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danornan

Hard Openings

wmw999

This is a marker thread for some hard opening discussion from Incidents. They deserve a thread of their own, because it's an important topic and I hope the discussion continues.

Message added by wmw999

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Posted (edited)

From above, "I later spent many, many hours going over the sequence trying to figure out "why". I was at a PIA conference and talking to Bill Booth. Bill listened to my description and then said "that's why I started using magnets on the riser covers". 

Has anyone with magnets on you riser covers had a hard opening?

 

Edited by danornan

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16 minutes ago, danornan said:

Has anyone with magnets on you riser covers had a hard opening?

 

I doubt it's ALWAYS riser covers causing hard openings, rather that they can be the explanation for more or less frequent hard openings (you can obviously easily cause a hard opening on any riser covers by leaving the slider down on packing).

Here's the Bill Booth briefly talking a bit about this (35m17s to 37m17s):

 

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On 8/6/2020 at 3:20 PM, JoeWeber said:

Man, I just hope things get better for you and faster than anyone imagines. Out of nowhere, I've had the holy crap knocked out of me back in the day with Sabre 1's. I really don't like thinking that this sort of thing is one of the risks, not these day's. Maybe it is time to go back to Dacron lines. 

I stupidly, trying to save money, just bought a Sabre 1. First terminal opening with the original slider was fast and hurt a little, but I felt it for days after. I put the pocket slider I had for my zp.exe 185 on it for two more terminal openings and while still fast, both were much more tolerable. I think this has convinced me to order a new canopy, since I'll be on a 170 for a while due to my aversion to rapid downsizing from a previous injury - and needing a new container for that anyhow. I'm going to read up on how Sabre 3s open, because if people are getting hard opens on them still, well, maybe I'll go for Safire 3 instead.

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4 hours ago, Binary93 said:

I doubt it's ALWAYS riser covers causing hard openings, rather that they can be the explanation for more or less frequent hard openings (you can obviously easily cause a hard opening on any riser covers by leaving the slider down on packing).

Here's the Bill Booth briefly talking a bit about this (35m17s to 37m17s):

 

I have had two hard openings this year, one bad enough to give me ringing in the ears and not being able to see right (black spots) for a couple of seconds. 

One of my riser covers tends to undo itself if I'm tracking fast or sit flying (not magnetic) however its been like this for the past 130 jumps and only this season I got the hard openings. I fly a Sabre2 and it has less than 300jumps, had the rigger inspect everything and all seems fine. Hasn't happened since but its scary nonetheless when its time to save your life and you're second guessing if this one will be soft and buttery (95% of my jumps) or an insta canopy.

I would love to be able to buy a whole brand new set up to take some of the doubts I have about mine.

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This is a marker thread for some hard opening discussion from Incidents. They deserve a thread of their own, because it's an important topic.

I recently bought a used Hornet because of its ease of packing; however, after using it for a day, I've probably retired it as opening too hard. It already has a giant slider, and I did psycho-pack it on the last try. However, I figure the chance of hurting myself trying to get it to open well is just not worth it.  BTW, what I consider to be a good opening is firmer than a lot of people like, so I'm not looking for a 1000-foot snivel or anything. Frankly, I just wanted something really easy to pack. I have a comparably-sized Stiletto...

So -- thoughts? And I'd like this to be a thread for people to talk about hard

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(edited)

1) The critical/center locking stows must not break.
I use tube stows for the first 2 locking stows because they are so much stronger. There is a reason the Racer speedbag has so many locking stows - you shouldn't trust just 2 regular rubber bands to hold the bag closed. 

2) Dacron lines
Not just because they absorb more shock, but also because they have a long history of limiting the speed at which a slider can move down them (my assertion). Whether it is just coefficient of friction or whatever, dacron lines and sliders grommets work well together.

3) Larger canopies
As discussed, real world testing experience showed the worst loads with smaller canopies. Whatever might cause an uneven body position/riser position, whether it is a tuck tab riser cover not releasing correctly, or just bad body position on opening, a larger canopy is less sensitive than a smaller canopy.

Edited by sundevil777

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On 8/24/2020 at 6:42 AM, danornan said:

Has anyone with magnets on you riser covers had a hard opening?

Yes. I've had a handful of bell-ringers, one of them on a V3 with magnets. It was nowhere near as bad as the ones I've had on rigs with tuck-tabs and/or velcro, however, and none of these caused any injury or discomfort that lasted into the following day.

One of the tough things about discussing heard openings, is that there is no standard on what is meant by "hard" - it's a totally subjective evaluation. For instance, we know a deployment that makes the jumper see stars, lose consciousness, or worse, qualifies as a Hard Opening. I don't think concussion and/or catastrophic injury is the appropriate threshold for a TOO Hard Opening. We need an objective metric, so we can gather info and meaningfully address the problem.

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3 hours ago, betzilla said:

 We need an objective metric, so we can gather info and meaningfully address the problem.

The only way you'll get a truly objective metric is with a calibrated sensor, in this case, an accelerometer.

