skydivingmonk 0 #1 Posted October 7, 2018 Hey all, I'm totally new, as in, I haven't even begun AFF yet, so maybe this concern is a bit unfounded. But I have noticed from most of the jumpers with a D next to their name that proper pack jobs can do a world of good for ensuring a soft opening. Am I wrong to think that the majority of issues people can encounter with the opening are typically addressed with a correct pack job? I see a lot of people saying that they "trash pack" or just wad up and go, and that seems like toying with chance. I don't want to discount any of the serious injuries or fatalities that occur, especially not with the veterans of the sport; but, in your opinion would most of those killed or serious hurt from hard openings be here today if their canopy was packed properly? Quote Share this post Link to post Share on other sites
skydiverek 61 #2 October 7, 2018 Watch this: https://www.youtube.com/watch?v=cVAoiLl2B6M Quote Share this post Link to post Share on other sites
peek 20 #3 October 7, 2018 A proper pack job is important, but is not the only thing needed for a nice opening on a parachute. It is a complicated system, and a certain amount of randomness exists. Also, some models and brands of parachute are noted for opening harder than others. I suggest doing a lot of searching and reading in the Gear and Rigging forum for discussions of this. Then come back with some more questions. And while you are at it, and just for fun, watch this: https://www.youtube.com/watch?v=i16HryVyRaI Quote Share this post Link to post Share on other sites
skydivingmonk 0 #4 October 7, 2018 Both of those videos were great. Thanks so much for the replies. Quote Share this post Link to post Share on other sites
yuri_base 1 #5 October 7, 2018 Hard openings, imho, are caused by slider being "shaken down" under the cover of the cocoon if there's even a slight delay in wind blowing it off. This is especially true for wingsuiting with non-fresh ZP and even tracking (even tracking on break-off after a non-tracking jump). Exposing the slider so it's pushed by relative wind into the stops the first moment the canopy is out of the D-bag, solves the problem. It also greatly helps with reducing the occurrence of line twists. (see attached video illustrating cocoon hesitation) [inline Cocoon.jpg] On the other, less serious hand, hard openings are not always a bad thing: when I was doing my AFF, a hard opening fixed a problem in my spine with displaced vertebrae (from a big wave crush on my back when body surfing in the ocean), it settled them in proper place. I felt like I was born again. PS. Exposing slider is for experienced enough jumper, of course. Don't do it without packing/jumping at least 100-200 of normal pack jobs. Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio CocoonHesitation.m4v Quote Share this post Link to post Share on other sites
billvon 2,734 #6 October 8, 2018 >Hard openings, imho, are caused by slider being "shaken down" under the cover of the >cocoon if there's even a slight delay in wind blowing it off. That is one of the many reasons for hard openings. >Exposing the slider so it's pushed by relative wind into the stops the first moment the >canopy is out of the D-bag, solves the problem. I would note that if "exposing the slider" allows the slider to move down the lines even a little during S-folding and insertion into the bag, then that technique will cause, not prevent, hard openings. Quote Share this post Link to post Share on other sites
yuri_base 1 #7 October 8, 2018 billvon>Hard openings, imho, are caused by slider being "shaken down" under the cover of the >cocoon if there's even a slight delay in wind blowing it off. That is one of the many reasons for hard openings. That doesn't mean that it doesn't need to be addressed. billvonI would note that if "exposing the slider" allows the slider to move down the lines even a little during S-folding and insertion into the bag, then that technique will cause, not prevent, hard openings. It won't move by itself, push the grommets all the way up the lines while folding and closing the bag.Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio Quote Share this post Link to post Share on other sites
Westerly 61 #8 October 8, 2018 yuri_base Hard openings, imho, are caused by slider being "shaken down" under the cover of the cocoon if there's even a slight delay in wind blowing it off. This is especially true for wingsuiting with non-fresh ZP and even tracking (even tracking on break-off after a non-tracking jump). Exposing the slider so it's pushed by relative wind into the stops the first moment the canopy is out of the D-bag, solves the problem. It also greatly helps with reducing the occurrence of line twists. (see attached video illustrating cocoon hesitation) On the other, less serious hand, hard openings are not always a bad thing: when I was doing my AFF, a hard opening fixed a problem in my spine with displaced vertebrae (from a big wave crush on my back when body surfing in the ocean), it settled them in proper place. I felt like I was born again. PS. Exposing slider is for experienced enough jumper, of course. Don't do it without packing/jumping at least 100-200 of normal pack jobs. I think the only people I have ever seen pack that way are AFF students. It seems that method could just as easily create a hard opening as prevent one. If those grommets move down at all while putting it in the bag, you're possibly going to get a hard opening. Why not just loosely wrap the top skin instead? For the PD Horizon, PD recommends very light wrapping of the top skin and leaving a small gap to let air through at the tip of the cocoon. I do a single wrap on the tail all the way at the bottom and that is it for WS jumps. I would think that effectively accomplishes the same thing you're trying to do, except it doesent leave the grommets exposed to get moved out of place while bagging the canopy (or extraction). Quote Share this post Link to post Share on other sites
