lift bag failure question

[lanun]

i dive wet in open water. have read with interest an article on Open Circuit/ Baffled/Gooseneck lift bag on the GUE website.

my questions are ...

1) one of the failure modes is listed as spill. does this refer to spill at the surface or spill while the bag is shooting to the surface (since we're supposed to maintain some tension on the line) ?

i am currently using a closed circuit SMB, inflated using the LP offa my BC inflator, primarily for safety stops.

2) if i am comfortable deploying the CC SMB, is there a significant advantage to getting an Open Circuit/ Baffled/Gooseneck lift bag to avoid disconnecting my lp hose ? perhaps someone who's used both can comment.

thanks in advance.

[Dryglove]

I believe spill is referred to when an open circuit lift bag hits the surface lays over and loses its air and deflates.This is remedied with a closed circuit bag or some sort of system to trap the air inside of the open circuit bag.

I also heard the open circuit lift/marker bag produced by halcyon is for wetsuit divers.This way there is no need to disconnect the LP hose from your bc inflator to fill your bag.You just switch to your back up reg and fill the bag with your primary reg.With the closed circuit i use my drysuit LP hose.

[detroit diver]

lal7176 once bubbled...
I believe spill is referred to when an open circuit lift bag hits the surface lays over and loses its air and deflates.This is remedied with a closed circuit bag or some sort of system to trap the air inside of the open circuit bag.

I also heard the open circuit lift/marker bag was produced by halcyon for wetsuit divers.This way there is no need to disconnect the LP hose from your bc inflator to fill your bag.You just switch to your back up reg and fill the bag with your primary reg.With the closed circuit i use my drysuit LP hose.

I agree with LAL7176 here. You really don't want to disconnect your BC inflator hose to blow a bag. That is your primary lift mechanism. If you don't have a drysuit inflator, then use an OC bag and inflate with your reg.

[WreckWriter]

"Spills" generally occur when the bag hits the surface. Often it will shoot out of the water a bit and fall back in on its side. If it doesn't have a "chute" in the throat it may dump.

Even so, I still recommend an OC bag, just get one with the chute installed. Most of decent quality have it, Should also have a dump/overpressure valve.

I don't like disconnecting an inflator, either BC or suit, and I also don't like have the bag and spool in so close to my body when I'm shooting it. I use OC and inflate it with my long hose, out away from my body.

Tom

[Fetch]

Mind you, I haven't tried with a really large lift bag, but with a reasonable sized CC bag we were able to orally inflate them without any problem (in DIRF class).

CC /are/ easier with an extra inflator hose, of course.

jeff

[caverkevin]

For those of you that think the open bags dump at the surface. Go out and watch a bag goto the surface. They usually dump before they reach the surface. As the bag ascends in an uncontroled fashion(no tension on the line) the bottom part of the bag will slide/roll past the top of the bag. Once the opening is above the air pocket, all the air rushes out leaving the bag dead in the water. Watching a bag do this reminds me of cars skidding on the ice in winter(which i'll soon be seeing). I really enjoyed watching this happen to my first mix student four times before he learned to control the line.

Kevin Jones

[Dryglove]

Hmmmmm.....learn something new everyday.......i have never used an open circuit bag so i wouldnt know any how.My closed circuit bag serves me just fine.

[WreckWriter]

caverkevin once bubbled...
For those of you that think the open bags dump at the surface. Go out and watch a bag goto the surface. They usually dump before they reach the surface. As the bag ascends in an uncontroled fashion(no tension on the line) the bottom part of the bag will slide/roll past the top of the bag. Once the opening is above the air pocket, all the air rushes out leaving the bag dead in the water. Watching a bag do this reminds me of cars skidding on the ice in winter(which i'll soon be seeing). I really enjoyed watching this happen to my first mix student four times before he learned to control the line.

Kevin Jones

In order for it to happen that way you would have to have zero tension on the line as it goes up, as you say. Simply gripping the spool with thumb and finger through the hole will prevent this.

If one were to just let the spool hang and spin I can see this happening pretty regularly.

I don't say it can't happen this way but it doesn't if you do it right. My explanation of a spill assumed reasonable technique :)

Tom

[lanun]

shooting the bag with the inflator LP does bring the bag a bit close to the body.

here's what i intend to do -
1) find someone with a oc bag and play with it.
2) try to oral inflate the cc smb - i've sen my son blow air into it but need to see how that works underwater.

anyways, thanks again for the inputs.

[madmole]

In the UK we use the long (2m) sausage type bags. If the water is clear (rare) you can see it go up.

