Making stow bites too big, a close one...

[GrumpySmurf 0]

Saturday morn, we get a 5 minute call and rain drops start hitting the ground, announcement was that the loads are only going to 10k due to cloud cover at 11k. After exiting the plane, there was a group consensus of 'OW!' 'OW!' 'OW!' - as we plummeted through some kind of half frozen hell-rain from 10K till 3K - I pitch at 3,700 or so (figured it would hurt less under canopy) - and immediately something was wrong - I was stood up, but the wind noise was the same, no sound of a snivelling canopy, zero pressure on the harness along with a sensation of 'falling'. Look at the red, the alti (3K now and winding down quick), look at the ground (freakin' corn!), mutter several obsenities and think, "At 2, she is gone" at 2.3 (according to the Pro-Track) - it openned with 6 line twists I kicked out down to around 2K, if it had been turning at all, it would have been chopped. On the ground, what was a brand new locking stow band was broken in two- I had me a bag lock that was corrected when the 1st locking stow band broke. Am I ever happy I use those cheap easy to break rubber bands now - a cutaway over the cornfield would have lost the main and freebag nice and good
My first thought was to look at the red cutaway and the altimeter when the openning felt 'off', not the main above me to ID the problem (DOH!). I had been experimenting with larger stow bites to see how it affected the force of the openning (I have been trying to get the canopy to open soft just after tracking without flaring out) - seems it locked the last locking stow shut. Word for the wise, in an attempt to prevent line dump via stow bite sizes - don't make your bites too big, you might get yourself quite an exciting ride.

[Chief 0]

Hi Grumpy:
Thanks for the info. Add this to the other 1 million things to be mindful of. Thanks for sharing.

[Cornholio 0]

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don't make your bites too big, you might get yourself quite an exciting ride

Are these "bites" referring to the length of lines that exceeds the rubber bands per stow ? Like a normal length is two inches past the rubber bands...what length were yours at ?

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[AggieDave 6]

Also, remember, if your earlier stows are larger then your later stows, there is a chance that the "bite" of one of the first stows will get caught in the "bite" of one of the later stows, that will cause a bag lock and much cursing.

Another note, line stows don't really effect how soft a canopy opens, that depends on the pack job, all it effects is how quickly you get line stretch. All and all it comes down to packing technique and canopy type, as well as freefall speed. Dumping in a sit, for example, will cause quicker line extention, that's not the killer, it will also cause quicker inflation of the canopy, which will cause a hard opening.

The short of it is, line stows don't actually effect how hard or soft an opening is (excluding some extreme cases, like total line dump, etc).

Good luck, too bad we're not in the same area, I could show you some tricks to make your openings butter smooth.

--"When I die, may I be surrounded by scattered chrome and burning gasoline."

[indyz 1]

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The short of it is, line stows don't actually effect how hard or soft an opening is

Hehe, at my summer DZ there is a guy who only stows at the grommets, then neatly coils the rest of the lines in the bottom of the pack tray. He claims to get softer openings, but everybody else is too scared to try it and see if he's right.

[AggieDave 6]

That's real similar to what BASE jumpers do, although i would be worried about tension knots occuring.

--"When I die, may I be surrounded by scattered chrome and burning gasoline."

[riggerrob 643]

indyz,
I am also too scared to free stow my lines.

If you look through the archives, you will find that free-stowing was popular for a short period, circa 1980. Free-stowing quickly fell out of fashion after a couple of guys died from line/container entanglements. Basically, their lines half-hitched around side flaps, so their mains never got to line stretch, nor could they clear their backs for reserve deployment.
Granted container design has improved in the interim, but no skydiver in their right mind free-stows today.
As for BASE jumpers - most of them use some sort of tail pocket to lift their lines clear of their containers.
Tail pockets used to be popular with CReW jumpers, now most of them use a few rubber bands on their center cell tail to lift the lines clear of the container.

In conclusion, free-stowing was tried 20 years ago and found to be unreliable.

[Stacy 0]

saw a new type of D bag on an odyssey this weekend that doesn't use rubber bands at all. hard to explain but there are two locking stows done with built in bungee like things, other lines coil on top loosely and a tuck tab-looking flap over top closes it. the guy jumping it hasnt' had any problems, although i'm assuming it's still in the test phase now.

[PhreeZone 20]

Sounds just like a freebag with tuck tabs instead of velcro.....

Yesterday is history
And tomorrow is a mystery

Parachutemanuals.com

[polarbear 1]

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Another note, line stows don't really effect how soft a canopy opens, that depends on the pack job, all it effects is how quickly you get line stretch.