yuri_base 1 #9 October 8, 2018 WesterlyIt seems that method could just as easily create a hard opening as prevent one. If those grommets move down at all while putting it in the bag, you're possibly going to get a hard opening. See my reply above. Why would anyone let the grommets move down, is it like they have this insane sliding power that the packer can't overcome? (Never happened to me while doing hundreds of jumps on this pack job.) QuoteWhy not just loosely wrap the top skin instead? For the PD Horizon, PD recommends very light wrapping of the top skin and leaving a small gap to let air through at the tip of the cocoon. I do a single wrap on the tail all the way at the bottom and that is it for WS jumps. I would think that effectively accomplishes the same thing you're trying to do, except it doesent leave the grommets exposed to get moved out of place while bagging the canopy (or extraction). The wrap on the tail helps with keeping grommets up during packing (not required, since grommets can be controlled all the way through closing the bag), but doesn't prevent them from sliding down under the cover of the cocoon. It tuns out (watch video attached in my post above), the cocoon - especially on WS jumps - likes to dance closed in the wind, just that extra fraction of a second, but that dance is what causes the slider to move down the lines, as well as spin the canopy around. This may not be noticeable on new, super slippery ZP, but as it gets more used, the cocoon is just happy to dance, because in WS deployment, the wind hits the cocoon from the bottom, which is wrapped by the tail and is a smooth surface. So, a small hole in the apex of the wrap is not sufficient - I tried that; it needs to be big, such as when slider is exposed. The most important thing in reefing the canopy to prevent hard openings is to let the slider be the first thing that "sees" the relative wind, and gets pushed against the stops for good. The worst thing to do is to "hide" the slider from relative wind, under the cocoon. As in wingsuits, acceptance of new things and brave thinking in skydiving/BASE is very slow. Most people just do what most other people do, copying others mechanically. They don't think through how, for example, opening actually works. And they are scared of any deviations from "official party line".Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio Quote Share this post Link to post Share on other sites
yuri_base 1 #10 October 8, 2018 Here's an illustration of cocoon hesitation. Yellow is center cell (tail wrap), cells get orange and red progressively towards the end cells; slider is red. t = 0 - canopy is out of the D-bag: [inline CocoonHesitation000.jpg] t = 20ms - cocoon is now open on the top (facing the sky), but closed on the bottom surface (facing the ground), as the relative wind hits it from the bottom at an angle due to canopy sagging below the wind line due to weight: [inline CocoonHesitation020.jpg] t = 40ms - cocoon is dancing still partially closed, slider possibly being shaken down the lines, still hidden by cocoon's tip: [inline CocoonHesitation040.jpg] t = 60ms - cocoon is still dancing, slider still not visible: [inline CocoonHesitation060.jpg] (unfortunately, cocoon goes out of frame, but it obviously doesn't look pretty out there) t = 133ms - cocoon is finally unwrapped, red slider is visible and inflated, but probably moved down the lines a bit due to shaking, and the canopy managed to make a full turn during the dance - hello, linetwists: [inline CocoonHesitation133.jpg] Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio Quote Share this post Link to post Share on other sites
Lukasz_Se 2 #11 October 8, 2018 Westerly Why not just loosely wrap the top skin instead? For the PD Horizon, PD recommends very light wrapping of the top skin and leaving a small gap to let air through at the tip of the cocoon. I do a single wrap on the tail all the way at the bottom and that is it for WS jumps. I would think that effectively accomplishes the same thing you're trying to do, except it doesent leave the grommets exposed to get moved out of place while bagging the canopy (or extraction). Once I started packing this way, my openings improved a lot during WS jumps. Quote Share this post Link to post Share on other sites
DJL 232 #12 October 8, 2018 yuri_base***>Hard openings, imho, are caused by slider being "shaken down" under the cover of the >cocoon if there's even a slight delay in wind blowing it off. That is one of the many reasons for hard openings. That doesn't mean that it doesn't need to be addressed. billvonI would note that if "exposing the slider" allows the slider to move down the lines even a little during S-folding and insertion into the bag, then that technique will cause, not prevent, hard openings. It won't move by itself, push the grommets all the way up the lines while folding and closing the bag. Yuri, you should know better than to try to dish out a slider-out packing method to a beginner over the internet."I encourage all awesome dangerous behavior." - Jeffro Fincher Quote Share this post Link to post Share on other sites
