do any other manufacturers or engineers support the speedbag?

[mjosparky 3]

Nancy made the following claims on 27 Feb. 2006. Since then there have been repeated requests for information to substantiate what she has said. So far there has been no response.

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I forgot to mention the other deficiency of the old style bungee stow/pouch freebag - the destruction of reserve canopies in the event of line strip. There've been several instances where lines tore from reserve canopies, or canopies blew up as a result of line strip. It's not that the canopies were not built strong enough - it's that the deployment system did not meter the lines out in a controlled manner, and sufficiently soften the opening. There has been more than one fatality as a result.

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Recent student harness failures are the direct result of line strip openings.

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All the major manufacturers use "special" bags wherein every stow is a locking stow so that the canopies will take the vicious openings encountered when you static line a 97 sq ft reserve with a 300 pound load at 180 mph! Then those canopies go out into the field where they are assembled into bags that practically guarantee a line dump.

These are some pretty strong statements, that if true, need to be addressed.

http://www.dropzone.com/cgi-bin/forum/gforum.cgi?post=2095386;search_string=speedbag;#2095386

My idea of a fair fight is clubbing baby seals

[deathtrap 0]

The problem is, is that there is only speculation that line dump or bag strip is a factor in these incidents.. I suspect that if you push hard enough for factual evidence, none will be found.

John Sherman even said at PIA that line dump happens so fast that it can't be seen on video. That's a crock of BS, IMO. If video runs at 30 frames/sec, and it takes say, 5 frames for the bag to get to end of the lines, SOMEWHERE in that 5 frames you will see uncontrolled lines if there is line dump. In order for there to be bag strip, you would need one of two scenarios to happen: line dump, with the unstowed line having enough mass to pull one of the locking stows free, or the safety stow must break. Has anyone ever seen a broken safety stow? I'm not talking about broken rubber strands inside, I'm talking where the nylon sheath has broken completely.

Think about this: Newton's first law of motion states that an object at rest tends to stay at rest. So a bridle starts to pull on the end of a freebag & the canopy inside the freebag wants to stay inside the container, correct? What's going to happen? the canopy will start to slide towards the closing flap, but the locking stow is keeping it shut. The locking stow will stretch while it's preventing the flap from opening all the way. When it stretches, it will get a TIGHTER grip on the lines that prevent it from getting pulled through the grommets. SO unless one of the bites gets pulled out, or the safety stow breaks, you're not going to strip the bag off the canopy.

[riggermick 6]

That aside, the speedbag seems like an awful lot of locking stows between my reserve and the freedom it deserves. I wonder if theres a middle-ground solution, like maybe four locking stows, with the reat in a pouch, or even just conventional stows.
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Middle 1980's Vectors had four "o" rings and a stow pouch on the free bag. The safety stow was designed to overcome the short comings of this locking stow method. Which begs the question why are they (jump shack) trying to go back in time?

There is ample SPECULATION about the evils of line dump but even it's greatist protagonist (John sherman) says that it can't even be captured on film, are we dealing with ST Elmos fire or ball lightning (often talked about but never filmed) here?

Any over loaded high speed deployment that causes catastrophic damage would be very easy to blame on the
DEMON line dump (the one with no pysical observation of it in action) much like the Salem witch hunts did for (then) unexplained phenomina.

Show me the empirical evidence of it's very existence (film of it actually occuring) and I'll start to entertain the validity of the line dump arguement.

Mick.


Edited to add: This not directed at you Dave, I just used your quote to start my post.

Mick.

[mjosparky 3]

You are preaching to the choir.

“Line dump” in my opinion does not exist or at the very least the term is misapplied. The only reason to stow the lines, in stow bands or in a pouch, is to stage the deployment sequence. How the lines are stowed does not effect how the canopy opens. The things that affect perceived “opening shock” are canopy design, slider design and placement during packing and speed and weight at deployment.

As far as “bag strip” on a reserve I find it hard to picture the bag leaving today’s tight containers without the canopy leaving with it. I suppose it could happen but I have never seen it or talked to anyone who has.

As fare as using the speedbag to prevent “line dump” or bag strip on a main I can’t see the reason. The P/C, bridle, bag and canopy are all connected. Where one goes the others will follow. I have over 1000 jumps on a main bag that used just 2 locking stows with the remainder of the lines in a pocket. The openings are always easy and on heading. My feeling is the center feed on the pocket helps prevent “bag whip” which can lead to poor openings.

