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Any additional techniques for preventing line twist?

 

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primetime  (D 17757)

Jan 18, 2013, 12:01 AM
Post #26 of 43 (1312 views)
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Re: [JohnSherman] Any additional techniques for preventing line twist? [In reply to] Can't Post

I agree with John about sitting up as the canopy deploys. Don't make it an exaggerated move...after awhile you can feel when the time is right to start transitioning to upright position. It also lessens the opening shock on your shoulders and neck.

On deployment, I focus upon keeping my shoulders and hips level and symmetrical as a unit. One thing I notice in alot of videos is people reaching up for their toggles too early and latching onto the risers, invariably yanking on one harder than the other and inducing a turn. I keep my hands in a symmetrical boxman until the wing is out of the bag (to be more precise, until the wing begins to come out of the bag). I also make sure to always look straight up to assess the canopy and not look over either shoulder.

A few times I have been able to look up and notice the beginning of line twists, but I was able to fly my body in the same direction as the spin until I caught up. Of course, there have been other times where I started kicking out of line twists and realized I was going the wrong way...doh!

Sounds like I need to get me one of them semi-stowless bags...


jerolim  (F License)

Jan 18, 2013, 1:40 AM
Post #27 of 43 (1297 views)
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Re: [Divalent] Any additional techniques for preventing line twist? [In reply to] Can't Post

One thing to consider is riser length. As longer risers go more around reserve, so less slack is needed in the lines. So number in inches is not important, important is that bag can be lifted without lines snagging reserve.


jcbfly  (D 30546)

Jan 18, 2013, 6:24 AM
Post #28 of 43 (1242 views)
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Re: [faulk04] Any additional techniques for preventing line twist? [In reply to] Can't Post

I have close to 500 jumps on the UPT semi-stowless bag. I stow the lines all the way to the risers and then just pull out what I need to align the risers in the packtray. Zero line twists since I started using the UPT bag. I use regular 2 inch stow bands and double wrap them.


Premier faulknerwn  (D 17441)
Moderator
Jan 18, 2013, 7:12 AM
Post #29 of 43 (1230 views)
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Re: [Deyan] Any additional techniques for preventing line twist? [In reply to] Can't Post

Especially with everyone having a crazy snaggable go-pro these days - having several feet of loose line flopping around in your burble can be a very scary thing. I usually leave about 12 inches excess when I pack ( with double stowed lines ) and its been a couple thousand jumps since I last had a line twist.

I remember bill booth posting on these forums a couple years ago about all the dangers of leaving a lot of excess lines and the history of why everyone stopped doing that from the free stowed lines days.


Zlew  (D 21616)

Jan 18, 2013, 8:15 AM
Post #30 of 43 (1213 views)
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Re: [BrianSGermain] Any additional techniques for preventing line twist? [In reply to] Can't Post

In reply to:
Really good question. As far as I can tell, leaving less than two feet on the UPT semi-stowless bag does not se to change the openings. I am still playing with that. Anyone else care to weigh in?

I just got my second UTP bag in yesterday, and the instructions they have show them stowing almost all of the line in the pouch. When they came to one of our boogies last year, they demonstrated it the same way (less than 6 inches of excess line?). Makes me a little nervous, but that seems to be their recommendation on the stowless bag. I would be interested to hear how you guys pack your stowless bags.


Empadinha  (D 32431)

Jan 18, 2013, 8:48 AM
Post #31 of 43 (1197 views)
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Re: [faulk04] Any additional techniques for preventing line twist? [In reply to] Can't Post

In reply to:
I don't do it on either of my rigs with the semi stowless bag... I go pretty much up to the risers and any excess that is needed comes out when I take the dbag and place it into my container. I've put about 300 jumps doing this method and haven't had any problems so far.

Same here.


RMURRAY

Jan 18, 2013, 9:13 AM
Post #32 of 43 (1188 views)
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Re: [BrianSGermain] Any additional techniques for preventing line twist? [In reply to] Can't Post

In reply to:
Be sure that the first three or four line stows to pull out are easily extracted. Double-stowing with a bite of more than 2.5 inches on the first several bites seems to be a mistake in most cases.

Also, make sure there is no less than TWO FEET of unstowed line above the risers. This allows the bag to get some speed before reaching line tension. The line stows are not usually in the middle of the bag, so low speed combined with asymmetrical loading can result in line twists.

Additionally, be sure that the unstowed line goes straight down the side of the rig, from the risers to the base of the rig, to prevent snagging on the bottom of the reserve container during slightly head up deployments.

-BSG-

I like these suggestions. semi stowless? not for me...I want the lines to be more in control during deployment.


