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# Preventing Hard Openings

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yuri_base

Further argumentation of the discovered mechanism of hard openings due to cocoon hesitation and of proper use of slider.

The packed canopy cocoon is like a cone, with some angle at the apex. The wind force tries to push the center cell tail surface forming the cocoon "up" this slope. The aerodynamic force acting on the angled surface of the cocoon is at some angle to the surface, and due to relatively high lift-to-drag ratio of the angled surface, this angle is actually close to perpendicular to the surface. (I'll draw a force diagram later.) Let's call this angle between perpendicular to the surface and aerodynamic force alpha.

We know from basic physics that for an object to slide on an inclined surface, tangent of the angle to horizon must be greater than the coefficient of friction k:

tan(alpha) > k

So for the tail to start sliding off the rest of the canopy, while experiencing friction against it, k must be below certain value as per formula above (read from right to left).

If for fresh ZP k is less than this value, it will slide off easily; if ZP is no longer fresh after few hundred jumps, k might exceed this value and then cocoon hesitations will start to happen.

This is the physical mechanism for cocoon hesitations (CH).

Now, let's consider what happens during the CH. When the cone stays closed for some extra tenths of a second (on WS jumps sometimes even one or two seconds, due to slower speed and angled deployment), the slider experiences zero force from the air, and its heavy grommets start sliding down under the cover of the cone. The apex of the cone itself cannot stop this, since it simply moves with the grommets pulled by gravity. Slider in this case is like a pilot in the cabin: there's no wind to push him against the seat, and if the plane is falling straight down nose first, the pilot will fall out of the seat forward on the dashboard. Slider moved a few inches down the lines - boom, a hard opening.

If slider is exposed, it's like a pilot with no cabin - he's pushed by the wind into the seat. Same with slider - it's pushed against the stops with significant force - probably, ~100lbs. It's not going anywhere and starts doing its primary function - reefing - immediately. When canopy starts inflating, it resists the expansion and slows down the opening.

This is the proper opening sequence - slider is inflated immediately and starts working. This is the proper way of packing. Slider MUST be exposed, not hidden.

While watching you try to explain chaos is entertaining, you have a lot of bad assumptions in there. Like so many I don't have the energy to go line by line through your post to correct them.

Everyone reading this, just make sure your slider is open and stowed tight against the grommets all through the packing process.

Bill can you axe this and move Yuri to a more appropriate post?

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LeeroyJenkins

Bill can you axe this and move Yuri to a more appropriate post?

Why?
I’m intrigued and intend to try it.

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Quote

We know from basic physics that for an object to slide on an inclined surface, tangent of the angle to horizon must be greater than the coefficient of friction k:

tan(alpha) > k

So for the tail to start sliding off the rest of the canopy, while experiencing friction against it, k must be below certain value as per formula above (read from right to left).

If for fresh ZP k is less than this value, it will slide off easily; if ZP is no longer fresh after few hundred jumps, k might exceed this value and then cocoon hesitations will start to happen.

Yuri, that's not an equation. I think I know what equation you're going for but you're leaving out just every real world concept and confusing statics, dynamics and fluid dynamics. And yes that's what my degree is in. What you're trying to say is that there's a relationship between friction, force and the angle of the fabric against each other. That's not something that can be modeled by back of the napkin math or really any mathematical equation as it applies to fabric at those wind speeds. You would do that in a wind tunnel with ultra high speed cameras if you really wanted to set up a perfect analysis.

Please continue with your experiments in the air and we'll be happy to learn from the results.
"I encourage all awesome dangerous behavior." - Jeffro Fincher

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Quote

While watching you try to explain chaos is entertaining, you have a lot of bad assumptions in there.

Agreed. He's also missing a lot of the forces involved, like acceleration during deployment. Indeed he explicitly ignores it - "Slider in this case is like a pilot in the cabin" - as if there are no acceleration forces on the slider.

Quote

Bill can you axe this and move Yuri to a more appropriate post?