My experience has been that the opposite is true. If tight line stows are used to stow the whole length of line, the force unstowing the lines from the bag help to slow it as it travels to line stretch. When the jumper reaches line stretch, they suddenly accelerate the bag, canopy (which is still uninflated at this point), and pilot chute back to the jumpers speed. This is called snatch force and will be significantly higher if loose line stows or fewer line stows are used. All of this can happen without line dump occurring.

I experimentd with this on my old Heatwave and found the most important thing to do for a soft opening (except for getting the slider placed right) was to get the lines stows even and tight. The PD recommended 8-12 lbs of necessary unstowing forces seems about right. Flaking the canopy more or less carefully only affected how off-heading the canopy would open.

It is true that some equipment set-ups use free stows or line stow pockets instead of rubber bands...these canopies are CrW, reserve, or BASE canopies that are all designed to open quickly if you have ever experienced or watched one of these openings you will see that they are not the softest.

"Holy s*** that was f***in' cold!"

[ltdiver 3]

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Another note, line stows don't really effect how soft a canopy opens, that depends on the pack job, all it effects is how quickly you get line stretch.

Ok...here's another question.

--Had my Spectre-135 relined by PD this past week. (430 jumps on it)
--Had my old pc/d-bag stolen by someone during night jumps that weekend (it was detached from the main I was borrowing...and it walked away)
--Got my main back and used an old tired pc/d-bag from the school while I waited for a new set to come from SunPath (Javelin container, ya know)
--Put 8 jumps in the main this way with BEAUTIFUL openings that were so sweet!!! Soft, on heading and wonderful!

--Then comes the new d-bag and pc. 28" F-111 pc and 3 grommet d-bag.

--Packing the exact same way as before. SLAMMER snatch force/line stretch that sits me up in the saddle before the canopy has the chance to try and inflate! Then followed by a sharp opening! 16 jumps this way (team training and needed to keep going).

--Tried various 'fixes' with each successive jump:
1) bigger bites,
2) double wrapping my 2nd and 3rd locking stows
3) smaller rubber bands
4) throwing the pc onto my back instead of out into open air (this actually worked pretty good, but I don't like the idea)
5) sitting up just before deployment (chest high) before dumping (the snatch force is too quick to do this -after-)
6) Thought about getting a hole punch and putting holes in the pc fabric (j/k)

Talked to riggers, instructors, other cameraflyers, Square1, and also called SunPath on Monday morning. They only make the 28" (and I wanted to try a 26" out and see if this would help). Their d-bag and pc come stitched together since 1998...so I couldn't swap pc's out anyway!

Any thoughts on this subject? riggerrob? Anyone!

Sore neck cameraflyer,
ltdiver

Don't tell me the sky's the limit when there are footprints on the moon

[Jimbo 0]

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Talked to riggers, instructors, other cameraflyers, Square1, and also called SunPath on Monday morning. They only make the 28" (and I wanted to try a 26" out and see if this would help). Their d-bag and pc come stitched together since 1998...so I couldn't swap pc's out anyway!

Any thoughts on this subject? riggerbob? Anyone!

It's a pretty trivial task I think to unstitch the pilot chute from the D-bag and resew a new one in. I had it done in about 40 minutes at a boogie a few years ago. It's probably only worth it though if you're sure that the 26" pilot chute will get you the results you're after.

-
Jim

"Like" - The modern day comma
Good bye, my friends. You are missed.

[PhreeZone 20]

You can mix the D bag and PC from pretty much any container to another one. I've had a D-bag from a Mirage, Reflex,Wings and Dolphin in my Javelin. Borrow a D-bag from someone with the size PC that you want to try and see if that works. If it helps... ditch the D-bag and 28 incher and jump a bag with the size PC that you want to. I'm getting tired of the 28 incher on my Jav too... and in another 200 jumps I'm thinking the F111 will start to wear out so I'm looking at putting a Wings or Mirage bag with a 26 ZP on if I jump a 150 or a 25 ZP if I go smaller.

Yesterday is history
And tomorrow is a mystery

Parachutemanuals.com

[ltdiver 3]

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It's probably only worth it though if you're sure that the 26" pilot chute will get you the results you're after.

Yes...I -hope- this can be the answer. Mirage and Infinity containers have a 28" pc for canopies over 150 sq ft and use a 26" for 150 and smaller. Don't know why Javelins can't come that way too. At over $200 a pop, I hope I can just trade this one out for the other if there is someone who wants to swap.

But...what if this doesn't help? Any other suggestions on how to slow down the deployment speed? (canopy packing and opening are fine, but the snatch and line stretch are the problem here).

ltdiver

Don't tell me the sky's the limit when there are footprints on the moon

[Jimbo 0]

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But...what if this doesn't help? Any other suggestions on how to slow down the deployment speed? (canopy packing and opening are fine, but the snatch and line stretch are the problem here).

