Hard openings are a function of....

[shah269 0]

Hard openings are a function of....

Regarding recent posts what are the most common causes of "hard" openings? As I understood it if the slider were placed correctly it's job was to prevent hard openings? Are there any other factors other than perhaps extreme body position which effect the rate at which a parachute properly inflates?

Life through good thoughts, good words, and good deeds is necessary to ensure happiness and to keep chaos at bay.

The only thing that falls from the sky is birdshit and fools!

[DaVinciflies 0]

A few things that spring to mind:

1. Slider position (and ensuring it is uncollapsed!)
2. Avoiding bag-strip
3. Canopy choice - certain models have a reputation for slammers.
4. Modifications (e.g changing the slider for an RDS) could change the opening characteristics.
5. Skydiver airspeed at deployment (e.g premature openings)

[shah269 0]

I'm sorry but what are
Bag-strip?
And
RDS?

Also from a beginners point of view unless the slider is all the way very low wouldn't the relative wind automatically push it up against the parachute prior to the parachute inflating?

Thank you

Life through good thoughts, good words, and good deeds is necessary to ensure happiness and to keep chaos at bay.

The only thing that falls from the sky is birdshit and fools!

[davelepka 4]

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Also from a beginners point of view unless the slider is all the way very low wouldn't the relative wind automatically push it up against the parachute prior to the parachute inflating?

Negative ghostrider. Ideally, the slider and the canopy leave the bag in a Mexican standoff. Neither has an adantage over the other, and everything stays put.

At this point the slider is all the way, and the canopy is snivelling. Your airspeed begins to decay from the slider/canopy in the airstream, and as it does, so does the pressure on the slider. Now the canopy begins to develop an advantage over the slider, and starts to push it downward. As the slider comes down, the canopy spreads, further slowing the jumper, further reducing the airspeed and pressure on the slider, further increasing the advantage of the canopy over the slider. This operation contunues until the slider is down to the links.

If your slider is not in position when it comes out of the bag, that's an instant advanatge to the canopy. it begins to inflate, and only further increases it's advanatge (and how hard it's going to open). You have to remember that you're throwing a canopy out in to 120 mph airstream, so if you give it an inch, it will take a mile and ruin your day.

Ever try to handle a canopy on a windy day? Ever have a hard time handling a canopy on a windy day (or seen someone else struggle)? That's on the ground with winds under 25mph. Translate that to 120mph winds at deployment, and you can see that forces a canopy can exert are huge.

The slider is your one shot to tame those forces. If they make it too big, the canopy might not open at all, so it has to be just big enough to slow the opening, but not too big. There's a youtube video of a guy having an 8000ft snivel on a test jump for a new canopy. The slider was just too big, but if you look at the video, you can't visually see that the slider is any larger than normal. It's a very fine line between too big and just right.

What that means to you is that the slider being all the way up, against the stops, is the key to avoiding hard openings. The majority of hard openings are due to the slider coming off the stops during the pack job, usually during the folding/bagging.

There are some other causes, but that's the big daddy of them all. You can even overcome higher deployment speeds with properly placed slider.

[TheCaptain 2]

bag strip is when the lines are unstowed prior to line stretch.

RDS is Removable Deployment System. These are generally used for competion swooping the D-bag and Pilot chute are attached to a removable slider. When the slider comes down the pilot removes it taking away any drag they may cause

Kirk
He's dead Jim

[DaVinciflies 0]

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bag strip is when the lines are unstowed prior to line stretch.

Sorry to disagree, but the way I meant it, bag strip is when the canopy is partially or completely out of the bag before line-stretch.

What you have described, to me, would be line dump. Or, in the case of a reserve or semi-stowless bag, totally normal!

[DaVinciflies 0]

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Ideally, the slider and the canopy leave the bag in a Mexican standoff. Neither has an adantage over the other, and everything stays put.

Dave - I believe I remember reading some work where the investigators theorized that the air pressure between the slider and the bottom skin of the canopy was lower than the force on the underside of the canopy so the slider was experiencing lift in a similar way to a wing.