I moved this out of Incidents where it really isn't appropriate. I think it is OK here. What Yuri described can indeed be deadly - but experienced skydivers (the people who read this forum) are adults and can try it if they want.

===================================

As a side note, what many people experience during their packing careers goes something like this:

They try to learn to pack. Their new ZP goes everywhere. They get hard, inconsistent, off heading openings.

Someone tells them to try psycho packing. They try it for 30 pack jobs or so. ZP goes everywhere. They get hard, inconsistent, off heading openings.

Someone tells them to try putting the top of the canopy in the bag first before the S-fold. They try it for 30 pack jobs or so. ZP goes everywhere. They get hard, inconsistent, off heading openings.

Someone tells them to use a hook. They try it for 30 pack jobs or so. ZP goes everywhere. They get hard, inconsistent, off heading openings.

Someone tells them to turn sideways while they are packing. They try it for 30 pack jobs or so. ZP goes everywhere. They get hard, inconsistent, off heading openings.

Someone tells them to pack on concrete instead of grass. They try it for 30 pack jobs or so. ZP goes everywhere. Their openings start to get better!

Their conclusion - packing on grass causes hard openings. They post on S+T to tell everyone the wonderful news, but lament that until someone like John LeBlanc tells everyone this obvious truth, people will still suffer hard openings.

What has really happened, of course, is they just did 150 pack jobs and got to be better packers. But packing is so complex, and so hard to learn - and improvement comes so slowly - that they chalk the improvement up to the last thing they tried.

I have a feeling the same thing is going on here. But everyone has to learn that for themselves.

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>>> He's also missing a lot of the forces involved, like acceleration during deployment. Indeed he explicitly ignores it - "Slider in this case is like a pilot in the cabin" - as if there are no acceleration forces on the slider. <<<

True, there are some acceleration forces acting on the slider once linestretch is achieved and canopy is out of the D-bag: because the whole system "jumper-canopy" is decelerating due to extra drag, slider is experiencing extra force, besides gravity of the grommets, that pulls it down the lines. Adding insult to the injury, so to speak. But the shake of the dancing cocoon, I think, is the dominating factor in shaking the slider down the lines under the cover of the cocoon-"cabin". Slider that is exposed and experiencing 100lbs+ force from the wind pushing it against the stops, is not going anywhere, neither by deceleration not the shake.

>>> As a side note, what many people experience during their packing careers goes something like this:

They try to learn to pack. Their new ZP goes everywhere. They get hard, inconsistent, off heading openings.

Someone tells them to try psycho packing. They try it for 30 pack jobs or so. ZP goes everywhere. They get hard, inconsistent, off heading openings.

Someone tells them to try putting the top of the canopy in the bag first before the S-fold. They try it for 30 pack jobs or so. ZP goes everywhere. They get hard, inconsistent, off heading openings.

Someone tells them to use a hook. They try it for 30 pack jobs or so. ZP goes everywhere. They get hard, inconsistent, off heading openings.

Someone tells them to turn sideways while they are packing. They try it for 30 pack jobs or so. ZP goes everywhere. They get hard, inconsistent, off heading openings.

Someone tells them to pack on concrete instead of grass. They try it for 30 pack jobs or so. ZP goes everywhere. Their openings start to get better!

Their conclusion - packing on grass causes hard openings. They post on S+T to tell everyone the wonderful news, but lament that until someone like John LeBlanc tells everyone this obvious truth, people will still suffer hard openings.

What has really happened, of course, is they just did 150 pack jobs and got to be better packers. But packing is so complex, and so hard to learn - and improvement comes so slowly - that they chalk the improvement up to the last thing they tried.

I have a feeling the same thing is going on here. But everyone has to learn that for themselves. <<<

This is a perfect example of dynamics of acceptance of new things in skydiving world. All these examples, "psycho packing", "putting the top of the canopy in the bag first", "use a hook", "turn sideways while they are packing", "pack on concrete instead of grass" are things that someone tried before and maybe in their particular situation (there are many variables) it helped. And these things got at least some acceptance, they're not considered to be "What Yuri described can indeed be deadly". But since nobody tried (except me, with good results) exposing the slider and is not something we hear at DZs as one of the advices on how to eliminate hard oepnings, it is perceived as "deadly". Chicken and egg. We're so scared to try new things (even fully backed up by problem identification, logical analysis, solution finding, and testing for hundreds of jumps) that we start justifying our unsubstantiated fear by calling it "deadly", "this is a bad thing to teach students", etc.

