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Main Lines Entangling With Flaps

 

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billbooth  (D 3546)

Mar 13, 2006, 7:08 PM
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Main Lines Entangling With Flaps Can't Post

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, 7:50 PM)


DeNReN  (B 5642)

Mar 13, 2006, 7:25 PM
Post #2 of 76 (6821 views)
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Re: [billbooth] Main Lines Entangling With Flaps [In reply to] Can't Post

WOW....36 in or more of hand stow.....eeek

18 I can see..have done that and seen that ....but what is the reasoning behind that much unstowed line???....bands are not that expensive.


Reginald  (D 28162)

Mar 13, 2006, 7:33 PM
Post #3 of 76 (6809 views)
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Re: [billbooth] Main Lines Entangling With Flaps [In reply to] Can't Post

I hear people say that by leaving more line free the chance of line twists is reduced. Ive heard many say 24 to 36 of unstowed line is about right. While line twists may not sound like a problem, on HP canopies they can be potentially serious, hence some of the debate about the appropriate length of lines.

A wise 40-year skydiver shared with me the history of problems due to lines catching main flaps, describing it almost exactly as Bill just did. His solution is to simply stow down to 15 but use only one wrap of a rubber band on the last stow. His explanation is that the lines only need to held clear of the flaps by the last stow not held tight like most of the stows. This both reduces the chances of lines catching the flaps and helps reduce the chances of line twists due to tight stows near the container giving the bag time to rotate.

Any thoughts?


wmw999  (D 6296)

Mar 13, 2006, 8:10 PM
Post #4 of 76 (6784 views)
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Re: [Reginald] Main Lines Entangling With Flaps [In reply to] Can't Post

I actually split the lines into two groups (one for each riser) for the last stow, which I make as short as possible -- 5 to 10".

I haven't had any line twists but once since starting this. Of course, that once I had to cut away Sly. There was a thread earlier where Bill Booth mentioned that he'd videoed the opening sequence a few times, and that the lines coming out of the container were incredibly chaotic.

Wendy W.


DeNReN  (B 5642)

Mar 13, 2006, 8:18 PM
Post #5 of 76 (6770 views)
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Re: [wmw999] Main Lines Entangling With Flaps [In reply to] Can't Post

Here's a thought...prob though of and tried before....

having a center loop for a band for the final stow to equalize the uneven hand stows from the side to side "normal" stows??????


wmw999  (D 6296)

Mar 13, 2006, 8:24 PM
Post #6 of 76 (6760 views)
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Re: [DeNReN] Main Lines Entangling With Flaps [In reply to] Can't Post

I thought about that, and decided not to. Not real sure why (as it is, there's a loop in one riser's stow because it comes back to the same side -- I have to be a little careful with it, but no more so than with loose lines).

Wendy W.


mjosparky  (D 5476)

Mar 13, 2006, 8:52 PM
Post #7 of 76 (6737 views)
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Re: [billbooth] Main Lines Entangling With Flaps [In reply to] Can't Post

I am one of the ones that had a line group wrap a container flap while free packing back in the 70s and early 80s. It was not a pleasant place to be. If it had not been for a diaper stowed round reserve I do not think I would have made it. I think with a free bagged ram air reserve there is a good chance you would be dead. For all you would be canopy engineers and want-to-be experts out there, most of what is done today has a very good reason proven by history. There are very few out there that have the knowledge or the experience to change what has been proven by time and people like Bill Booth.

Sparky


stratostar  (Student)

Mar 13, 2006, 9:00 PM
Post #8 of 76 (6727 views)
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Re: [billbooth] Main Lines Entangling With Flaps [In reply to] Can't Post

What is really funny is when you see a guy doing this they give all kinds of stupid answers as to why they do it.

Had a jumper who was leaving about 3ft unstowed in the pack tray, when I asked him WTF is wrong with him he said he wanted his bag to speed up as it left the pack tray.

Quote:
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...

Your not the only one who thinks it is a cause.

