Can a D bag effect opening shock?

[airdvr 200]

Just got my new Racer. The D bag is alot smaller than the one I was using. Canopy is a Tri 190 and it was slamming me all weekend. It's on its way to Aerodyne for a look. Seems these snappers started whne we put the canopy in the new container.

Please don't dent the planet.

Destinations by Roxanne

[isaiah85 0]

Hey,

All the components play a role in the deployment process, the hard openings could be contributed to any number of things, pilot chute, d-bag, rubber bands...etc. All these things factor in. Another thing to consider is that maybe with the smaller d-bag, your not putting the canopy in the bag as neat. If your having a little trouble getting the bag closed, you might be moving the slider grommets around. if the slider grommets are not tight on the stops, it will cause harder openings. I'm not saying it's defiantly sloppy packing, just something to consider. Chances are if the canopy was working fine before you changed the components it's not the canopy. It might not be the components either, just might require a different method of packing.

Take it easy!
Isaiah

[mjosparky 3]

No, opening shock occurs after the bag is out of the picture.

Sparky

My idea of a fair fight is clubbing baby seals

[airdvr 200]

I thought packing might have been the issue but it cracked me 5 times in a row. While I have to believe it might happen once or twice due to packing I don't think 5 times is possible. While I was having a rigger look at it I jumped another Tri they let me use which was packed by the same person...it opened really nice. Can't tell you how it feels when you turn and burn thinking "maybe this would hurt less if I didn't pull"

Other thing is when I bought it used there was a pocket sewn on the slider. I originally thought that it sniveled way too much so I had it taken off. In retrospect it was just old school me not used to how long ZP canopies need to open comfortably. I had it re-installed and the last jump of the day was a much slower opening although the canopy turned almost 360 degrees while the slider was still up.

Please don't dent the planet.

Destinations by Roxanne

[base283 0]

Most definitely, The D bag is meant to contain the canopy until line stretch. If it does not do this, then, the canopy can actually start inflating before line stretch is achieved and the resulting opening shock can be strong enough to do damage to jumper and gear. It´s likely that the stow bands are too loose on the newly installed D bag and you are getting out of sequence openings. Search for terms like "line dump" or "inertial bag strip". PD had some good reading on this.
take care,
space

[mjosparky 3]

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Most definitely, The D bag is meant to contain the canopy until line stretch. If it does not do this, then, the canopy can actually start inflating before line stretch is achieved and the resulting opening shock can be strong enough to do damage to jumper and gear. It´s likely that the stow bands are too loose on the newly installed D bag and you are getting out of sequence openings. Search for terms like "line dump" or "inertial bag strip". PD had some good reading on this.
take care,
space

Your reserve has only 2 stows and you don't get "line dump" A ram air canopy will not inflate until there is tension on the lines, there is nothing to hold the shape of the wing. Opening shock is a result of deployment speed and fill time. You can reduce fill time by how the nose is packed and the size and position of the slider. There is also canopy design, which you have no control over. Angle of attack, depth of cells and brake settings all come into play.

Sparky

My idea of a fair fight is clubbing baby seals

[airdvr 200]

Thanks base...something that never occurred to me is the possibility of the stows on the bag opening early. That makes a lot of sense since this seemed to start when I got my new container. Gotta make a mental note of that one. Just as soon as my balls stop slapping against my ankles from those cracker openings

I see your point Sparky but at these speeds even a hair of canopy beginning to open before line stretch could be an issue.

Please don't dent the planet.

Destinations by Roxanne

[base283 0]

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Your reserve has only 2 stows and you don't get "line dump". A ram air canopy will not inflate until there is tension on the lines, there is nothing to hold the shape of the wing. Opening shock is a result of deployment speed and fill time. You can reduce fill time by how the nose is packed and the size and position of the slider.

Sparky

Here is an easy table top test:
1.open a packed rig but keep the bag at the container. 2. unstow the lines from the locking stows holding the bag closed and stuff them back in the container tray. 3. lift the opened deployment bag via the bridle attachment point above your head and watch as the canopy unfolds, spreads out some and slider falls down the lines. 4. place it back in the bag with out squeezing any air out.

1. is to simulate deployment sequence after PC deployment and container opening.
2. is to simulate "line dump",
3. is to simulate canopy extraction before line stretch in a line dump scenario and it's effect on the positions of the slider and canopy.
4. is to show that the canopy has inflated somewhat. Maybe expanded would be a better word.

The air would be hitting an expanded canopy which has more surface area exposed and the slider has fallen out of position more than likely down the lines.

Hope this helps.
Reserves that are free bagged have 2 locking stows also. But the instructions the rigger follows ie 1.5" stows, bungee safety stow dimensioned for that particular bag is designed to prevent this from happening. (It has happened on reserve packs). Quite unlike the environment the skydiver packs in. elongated rubber bands or tube stows or even the wrong type with not enough holding power can very easily lead to this situation causing hard openings.
I speculate that because he has a new D bag that has different stow values for the locking stows, this is the source of his hard openings because of the reasons of line dump.
But note: I think we have a miscommunication on what is inflation. Maybe expansion is a better word. My bad. A normal extraction speed of 30 to 50 fps will induce that amount of air passing around the canopy distorting it much more than the table top test.
think about it.
take care,
space

[mark 105]

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Quite unlike the environment the skydiver packs in. elongated rubber bands or tube stows or even the wrong type with not enough holding power can very easily lead to this situation causing hard openings.
I speculate that because he has a new D bag that has different stow values for the locking stows, this is the source of his hard openings because of the reasons of line dump.