By the way, I didn't arrive at fully exposed slider at once, I did it gradually over several jumps, making a 1-inch hole in the apex, 2-inch, 3-inch... (with slider still hidden by the cone; and of course, the wraps were very light, barely enough to keep the packjob from falling apart) And when I found that nothing bad happens, but the problem still persists, I finally fully exposed the slider grommets, and BOOM! problem's gone. So, anyone who wants to try, but scared, just do it gradually over several jumps. And then maybe we'll have enough chickens to start multiplying.

Exposed Slider method will be more noticeable by wingsuiters with aging ZP canopies who are experiencing frequent delayed openings, linetwists, and sometimes hard-ish or hard openings. The improvement of proper staging the opening thanks to ES method, will be less noticeable for fresh ZP and belly-down deployments.

However, I'm claiming something bigger, and it's not only possible solution for problems when they start: I'm claiming that exposing the slider, i.e. presenting it to the wind as the very 1st thing in opening sequence, is THE right way of staging the deployment, it is THE right way to pack, while hiding it is THE wrong way to pack and may occasionally stage the opening incorrectly and lead to injury or even death from extremely hard opening.

Very hard openings are relatively rare and impossible to predict, so the improvement in reducing their occurrence may not be immediately noticeable; but in the long run, the effect should be noticeable by not reading anymore in Incidents forum that someone died of hard opening. For this to happen, the method should be widely accepted, taught to students, included in packing videos, etc. But it won't happen anytime soon... Maybe, Bill Booth will come and say, "Yuri has the valid point. I tried it and I think this is the way to proper stage the opening. I recommend it." And everyone will throw their hats in the air, "Hooray! Genius! Bill does it again! Bill reinvents the properly staged opening! And doesn't even patent it! Hallelujah!" Unfortunately, this is how things work, widespread acceptance needs The Authority to endorse it. Not some unknown dude Yuri.
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There’s a nugget...

“Some unknown dude Yuri.”

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Quote

ZP goes everywhere. They get hard, inconsistent, off heading openings.

Just one guy's experience: "ZP goes everywhere" is definitely what happens to me. I also do at least a couple things that are listed as causing hard openings in the PD video (locking stow rubber bands stretch across a lot of fabric to get the bag closed and even with medium-length rubber-bands I single-stow the locking stows, simply because that's all I CAN do, considering the tension on them...I've got a 230sqft canopy and it's probably the maximum for that container)
I also used packers on 90% of my first 200 jumps (100 on that canopy) and their pack jobs look only marginally better than mine.
BUT: Ever since I have that canopy, I've not had a single bad opening. It seems, no matter what I do, it comes out nicely.
I'm jumping a Spectre.

...just sayin...

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>>> I think I know what equation you're going for but you're leaving out just every real world concept and confusing statics, dynamics and fluid dynamics. <<<

These are just empty words, no value. Diagrams, equations, argumentation to back this up?

>>> And yes that's what my degree is in. <<<

Ph.D. in Physics here. Worked in both experimental and theoretical physics. (Currently a programmer.)

>>> What you're trying to say is that there's a relationship between friction, force and the angle of the fabric against each other. That's not something that can be modeled by back of the napkin math or really any mathematical equation as it applies to fabric at those wind speeds. <<<

Sure, exact modeling is complex. But as an illustration of the concept, it is sufficient.

>>> Please continue with your experiments in the air and we'll be happy to learn from the results. <<<

Nope, not gonna happen. I quit jumping skydiving canopy (Spectre) several years ago. Skydiving my BASE canopy ever since, and totally love it always jumping the same canopy in any environment. So, packing is very different, and Exposed Slider method does not apply... actually, in BASE packjob slider is always exposed, there's no cocoon. The ~400 jumps I did on the ES packjob in 2009-2013 are final.