yuri_base 1 #13 October 8, 2018 DJL******>Hard openings, imho, are caused by slider being "shaken down" under the cover of the >cocoon if there's even a slight delay in wind blowing it off. That is one of the many reasons for hard openings. That doesn't mean that it doesn't need to be addressed. billvonI would note that if "exposing the slider" allows the slider to move down the lines even a little during S-folding and insertion into the bag, then that technique will cause, not prevent, hard openings. It won't move by itself, push the grommets all the way up the lines while folding and closing the bag. Yuri, you should know better than to try to dish out a slider-out packing method to a beginner over the internet. I'm not talking to anyone in particular, the thread is read by hundreds of people of all experience levels, and the info I'm sharing is universal.Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio Quote Share this post Link to post Share on other sites
yuri_base 1 #14 October 8, 2018 Ooops, the times should be multiplied by 10: 0.2s, 0.4s, 0.6s, and 1.33s. My math is terrible. 6 frames at 30fps is 200ms, not 20!Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio Quote Share this post Link to post Share on other sites
billvon 2,734 #15 October 8, 2018 >It won't move by itself, push the grommets all the way up the lines while folding >and closing the bag. Nothing "moves by itself." Yet a very big cause of hard openings is parts of the pack job moving around while trying to get it into the bag. If you doubt this, watch any newer jumper with a brand new ZP canopy struggling to get it packed. Control of the pack job while it is going in the bag is a critical part of any pack job. Leaving the grommets exposed can cause loss of control of the slider. I am sure you can make it work just fine - but I'm also sure you would be upset if your advice caused a newer packer to have a catastrophically hard opening. Quote Share this post Link to post Share on other sites
DJL 232 #16 October 8, 2018 skydivingmonkHey all, I'm totally new, as in, I haven't even begun AFF yet, so maybe this concern is a bit unfounded. But I have noticed from most of the jumpers with a D next to their name that proper pack jobs can do a world of good for ensuring a soft opening. Am I wrong to think that the majority of issues people can encounter with the opening are typically addressed with a correct pack job? I see a lot of people saying that they "trash pack" or just wad up and go, and that seems like toying with chance. I don't want to discount any of the serious injuries or fatalities that occur, especially not with the veterans of the sport; but, in your opinion would most of those killed or serious hurt from hard openings be here today if their canopy was packed properly? In conclusion, learn to pack under the guidance of your instructors and established methods (Look up Performance Designs Pro Packing). Don't do gimmicks and tricks and voodoo and bullshit, just learn how to pack correctly from the get go. If you're struggling it's because you're learning, not because you're failing."I encourage all awesome dangerous behavior." - Jeffro Fincher Quote Share this post Link to post Share on other sites
yuri_base 1 #17 October 8, 2018 billvon>It won't move by itself, push the grommets all the way up the lines while folding >and closing the bag. Nothing "moves by itself." Yet a very big cause of hard openings is parts of the pack job moving around while trying to get it into the bag. If you doubt this, watch any newer jumper with a brand new ZP canopy struggling to get it packed. Control of the pack job while it is going in the bag is a critical part of any pack job. Leaving the grommets exposed can cause loss of control of the slider. I am sure you can make it work just fine - but I'm also sure you would be upset if your advice caused a newer packer to have a catastrophically hard opening. Slider is actually much easier to control when grommets are exposed. Just keep pushing the grommets all the way by reaching them with fingers while closing the flap with the first rubber band. They are not going anywhere. Again, this disclaimer applies: yuri_baseExposing slider is for experienced enough jumper, of course. Don't do it without packing/jumping at least 100-200 of normal pack jobs. Another side benefit of this pack job is that it saves, perhaps, a couple of hundred of feet of unnecessary towing of the cocoon, as the opening is more "definite", immediate - you "fall" on the inflated slider, so the initial tug on the shoulders, before main inflation starts, is more definite. Not hard, just more "concrete". Many people died because they didn't have those couple of hundred of feet, because they were unnecessarily "falling into pillows" on opening. And another benefit is heading performance. When you fall on a quartered, inflated slider, it sets the firm heading which is maintained through the opening as long as the steering through the opening is even. And another benefit is no linetwists. Like... gone! Because canopy doesn't have time to spin around as a dancing cocoon. I've been packing like this for years and hundreds of jumps (before switching to skydiving my BASE canopy full time), it works like a charm. First shared it 5 years ago, no one is interested. It's ok, I'm used to it. People need The Authority (John le Blanc, Brian Germain, etc.) to tell them something, not some random guy, and not their own logical thinking. PS. The video of cocoon hesitation above is from 2009, me flying in Phantom-1. That's when I had the 'Eureka!' moment, and started packing with slider exposed. BOOM! Problem solved.Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio Quote Share this post Link to post Share on other sites
