Question about using a lift bag for redundant buoancy

[Reg Braithwaite]

Yes it would be. I just don't have new drysuit kind of money currently(finding a used one that fits has been impossible) Like I said I went alittle crazy buying gear because of the deal I got on everything. I do plan to practice this. Just un sure of the best procedure to follow.

Okily dokily, and all my best wishes for working things out!

 

[Makhno]

1. If you have a wing failure, it is unlikely to vent all of your gas.
1. a. Suppose the failure is the dump valve at the bottom of the wing, down by your butt. Well, if you adjust your body so that your head is up and your feet are down, very little gas will escape through that hole, because it is all up higher in the wing, near your shoulders. (Don't worry much about your trim not being perfectly horizontal if you have a catastrophic wing failure).
1.b. Suppose the failure is where the inflator hose attaches to the shoulder: again, how about feet up and head down (so that the hole is below the gas)? OK, that one's a lot harder, but is still feasible. . .

2. Here's how NOT to use a lift bag or an SMB for redundant buoyancy:
2.a. DON'T send it up attached to a reel or a spool or anything like that. That nylon line may be strong, but maybe it isn't strong enough to hold you and all your heavy kit up. (And anyway, you can't do anything with a bag that's way up there on the surface while you're down below, holding onto a string for dear life.) And if it gets caught in a boat propeller, you're toast.
2.b. DON'T inflate it and attach it to your harness or BC or whatever. Keep control of it by holding it in your hands -- so you can let it go if necessary.

3. Here's how to properly use a lift bag or SMB for redundant buoyancY:
3.a. Start kicking hard and swimming up, or grab ahold of a buddy's harness, or hold onto the reef or the wreck, or whatever you need to do to try to maintain neutral buoyancy for the next 30 seconds or so.
3.b. Take out the bag or SMB. Keep it mostly rolled-up.
3.c. Find the valve or open hole or whatever part that you use to inflate it, unroll it a few inches to either side, and start to inflate it -- while holding onto it. As you inflate it, while holding onto it, it will pull you up by your hands. Hold tight!
3.d. Continue to inflate it, while holding onto it, until you achieve neutral buoyancy.
3.e. As you ascend, vent a little bit of gas out as the gas expands, so you maintain neutral buoyancy.

Keep the bag or SMB mostly rolled-up (with the bag's inflate valve and the dump valve both readily accessible), and held tightly in your hand(s), and only a breath or two of gas should be adequate to keep you from plummeting down. If not, add another breath or two.

The only downside to this is that now you don't have a bag to shoot to the surface to alert the boat. However, if you're diving in a team then someone else should have a bag to shoot. If you're diving solo, get two bags/SMBs.

This is really quite easy. I am half-asleep, though, so I perhaps I haven't explained it articulately enough. If you're confused, I'll try again tomorrow.

 

[Reg Braithwaite]

I have no intention to dive this setup where a hard bottom would be deeper than rec limits with out a drysuit.

A clarification: Besides not diving deeper than recreational limits, are you also not exceeding your "No Deco" times (however you may calculate them)? There is, obviously, a vast difference in how you approach the question of handling an equipment failure at 72' depth between having no deco obligation and needing to execute one or more deco stops correctly on your way back to the surface.

 

[maniago]

A quick break down of my math old setup I needed 27lbs.

Did you happen to look up the lift calculator in the BCD equipment section?. It works pretty good, just make sure you go to the end of the sticky thread and get the latest link.
http://www.scubaboard.com/forums/bu...ems/158370-ultimate-wing-lift-calculator.html

 

[PfcAJ]

1. If you have a wing failure, it is unlikely to vent all of your gas.
1. a. Suppose the failure is the dump valve at the bottom of the wing, down by your butt. Well, if you adjust your body so that your head is up and your feet are down, very little gas will escape through that hole, because it is all up higher in the wing, near your shoulders. (Don't worry much about your trim not being perfectly horizontal if you have a catastrophic wing failure).
1.b. Suppose the failure is where the inflator hose attaches to the shoulder: again, how about feet up and head down (so that the hole is below the gas)? OK, that one's a lot harder, but is still feasible. . .