If anyone wants to collect statistical data, they'll have to do it themselves.
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I am also an engineer of the mechanical design variety. As you no doubt know, engineers love to pick apart other's ideas. I cannot think of a valid reason against the ES method. Other critics in this thread I think are like a group of engineers out for a beer arguing about why tapping the top of a beer bottle causes it to foam up.

Isn't this an easy thing to confirm? A properly oriented camera running a fast shutter speed...Does that more detailed evidence already exist? The pics you provided aren't enough to convince. The number of jumps you've done with ES is quite significant, but it is reasonable to want better visual proof.

We all agree that we want the slider to stay up against the stops. Why prevent the air from doing that right away?

I find this discussion very interesting, and an 11 out of 10 on the importance meter.
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
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yuri_base

>>> He's also missing a lot of the forces involved, like acceleration during deployment. Indeed he explicitly ignores it - "Slider in this case is like a pilot in the cabin" - as if there are no acceleration forces on the slider. <<<

True, there are some acceleration forces acting on the slider once linestretch is achieved and canopy is out of the D-bag: because the whole system "jumper-canopy" is decelerating due to extra drag, slider is experiencing extra force, besides gravity of the grommets, that pulls it down the lines. Adding insult to the injury, so to speak. But the shake of the dancing cocoon, I think, is the dominating factor in shaking the slider down the lines under the cover of the cocoon-"cabin". Slider that is exposed and experiencing 100lbs+ force from the wind pushing it against the stops, is not going anywhere, neither by deceleration not the shake.

>>> As a side note, what many people experience during their packing careers goes something like this:

They try to learn to pack. Their new ZP goes everywhere. They get hard, inconsistent, off heading openings.

Someone tells them to try psycho packing. They try it for 30 pack jobs or so. ZP goes everywhere. They get hard, inconsistent, off heading openings.

Someone tells them to try putting the top of the canopy in the bag first before the S-fold. They try it for 30 pack jobs or so. ZP goes everywhere. They get hard, inconsistent, off heading openings.

Someone tells them to use a hook. They try it for 30 pack jobs or so. ZP goes everywhere. They get hard, inconsistent, off heading openings.

Someone tells them to turn sideways while they are packing. They try it for 30 pack jobs or so. ZP goes everywhere. They get hard, inconsistent, off heading openings.

Someone tells them to pack on concrete instead of grass. They try it for 30 pack jobs or so. ZP goes everywhere. Their openings start to get better!

Their conclusion - packing on grass causes hard openings. They post on S+T to tell everyone the wonderful news, but lament that until someone like John LeBlanc tells everyone this obvious truth, people will still suffer hard openings.

What has really happened, of course, is they just did 150 pack jobs and got to be better packers. But packing is so complex, and so hard to learn - and improvement comes so slowly - that they chalk the improvement up to the last thing they tried.

I have a feeling the same thing is going on here. But everyone has to learn that for themselves. <<<

This is a perfect example of dynamics of acceptance of new things in skydiving world. All these examples, "psycho packing", "putting the top of the canopy in the bag first", "use a hook", "turn sideways while they are packing", "pack on concrete instead of grass" are things that someone tried before and maybe in their particular situation (there are many variables) it helped. And these things got at least some acceptance, they're not considered to be "What Yuri described can indeed be deadly". But since nobody tried (except me, with good results) exposing the slider and is not something we hear at DZs as one of the advices on how to eliminate hard oepnings, it is perceived as "deadly". Chicken and egg. We're so scared to try new things (even fully backed up by problem identification, logical analysis, solution finding, and testing for hundreds of jumps) that we start justifying our unsubstantiated fear by calling it "deadly", "this is a bad thing to teach students", etc.

