Line dump, bandless bags, fewer rubberbands

[DJL 235]

Breaking off from the 7cell vs. 9cell thread. I have some questions about this. I've read that line dump doesn't lead to a hard opening as long as it's not the locking stows, Jimbo says he's left 6 to 8 ft of unstowed line with no problem on opening. On the other hand I was told that bandless bags had to fit an exact pack volume. Is this because there is not a locking stow so whatever mechanism keeps the bag shut until line stretch needs to be tight?

"I encourage all awesome dangerous behavior." - Jeffro Fincher

[PhreeZone 20]

Bandless bags have to have pretty exact measurements since they use the volume of the canopy to hold the lines in place under the flaps. Too much canopy and the flaps might not release, too little and the flaps will just fall open. Flaps opening before the canopy gets to line strech is bag dump.

I used to leave about 8 feet of lines just coiled in the bottom of my contaner and place the dbag on top of that. I had enough I'd end up getting the locking and maybe 1 stow on each side. A few people have seen me packing this way and it always draws a few strange looks.

Line dump is when the canopy comes out of the Dbag before you reach line strech. Tail pocket canopes are easy to get line dump on since you are able to present the nose to the air before the canopy is all the way at line strech. Once the nose is exposed the canopy wants to inflate and its slowing down even as you are still falling away from it. When you finally reach line strech the canopy is partly inflated and you come to a sudden stop at the end of the lines.

Yesterday is history
And tomorrow is a mystery

Parachutemanuals.com

[rigging65 0]

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Line dump is when the canopy comes out of the Dbag before you reach line strech.

Ummm...NO...

LINE DUMP (or LINE STRIP) is when the lines come off the bag before reaching full stretch.

BAG DUMP is when the canopy is out of the bag before reaching line stretch.

They are not the same, and one is not dependent on the other. That is, you can have Line Dump without Bag Dump, or the other way around.

Please use these correctly, as they are very different terms. One isn't a big deal, the other is a HUGE deal.

"...and once you had tasted flight, you will walk the earth with your eyes turned skyward.
For there you have been, and there you long to return..."

[DJL 235]

Found a picture:

http://www.sunpath.com/bergerbag2.htm

Are there any bags like this that have locking stowes so that you don't have to worry so much about the fit? Or, could the same effect be achieved just by single stowing non-locking bands. Or is there really any point to all of this besides splitting threads on something that already works. Tube stows better? I'll go do a search on those.

Also, don't you have any worries about your coiled lines catching on something as they unspool from your back up, rather than your bag down? Perhaps a loop catching on the closing loop tab?

"I encourage all awesome dangerous behavior." - Jeffro Fincher

[NeedToJump 0]

I don't know all the advantages of the stow-less bags other than the fact that you don't have to replace broken rubber bands. Rubber bands to seem to be out of place on a rig IMO. You have thousands of dollars of gear developed specifically for skydiving... and rubber bands.

Being in DeLand I see a lot of people using these bags and they all seem to like them (especially the packers.) I personally cannot wait until they are released. Also, AFAIK the BergerBag has gone through another revision and the latest version is slightly different than the pictured one.

Wind Tunnel and Skydiving Coach http://www.ariperelman.com

[AggieDave 6]

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Tube stows better? I'll go do a search on those.

Well, RWS recommends them for your locking stows.

Basically, their research shows that when you deploy, your canopy tries to stay in place (in the container), but the PC and bag try to excellerate away from the container. Thus the bag strains against the locking stows to pull the canopy with it. They have or had a really cool power point presentation with all sorts of pictures and stuff showing this.

They say that tube stows will give more stretch and will be less likely to break, thus cutting down on your chance to have bag-strip.

RWS does say that regular packing rubber bands are fine for the rest of your stows, though, since they don't take the direct force of the initial deployment.

--"When I die, may I be surrounded by scattered chrome and burning gasoline."

[relyon 0]

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Tail pocket canopes are easy to get line dump on since you are able to present the nose to the air before the canopy is all the way at line strech.

Freestowed tailpockets (ie. a closing stow and a line pouch) line dump pretty much by design. Depending on how you treat the nose, you can get anything from the equivalent of a bag dump (though there is no bag) to fairly snively behavior. I freepacked a Triathlon 160 once (no bag, no pouch, single tight band, lines in the pack tray) and took it to terminal. It opened the same as if it had a bag.

Bob

[chuckbrown 0]

A little more description on freepacking without a tail pocket, please. I take it the locking stowe is loose and placed similar to where it would be on a tail pocket canopy?

[sundevil777 102]

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They say that tube stows will give more stretch and will be less likely to break, thus cutting down on your chance to have bag-strip.

Exactly, the ability to break is not an advantage for the middle locking stows. The locking stows at the end can break without much danger of bag dump.