They Zig, zag up, alternating ends that go first, if you put tension on the line then the zig zags get smaller, but they will dump a lot of air on the way if the end isn't self closing. Its quite amazing to watch

If you put more tension on the line then you just go up as well (us YBOD divers cant breath out to get another 5Kg of negative buoyancy:( )

One on the surface you just keep some tension on the line and the stay upright (very visable), some add a 1 kg weight on the bottom to help them stay upright

[nradov]

lanun once bubbled...
2) try to oral inflate the cc smb - i've sen my son blow air into it but need to see how that works underwater.
With Halcyon's small closed-circuit SMB this works fine. A single breath into it at 50ft is plenty of gas to leave it fully inflated at the surface. Stick the inflator all the way into your mouth so you get a good seal.

I really don't like the idea of disconnecting my drysuit inflator hose to fill a lift bag. That can turn into a real CF if you need to quickly descend again to rescue someone. Having the bag in close to your body increases the risk it will snag on something. And I have seen divers forget to reconnect the drysuit inflator afterwards, or, worse yet, connect it back over the top of the long hose.

[Green_Manelishi]

If diving in cold water I'd suggest NOT placing a second stage
under the bag opening and pressing the purge button.

1) you now have BOTH hands occupied with different objects
and one of them is a regulator that could ... (read #2)

2) you might cause a free flow and now you have that
problem to sort out in addition to handling an inflated/inflating
bag

Better idea:

1) hold the bag opening over the exhaust tee and exhale
into the bag

[ericfine50]

Or.. better yet, make it a two man job - one man is reel guy the other is the bag man.

Eric

[WreckWriter]

Green_Manelishi once bubbled...
If diving in cold water I'd suggest NOT placing a second stage
under the bag opening and pressing the purge button.

1) you now have BOTH hands occupied with different objects
and one of them is a regulator that could ... (read #2)

2) you might cause a free flow and now you have that
problem to sort out in addition to handling an inflated/inflating
bag

Better idea:

1) hold the bag opening over the exhaust tee and exhale
into the bag

Since I don't general do cold water diving I never thought of that issue, makes sense though. In general though I'm much less than comfortable with the bag and rigging that close to my head while being inflated. I'm sure you cold water folks have developed a special technique for avoiding fouling the bag/line with your head?

Tom

[WreckWriter]

ericfine50 once bubbled...
Or.. better yet, make it a two man job - one man is reel guy the other is the bag man.

Eric

The only reason I don't recommend this method is that in the event of seperation you end up with 2 divers who aren't well practiced in bag deployment by themselves.

Tom

[madmole]

I am a cold water diver (like all in UK), we never use the exhaust gas to fill, its far to hit or miss, takes too long (we use large bags) and the risk of sending your DV up with the bag is too great

Personally I use my own DV if on OC (posiedon jetstream) with it switched to the - setting. If I'm on the Yellow death trap I use the auto air. Can deploy, hold reel and DV in right hand and bag in left. Sneak mouthpiece under bag, Give purge a BIG belt and the moment I start to move, let go of bag. Use left hand to put mouthpiece back in, while right hand controls blob reel

Personally I've never had a free flow in 2800 dives including many under ice. (seen plenty though)

The buddy clips their reel onto yours and watches. If yours jams they let theirs run. That way the bag always gets to the surface and you get back any reels that tangle (touch wood, mine never has)

[Green_Manelishi]

Cripes, sounds like a bank robbery :-)

The best way to begin is to have a bag that does not
require two hands to hold it open.

To prevent snagging yourself simply "gather" the
nylon straps at the bottom of the bag and hold them
up against the bottom of the bag as you hold it above
the exhaust tee. Don't be afraid to "roll over" onto your
side a bit so the exhaust heads straight up (basic
physics) out of the higher of the two exhaust ports
and directly into the bag.

You don't have to place the opening of the bag AROUND the
exhaust, just place it a few inches ABOVE the exhaust.

By *NOT* using press-the-purge-button method you
have the benefit of both hands to use in controlling the
bag, reel/spool, etc.

Be smart: practice in a controlled environment BEFORE your
life is in danger. Also, carry TWO bags and reels.

[tinman]

"The buddy clips their reel onto yours and watches. If yours jams they let theirs run. That way the bag always gets to the surface and you get back any reels that tangle (touch wood, mine never has)."

This beats my buddy poised with knife routine I believe. We'll give this a try. It is a good day when an old dog can learn a new trick....