By the way, I didn't arrive at fully exposed slider at once, I did it gradually over several jumps, making a 1-inch hole in the apex, 2-inch, 3-inch... (with slider still hidden by the cone; and of course, the wraps were very light, barely enough to keep the packjob from falling apart) And when I found that nothing bad happens, but the problem still persists, I finally fully exposed the slider grommets, and BOOM! problem's gone. So, anyone who wants to try, but scared, just do it gradually over several jumps. And then maybe we'll have enough chickens to start multiplying.

Exposed Slider method will be more noticeable by wingsuiters with aging ZP canopies who are experiencing frequent delayed openings, linetwists, and sometimes hard-ish or hard openings. The improvement of proper staging the opening thanks to ES method, will be less noticeable for fresh ZP and belly-down deployments.

However, I'm claiming something bigger, and it's not only possible solution for problems when they start: I'm claiming that exposing the slider, i.e. presenting it to the wind as the very 1st thing in opening sequence, is THE right way of staging the deployment, it is THE right way to pack, while hiding it is THE wrong way to pack and may occasionally stage the opening incorrectly and lead to injury or even death from extremely hard opening.

Very hard openings are relatively rare and impossible to predict, so the improvement in reducing their occurrence may not be immediately noticeable; but in the long run, the effect should be noticeable by not reading anymore in Incidents forum that someone died of hard opening. For this to happen, the method should be widely accepted, taught to students, included in packing videos, etc. But it won't happen anytime soon... Maybe, Bill Booth will come and say, "Yuri has the valid point. I tried it and I think this is the way to proper stage the opening. I recommend it." And everyone will throw their hats in the air, "Hooray! Genius! Bill does it again! Bill reinvents the properly staged opening! And doesn't even patent it! Hallelujah!" Unfortunately, this is how things work, widespread acceptance needs The Authority to endorse it. Not some unknown dude Yuri.

Why do you recommend this method for WS jumps but not standard terminal jumps? If the cone hiding the slider from the wind is the issue, the cone is still wrapped around the slider on belly jumps too you know.

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>>> Why do you recommend this method for WS jumps but not standard terminal jumps? If the cone hiding the slider from the wind is the issue, the cone is still wrapped around the slider on belly jumps too you know. <<<

Quote

I fully recommend it for any environment. This is simply how parachute deployment should work!

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sundevil777

The pics you provided aren't enough to convince. The number of jumps you've done with ES is quite significant, but it is reasonable to want better visual proof.

I posted both before and after videos (they're small to fit under 1MB limit, but enough to show the gist). They are 30fps, can be examined frame by frame. Doing more fps won't produce more evidence, just more of fabric flapping in the wind. But everyone is welcome to, it won't be coming from me anymore!
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I found an example at 120fps, but not sure if Youtube retains 120 or downconverts it to 60fps. Anyway, try setting 720p60 in Quality and 0.25 in Speed. If you view frame by frame, you'll see that the slider got a bit "confused" in the first moments probably because it was not quartered well, it took a few moments to quarter itself.

Presenting more videos like this won't show anything new, the openings become 1:1, carbon copy of each other. Immediate and on heading. Boring, no variability. Those who crave the excitement of "panoramic linetwists" and cutaways, can always hide the slider under the cocoon.

For wingsuiters, I recommend dropping all this collapsing PC BS and getting a non-collapsing PC. With big wingsuits (this is V-4 in the video, that's not very big) the burble is massive, even when pulling from full flight. The burble causes the lines go all over the place. Non-collapsible PC will keep the lines straight throughout the deployment.

My "burden of proof" is officially furnished. It's now up to you, ma chickenz, to multiply and lay more eggs!
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yuri_base

For wingsuiters, I recommend dropping all this collapsing PC BS and getting a non-collapsing PC. With big wingsuits (this is V-4 in the video, that's not very big) the burble is massive, even when pulling from full flight. The burble causes the lines go all over the place. Non-collapsible PC will keep the lines straight throughout the deployment.

How does a non-collapsible PC keep the lines straight? Both a collapsible and non-collapsible PC will be fully inflated until the canopy is completely out of the bag. The lines in your video dident look any more 'all over the place' any more than a standard belly jump. Slowing down the video, the lines were most chaotic right after a stow released them, suggesting a semi-stowless bag would be of greater benefit to prevent that.