DBCOOPER  (D 24112)

Jan 18, 2013, 2:44 PM
Post #33 of 43 (1127 views)
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Re: [BrianSGermain] Any additional techniques for preventing line twist? [In reply to] Can't Post

From the past...



Main Lines Entangling With Flaps Quote | Reply

--------------------------------------------------------------------------------

In the past few years, I have heard of 5 cases of main suspension lines entangling with container flaps. Three of these were on Vectors. While this malfunction is quite rare (well under one in a million jumps) it is nonetheless quite serious.

While we might debate several causes for this problem, let me suggest the one I believe is most likely. I am rather sure that this is the main cause, because I have seen it cause line/flap entanglements before...and the solution that worked way back then will probably work just as well again now.

A little history lesson is indicated. For a brief time in the 70's, "free-packing" mains (no deployment bag...just coil all of the lines in the packtray, and fold the canopy on top) was popular. Some jumpers even did away with the pilot chute and bridle, and just attached a pull-out handle directly to the canopy.

Aside from the hard openings, one other problem reared its ugly head. Suspension line kept getting entangled with the main flaps. The reason was obvious. Just after the main flaps were pushed apart by the canopy leaving, they hit the air flowing around the jumper, and "dove" right back into the pack tray, and all those looped lines. It was a miracle they didn't entangle every time!

This problem was quickly solved, of course, by putting the main canopy back in its deployment bag and stowing the lines so that everything left at once, there was little or nothing for the flaps to entangle with when they were thrown back into the packtray following bag extraction.

So, what has this got to do with now...we all use bags, don't we? Yes, but do we still stow ALL of the suspension line to that bag? The answer is NO. I went over to the DZ, and did an informal poll. What I found out shocked me. Almost all of the packers left over (sometimes WAY over) 36" (the "minimum" amount of unstowed line required to allow this problem) of line unstowed, and worse yet, COILED in the pack tray under the bag. I should get out more. I had no idea this very dangerous practice had crept back into the sport.

Because I had remembered the past problem, on page 39, paragraph 2 of our Vector III packing manual it states:" Leave no more than 15" of lines unstowed between the bag and the connector links." This is something I thought everybody already knew, but I put it in just to be sure. Apparently it didn't do a lot of good, did it?

The point here: Read your owners manual, and do what it says. There are good reasons for every word in there, although those reasons are not always given. Otherwise, we are all condemned to re-live the mistakes of the past...again and again.


(This post was edited by billbooth on Mar 13, 2006, 10:50 PM)


BKW82  (A License)

Jan 18, 2013, 4:31 PM
Post #34 of 43 (1112 views)
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Re: [BrianSGermain] Any additional techniques for preventing line twist? [In reply to] Can't Post

In reply to:
In reply to:
Does having a little forward motion or slight heads down postion on deployment help or are there any other body position tips other than what has been discussed?.. stable, symetrical, etc.

Although head-down attitude seems imprudent on deployment, I do notice more on-heading openings when I have a bit of forward coast left over from my tracking. This is not high decent rate, mind you, just forward movement. It seems to give the canopy a place to go. If anyone else does this as well, please chime in.

+1

I always deploy while tracking flat... softest openings and consistently on-heading.


(This post was edited by BKW82 on Jan 18, 2013, 4:31 PM)


Skydivesg  (D 10938)

Jan 18, 2013, 8:43 PM
Post #35 of 43 (1076 views)
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Re: [RMURRAY] Any additional techniques for preventing line twist? [In reply to] Can't Post

I like these suggestions. semi stowless? not for me...I want the lines to be more in control during deployment.
I certainly understand your reluctance with the semi stowless bag. I was in your same shoes when the three ring cutaway system first came out.

But think about this: in all my years of skydiving I can count on one hand the people who always change out ALL their rubber bands when ever one breaks.

The rest of us change them as they break and some of us even hope for that one-last-deployment while we gingerly put the line stow in to keep that band from breaking while we're packing. yeah admit it - you've done it - we've all done it.

My point is: our stow bands are never in equal strength. some are new - some have been on our bag since the beginning of the season or even longer.

Which means you're in less control not more.

I shoot video and have dozens of pictures of out of sequence line deployments - both tandem and sport rigs. I have witnessed and filmed bag dance from strong bands combined with weak bands. Some hang on longer that others. Many of these pictures I have scare the crap out of me and those jumpers I was filming.

I'm convinced many off heading openings and line twists are due to the bag turning during the line deployment not the canopy.

The bands are only there to keep our lines in place until we need them - which is during deployment.

The semi-stowless bag keeps the lines in place and then allows them to play out in an orderly, straight and equal tension fashion. The video I've shot of those deployments are always very clean.

When I first saw the three ring cutaway system (before it was actually TSOd and in use) I predicted that some day, everyone would have them on their rigs.

I also predict that some day- everyone will be using some sort of stowless bag.