Westerly 61 #18 October 9, 2018 yuri_base***>It won't move by itself, push the grommets all the way up the lines while folding >and closing the bag. Nothing "moves by itself." Yet a very big cause of hard openings is parts of the pack job moving around while trying to get it into the bag. If you doubt this, watch any newer jumper with a brand new ZP canopy struggling to get it packed. Control of the pack job while it is going in the bag is a critical part of any pack job. Leaving the grommets exposed can cause loss of control of the slider. I am sure you can make it work just fine - but I'm also sure you would be upset if your advice caused a newer packer to have a catastrophically hard opening. Slider is actually much easier to control when grommets are exposed. Just keep pushing the grommets all the way by reaching them with fingers while closing the flap with the first rubber band. They are not going anywhere. Again, this disclaimer applies: yuri_baseExposing slider is for experienced enough jumper, of course. Don't do it without packing/jumping at least 100-200 of normal pack jobs. Another side benefit of this pack job is that it saves, perhaps, a couple of hundred of feet of unnecessary towing of the cocoon, as the opening is more "definite", immediate - you "fall" on the inflated slider, so the initial tug on the shoulders, before main inflation starts, is more definite. Not hard, just more "concrete". Many people died because they didn't have those couple of hundred of feet, because they were unnecessarily "falling into pillows" on opening. And another benefit is heading performance. When you fall on a quartered, inflated slider, it sets the firm heading which is maintained through the opening as long as the steering through the opening is even. And another benefit is no linetwists. Like... gone! Because canopy doesn't have time to spin around as a dancing cocoon. I've been packing like this for years and hundreds of jumps (before switching to skydiving my BASE canopy full time), it works like a charm. First shared it 5 years ago, no one is interested. It's ok, I'm used to it. People need The Authority (John le Blanc, Brian Germain, etc.) to tell them something, not some random guy, and not their own logical thinking. PS. The video of cocoon hesitation above is from 2009, me flying in Phantom-1. That's when I had the 'Eureka!' moment, and started packing with slider exposed. BOOM! Problem solved. If this method is so fantastic and fixes everything, why are you the only person who uses it? I am sure PD and Squirrel has seen this method before. Anyway, I tried your method of leaving the slider grommets fully exposed. I did 7 WS jumps today and tried it on all of them. I dident notice any difference from how I normally pack. It dident open any faster from what I could tell and it certainly dident open any more on heading than it normally does (which is usually not on heading at all). Quote Share this post Link to post Share on other sites
yuri_base 1 #19 October 9, 2018 >>> Anyway, I tried your method of leaving the slider grommets fully exposed. I did 7 WS jumps today and tried it on all of them. I dident notice any difference from how I normally pack. It dident open any faster from what I could tell and it certainly dident open any more on heading than it normally does (which is usually not on heading at all). <<< The difference is not necessarily noticeable. It won't be noticeable if, for example ZP is fresh and superslippery, since it unwraps itself very quickly, especially if it's wrapped lightly and a hole is left at the apex of the cocoon. It won't be noticeable if one uses non-collapsible PC, as continuous stretching of the packjob by inflated PC helps with quick unwrap of the cocoon. It won't be [much] noticeable if one pulls not from full WS flight (with canopy being extracted at a shallow angle), but collapses wings to kill forward speed and deploy "old way", falling more down than moving forward, since in this case, the mechanism for long hesitations (relative wind hitting the smooth bottom surface of the cocoon that sags under the windline under its weight) is not so strong. All this doesn't mean that the method with exposed slider doesn't work; only sudden disappearance of hard and twisted openings in the long run, like it was in my case, confirms that it works. I strongly believe this is the only, proper way of controlling the slider: it MUST be exposed to relative wind INSTANTLY when canopy is out of the bag. It must NOT be hidden by a cocoon. I believe the idea of wrapping the slider when PRO pack was invented and became mainstream, what, 40+ years ago? - was a wrong choice. And now, because of this huge momentum of being taught this for decades, we can't even fathom exposing the slider, we think that it's sketchy and will result in hard openings... while it's the opposite! The Emperor has no clothes!Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio Quote Share this post Link to post Share on other sites