On the rare occasion that I pack for myself anymore I usually double wrap the locking stows and triple wrap everything else. You have to be careful here as the potential for bag-lock is increased, regular rubberbands help here. When I do this I can feel each and every stow pop off on deployment. Nice and slow.

-
Jim

"Like" - The modern day comma
Good bye, my friends. You are missed.

[petur 0]

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"...I can feel each and every stow pop off on deployment. Nice and slow."

Eeeek! That would totally freak me out! 1 stow... 2 stows... 3stows... still 3stows... hmmm...

P.

---
P.
"It Hurts to Admit When You Make Mistakes -
But When They're Big Enough, the Pain Only Lasts a Second."

[AggieDave 6]

Thats freaky man. If you're having to double *and* triple wrap the rubberbands on some of your stows, you should just use small rubberbands. Doubling your stows is just asking for a problem. That takes the rubberband's ability to break (one of its good features) just about totally away.

Double wrapping tube stows is just plain out wrong, if you're having to do that, consult the instructions again, you'll read a couple things. One, you're not supposed to do that, two you need a different size of tube stows.

Let me ask you a question, so you experience line twists very often?

--"When I die, may I be surrounded by scattered chrome and burning gasoline."

[diverds 0]

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Doubling your stows is just asking for a problem.

Sorry but I have to dissagree with that statement. Double or triple stowing ruberbands does not take away their ability to break. I always double stow to help slow down the snatch force on my deployments and I break rubber bands on a regular basis. You should not double stow tube stows or bungee stows though.

Your line stows have a huge effect on your opening and if you can get them tight to keep the acceleration of the bag down on deployment you will get softer openings.

Skydive Radio

[Jimbo 0]

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Let me ask you a question, so you experience line twists very often?

Only occasionally and only due to bad body position.

-
Jim

"Like" - The modern day comma
Good bye, my friends. You are missed.

[AggieDave 6]

I know you have a lot more experience and time in the sport then I do, I just have hard time believing that there is not an increased saftey risk by doubling the rubberbands on your stows. (This conclusion isn't totally my own either, this was from a conversation I had with 2 riggers about 6 months ago.)

--"When I die, may I be surrounded by scattered chrome and burning gasoline."

[AggieDave 6]

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Only occasionally and only due to bad body position

Ok, the reason behind that question is I've seen bags spin up from really tight stows before. The bag starts to turn when the first stow pulls and continues in the spin as the second stow jerks the bag when it comes out, etc.

--"When I die, may I be surrounded by scattered chrome and burning gasoline."

[diverds 0]

Dave,
I'm trying to understand your conern with double stowing? You said in an earlier post that you are worried the band will not break if it is double stowed. I'm no rubber engingeer but it seems to me that the further the band is streched the closer it is to its breaking point. How does double stowing make it harder to break? Most manufactures I have talked to recomend double stowing.

Skydive Radio

[billvon 3,120]

>Ok, the reason behind that question is I've seen bags spin up from
> really tight stows before.

While I think this can happen, a few things to keep in mind:

1. Opposite stows spin the bag opposite ways (assuming the same bag attitude) so they tend to cancel.

2. Closer stows (i.e. centerline rather than outside) stows can help here.

3. The farther from the risers the stow is, the less effect it will have on bag position - so it's safer to make the first stows tighter than the final ones. PD, in fact, recommends no stows on the last 18" or so of line, partly for this reason (I think.)

[polarbear 1]

That's all in agreement with what I've found. Following a tight stow with a loose one can spin the bag, but if all the stows are tight, there shouldn't be a problem. I stow all my lines REAL tight and never get line twists.

As far as double wrapping goes, I double wrap stows regularly and have the rubber bands break. You could claim that because there are two wraps, the force is split in two and therefore the band is less likely to break. However, you have to remember that those two wraps ONLY encompass the stow...they aren't doubled down to the d-bag. When the lines unstow, there is still the same amount of rubber holding the stow to the d-bag, and it is already stretched farther because of the double-wrapping...therefore it is not any less likely to break.

Pretty much everyone at my DZ double wraps at least some stows and we have yet to see a problem.

"Holy s*** that was f***in' cold!"

[AggieDave 6]

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You could claim that because there are two wraps, the force is split in two and therefore the band is less likely to break.

That was my reasoning.

Thanks to everyone who cleared up my misconception.
Now I know and knowing is half the battle.

--"When I die, may I be surrounded by scattered chrome and burning gasoline."