0
skydivingmonk

Preventing Hard Openings

Recommended Posts

PhreeZone

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.



These are just weak excuses, once it's admitted that it's "officially" (from PD) OK to just "lay" the mouth on top of the grommets (there's no tension, no resistance there), or make them even barely visible through the hole, one might as well just "go big" and expose them fully. The way it's done in my photo actually keeps the bulk of the slider under some tension of the "neck", there's no tension whatsoever in the PD Horizon photo.





It's fascinating to watch how resistance to any deviation from habits and dogmas works. "This is PD, this is OK, but not even an inch lower! Once even 1 millimeter of the shiny grommets becomes visible, bad things will happen catastrophically!" Hard to believe, but it proves to be true - very experienced jumpers with many thousands of jumps are scared to do 2-3 jumps with gradually lowering the cocoon.

And it's not about "Soft and gentle", it's about priorities, it's about doing things right, it's about staging the opening properly. And to stage it properly, slider must be numero uno thing that is presented to the wind. Not the cocoon... slider. Period! The openings become more immediate, without wasting altitude to "Soft and gentle". How many times we've read in fatality reports, that "after cutaway, the reserve was activated but didn't have enough altitude to fully inflate"? (extra 100-200ft would make a huge difference.) That's because of wasting altitude to "falling into pillows", "Soft and gentle". We're not jellyfish, we don't need to fall into pillows, we can take an opening that starts immediately, but is not hard by any measure.
Android+Wear/iOS/Windows apps:
L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP
iOS only: L/D Magic
Windows only: WS Studio

Share this post


Link to post
Share on other sites
https://www.youtube.com/watch?v=Bg8O5-6fDz0

This is a tracking jump pulling from full flight, and since I'm heavy (260lbs out the door), the speed is "superterminal" for sure, perhaps, ~140-150mph? Not a problem for Exposed Slider method. The opening is not "falling into pillows", but is not hard either. Yes, I've got an offheading 90 degrees, but taking into account that I rarely jump my tracksuit (almost 100% - wingsuit), it's not too shabby.

**Insults removed** Try it in 2-3 jumps moving the mouth of the cocoon down 1 inch at a time. When the logic of presenting the slider to relative wind as #1 stage in the openings sequence (after D-bag opens) becomes obvious and tried, stand in the middle of the hangar and loudly proclaim: "Guys, I just had my FIRST properly staged opening! Beeeeeeeeeeeeerrrrrrrr!!!" :D :D :D :D
Android+Wear/iOS/Windows apps:
L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP
iOS only: L/D Magic
Windows only: WS Studio

Share this post


Link to post
Share on other sites
Quote

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.


Yep. Which is the same way I do BASE pack jobs. (Neither of which, of course, having "slow comfortable deployment" as a goal.)

Share this post


Link to post
Share on other sites
>>> BASE pack jobs. (Neither of which, of course, having "slow comfortable deployment" as a goal.) <<<

Exactly - when saving life is paramount, having "slow comfortable deployment" is not a goal. But deploying main in skydiving *is* an act of saving life, too. So, having "slow comfortable deployment" should not be a goal, neither. Having comfortable, but not slow, opening should be a goal. ES method provides perfect middle ground between slow opening wasting too much of our most valuable asset - altitude - and hard opening that consumes little altitude but makes us unable to have fun due to pain. Its speed of opening is an optimal balance between comfort and safety.
Android+Wear/iOS/Windows apps:
L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP
iOS only: L/D Magic
Windows only: WS Studio

Share this post


Link to post
Share on other sites
Quote

But deploying main in skydiving *is* an act of saving life, too. So, having "slow comfortable deployment" should not be a goal, neither. Having comfortable, but not slow, opening should be a goal. ES method provides perfect middle ground between slow opening wasting too much of our most valuable asset - altitude - and hard opening that consumes little altitude but makes us unable to have fun due to pain.


And could kill someone if they lose control of the slider.

The reason your method can be dangerous is that it allows people to more easily lose control of the slider. Wrapping the tail helps people (especially newer packers) keep the slider under control - and that additional control can save packers from dangerously hard openings. I have no doubt that you have made your pack jobs work. Riggers and BASE jumpers make similar pack jobs work all the time. That does not necessarily port to newer jumpers trying to pack ZP mains.

Also, enough with the ego comments and the attacks on the "pussys" who don't appreciate your amazing pack job. I deleted those comments from your previous post.

Share this post


Link to post
Share on other sites
Here's the diagram I promised. I didn't find the pressure distribution around a cone, but by analogy with the pressure distribution on the bottom surface of an airfoil -

[inline AirfoilPressureDistribution.gif]

- pressure is nearly perpendicular to the surface of the cocoon, so it tries to compress the cocoon, not to "skin" it. Fresh ZP is happy to unwrap itself as it's so slippery and springy, but used ZP's friction can keep the cocoon closed for an extra fraction of a second and cause the slider to slide down the lines as it encounters no resistance from the wind - it's inside the "cabin" of the cocoon. With wingsuit, due to sagging, the air mostly hits the bottom of the cocoon which is a smooth surface and it's just happy to stay closed and trailing behind.

