to

"America will never be destroyed from the outside,
if we falter and lose our freedoms,
it will be because we destroyed ourselves."
Abraham Lincoln

[sundevil777 93]

So there is an example of a bag lock that you could say was caused by too strong of a locking stow. I am always extremely careful with my stows, especially the locking stows, so I think the trade-off with tube stows (I make my own very easily) is worth it.

What is more important is that much more than lines may come out early if locking stows break when they shouldn't. The entire canopy may come out when a locking stow breaks. My contention is that locking stows break often when we would not want them to, and that may be the cause of some bad/harsh openings without ever being realized that it may be the cause.

People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am

[sundevil777 93]

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Not a myth

If you cross one line from the stow it is supposed to be in to another one you can make a very effective friction type knot. It was quite clear once my d bag was found with the main still in it.

Again, I was using those super banz. I loved them and they lasted forever but, they will not break when you need them to

Others have witnessed bag locks with regular rubber bands used. Your incident may still have happened with regular rubber bands.

Either way, I still prefer the trade-off. There is a very good reason that reserves are closed with such very strong locking stows - you don't want it to break.

People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am

[rushmc 18]

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Not a myth

If you cross one line from the stow it is supposed to be in to another one you can make a very effective friction type knot. It was quite clear once my d bag was found with the main still in it.

Again, I was using those super banz. I loved them and they lasted forever but, they will not break when you need them to

Others have witnessed bag locks with regular rubber bands used. Your incident may still have happened with regular rubber bands.

Either way, I still prefer the trade-off. There is a very good reason that reserves are closed with such very strong locking stows - you don't want it to break.

You have nailed it
Every choice has a trade off
And if I had taken the time to walk all the stows like I usually did, I would not have had the problem.

I went back to rubber because I wanted to take one more issue (as I saw it) out of the equation. I have always felt that skydiving is a sport where one has to manage risk because you can not remove it

Anyway


I still have a few of those super banz left
I have sold most of them cause I dont think anyone makes them anymore. And they do work very very well

Marc

"America will never be destroyed from the outside,
if we falter and lose our freedoms,
it will be because we destroyed ourselves."
Abraham Lincoln

[NovaTTT 1]

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Might be a dumb question but what exactly is the difference between a line dump and a bag strip?

Line dump happens when the lines are released from the stows prior to linestretch, usually upon extraction of the bag from the container.

Bag strip is where the parachute prematurely escapes the bag. The parachute then inflates, or begins to inflate, and the jumper reaches linestretch to find himself hammered under an anchor in the sky.

ETA: It's not a dumb question. You have to ask if you want to learn.

"Even in a world where perfection is unattainable, there's still a difference between excellence and mediocrity." Gary73

[AndyMan 7]

Nothing would make me happier than to see video evidence of either of these phenomena actually happening.

I've heard from people with second or third hand information of such video existing, but I've never seen it - nor heard directly from someone who has.

Me, I've directly witnessed hundreds of openings as an AFFI, and I've shot many hundreds more as a videographer. I've heard many complaints of hard openings, and I've heard many prognosticators on the ground state definitively: "You had bag-strip/Line-dump/bag-dump" - yet video evidence of these theories remain remarkably absent.

I'm skeptical, but still inquisitive. I'd love to see some video.

_Am

__

You put the fun in "funnel" - craichead.

[sundevil777 93]

Indeed it would be great to see actual video of such incidents and to have knowledge that they were associated with bad openings.

Locking stows break so often, why shouldn't we think that they are busting at "lift off"? It seems to be at least as likely as them breaking when they are releasing the line group (when it no longer matters if they break). Some might even be breaking while the container is still closed, and of course once one breaks, the others are more stressed during lift-off.

People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am

[AndyMan 7]

I don't know whether it happens or not, I'm just skeptical. Ultimately if this happened a fraction of the time that it's credited, we'd be seeing direct evidence of it including video.

My understanding of physics is rudimentary at best, but ultimately I think that nylon simply lacks the density of mass to do this type of damage. Secondly, when I imagine the direction of forces involved in bag-liftoff, I just don't see those forces lining up with the rubber bands. I can imagine some force being put on the closing flap, I see only a small fraction of those forces being transferred directly to the rubber band. Lastly, most of these scenarios require that all locking stows release. One broken stow isn't enough, I think they all have to break. On some rigs this means 3 stows. The force required to do this is huge.

I think - given the two explanations for broken bands being 1: line dump/bag dump/bag strip, etc and 2: line stretch pulling on the bands - the second option makes SO much more sense.

Also, as for explaining hard openings, packing issues including slider and nose placement seems to be much more likely occurrences.

I don't reject it altogether, the explanations are gospel to people a lot smarter than I am, but truth be told that I just don't get it. I'd love to see some video.

_Am

__

You put the fun in "funnel" - craichead.

[billvon 2,396]

>I realize a lot of people say "line dump" when they really mean "bag strip",
>but I wonder if bag strip really isn't a whole lot more common than we
>realize, but for a different reason than we realize.