[madmole]

After 20 years of letting bags rip from 50-80m down you tend to get it right ;)

Plus they are too expensive to just let go of if theres a problem

Best technique is to tie reel to wreck, let rip, untie. If it does jam you get a chance to untangle

[Fetch]

Not to pick fights as I am far from a technical diver, BUT: wouldn't it just be easier all around to use a spool? No worrying about jams, etc.

jeff

[madmole]

Reels are just dam useful, Can use em as distance lines and wreck penetration lines, Buddy line, easy to deply at bottom or mid water and a lot smaller than carrying a spool. Much easier and faster to wind in

Spools are unheard of in UK, never used one so cant really compare on ease of use

[MechDiver]

Fetch once bubbled...
Not to pick fights as I am far from a technical diver, BUT: wouldn't it just be easier all around to use a spool? No worrying about jams, etc.

jeff

Spools have a limited amount of line on them and, IMO, are more hassle to wind up. I always have a spool in my drysuit pocket, but if I'm gonna use a bag, I take a reel.

[Fetch]

Madmole: size - a spool is 3" in diameter by approximately 2" wide.

MechDiver - you can get 150' (maybe even bigger) spools. I agree, btw, winding them up is a hassle, but at the rate you need to wind them for ascent (assuming a nice slow ascent speed), they really aren't much of a hassle for shooting a bag.

*shrug* Madmole, you might wanna try one in the pool or something (spool runs about $30). Not having to worry about jams is VERY nice.

I do understand it would be less useful in a penetration/exploration context, btw.

jeff

(edit: typo)

[madmole]

Ahhhhh you mean an open reel, I assumed you meant those dirty great up line spools you see US divers lugging around the size of an 80 strapped on their back

Open reels have been tried, they jam more than winder reels on long ascents as they have no feeder arm and there is no tension on them (from the bearing or the operator). They do work for shallow deployment from say 10m

I have a buddy who uses one for shallow dives, but >50m he swaps to a proper reel

[padiscubapro]

Madmole,

You are were thinking about "jersey Uplines", personally I use a reel and a bag but the uplines do have a use.. They are popular on the deep offshore wrecks.. shooting a bag from >70m in a ripping current is a crapshoot(and now you need to carry an explorer type reel with heavy line, my largest reel with heavy line just makes about 100m, not much of a margin).. All the boats up here anchor into the site so a blue water hang is not an option.. With the jersey upline just tie into the wreck and begin an ascent, when you get to the surface cut the line... Its generally sisal so its biodegradable ..., I have also seen people shoot a bag on their last deco stop while still hanging onto the upline.. This gives the boatr a chance to get a line out to you so you don't have to fight a ripping current in full gear, its muc easier for someone in just mask and fins...

[madmole]

Thats why our reels tend to big bigger than the Dive rite and other US ones, and our bouys bigger. We also have strong currents as normal.

The advantge of shooting a buoy is that the moment you let go of the wreck, you are drifting and hence dont have to fight any current. The large (6'-10'/2m-3m) sausage upright on the surface allows the boat to easily follow. If you were on a 50m upline on some of our wrecks you'd just be 50m from the wreck horizontally (one wreck we do regularly has 6 knots over it apart from the 20 min window)

Also here leaving 80m of line on a wreck would be considered ecologically bad and dangerous to the next wave of divers. Many of out popular deeper wrecks may have 100 divers each weekend on them. If each pair left a line!!!!!!!

Shooting works well, especailly for us non bubblers, by the time we pop up, all the others have been up and back on board for 30 mins :D we normally arrange that the boat leave us on the surface for 5 mins before picking us up so we can have a good 100% session before climbing out (although our normal boat has a tail lift (bliss!))

[padiscubapro]

people leaving uplines on our wrecks isn't really a problem.. Shooting a bag is considered an emergency situation.. The ships tie into the wreck and can't really chase divers.. if you shot a bag for a legimate reason great, if you shot a bag because you got lost, you'll generally get a lecture from one of the captains about navigating a wreck.. do this too many times and you'll end up on the "boat's full" list on more than one diveboat.. if you do a free ascent and have the boat chase you and you bought the entire boat drinks...

[madmole]

No boat here anchors to the wreck, its too rough and in almost zero vis you'd need to run distance lines to find the upline again

Normally we just drop a shotline on the wreck as a downline. every one shoots a blob to come up. If we tried coming up a static line we'd have 6 ft arms or need jon lines an inch thick!!!!

Amazing all the different ways each country throws up to solve the same problems

[padiscubapro]

yup,
we all run reels from the downline(actually tie in near it), and use jonlines at the hangs..
although sometimes we get blessed with viz in the 5m-10m range on the closer inshore wrecks 3m is about normal most of the year.. Some of the offshore wrecks can have excellent viz.. but its all a crapshoot.. I remember one day getting at least 30m viz and went back the NEXT day to the same wreck and had 1-2m at best!!!!

the further offshore wrecks 40+ miles/65km off shore we can get 20m viz during the summer if we get a good stretch of weather without any major storms