Before you make your final decision about the semi stowless bag, please talk to someone who is knowlegable. I think you may just change your mind.

PM me if you like. I have much more than I can post.

.


(This post was edited by Skydivesg on Jan 18, 2013, 8:45 PM)


BrianSGermain  (D 11154)

Jan 18, 2013, 8:48 PM
Post #36 of 43 (1069 views)
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Re: [Skydivesg] Any additional techniques for preventing line twist? [In reply to] Can't Post

In reply to:
I like these suggestions. semi stowless? not for me...I want the lines to be more in control during deployment.
I certainly understand your reluctance with the semi stowless bag. I was in your same shoes when the three ring cutaway system first came out.

But think about this: in all my years of skydiving I can count on one hand the people who always change out ALL their rubber bands when ever one breaks.

The rest of us change them as they break and some of us even hope for that one-last-deployment while we gingerly put the line stow in to keep that band from breaking while we're packing. yeah admit it - you've done it - we've all done it.

My point is: our stow bands are never in equal strength. some are new - some have been on our bag since the beginning of the season or even longer.

Which means you're in less control not more.

I shoot video and have dozens of pictures of out of sequence line deployments - both tandem and sport rigs. I have witnessed and filmed bag dance from strong bands combined with weak bands. Some hang on longer that others. Many of these pictures I have scare the crap out of me and those jumpers I was filming.

I'm convinced many off heading openings and line twists are due to the bag turning during the line deployment not the canopy.

The bands are only there to keep our lines in place until we need them - which is during deployment.

The semi-stowless bag keeps the lines in place and then allows them to play out in an orderly, straight and equal tension fashion. The video I've shot of those deployments are always very clean.

When I first saw the three ring cutaway system (before it was actually TSOd and in use) I predicted that some day, everyone would have them on their rigs.

I also predict that some day- everyone will be using some sort of stowless bag.

Before you make your final decision about the semi stowless bag, please talk to someone who is knowlegable. I think you may just change your mind.

PM me if you like. I have much more than I can post.

.
Couldn't have said it better myself.


dpreguy  (D 835)

Jan 20, 2013, 7:55 AM
Post #37 of 43 (1000 views)
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Re: [BrianSGermain] Any additional techniques for preventing line twist? [In reply to] Can't Post

"unstowed line goes straight down the side of the rig... riser to the base of the container...."
Got a picture of that? "S" fold that excess line separately on each side? Two coils -one on either side? Can you show?

2 to two and a half feet. 24 to 30 inches of line is a lot of loose line. A photo would be good, not just leave it to each parachutist to invent how to leave it laying in there.


yuri_base

Jan 20, 2013, 8:38 PM
Post #38 of 43 (931 views)
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Re: [arm900fj] Any additional techniques for preventing line twist? [In reply to] Can't Post

While bags and line excess seem to be thoroughly covered by answers so far, I want to share a packing technique that helped me reduce the occurrence of line twists to zero (well, zero in 300-400 jumps since I've started using this technique - nothing is "absolute zero", of course). Note that this technique does its magic mostly for wingsuit and tracking jumps and for canopies with ZP that starts getting gritty after 200+ jumps, especially on the tail end of the center cell which you grab when you cocoon the canopy. However, I believe it is good for no-forward-movement deployments and new ZP as well.

At some point, I started getting long hesitations when flying wingsuit and sometimes even when tracking. I would feel the bag leaving my back, then my shoulders would get a gentle tug, and then... nothing. Nothing for long enough that I'd start worrying if it's going to open at all. (What seemed to be "eternity" during deployment later measured to "just" 1-2s on video, but still, this is not a normal deployment.) I would continue flying while trailing something behind my back. Then it would open, eventually - but bad. As a result of these hesitations, I was getting line twists quite often and sometimes even hard openings.

I have pretty much standard arsenal of wingsuit-specific gear choices on my rig: 9ft bridle, 30-inch PC, dynamic corners. Nevertheless - horrendous hesitations. Pulling from full flight or slowing down - same thing: bad openings, frequent line twists.

So after being thoroughly puzzled by trying everything imaginable and nothing working, I finally started investigating. Mounted camera facing rear and started hunting. Finally, I caught it red-handed: the canopy gets to line stretch (at which point I would feel a slight tug on the shoulders) - no problem there - but then it stays there in cocoon, fully closed, not inflating, with cocoon just dancing in the wind, PC collapsed and not stretching the lines anymore, cocoon oftentimes rotating, and lines dancing in the burble like crazy. A-ha! No wonder that line twists would ensue after such a dance. Moreover, the slider, staying inside the cocoon, sometimes would start moving from wild shaking and as a result, a hard opening would occur.