Initially, the locking stows need only be tight enough to retain the lines until the canopy slumps inside the bag as the bag lifts off. Then the weight of the canopy against the stows is usually enough added pressure to keep the stows secure.

Locking stow tightness isn't likely an issue here, though: the D-bag is smaller than before. Either way, I'd be surprised if "line dump" (canopy-first deployment, actually) is to blame.

In addition to the new D-bag, there's a new pilot chute, isn't there?

Mark

[airdvr 200]

No new pilot chute. It came with a non-collapsible but I just bought a new kill line last year. The PC had maybe 10 jumps on it before last weekend. Can a PC be mismatched to the D-bag?

I'm really running this over in my head now. The grommet for the bag was too small for the old PC so we had to install a larger one.

Please don't dent the planet.

Destinations by Roxanne

[mjosparky 3]

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I see your point Sparky but at these speeds even a hair of canopy beginning to open before line stretch could be an issue.

I have been jumping a bag with only the 2 locking stows for over a 1000 jumps now and have not had a problem.

Keep your slider up against the stops and roll the nose. Your bag has nothing to do with "opening shock".

Sparky

My idea of a fair fight is clubbing baby seals

[EvilLurker 2]

Isn't it amazing how hard those Triathlons can open without damaging themselves? Hard enough to make me sell mine. You're going to flinch every time you throw your pilot chute, and it takes a lot of fun out of jumping. I hope Aerodyne has a solution, but I really have my doubts. You never had a hard opening before switching containers? Very weird.

[mjosparky 3]

In stead of a table top test, how about this. I have a little over 400 jumps on a ram air canopy without the use of a bag at all. I have over 1000 jumps on a ram air canopy with just 2 locking stows and the rest of the lines in a pouch. In either case there was not a noticeable increase in "opening shock". Line stows are for neatness not to control deployment. They cause bag whip during deployment and create snag points for the rest of the lines during deployment.

Of course this is just my opinion. I have been doing test work, both drop tests and live jumps, of a variety of canopies and systems for over 20 years though and after watching film and video of deployment over and over again I feel the above to be true.

Sparky

My idea of a fair fight is clubbing baby seals

[base283 0]

search for "line dump" returned 464 results in 0.444s.

Re: [ianmdrennan] Line Dump Incident mjosparky Skydiving: Incidents Jun 3, 2003, 8:32 PM
Mojosparky wrote:
“I have been using a main D bag with a line storeage pocket similar to a molar/reserve bag with just 2 locking stows for several years now. I think Mark nailed it, we need to change our terms. If the locking stows are loose, snatch force can jerk the bag off the canopy and instant parachute. I hope that makes sense?
Sparky”

As I stated “inertial bag strip””
Take care,
space

[airdvr 200]

I don't think it's the Tri. Something changed somewhere and the good people at Aerodyne will figure it out. Did I mention they're letting me demo a Pilot?

It is amazing that the Tri took so much abuse...much more than I could. And I jumped another Tri while the rigger was looking at mine and it opened "like butter".

Please don't dent the planet.

Destinations by Roxanne

[phoenixlpr 0]

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Did I mention they're letting me demo a Pilot?

How was the Pilot?

[JerryBaumchen 1,080]

Sparky,

How about contacting me off the board? I want to talk to you about this 2-stow bag of yours.

Call me on 503-481-4714; before 11:00 PM and not before 9:00 AM.

Thanks

[mjosparky 3]

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Sparky,

How about contacting me off the board? I want to talk to you about this 2-stow bag of yours.

Call me on 503-481-4714; before 11:00 PM and not before 9:00 AM.

Thanks

Jerry,

Will do.

Sparky

My idea of a fair fight is clubbing baby seals

[mjosparky 3]

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search for "line dump" returned 464 results in 0.444s.

Re: [ianmdrennan] Line Dump Incident mjosparky Skydiving: Incidents Jun 3, 2003, 8:32 PM
Mojosparky wrote:
“I have been using a main D bag with a line storeage pocket similar to a molar/reserve bag with just 2 locking stows for several years now. I think Mark nailed it, we need to change our terms. If the locking stows are loose, snatch force can jerk the bag off the canopy and instant parachute. I hope that makes sense?
Sparky”

As I stated “inertial bag strip””
Take care,
space

I am not sure what your point is. We were talking about "opening shock" not snatch force. Snatch force occurs before opening shock, so once again the bad is not involved.

Sparky

My idea of a fair fight is clubbing baby seals

[base283 0]

Ummm... you´re confusing me now. Did you mean instant canopy by just adding water? Or did you mean "if the locking stows are loose, snatch force can jerk the bag off the canopy and instant parachute."?. Are"instant parachute" and "hard opening" different terms meaning the same thing?
let me know, I think we just have different terminology but we speak of the same think.
take care,
space

[airdvr 200]

Quote

Quote

Did I mention they're letting me demo a Pilot?

How was the Pilot?

Don't have it yet but I'll let you know.

Please don't dent the planet.

Destinations by Roxanne

[airdvr 200]

OK...Aerodyne was really nice about the problems with my Tri. Gave me a Pilot to demo. Here's the rub. Aerodyne says my Tri was not manufactured correctly. Says the top skin is too large in relation to the bottom skin. The mod they did consists of "pinching" the nose closed by taking a small gather of canopy in each cell at the nose and stitching it up. In effect puliing the nose just a bit closed. Didn't seem to effect the flight characteristics. Seems kind of strange. It opened OK..anything was better than being slammed. Anyone ever heard of this type of mod or the problems Aerodyne told me about mis-manufactured canopies?

Please don't dent the planet.

Destinations by Roxanne

[jumpwally 0]

How was the Pilot Demo?

smile, be nice, enjoy life
FB # - 1083