When pointing out the same history lesson you just posted, we older guys get the what do you old fucks know (attitude) "your just not with it when it comes to todays gear and hiperformance canopies", unless your someone like Bill Booth, then they listen.
While I may not jump that hotrod crap I have seen a lot of jumpers die from doing stupid shit and it don't take a rocket engineer to have a clue.



Kind of funny how history repeats its self, like people catching cutways and learning the hard way as to why we don't do that and haven't been doing it from the late 70's early 80's when back then it proved to be a stupid human trick.

Quote:
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.

Thanks for posting your input on the 3d tandem jumping too, as many of us posted we didn't think it was a good idea to do so, most of us that have been around the sport awhile knew that you must have had a good reason as to why you have said for years what not to do using your gear, and the testing data to back up your claim.
Again thanks for your post and history lesson.
Yes you need to get out more!Tongue

~


stratostar  (Student)

Mar 13, 2006, 9:09 PM
Post #9 of 76 (6719 views)
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Re: [DeNReN] Main Lines Entangling With Flaps [In reply to] Can't Post

Quote:
having a center loop for a band for the final stow to equalize the uneven hand stows from the side to side "normal" stows???

Why not just stow the line groups in a "normal" way?
It's has a prove track record.
If you want to leave extra line in the pack tray, why not have your master rigger put in a stow band attachment at the top of the tray to hold the line like a sweethog container, also a proven track record.

~


DeNReN  (B 5642)

Mar 13, 2006, 9:58 PM
Post #10 of 76 (6685 views)
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Re: [stratostar] Main Lines Entangling With Flaps [In reply to] Can't Post

Are there modern D bags in use with a bag stow ending center band? I dont know. please enlighten me.


diablopilot  (D License)

Mar 13, 2006, 10:12 PM
Post #11 of 76 (6677 views)
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Re: [DeNReN] Main Lines Entangling With Flaps [In reply to] Can't Post

Yes. The Mirage G4 is avaliable with a center locking stow (which also serves to hold the split bag shut) as well as a center finishing stow.

There may be others I'm forgeting.


DeNReN  (B 5642)

Mar 13, 2006, 10:13 PM
Post #12 of 76 (6674 views)
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Re: [diablopilot] Main Lines Entangling With Flaps [In reply to] Can't Post

TY Smile

Are there any bags with a seperate middle stow...in sequence....of the side stows?

reasons for or against using a last stow centered on the bag ?

bueller?


(This post was edited by DeNReN on Mar 13, 2006, 10:22 PM)


diablopilot  (D License)

Mar 13, 2006, 11:07 PM
Post #13 of 76 (6637 views)
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Re: [DeNReN] Main Lines Entangling With Flaps [In reply to] Can't Post

I don't think center stows make much of a difference. I do like the split bag however.

I do think that on a rig with shorter risers where the links don't make it well down into the main tray, that 15" or less of slack line increases the chance of linetwists, and/or a hang up on the reserve container.


Well designed main flaps, and risers long enough to suit the container, should allow in my opinion one to use up to but not exceeding 24" of slack line.


fcajump  (D 15598)

Mar 14, 2006, 5:48 AM
Post #14 of 76 (6528 views)
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Re: [wmw999] Main Lines Entangling With Flaps [In reply to] Can't Post

Sounds like we learned from the same person... I've used that style for >1k jumps and like it.

Jim


KellyF  (D 13826)

Mar 14, 2006, 8:56 AM
Post #15 of 76 (6446 views)
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Re: [billbooth] Main Lines Entangling With Flaps [In reply to] Can't Post

This is also a good time to remind everyone to stow your excess brake lines. Reducing snag hazards is a high priority when rigs are designed, it should also be a high priority when they are being packed.

In reply to:
Otherwise, we are all condemned to re-live the mistakes of the past...again and again.
Only the really lucky ones get to re-live them again and againWink


riggerrob  (D 14840)

Mar 14, 2006, 9:16 AM
Post #16 of 76 (6433 views)
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Re: [wmw999] Main Lines Entangling With Flaps [In reply to] Can't Post

In reply to:
I actually split the lines into two groups (one for each riser) for the last stow, which I make as short as possible -- 5 to 10".