There was a time in the early 80’s where 1000’s of jumps were made on ram air canopies with the use of any deployment device. They were terminal deployments on plain un-reinforced F-111 type rip stop nylon.

I will be the first to admit that thoughts on this could be all fu%*ed up. But I have not seen anyone produce any hard evidence to change my mind.

As Mick said, if it can’t be seen on tape or film with the equipment available today, I find it hard to believe it exists.

My idea of a fair fight is clubbing baby seals

[RMURRAY 1]

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I have over 1000 jumps on a main bag that used just 2 locking stows with the remainder of the lines in a pocket. The openings are always easy and on heading. My feeling is the center feed on the pocket helps prevent “bag whip” which can lead to poor openings.

how many openings do you have with your setup at 180mph and not in an optimum body position? The speedbag deployments are supposed to improve at HIGH speed - apparently it works well at low speeds as well. I would also like to see an A to B test. Video would not even be needed. If one reserve blows up and the other does not that would be good enough for me. It should be possible (without putting anyone at risk).

rm

[deathtrap 0]

How exactly is a speed bag going to help the canopy survive an opening from a less than ideal body position? The canopy is still going to be loaded wrong when it comes out of the bag.

So you would be satisfied with a single drop test on each style of bag? There have been many drop tests done with standard safety stow/freestow pocket freebags at over 200 knots......... There's even video of them if you can sweet talk the right manufacturers. Seems Jump Shack can't come up with video of line dump or bag strip though because it happens "too fast"............

[mjosparky 3]

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how many openings do you have with your setup at 180mph and not in an optimum body position?

I don't do test jumps at 180 mph, that is what torso dummies are for.

Just about every reserve canopy on the market today was tested with a load not less then 264 pounds at a speed not less then 180 KEAS, that’s 207 mph. And the same unit is tested three times at those figures. And as said before there is video of most of these tests.

I have been involved in at least one test program where the canopy, a popular ram air reserve, was loaded at 376 pounds and dropped at 200 KEAS. I then did live jumps on the same canopy and did cutaways from a fully open main. Thats really low speed. All these test were done with a standard molar type bag in use through out the industry today. But remember, skydivers could screw up just about anything and all this testing does not mean that any given reserve will not turn to shit on the next deployment. Most canopy design is a compromise. If you design for high seed there is trade off in low speed. With out some really complicated reefing it is tough to have it both ways. I don't have any figures to support this, but it seems we have far more low speed reserve depolyments, less then 150 mph, then we to high speed, more than 150 mph.

I know what the speed bag is supposed to do, and it may do that very well. What I question is the following statements”

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There has been more than one fatality as a result.

Recent student harness failures are the direct result of line strip openings.

All the major manufacturers use "special" bags

There seems to be a lack of any supporting information to what has been stated at fact.

My idea of a fair fight is clubbing baby seals

[teason 0]

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I don't do test jumps at 180 mph, that is what torso dummies are for.

Who you calling a torso dummy?

There are more than few test jumpers for CPS, Butler and Jumpshack that might take exception...



...Then we'd think about and say"yeah, we were dummies!"

I would rather be a superb meteor, every atom of me in magnificent glow, than a sleepy and permanent planet.

[mjosparky 3]

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Who you calling a torso dummy?

You deployed at 180 mph?

My idea of a fair fight is clubbing baby seals

[teason 0]

Static line, 350 canopy, 320lbs, 14000'. Actually, I believe it was 130 knots but the phrase "torso dummy" came up.

They needed live tests. Luckily, I had my speedbag

I would rather be a superb meteor, every atom of me in magnificent glow, than a sleepy and permanent planet.

[darnknit 0]

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They needed live tests.

why would someone need live tests when there is a static line involved in the deployment?

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Luckily, I had my speedbag

this is where i start to get confused. if this was a test jump to get TSO approval for a canopy, wouldn't a TSO'd safety stow freebag have done the trick?

if it was a test jump to get TSO approval for an h/c using a speedbag then luck wouldn't be a factor. the speedbag would need to be used in the test jump.

so, what were you test jumping?

pulling is cool. keep it in the skin

[mjosparky 3]

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if this was a test jump to get TSO approval for a canopy,

TSO tests are not normally done at 14,000 feet. This was probably for something other than your normal sport gear. Sport or commercial gear is only about 1/3rd. of what military sales are. And I believe all the major manufactures have developed products for military use. Look at CPS.