2. Here's how NOT to use a lift bag or an SMB for redundant buoyancy:
2.a. DON'T send it up attached to a reel or a spool or anything like that. That nylon line may be strong, but maybe it isn't strong enough to hold you and all your heavy kit up. (And anyway, you can't do anything with a bag that's way up there on the surface while you're down below, holding onto a string for dear life.) And if it gets caught in a boat propeller, you're toast.
2.b. DON'T inflate it and attach it to your harness or BC or whatever. Keep control of it by holding it in your hands -- so you can let it go if necessary.

3. Here's how to properly use a lift bag or SMB for redundant buoyancY:
3.a. Start kicking hard and swimming up, or grab ahold of a buddy's harness, or hold onto the reef or the wreck, or whatever you need to do to try to maintain neutral buoyancy for the next 30 seconds or so.
3.b. Take out the bag or SMB. Keep it mostly rolled-up.
3.c. Find the valve or open hole or whatever part that you use to inflate it, unroll it a few inches to either side, and start to inflate it -- while holding onto it. As you inflate it, while holding onto it, it will pull you up by your hands. Hold tight!
3.d. Continue to inflate it, while holding onto it, until you achieve neutral buoyancy.
3.e. As you ascend, vent a little bit of gas out as the gas expands, so you maintain neutral buoyancy.

Keep the bag or SMB mostly rolled-up (with the bag's inflate valve and the dump valve both readily accessible), and held tightly in your hand(s), and only a breath or two of gas should be adequate to keep you from plummeting down. If not, add another breath or two.

The only downside to this is that now you don't have a bag to shoot to the surface to alert the boat. However, if you're diving in a team then someone else should have a bag to shoot. If you're diving solo, get two bags/SMBs.

This is really quite easy. I am half-asleep, though, so I perhaps I haven't explained it articulately enough. If you're confused, I'll try again tomorrow.

Or

1. Dive a balanced rig.

 

[nimoh]

2. Here's how NOT to use a lift bag or an SMB for redundant buoyancy:
2.a. DON'T send it up attached to a reel or a spool or anything like that. That nylon line may be strong, but maybe it isn't strong enough to hold you and all your heavy kit up. (And anyway, you can't do anything with a bag that's way up there on the surface while you're down below, holding onto a string for dear life.) And if it gets caught in a boat propeller, you're toast.

the line is stronger than you might think. A large SMB has about 50 lbs of lift, while most people carry smaller ones. #24 braided nylon line is rated for about 600 lbs.

It doesn't matter how heavy your gear is, the maximum strain put on the line will be determined by the lift capacity of the bag. For the large bag mentioned, if you are more than 50lbs negative (pretty extreme weighting), you will be pulling the bag down rather than pulling yourself up. Getting the bag caught in a boat propeller would definitely suck, but if you are in an area where this is a danger, you probably shouldn't be surfacing there anyway.

However, as AJ said, diving a balanced rig is a much better way to go. If you blow out your wing, you can react immediately by swimming up rather than sinking down another 100 feet or so while you get out your smb. And, another alternative is that your buddy can probably spare a few pounds of lift to help you out.

 

[Makhno]

OK, so what do you consider a "balanced rig" in 23C-27C waters, when all that are available locally are AL80s [and maybe AL40s . . . or maybe not] for divers who use wetsuits?

Try swimming up 2x AL80 twins, plus 1x AL80 travel gas bottle, plus 1x AL80 bottle of EAN50, plus 1x AL40 bottle of O2, in a wetsuit, at the beginning of a dive when all cylinders are full -- I doubt you can do it without a lot of effort. I've tried it wearing a full-body 5mm wetsuit plus a 3mm hooded vest. That wasn't enough buoyancy for all 5 full bottles plus me, even though several DIR divers had done a lot of math to advise me about a "balanced rig."

AL bottles are quite buoyant when empty. They're really heavy when there are 5 of them and they're all full. Tech divers need to be adequately weighted, and that's hard to ensure when diving with a lot of AL cylinders while wearing a wetsuit.

If a diver uses a single-bladder wing, it can't hurt to know how to use a bag for redundant buoyancy.