They proposed that anything which causes a premature "leak" between the slider and bottom skin allowing ingress of high pressure air would disrupt that equilibrium and cause the slider to descend faster.

This would seem to explain the effectiveness of domed sliders.

Does that sound familiar to anyone?

[davelepka 4]

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Dave - I believe I remember reading some work where the investigators theorized that the air pressure between the slider and the bottom skin of the canopy was lower than the force on the underside of the canopy so the slider was experiencing lift in a similar way to a wing.

They proposed that anything which causes a premature "leak" between the slider and bottom skin allowing ingress of high pressure air would disrupt that equilibrium and cause the slider to descend faster.

I don't know about that. It plausable, but it could also just be the pressure from the relative wind holding it up, and the span of the slider physically restraining the canopy from opening.

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This would seem to explain the effectiveness of domed sliders.

You could also look to the increased surface area of a domed slider, and thus the increased PSI of pressure from the relative wind holding the slider up.

[DaVinciflies 0]

I found the link. Maybe Peek would like to chime in here!

www.pcprg.com/sliderdragcancel.pdf

[TheCaptain 2]

I stand corrected, I was thinking of line dump

Kirk
He's dead Jim

[airtwardo 7]

...what are the most common causes of "hard" openings?

[peek 21]

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I found the link. Maybe Peek would like to chime in here! www.pcprg.com/sliderdragcancel.pdf

If you want any technical explanation you will need to contact Potvin, because most of this paper is his. I think numbers 1 and 3 in your answer above are going to be most relevant to Shah's question. We might be getting too technical if we talk about much else.

[AdD 1]

Steering line length and brake settings also effect opening.

Life is ez
On the dz
Every jumper's dream
3 rigs and an airstream

[shah269 0]

No guys, the info is great! Please continue.
I have learned so much!

Life through good thoughts, good words, and good deeds is necessary to ensure happiness and to keep chaos at bay.

The only thing that falls from the sky is birdshit and fools!

[theonlyski 8]

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...what are the most common causes of "hard" openings?

Deployment

[airtwardo 7]

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...what are the most common causes of "hard" openings?

Deployment

Wind

[DaVinciflies 0]

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...what are the most common causes of "hard" openings?

Deployment

Wind

[theonlyski 8]

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...what are the most common causes of "hard" openings?

Deployment

Wind

Can you expand a little on this, or confirm that you are joking?

Thanks.

Well, if you're standing on the ground, and you throw your pilot chute... it's probably not going to be a hard main opening.

"I may be a dirty pirate hooker...but I'm not about to go stand on the corner." iluvtofly
DPH -7, TDS 578, Muff 5153, SCR 14890
I'm an asshole, and I approve this message

[phoenixlpr 0]

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...what are the most common causes of "hard" openings?

Deployment

Wind

Can you expand a little on this, or confirm that you are joking?

Thanks.

[DaVinciflies 0]

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-line dump.

I don't believe this causes hard openings. Bag strip will, but line dump?

[lowapproach 0]

I recently was plagued by a long series of hard openings, the kind where people watching the video wince. Someone watched me pack and noticed that when I rolled the tail i was rolling it while pulling the canopy towards the folds, effectively allowing the canopy to spread open inside. The corrective action was to roll the tail toward the canopy and my openings have been fantastic since.

[DaVinciflies 0]

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Well, if you're standing on the ground, and you throw your pilot chute... it's probably not going to be a hard main opening.

Oh got ya! I thought this was some BS about how strong the uppers were!

[Andy9o8 2]

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Hard openings are a function of....

Thunderstorms.

[topdocker 0]

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Hard openings are a function of....

Mesh slider, new zero-P fabric, one stow, and a canopy designed to open quickly.

Oh yeah, body position.

top

Jump more, post less!

[airtwardo 7]

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Hard openings are a function of....

Mesh slider, new zero-P fabric, one stow, and a canopy designed to open quickly.

Oh yeah, body position.

top

I bet THAT will clear out the sinuses huh Top?

~ If you choke a Smurf, what color does it turn? ~