See attached table.

I have deployed above 25,000 msl a number of times with an exit speed of 130/135 KEAS without the use of a speedbag. While the openings were not something I would like a steady diet of I do not believe a speedbag would have had any affect at that speed. jmo

Note: Still waiting for someone to respond to Nancy’s statements:

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There has been more than one fatality as a result.

Recent student harness failures are the direct result of line strip openings.

All the major manufacturers use "special" bags

My idea of a fair fight is clubbing baby seals

[badlock 0]

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“Line dump” in my opinion does not exist or at the very least the term is misapplied. (...)
As Mick said, if it can’t be seen on tape or film with the equipment available today, I find it hard to believe it exists.

If I remember right, John LeBlanc explained the "Line dump" phenomena in "Break Away" as a "horrible hard" opening by a canopy that inflatet partially before line strech.

Luckily, I found a video online that seems to bring the line dump myth into big trouble.
I made some screen shots from this video ("Birdman - Low pull in slovenia").
You can see the screenshots on my page here.
As you can easily see, the canopy inflates only if there is some tension on the lines.

NOTE: If you are the owner of the video and unhappy to see your "stolen" images on this site, please contact me via PM before you contact your lawyer

Don't be a Lutz!

[divnswoop 0]

....completely different gear. He is jumping BASE gear that doesn't even have a bag.

[riggerrob 558]

Luckily, I found a video online that seems to bring the line dump myth into big trouble.
I made some screen shots from this video ("Birdman - Low pull in slovenia").
You can see the screenshots on my page here.
As you can easily see, the canopy inflates only if there is some tension on the lines.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Perhaps we should enlighten you about the finer points of BASE packing.

Most BASE jumpers stow their suspension lines in a tail pocket, then wrap a rubber band around all the lines, holding the bottom skin closed until line stretch.

[pchapman 261]

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In order for there to be bag strip, you would need one of two scenarios to happen: line dump, with the unstowed line having enough mass to pull one of the locking stows free, or the safety stow must break.
[...]
SO unless one of the bites gets pulled out, or the safety stow breaks, you're not going to strip the bag off the canopy.

There might be one more failure mode too, where the canopy starts to dump out one of the lower corners of the freebag, before the safety stow releases or all lines are paid out.

This would result from freebag that is fairly open in the corners, and an old or weak safety stow stretching a lot, and maybe some sort of asymmetry in the deployment process.

I believe this is something Jump Shack recently claimed in one of the threads about damaged reserves, but I don't recall exactly where. The point was that the safety stow didn't have to break for the canopy to get dumped.

I don't know how likely this really is, but the idea should be part of the whole argument.

[badlock 0]

Quote

Luckily, I found a video online that seems to bring the line dump myth into big trouble.
I made some screen shots from this video ("Birdman - Low pull in slovenia").
You can see the screenshots on my page here.
As you can easily see, the canopy inflates only if there is some tension on the lines.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Perhaps we should enlighten you about the finer points of BASE packing.

Most BASE jumpers stow their suspension lines in a tail pocket, then wrap a rubber band around all the lines, holding the bottom skin closed until line stretch.

OK, accepted, but how can this prevent a unbagged canopy from inflating?

Don't be a Lutz!

[mjosparky 3]

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OK, accepted, but how can this prevent a unbagged canopy from inflating?

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You were partially correct in your last post. A ram air canopy needs tension on the lines to inflate and take shape unlike a round.

Ram Airs can and have been jumped at terminal without the use of any deployment device at all.

My idea of a fair fight is clubbing baby seals

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[riggerrob 558]

There might be one more failure mode too, where the canopy starts to dump out one of the lower corners of the freebag, before the safety stow releases or all lines are paid out.

This would result from freebag that is fairly open in the corners ...

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Flexon freebags have the biggest openings in their lower cornes, but have never "dumped" a canopy.

Back in December 1994, I helped Rigging Innovations with TSO C23D drop testing of Flexon, etc. containers. We loaded rubber dummies with lead until they weighed 340 pounds - or more - and dropped them from a B-25 bomber flying at 205 knots. None of those dummies dumped lines or canopies.

We used to tease Sandy Reid by telling him that he made original Talon freebags too tight, Flexon freebags too loose, and that he finally got it right on the Talon 2 freebag.