I don't think either one is common. I mean, try your very best to pack a 'bag strippable' pack job and then try to pull hard enough on the bridle to make just the canopy and not the bag emerge from the container. It's pretty hard to do.

And while it's common for the first few stows to be either loose or nonexistent (many packers just coil the last few feet of lines in the container) the odds of every stow coming out during bag liftoff is really low as well. Again, a ground experiment could demonstrate the risks here. I think you have to have some pathologic conditions (a canopy several sizes too small for the bag, large rubber bands single stowed around microlines etc) for this to be a worry.

Line dump/bag strip can result in fatally hard openings, so a _really_ hard opening, no matter what the cause, is often described as one of the two as a euphemism for "a really hard opening." The reasoning usually goes "Wow, that almost knocked me out! It must have been line dump."

The first time I jumped through serious rain I thought it was ice because it really hurt. Then I jumped through ice one day. After that I didn't confuse the two.

[davelepka 4]

Another problem with locking stows, and this would also be a contributing factor to bag strip, is poor packing technique, or over-stuffed bags.

I see many jumpers who have to stretch their locking stows several inches just to get the bag shut. When they do, the stows remain stretched, and the bag is not excactly what I would call 'closed'.

In this configuration, the locking stows are under far more tension than the other stows, and the gap beteen the flap and the rim of the bag is considerable. So you have stows that are more likely to break, and the room for the canopy to 'squirt' out of the bag.

Properly sized d-bags for the canopy, and proper packing technique will keep the tension on the locking stows within reason, and keep the canopy better contained throughout the deployment.

I have a bag that fits my canopy, and when the bag is closed, there is virtually no canopy visible from the outside. This means the only tension on my locking stows is the tension they provide around the bight of line, and I get a good number of jumps from my locking stows.

I actually get more jumps from my locking stows then my regular stows. I use a standard Dacron line sized rubber band for all my stows (on 500 Vectran line), and I single stow the locking stows, and double stow all the rest. The locking stows will last 20+ jumps, while the other stows sometime only make it a couple jumps.

I hear what you're saying about rubber bands, and the pros and cons of different strengths. Between standard rubber bands, tandem bands, micro-line bands, single stow or double stow, and different combinations of the above, there's a combination that will make you happy, and give you the security and band life you're after. Using an unbreakable stow anywhere on your bag is not the answer. I used bungee stows for awhile about 15 years ago, and they lack the elasticity of rubber bands, wear out quickly, and are just a bad idea in general.

In a freebag application, with the single safety stow that rides free in a channel, is much different than on a regualr D-bag. Even if the stow won't break, it will release from the bag if one side or the other comes out, a feature not found on a regular d-bag.

[nitrochute 2]

it DOES indeed happen. i studied the phenomenon in some detail back in the mid 70's as it pertained to static line direct bag deployments.
Manley Butler studied it in great detail including wind tunnel tests done for Para flite around 1982.the result of his work was the invention of the safety stow which was designed by Manley/ Para flite and released to the industry.his work was the result of a fatality involving a ram air reserve bag strip. at the time reserve free bag locking stows were held with "O" rings made of Buna N compound

[sundevil777 93]

I understand what you and billvon are saying, but the condition of relatively stretched out locking stows is a common reality, even if it is not the ideal. Doing ground experiments pulling on it doesn't impart the acceleration and its result (sometimes called bag slump).

I like having greater confidence that my locking stows won't break. I accept that it isn't for everyone.

People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am

[billvon 2,396]

>I understand what you and billvon are saying, but the condition of relatively
> stretched out locking stows is a common reality, even if it is not the ideal.

Agreed. But you need a pretty pathologic combination of very short bights, very loose stows and a loose canopy to get anything like bag strip. Even with very loose stows, properly sized bights will keep the canopy from coming out, since the loads on the lines will tend to keep the bag closed during acceleration away from the container.

(Not to say that it can't happen, but I think it's far less common than people think.)

[NovaTTT 1]

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I don't know whether it happens or not, I'm just skeptical. Ultimately if this happened a fraction of the time that it's credited, we'd be seeing direct evidence of it including video.

There was a video posted a several months ago of a tandem bag-strip. It was pretty nasty. I don't have time to search for it, but IIRC it was misidentified as a "line dump" in the thread subject.

"Even in a world where perfection is unattainable, there's still a difference between excellence and mediocrity." Gary73

[glgflyer 0]

I jump a Hornet 170 with spectra lines. It is in a Javelin J3. I psycho pack (personal reasons). When I get the canopy in the bag, it fits so neatly that I can pull the flap right up to the locking stow bands with no effort. I use small rubber bands for my locking stows (actually for all my stows). The only tension on the locking stows is after I insert the lines into the rubber band.
QUESTION: Is this too loose of a pack job or is this ok?

[jumpwally 0]

I think you just pinpointed an important item,,i've also noticed it but never gave it any serious thought till you just mentioned it......proper fitting bag, i think that is a huge factor and its unbelievable as you look at people packing , the amount of bad bags

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