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

We did that last year at a static-line specific DZ. When packing Skymaster 290s into Javelin J-7s, we found that it lifted the main risers out of the pack tray early in the deployment process and vastly reduced the incidence of line twists, etc.

Since then I have applied a similar line stow method to my Stiletto 135 packed into a Talon 2 and gotten fewer off-heading openings.
The key to preventing main risers from snagging on reserve container lower corners is to lay them along the SIDES of the main container.
Wendy's line stow method makes that easier.


riggerrob  (D 14840)

Mar 14, 2006, 9:21 AM
Post #17 of 76 (6427 views)
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Re: [DeNReN] Main Lines Entangling With Flaps [In reply to] Can't Post

At a PIA Symposium 5 or 7 years ago, we posed this question to John Leblanc (PD), Brian Germain (Big Air), John Sherman (Jump Shack), etc. and the consensus was "a minimum of 18 inches between the last stow and the connector links."
Much less than that and you risk snagging a main riser under the corner of the reserve container.
Much more than that and you risk lines half-hitching around a main flap.


amy  (D License)

Mar 14, 2006, 1:43 PM
Post #18 of 76 (6321 views)
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Re: [diablopilot] Main Lines Entangling With Flaps [In reply to] Can't Post

Quote:
The Mirage G4 is avaliable with a center locking stow (which also serves to hold the split bag shut) as well as a center finishing stow.

The Talon FS also has a center locking stow. It does not have a center finishing stow.

Amy


billbooth  (D 3546)

Mar 14, 2006, 4:14 PM
Post #19 of 76 (6256 views)
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Re: [wmw999] Main Lines Entangling With Flaps [In reply to] Can't Post

In reply to:
I actually split the lines into two groups (one for each riser) for the last stow, which I make as short as possible -- 5 to 10".

I haven't had any line twists but once since starting this. Of course, that once I had to cut away Sly. There was a thread earlier where Bill Booth mentioned that he'd videoed the opening sequence a few times, and that the lines coming out of the container were incredibly chaotic.

Wendy W.
We have been test jumping this line stow method for a while now. I really like it. It leaves the absolute minimum of line unstowed, and still allows both risers to be stowed down the sides of the container. Speaking of risers...their main purpose is to keep "things" from entangling with the deploying suspension lines. Ideally, they should be long enough to reach the BOTTOM of the container...like they still do in reserve containers. Main risers, however, have gotten much shorter so that pocket rocket drivers can reach up and either collapse or pull down the slider. This shortening of the main risers has had, as usual, unintended consequences. 1. With risers this short, the main turn toggles are no longer in, or at least very close to in, the main container where they should be. This makes it possible for the toggles to get free without the main container being open. This has killed several people. My answer to this new problem was secondary riser covers. 2. The shorter the risers, the longer the unstowed suspension line has to be, thus increasing the chance of entanglement. I don't yet know what my answer to this problem will be, but I am working on it.

As to why line twists happen, I suspect that unstowed line length has very little to do with it. My two leading suspects (other than body position and the old reliable "shit happens") are: 1. Too small or improperly made pilot chutes. (The longer the time to line stretch, the longer the rather unsymetrical bag is exposed to the slipstream, and therefore, the more likely it will spin) 2. The often very different forces that are required to open the left and right tuck tab riser covers. If one cover releases just a split second later than the other, it simply can't help things very much, can it? Velcro riser covers didn't suffer from this problem, but alas, they are no longer cool. Some people also think (Bill Coe included) that uneven riser cover release is a main contributing factor to hard openings. This is another problem I am working on.


tr027  (D License)

Mar 14, 2006, 5:10 PM
Post #20 of 76 (6225 views)
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Re: [billbooth] Main Lines Entangling With Flaps [In reply to] Can't Post

 
Could someone post a couple pics demonstrating this split stowing method? I'm having trouble visualizing what this is supposed to look like. So the last stowage requires two stow locations, one for each riser. Thanks.


(This post was edited by tr027 on Mar 14, 2006, 6:37 PM)


freakyrat  (D 12700)

Mar 14, 2006, 7:30 PM
Post #21 of 76 (6140 views)
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Re: [DeNReN] Main Lines Entangling With Flaps [In reply to] Can't Post

The Mirage G4 split main bag has this center stow.