[deathtrap 0]

Not to mention that even if canopy found it's way out the sides of the bag, the only way it could inflate is if the locking stows came out, allowing the slider and bottom skin to spread. Until that happens, you have something similar to a diaper keeping the canopy closed.

[billbooth 10]

Back in December 1994, I helped Rigging Innovations with TSO C23D drop testing of Flexon, etc. containers. We loaded rubber dummies with lead until they weighed 340 pounds - or more - and dropped them from a B-25 bomber flying at 205 knots. None of those dummies dumped lines or canopies.
____________________________________________________________________________

I have also watched many, many, many high speed, sport parachute system test videos of "freebag" deployments, and have also yet to see a "bag strip". That puts them in the "hypothetical malfunction" category, at normal skydiving speeds, as far as I'm concerned. However, for our very high speed/high altitude military systems we have been using a freebag with a lot more than two locking stows, for many years now. Because above 250 mph, the wind can blow a canopy right out of a bag, without without even releasing "normal" locking stows.

What I have seen is line dump on rubber banded main bags. I have also investigated very hard main openings and broken main canopies, and very often, the locking stow rubber bands are broken. We continue to use the original Para-Flite freebag system simply because of it's simplicity, and the fact that it has been so thoroughly tested for so many years. All that said, I see nothing wrong with "speedbags". As I said, we have been using something similar (no rubber bands, however) for years.

[mjosparky 3]

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I have also watched many, many, many high speed, sport parachute system test videos of "freebag" deployments, and have also yet to see a "bag strip". That puts them in the "hypothetical malfunction" category, at normal skydiving speeds, as far as I'm concerned.

While I have not viewed any where near the number of high speed videos as you have, the ones I have watched lead me to agree with you completely. I have never seen one nor have I talked with anyone who has seen one. Urban myth comes to mind.

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What I have seen is line dump on rubber banded main bags.

Could you define what you mean by “line dump”? I don’t think everyone is on the same page with the use of this term.

My idea of a fair fight is clubbing baby seals

[billbooth 10]

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I have also watched many, many, many high speed, sport parachute system test videos of "freebag" deployments, and have also yet to see a "bag strip". That puts them in the "hypothetical malfunction" category, at normal skydiving speeds, as far as I'm concerned.

While I have not viewed any where near the number of high speed videos as you have, the ones I have watched lead me to agree with you completely. I have never seen one nor have I talked with anyone who has seen one. Urban myth comes to mind.

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What I have seen is line dump on rubber banded main bags.

Could you define what you mean by “line dump”? I don’t think everyone is on the same page with the use of this term.

Line dump occurs when lines come out of rubber bands out of sequence, either by inertia or broken rubber bands, or, in other words, before they are pulled out of the stows in the normal fashion by the departing bag. Line dump is usually only serious when it is the locking stows that fail, allowing the canopy out of the bag before all the lines are unstowed. This is the classic definition of an "out-of-sequence" opening...which is what the bag was supposed to prevent in the first place. Any other stows "dumping" before they should, should NOT produce a hard opening, although this could, on rare occasion, produce a bag lock. This is why you have to "match up" your pilot chute size, suspension line thickness, choice of rubber band (tube stow), and your average deployment velocity, if you want to have consistent openings.

[darnknit 0]

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All that said, I see nothing wrong with "speedbags".

until now, i have only recieved a few PMs and some references to unnamed engineers that are speedbag supporters. this is as close to support as i believe i will get.


on a side note, every single PM, and even Bill Booth's reply seems to allude to high-speed, high-load military applications.

i still don't have enough information to understand why the change in design was deemed necessary or advantageous for sport rigs.

pulling is cool. keep it in the skin

[RMURRAY 1]

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All that said, I see nothing wrong with "speedbags".

until now, i have only recieved a few PMs and some references to unnamed engineers that are speedbag supporters. this is as close to support as i believe i will get.


on a side note, every single PM, and even Bill Booth's reply seems to allude to high-speed, high-load military applications.

i still don't have enough information to understand why the change in design was deemed necessary or advantageous for sport rigs.

you have been jumping long enough to know that skydiving has changed over the years. The speedbag is not deemed necessary by all, it is only deemed necessary by JumpShack (so far) and it is to guard against line dump / bag strip during a high speed reserve deployment. For example, like a freeflyer who is saved by an AAD or accidental deployment during a FF jump. I have a racer but may not replace my old style bag because i don't FF and never will...

rm