The only altimeter I know of with an accelerometer is the Dekunu (https://dekunu.tech/tech-specs#tech-specs-1)

Then you would need to determine your variables that you'd like to correlate with, and collect this data (line type, broken stows, riser type, etc.), if you are looking for root cause.  Otherwise it could go back to subjective (your accels said it was an instantaneous shock of 10Gs - did you see stars? break/dislodge anything?), or you could compare it to a military standard that has done the research to identify what G-forces cause what effects.

Then do some statistics magic (ugh) with your questionable sample size vs the population and huge variability of gear, technique, etc.

 

It's not impossible - it just requires a lot of stars to align.  So back to the "objective metric" - what are we trying to measure, and why?  Are we trying to find a correlation?

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On 8/24/2020 at 7:42 AM, danornan said:

 

Has anyone with magnets on you riser covers had a hard opening?

 

I hear him make the claim that tuck tabs can lead to hard openings in the PIA video. I asked Mirage about that and they said they have made tens of thousands of rigs with tuck tabs and they said they disagree that tuck tabs cause hard openings.

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30 minutes ago, ty_tanium said:

 

It's not impossible - it just requires a lot of stars to align.  So back to the "objective metric" - what are we trying to measure, and why?  Are we trying to find a correlation?

i would say we need to evaluate what the g force is that would incapacitate someone and call that dangerous.  then evaluate what would be significant enough to cause a slight concussion or some sort of bell ringing without being incapacitated and call that hard.  that one would be a bit more difficult to quantify i would imagine.

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20 hours ago, wmw999 said:

This is a marker thread for some hard opening discussion from Incidents. They deserve a thread of their own, because it's an important topic.

I recently bought a used Hornet because of its ease of packing; however, after using it for a day, I've probably retired it as opening too hard. It already has a giant slider, and I did psycho-pack it on the last try. However, I figure the chance of hurting myself trying to get it to open well is just not worth it.  BTW, what I consider to be a good opening is firmer than a lot of people like, so I'm not looking for a 1000-foot snivel or anything. Frankly, I just wanted something really easy to pack. I have a comparably-sized Stiletto...

So -- thoughts? And I'd like this to be a thread for people to talk about hard

I used to roll the outer nose cells on my hornet, and stuff them into the center cells. It still opened hard.;P Other than that characteristic I really did like that canopy.

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4 minutes ago, sfzombie13 said:

significant enough to cause a slight concussion or some sort of bell ringing without being incapacitated and call that hard.  that one would be a bit more difficult to quantify i would imagine.

exactly.

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(edited)
4 hours ago, sundevil777 said:

3) Larger canopies

As discussed, real world testing experience showed the worst loads with smaller canopies. Whatever might cause an uneven body position/riser position, whether it is a tuck tab riser cover not releasing correctly, or just bad body position on opening, a larger canopy is less sensitive than a smaller canopy.

Can you please clarify what you mean with a larger is less sensitive than ….. ? As in sensitive to the shock and will be more abrupt ? I fly a larger canopy (SA2 210) loaded 1.2 but last year was closer to 1.3

Thx

Edited by Nabz

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On 8/25/2020 at 2:51 PM, Nabz said:

Can you please clarify what you mean with a larger is less sensitive than ….. ? As in sensitive to the shock and will be more abrupt ? I fly a larger canopy (SA2 210) loaded 1.2 but last year was closer to 1.3

Thx

A larger canopy is less sensitive than a small canopy to uneven riser position due to bad body position, or a riser cover on one side that doesn't release at first, or anything else.

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6 minutes ago, sundevil777 said:

A larger canopy is less sensitive than a small canopy to uneven riser position due to bad body position, or a riser cover on one side that doesn't release at first, or anything else.

Thank you for clarifying. 

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Have had two hard, but reading yours, not that hard, openings. Beginners mistakes I reasoned, First one my legs and feet tlew forward to such extent that was seeing them and the canopy pretty much simultaniously as the slider made such wissling noice and hit the bottom fast. Nothing else but mentally shaken and landed out. Second time I pulled and got the pilot in my hand as I began to go towards a dive and roll, released it and it pulled me back and in a harnest oversized I got all of the pressure on my right leg and my hamstring got injured/torn and held me from jumping 5-6 weeks. Canopy on both occassions Sabre1, but  its bothering to read all earlier in this thread. I hate it when there is not a fully reasonable way to explain the opening seqvens thru wich a hard opening could be detected, meaning inclusive weather and human factor. It simply seems not to be a guaranteed way to eliminate that. This during the space-and dataage. I had no such issues since and not using that gear anyway, as its no moore. Swedish skydivier, if any doubts of my english. Following this continously, thanks.  

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The military has already done a bunch of testing on parachute opening forces. They determined the maximum safe force a parachutist (presumably someone young and healthy since it's the military) can sustain on opening without injury is 12G. Above that and they risk injury. in fact this research is so well known that other industries use this as a golden standard for designing products. For example the international organization that oversees rock climbing gear certification (the UIAA) limits rope shock loads to 12 kN/ 12G based on this parachute study. 

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