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Westerly

For wingsuiters, I recommend dropping all this collapsing PC BS and getting a non-collapsing PC. With big wingsuits (this is V-4 in the video, that's not very big) the burble is massive, even when pulling from full flight. The burble causes the lines go all over the place. Non-collapsible PC will keep the lines straight throughout the deployment.

How does a non-collapsible PC keep the lines straight? Both a collapsible and non-collapsible PC will be fully inflated until the canopy is completely out of the bag. The lines in your video dident look any more 'all over the place' any more than a standard belly jump. Slowing down the video, the lines were most chaotic right after a stow released them, suggesting a semi-stowless bag would be of greater benefit to prevent that.

Quote

Non-collapsible PC will keep the lines straight throughout the deployment.

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What's interesting that in the old illustrations of PRO pack we've all seen in the manuals, it shows slider grommets exposed, with a big "mouth" of the cocoon making grommets visible:

[inline OldPROPackIllustration.gif]

(is this John LeBlanc, a sketch made from a photo?)

So, maybe it was taught like this in the beginning (1970's?), but people just started wrapping the cocoon tightly above the grommets, and it just stuck, and exposed grommets became a "no-no"?

But in the video, we see a tightly closed cocoon with no hole in the apex and no slider grommets visible.

INCORRECT:

[inline PDIncorrect1.jpg]

INCORRECT:

[inline PDIncorrect2.jpg]

INCORRECT:

[inline PDIncorrect3.jpg]

CORRECT:

(Forgot: yet another benefit of the ES method is it makes squeezing air out much much easier.)

According to USPA, about 3 million jumps are made every year. Worldwide, probably about 5 million? Every jumper experiences a hard opening once in a while. Let's be conservative and say that on average, hard opening occurs only once in 1000 jumps. That's ~5000 hard openings a year. Some of them are hard enough to cause at least some injury (spine, neck). And some of them are hard enough to kill. (probably, an average of 1 per year? some deaths that are chalked up to "medical condition" may have been caused by a hard opening as a trigger of that medical condition)

If we can develop a method that reduces hard openings by at least some factor - 10, 100, whatever - that's a great achievement, there will be many thousands of people (over the years) without back/neck problems, and dozens of people (over the years) alive today. Imagine they're alive and knew that they were destined to be killed by a hard opening - you could organize a boogie and invite these "dead men walking" and celebrate life!

I - very strongly - believe that Exposed Slider is such a method.*

Don't hide the slider from the blast of fresh air it likes so much! Free the nipple slider!

* I'm only a human, so might be wrong. Only widespread courage of experienced jumpers willing to test it, can prove it right or wrong. I've done 400 tests, I'm done with this. The ball is in YOUR court now.
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I think the physics of what you say is difficult to refute. I agree with the idea. Safe implementation might be a practical issue, but implementation of the 'standard' method is also potentially a practical problem.

Out of curiosity, I downloaded a PD reserve manual to see what the practice is on (a) reserve parachute. It's a TR-375, which was just the first manual that I happened upon.

The attached photograph shows the slider packing method to be ES

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yuri_base

What's interesting that in the old illustrations of PRO pack we've all seen in the manuals, it shows slider grommets exposed, with a big "mouth" of the cocoon making grommets visible:

(is this John LeBlanc, a sketch made from a photo?)

So, maybe it was taught like this in the beginning (1970's?), but people just started wrapping the cocoon tightly above the grommets, and it just stuck, and exposed grommets became a "no-no"?

But in the video, we see a tightly closed cocoon with no hole in the apex and no slider grommets visible.

INCORRECT:

INCORRECT:

INCORRECT:

CORRECT:

[.image]http://www.dropzone.com/cgi-bin/forum/gforum.cgi?do=post_attachment;postatt_id=150637;[/image]

(Forgot: yet another benefit of the ES method is it makes squeezing air out much much easier.)