yuri_base 1 #20 October 9, 2018 Here's an illustration of cocoon hesitation leading to line twists and harder than normal opening, vs. exposed slider opening leading to immediate (but not hard), properly staged opening, with no useless altitude loss while trailing the dancing cocoon (dt=1/15s (2 frames at 30fps) is the step between frames (0.15s is a typo), 0.6s for the last frame): [inline CocoonHesitationVsExposedSlider.jpg] Note that the 1st thing that shows up when D-bag opens is yellow on the left (this is tail/cocoon, center cell is yellow) and red on the right (this is the slider), and slider is instantly inflated and quartered - this is what we want! Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio Quote Share this post Link to post Share on other sites
LeeroyJenkins 3 #21 October 9, 2018 yuri_baseHere's an illustration of cocoon hesitation leading to line twists and harder than normal opening, vs. exposed slider opening leading to immediate (but not hard), properly staged opening, with no useless altitude loss while trailing the dancing cocoon (dt=0.15s is the step between frames, 0.6s for the last frame): Note that the 1st thing that shows up when D-bag opens is yellow on the left (this is tail/cocoon, center cell is yellow) and red on the right (this is the slider), and slider is instantly inflated and quartered - this is what we want! With the chaos of openings your sample size it not enough to prove anything. Quote Share this post Link to post Share on other sites
yuri_base 1 #22 October 9, 2018 >>> With the chaos of openings your sample size it not enough to prove anything. <<< Yes, this is a classic chicken and egg problem. If out of 100,000,000 jumps 50M were done with slider hidden and 50M with slider exposed, we would have solid stats of which causes more of catastrophic hard openings. With only one jumper having done ~400 jumps with slider exposed (BTW, I no longer skydive my Spectre, only freepacked BASE canopy, so no longer pack like this), sample size is negligibly small. But if nobody tries or doesn't continue jumping slider exposed, we'll never know! Free the slider, everyone! Try it! Trust me, it won't hurt.Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio Quote Share this post Link to post Share on other sites
yuri_base 1 #23 October 10, 2018 An example of Cocoon Hesitation was posted above; here is an example of an opening (same canopy, Spectre 190) with the Exposed Slider method. The opening is more immediate, with stronger initial jolt on the shoulders due to towing the inflated slider in the first moments, but the openings are comfortable, just not wasteful of altitude. And I've had ~400 of such openings like this one, 1:1, virtually exact replica. Openings become very consistent, and with very good heading performance (thanks to inflated slider anchoring the heading). It feels like it even 'corrects' your body position! (because the inflated slider is hard to turn, it turns your body is you drop one shoulder; with cocoon-cigar, dropped shoulder spins the cigar very easily, besides its own dance) And... ZERO line twists. (before, linetwists were like 1 in 3-4 jumps, that would be >100 linetwisted openings out of 400 jumps!) I'm no longer jumping my skydiving canopy, so if anyone asks to take a video of packing or opening, I can't do this. If nobody jumps this pack job, the idea will be buried, but I'll remind again in 5 years, since in skydiving world any fresh idea takes decades to pick up.Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio OpeningWithSliderExposed.m4v Quote Share this post Link to post Share on other sites
yuri_base 1 #24 October 10, 2018 >>> This technique might work for the slower environments of Wingsuiting but it is not recommended to do it in a terminal environment. <<< Not recommended by who? Anyone actually tried? I've done many, many deployments with Exposed Slider method on non-WS jumps as well, pulling from full track without even slowing down (and I'm 260lbs out the door, my track speed, especially in tracksuit, is way more than standard 120mph belly speed), and always got good openings. I fully recommend it for any environment. This is simply how parachute deployment should work! Also, deleted effort from the Incidents thread: "Two worst things one can do to the slider: hide it from the deployment airflow, and hide it from sight when packing. With decades and millions of packjobs, we have this tattooed in our brains that exposed slider is bad. While if we were taught the other way, with the understanding of how deployment actually works, hiding the slider would be considered as a no-no. And many jumpers who died from hard openings would be alive today." "If we were taught this, "the slider MUST be the very 1st thing that is blasted by the wind" for 40+ years, the thought of hiding the slider by cocoon would sound totally bizarre and sketchy today! It's all about our perceptions... We took a wrong turn in the fork." "As I said, if students were taught to pack like this in the first place, and exposing the slider was a dogma instead of hiding the slider, people would have the same arguments if one proposed to hide the slider. It's all just resistance to a new thing. New is always scary. We like to do what we're taught and what others are doing. We don't deviate from dogmas hammered in our brains until some Authority like John le Blanc tells us."Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio Quote Share this post Link to post Share on other sites
yuri_base 1 #25 October 10, 2018 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.Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio Quote Share this post Link to post Share on other sites