I think that for most rigs, the first locking stow really needs to be stretched. Or at least I like being able to really stretch it rather than compressing the canopy before I get the first stow applied. Rubber bands would always partially tear, even when using new, longer bands. My first 2 locking stows are tube stows (I have 4 locking on my wide bag), but everything else is rubber. It seems that tube stows have to get really tiny to hold at all if they don't get stretched, and then they are a pain to work with. Rubber bands are wide (don't roll) and have high friction, so they are good (hold the lines well) even when they are not stretched.

I used to put 2 rubber bands together to make a super long band for the first locking stow on my first generation Sweethog. This made sense to me because the first stow would always 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

[relyon 0]

Exactly. All I did was double wrap a band around the lines and an inch or so of the center cell trailing edge at the unsupported rib. It's also easy to bartack an attachment point at the same location so you don't lose the band.

Bob

[riggerrob 643]

Also, don't you have any worries about your coiled lines catching on something as they unspool from your back up, rather than your bag down? Perhaps a loop catching on the closing loop tab?

[ZigZag 0]

Think about your reserve and the system it uses.
The lines are stowed very much in the same way as some of the newer 'd-bags' in circulation. They are still in an experimental stage, but it stands to reason that more people will end up using this system, if only because they have seen it and want it!!!

The thought behind it is that the lines reach line-stretch without the d-bag oscillating side to side due to line bights having to overcome the tension of rubber bands. This, in theory, helps prevent line-twist
and provides for an increased probability of an on- heading opening.

For reserves it also means less forces to overcome in order to provide a rapid deployment of the canopy!!! In a sense you could call it line dump, but far more important is the line tension within the canopy as it is folded and placed into the bag. The tension should be proportional to the line attachment points and the overall exposure to the wind stream the canopy is exposed to during deployment. In theory.
Then shit happens and you start at the beginning.

In other words, if you pack and place your canopy into the d-bag with slack lines, brace your self. It is about creating a load path without slack. The same can be said for lines that have been stowed assymetrically between the left and right side of the Main Lift Web, or your risers not being even during deployment.
Does any of this make sense?

[nael 0]

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LINE DUMP (or LINE STRIP) is when the lines come off the bag before reaching full stretch.

BAG DUMP is when the canopy is out of the bag before reaching line stretch.

Please use these correctly, as they are very different terms. One isn't a big deal, the other is a HUGE deal.

Just reading through some old threads and this one brought up a few questions, since I have just started learning about all this stuff.
Can someone explain what the results of a bag dump and a line dump would be and what actions would need to be taken? The way I am picturing it, i am thinking both would just make the opening of the canopy slower, but obviously this is wrong if one of them is a "huge deal". Thanks.

www.TerminalSports.com.auAustralia's largest skydive gear store

[mjosparky 4]

I have been jumping a bag with just 2 locking stows and the rest of the lines in a velcro pocket for well over 5 years and several hundred jumps. I have yet to have a problem with "line dump" or any problem for that matter. The bag deploys the lines with much less "line whip" and the bag seems to stay stable through out deployment. I don't recommend just S-folding them in the pack tray, I am one of the guys RiggerRob refers to that had a line group entangle with a side flap. No I didn't die, a diapered round reserve made it through the mess. But I did go to a tail pocket after that.
Sparky

My idea of a fair fight is clubbing baby seals

[gus 1]

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Can someone explain what the results of a bag dump and a line dump would be..........i am thinking both would just make the opening of the canopy slower

This is line dump:

[inline linedump.gif]

General opinion seems to be that this isn't a problem since once the lines are taut (and you reach linestretch) your deployment continues as normal.

[inline linestretch.gif]

Bagdump is where the canopy has escaped the bag and has started to inflate before you reach linestretch:

[inline bagdump.gif]

The problem with bagdump is the rate at which you'll decelerate when your lines go taut - your opening could be hard enough to damage you and/or your equipment.

I think I deserve a medal for those drawings.

Gus

OutpatientsOnline.com

[mr2mk1g 10]

for the drawings teacher gives you...

I interpret it as with a bag dump, the canopy effectivly stops while you carry on at 120mph... for the length of the lines... then you are promptly also brought to a stop...

200lb of meat going from 120mph - 0mph in 0ft/0sec - thats gonna hurt and puts a lot of stress on your gear.

[nael 0]

Ahh it all makes sense now! Thanks for explaining it to me gus, the drawings were beautiful by the way - you earnt every bit of the teachers gold star!

www.TerminalSports.com.auAustralia's largest skydive gear store

[Falko 0]

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for the drawings teacher gives you...

hilarious

What I've taken away from this thread is to REPLACE a locking stow (tube), as soon as it shows any sign of damage. I can remember using that last black locking stow for many jumps while it was almost torn (just 2mm or so left). The "plan" was to replace it after it would brake.

Now I know better, thanks everyone!

Bag dump sounds like a really serious malfunction.

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[mjosparky 4]

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Bag dump sounds like a really serious malfunction.

It's not necessarily a malfunction, but it can make your lights blink in several colors.
Sparky

My idea of a fair fight is clubbing baby seals

[skymedic 0]

if not shut the lights off forever in the process....

Marc
otherwise known as Mr.Fallinwoman....