Chris


mjosparky  (D 5476)

Mar 14, 2006, 9:00 PM
Post #22 of 76 (6112 views)
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Re: [billbooth] Main Lines Entangling With Flaps [In reply to] Can't Post

In reply to:
In reply to:
I actually split the lines into two groups (one for each riser) for the last stow, which I make as short as possible -- 5 to 10".

I haven't had any line twists but once since starting this. Of course, that once I had to cut away Sly. There was a thread earlier where Bill Booth mentioned that he'd videoed the opening sequence a few times, and that the lines coming out of the container were incredibly chaotic.

Wendy W.
We have been test jumping this line stow method for a while now. I really like it. It leaves the absolute minimum of line unstowed, and still allows both risers to be stowed down the sides of the container. Speaking of risers...their main purpose is to keep "things" from entangling with the deploying suspension lines. Ideally, they should be long enough to reach the BOTTOM of the container...like they still do in reserve containers. Main risers, however, have gotten much shorter so that pocket rocket drivers can reach up and either collapse or pull down the slider. This shortening of the main risers has had, as usual, unintended consequences. 1. With risers this short, the main turn toggles are no longer in, or at least very close to in, the main container where they should be. This makes it possible for the toggles to get free without the main container being open. This has killed several people. My answer to this new problem was secondary riser covers. 2. The shorter the risers, the longer the unstowed suspension line has to be, thus increasing the chance of entanglement. I don't yet know what my answer to this problem will be, but I am working on it.

As to why line twists happen, I suspect that unstowed line length has very little to do with it. My two leading suspects (other than body position and the old reliable "shit happens") are: 1. Too small or improperly made pilot chutes. (The longer the time to line stretch, the longer the rather unsymetrical bag is exposed to the slipstream, and therefore, the more likely it will spin) 2. The often very different forces that are required to open the left and right tuck tab riser covers. If one cover releases just a split second later than the other, it simply can't help things very much, can it? Velcro riser covers didn't suffer from this problem, but alas, they are no longer cool. Some people also think (Bill Coe included) that uneven riser cover release is a main contributing factor to hard openings. This is another problem I am working on.

Come on you all, lets see the arugments with what this poor lost soul has to say.

Sparky


rmsmith

Mar 15, 2006, 12:36 AM
Post #23 of 76 (6067 views)
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Re: [billbooth] Main Lines Entangling With Flaps [In reply to] Can't Post

In reply to:
"2. The often very different forces that are required to open the left and right tuck tab riser covers. If one cover releases just a split second later than the other, it simply can't help things very much, can it? Velcro riser covers didn't suffer from this problem, but alas, they are no longer cool. Some people also think (Bill Coe included) that uneven riser cover release is a main contributing factor to hard openings. This is another problem I am working on."

I had to go with a larger slider on my Sabre2 (thanks Rusty) due to this exact problem. I never had this problem with the Spectre because its slider stayed put against the stops long enough for total line stretch and for my body to transition into a standing position before the canopy's inflation forced the slider downward.

Scott Miller just released an article regarding body position during deployment; I noticed that one photo showed the risers unstowed and pointing toward the sky while the lines were still being unstowed from the d-bag. This is not the case with many rigs that use double flaps to stow the risers.

The Sabre2's reputation for off-heading openings and the occasional slammer probably have more to do with this riser issue than construction geometry flaws, IMHO.


krkeenan  (C 7860)

Mar 15, 2006, 10:14 AM
Post #24 of 76 (5947 views)
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Re: [rmsmith] Main Lines Entangling With Flaps [In reply to] Can't Post

In reply to:
Scott Miller just released an article regarding body position during deployment;

Where can the Scott Miller article be found ??

Kevin


wmw999  (D 6296)

Mar 15, 2006, 10:16 AM
Post #25 of 76 (5945 views)
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Re: [tr027] Main Lines Entangling With Flaps [In reply to] Can't Post

I can after the weekend if no one else does -- my rig's at the DZ.

Wendy W.


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