[inline MechanismOfCocoonHesitation.jpg]

Anyway, I feel I said everything I wanted to say, tested the ground 5 years after first sharing this (after about 4 years of testing it), and it's still infertile. Oh well, not the first time, not the last. I'll revisit the topic in a few years to see if it's a good time to plant the seed. Bye bye now! ;)
Android+Wear/iOS/Windows apps:
L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP
iOS only: L/D Magic
Windows only: WS Studio

AirfoilPressureDistribution.gif

MechanismOfCocoonHesitation.jpg

Share this post


Link to post
Share on other sites
yuri_base

Here's the diagram I promised. I didn't find the pressure distribution around a cone, but by analogy with the pressure distribution on the bottom surface of an airfoil -



- pressure is nearly perpendicular to the surface of the cocoon, so it tries to compress the cocoon, not to "skin" it. Fresh ZP is happy to unwrap itself as it's so slippery and springy, but used ZP's friction can keep the cocoon closed for an extra fraction of a second and cause the slider to slide down the lines as it encounters no resistance from the wind - it's inside the "cabin" of the cocoon. With wingsuit, due to sagging, the air mostly hits the bottom of the cocoon which is a smooth surface and it's just happy to stay closed and trailing behind.



Anyway, I feel I said everything I wanted to say, tested the ground 5 years after first sharing this (after about 4 years of testing it), and it's still infertile. Oh well, not the first time, not the last. I'll revisit the topic in a few years to see if it's a good time to plant the seed. Bye bye now! ;)




Are you trying to argue that the pressure caused by the relative wind is greater than the core of the wind blowing on the top skin tail so much so that it prevents the canopy from opening as fast?

It seems you assume that the cacoon won’t be parrle with the relative wind, I don’t know what you are basing that idea on but it seems like you are inventing a fixed point while there are none.

Share this post


Link to post
Share on other sites
Quote

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.



LOVE THIS. Soooooo much truth in here.

Share this post


Link to post
Share on other sites
Quote

sed ZP's friction can keep the cocoon closed for an extra fraction of a second and cause the slider to slide down the lines as it encounters no resistance from the wind - it's inside the "cabin" of the cocoon.


In that case, what force do you imagine is accelerating the slider downwards?

Share this post


Link to post
Share on other sites
yuri_base

>>> 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.



Curious; You do know that the PD Horizon has the little plastic snaps on the slider to secure it to the canopy as it comes out of the bag and you get to line stretch. Yuri: How does that figure into your theory? Just wondering....

Share this post


Link to post
Share on other sites
yuri_base

Here's the diagram I promised. I didn't find the pressure distribution around a cone, but by analogy with the pressure distribution on the bottom surface of an airfoil -



- pressure is nearly perpendicular to the surface of the cocoon, so it tries to compress the cocoon, not to "skin" it. Fresh ZP is happy to unwrap itself as it's so slippery and springy, but used ZP's friction can keep the cocoon closed for an extra fraction of a second and cause the slider to slide down the lines as it encounters no resistance from the wind - it's inside the "cabin" of the cocoon. With wingsuit, due to sagging, the air mostly hits the bottom of the cocoon which is a smooth surface and it's just happy to stay closed and trailing behind.



Anyway, I feel I said everything I wanted to say, tested the ground 5 years after first sharing this (after about 4 years of testing it), and it's still infertile. Oh well, not the first time, not the last. I'll revisit the topic in a few years to see if it's a good time to plant the seed. Bye bye now! ;)



Why not just wrap the top skin without folding it? That's what I do when I pack. I leave the nose out, and I dont wrap the tail whatsoever. I just wrap it around the canopy and then lay it on the ground. Then when it comes out of the bag, regardless of whether the air is pushing on the bottom of the cocoon or trying to strip the fabric off, there is really not much to hold it in place since the tail is not wrapped at all.

Share this post


Link to post
Share on other sites
Interesting topic. When I first moved from rounds to squares, and before I learned how to PRO and eventually psycho pack, I used to flat pack. In that packing sequence, the entire canopy was folded into a d-bag wide "sausage" with its top end into the d-bag before I even move the slider up right before s-folding everything into the bag. While I did quarter the slider and tucked its center into the pack job, I used to grab its quarters sticking out in between the line groups and WRAPED THOSE AROUND THE BOTTOM OF THE PACKJOB pulling those upwards a bit to ensure slider grommets are against the stops at all times. So, essentially my slider was covering the bottom of my pack job and not the other way around, so the slider was always the first thing exposed during the opening. Can't remember having any problems with openings with that method. Not taking any sides here - just something I forgot about and this thread brought this up to my attention.

I do find it interesting though that PD explicitly shows SE pack job as "WRONG" - given their unparalleled reasearch and testing capacity I never questioned their recommendations.

Share this post


Link to post
Share on other sites

Anyone else like the idea of having an exposed slider outside the tail wrap?  This got me thinking.  I use to pack that way.  Mostly because I wanted to see where my grommets were just before putting them in the bag and to make sure my slider was all the way up.  I started packing with a more traditional tight wrap around the lines.  I was having a problem with hard openings but didn't think this might be the problem.  I am also a heavy jumper, more so than yuri.  I recently had pd make me a dome slider and it softened up my openings tremendously.  Now I'm thinking about going back to having an exposed slider so it's the first thing the wind hits.  Any thoughts on how much tail wrap around the main part of the canopy?  I do probably more than I should to make an easier pack job.

Share this post


Link to post
Share on other sites
7 hours ago, Elpnor said:

Anyone else like the idea of having an exposed slider outside the tail wrap?  

Nope.  At most, include the slider in the tail roll (so it is kept under control a bit longer) but do not expose it. Exposing it exposes it to all the manipulations you do to the parachute to get it in the bag - and many of those will try to push the slider away from grommets.

  • Like 2

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account. It's free!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
0