According to USPA, about 3 million jumps are made every year. Worldwide, probably about 5 million? Every jumper experiences a hard opening once in a while. Let's be conservative and say that on average, hard opening occurs only once in 1000 jumps. That's ~5000 hard openings a year. Some of them are hard enough to cause at least some injury (spine, neck). And some of them are hard enough to kill. (probably, an average of 1 per year? some deaths that are chalked up to "medical condition" may have been caused by a hard opening as a trigger of that medical condition)

If we can develop a method that reduces hard openings by at least some factor - 10, 100, whatever - that's a great achievement, there will be many thousands of people (over the years) without back/neck problems, and dozens of people (over the years) alive today. Imagine they're alive and knew that they were destined to be killed by a hard opening - you could organize a boogie and invite these "dead men walking" and celebrate life!

I - very strongly - believe that Exposed Slider is such a method.*

Don't hide the slider from the blast of fresh air it likes so much! Free the nipple slider!

* I'm only a human, so might be wrong. Only widespread courage of experienced jumpers willing to test it, can prove it right or wrong. I've done 400 tests, I'm done with this. The ball is in YOUR court now.

Why dont you just email John LeBlanc and ask him what he thinks?

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dgw

I think the physics of what you say is difficult to refute. I agree with the idea. Safe implementation might be a practical issue, but implementation of the 'standard' method is also potentially a practical problem.

Out of curiosity, I downloaded a PD reserve manual to see what the practice is on (a) reserve parachute. It's a TR-375, which was just the first manual that I happened upon.

The attached photograph shows the slider packing method to be ES

Haha, this is awesome, thanks!

[inline ReserveWithExposedSlider.jpg]
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yuri_base

***I think the physics of what you say is difficult to refute. I agree with the idea. Safe implementation might be a practical issue, but implementation of the 'standard' method is also potentially a practical problem.

Out of curiosity, I downloaded a PD reserve manual to see what the practice is on (a) reserve parachute. It's a TR-375, which was just the first manual that I happened upon.

The attached photograph shows the slider packing method to be ES

Haha, this is awesome, thanks!

That looks similar to what PD recommends for packing the Horizon. They state to leave a small mouth open at the tip of the cocoon.

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>>> Why dont you just email John LeBlanc and ask him what he thinks? <<<

I feel zero need. The "authorities"*, from my experience, are virtually always dismissive. For example, I've tried to talk to wingsuit manufacturers back in 2005-2010 about ideas like leg wing-only half-wingsuit, angle of incidence, balance, instrumentation, flight analysis and modeling, etc. - they've always been dismissive, ridiculing sometimes even. "This won't work, you're wrong, you don't know what you're talking about, ..." etc. etc.

Besides, it's funnier when the revolution comes from within, from the "masses". When manufacturers are late to the party. Just shows how little fresh thinking they do, they just sit on their throne for decades. I'm just that little spark that ignites the fire under their throne.

* no disrespect to anyone in particular
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>>> That looks similar to what PD recommends for packing the Horizon. They state to leave a small mouth open at the tip of the cocoon. <<<

Leaving small mouth open didn't work for me when I had troubles with my Spectre. I started opening it more and more over 2-3 jumps, until got brave enough to "go big" and expose the grommets fully. BOOM, problem solved. Apparently, the air pressure near the tip of the cocoon in angled deployment works in such a way that it can close the small mouth. (probably, works better for belly deployment) When grommets are exposed, that doesn't matter, because slider starts inflating immediately and pushes the cocoon open.
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The attached is from the PD Horizon manual.

I'll leave the physics to Yuri.

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In that photo the grommets are not exposed, they just did not cocoon it as tight as some jumpers do for the photos.

The reason that in the reserve manual they are shown that way is since you need to stack the grommets on top of each other for each side while creating an and at no point are you wrapping the tail all the way around the canopy. Reserve openings from terminal are rarely described as "Soft and gentle" - the method we use to pack reserves is to give the canopy the best chances of opening on heading in the fastest possible way while consuming the least amount of altitude while not causing openings that are excessively hard. We leave the nose exposed and don't wrap anything.
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