So I realized that due to angled extraction and canopy somewhat sagging between the PC and the rig, the cocoon has a good chance to stay closed for a while, especially if the ZP fabric on the cocoon's apex and the twisted "lock" is no longer slippery and springy. The air hits the bottom, flat part of the cocoon at a small angle, the apex gets little pressure and the cocoon simply has no reason to fall apart - until it is shaken enough that is does. But then it's too late for good opening.

So I started packing in such a way as to leave a large opening in cocoon's apex - and voila, the problem instantly disappeared. No hesitations, no line twists, no hard openings. Basically, you simply wrap the packjob by the tail not on top of the lines, but a few inches lower. The slider is half-exposed this way. On linestretch, the first thing the air "sees" are 2 things: slider and a large "mouth" of the cocoon which opens the cocoon instantly. Slider catches air immediately, gets pressed against the stops and ensures good, staged opening. Quickly exposed nose firmly sets the opening direction, and ensured immediate, firm coupling between you and the canopy, allowing you to easily follow the off-heading opening, if that happened due to bad body position and packjob. The initial tug is now satisfyingly firm and the whole opening sequence is shorter (initiates faster), but not hard. The technique shaves off probably 100-200ft of unnecessary soft "falling into pillows" part of deployment which just robs you of altitude for no real benefit.

I believe that tightly closed cocoon is not good for no-forward-movement openings as well. Most of the time, it opens fast, but sometimes the tight apex prevents air from entering, with unpredictable openings as a result.

I've never seen anyone packing like this, but then again, nothing is new under the sun, maybe someone else came to the same technique independently.

Anyway, just wanted to share something that helped me eliminate the problem which kept me puzzled - and twisting - for quite a while.

Hope this helps.
Yuri


yuri_base

Jan 21, 2013, 4:45 PM
Post #39 of 43 (851 views)
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Re: [yuri_base] Any additional techniques for preventing line twist? [In reply to] Can't Post

 
Attachments: Cocoon.jpg (136 KB)


popsjumper  (D 999999999)

Jan 21, 2013, 7:00 PM
Post #40 of 43 (824 views)
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Re: [yuri_base] Any additional techniques for preventing line twist? [In reply to] Can't Post

Wouldn't it be easier to just wrap the tail around the lines loosely instead of tightly?


yuri_base

Jan 21, 2013, 8:02 PM
Post #41 of 43 (816 views)
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Re: [popsjumper] Any additional techniques for preventing line twist? [In reply to] Can't Post

In reply to:
Wouldn't it be easier to just wrap the tail around the lines loosely instead of tightly?

I tried it before settling on the more radical approach - it didn't work.

In angled deployment, the extracted cocoon is sagging below the relative wind line drawn from your shoulders, due to its weight. As a result, relative wind is hitting the cocoon not "heads on", but at some angle. The pressure of wind in this case presses the tail of the center cell, which is wrapping the packjob, against the rest of the packjob, making it "stick". A little hole in the apex of a loosely wrapped cone is not enough to overcome this.


primetime  (D 17757)

Jan 21, 2013, 11:40 PM
Post #42 of 43 (783 views)
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Re: [yuri_base] Any additional techniques for preventing line twist? [In reply to] Can't Post

I have not seen this packing method before (slider exposed) but it makes sense to me. There would also be less wear and tear on the center cell from the slider grommets during extraction. However, I think it would be more appropriate for WS and tracking dives, as the openings might be too "brisk" when deploying without forward motion. Can you post a picture of this pack job with the d-bag closed? I would like to see how you position the slider. Thanks Yuri.


yuri_base

Jan 22, 2013, 1:14 PM
Post #43 of 43 (711 views)
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Re: [primetime] Any additional techniques for preventing line twist? [In reply to] Can't Post

I'll take a pic next time I jump, but there's no difference in the rest of the pack process. You fold the cocoon and put it in the bag exact same way as you usually do. Of course, always make sure the slider grommets are pushed all the way up the lines.

Here is a 3.5yo video which helped me first realize what the problem is and how to solve it. It shows "only" a 0.7s (22 frames at 30fps) cocoon hesitation, but I've experienced some 2-3x longer hesitations as well.

If you watch frame-by-frame, you'll see that the cocoon stays closed and is dancing, morphing and rotating in the air, resulting in line twists even with good body position. Sometimes, hard openings would occur due to slider grommets sliding down the lines under the wildly dancing cocoon.

Note that I never wrap the cocoon tightly - you can see that the top part of the cocoon falls apart in 2-3 frames, while the bottom part (facing earth) stays "glued" to the packjob for the whole 22 frames due to pressure of airflow hitting the pack job at an angle.

Yellow is the center cell; orange is adjacent cells; red is side cells and the slider.
Attachments: Cocoon Hesitation.m4v (269 KB)


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