---------- Post added March 25th, 2014 at 02:16 AM ----------

Sorry, let me clarify: I am not at all against a "balanced rig." In fact, I am trying to achieve a balanced rig. It isn't always easy in 3rd World places with limited equipment options.

What I meant to say is that achieving a balanced rig is not always possible . . . and in any case, isn't it a good idea to know some useful techiques one might use in an emergency?

 

[nimoh]

OK, so what do you consider a "balanced rig" in 23C-27C waters, when all that are available locally are AL80s [and maybe AL40s . . . or maybe not] for divers who use wetsuits?

Try swimming up 2x AL80 twins, plus 1x AL80 travel gas bottle, plus 1x AL80 bottle of EAN50, plus 1x AL40 bottle of O2, in a wetsuit, at the beginning of a dive when all cylinders are full -- I doubt you can do it without a lot of effort. I've tried it wearing a full-body 5mm wetsuit plus a 3mm hooded vest. That wasn't enough buoyancy for all 5 full bottles plus me, even though several DIR divers had done a lot of math to advise me about a "balanced rig."

AL bottles are quite buoyant when empty. They're really heavy when there are 5 of them and they're all full. Tech divers need to be adequately weighted, and that's hard to ensure when diving with a lot of AL cylinders while wearing a wetsuit.

If a diver uses a single-bladder wing, it can't hurt to know how to use a bag for redundant buoyancy.

like I said, "a balanced rig is a much better way to go", but for a number of factors, it may not always be possible. In which case you may need to rely on a buddy for help with a blown wing, or as a last resort, use your smb.

 

[MXGratefulDiver]

Even with a balanced rig, double 108's are going to put you close to 15 lbs overweighted at the beginning of the dive when the tanks are full.

It's simple to sit in front of a keyboard and make suggestions, but without actually seeing you in the water it'd be difficult to tell you how to approach this and what skills to work on. Best thought I can offer is that if you want to use a small (20-30 lb) lift bag for redundant buoyancy then get out in shallow water and practice deploying it, and with full tanks and no air in your wing try using it to ascend to the surface. Use just the bag to control your buoyancy ... and practice until you can stop at will at whatever depth you want. Then attach a weight pocket or something on the order of 15# to it and repeat the practice until you can stop at whatever depth you want and hold there for as long as you want.

It's not rocket surgery ... but it does take some practice to get the hang of managing your buoyancy using a bag you're holding in your hands. And until you're completely comfortable doing so, I wouldn't take it down assuming you that you have anything like an effective means of backup buoyancy ...

... Bob (Grateful Diver)

 

[mod8521]

1. If you have a wing failure, it is unlikely to vent all of your gas.
1. a. Suppose the failure is the dump valve at the bottom of the wing, down by your butt. Well, if you adjust your body so that your head is up and your feet are down, very little gas will escape through that hole, because it is all up higher in the wing, near your shoulders. (Don't worry much about your trim not being perfectly horizontal if you have a catastrophic wing failure).
1.b. Suppose the failure is where the inflator hose attaches to the shoulder: again, how about feet up and head down (so that the hole is below the gas)? OK, that one's a lot harder, but is still feasible. . .

2. Here's how NOT to use a lift bag or an SMB for redundant buoyancy:
2.a. DON'T send it up attached to a reel or a spool or anything like that. That nylon line may be strong, but maybe it isn't strong enough to hold you and all your heavy kit up. (And anyway, you can't do anything with a bag that's way up there on the surface while you're down below, holding onto a string for dear life.) And if it gets caught in a boat propeller, you're toast.
2.b. DON'T inflate it and attach it to your harness or BC or whatever. Keep control of it by holding it in your hands -- so you can let it go if necessary.

3. Here's how to properly use a lift bag or SMB for redundant buoyancY:
3.a. Start kicking hard and swimming up, or grab ahold of a buddy's harness, or hold onto the reef or the wreck, or whatever you need to do to try to maintain neutral buoyancy for the next 30 seconds or so.
3.b. Take out the bag or SMB. Keep it mostly rolled-up.
3.c. Find the valve or open hole or whatever part that you use to inflate it, unroll it a few inches to either side, and start to inflate it -- while holding onto it. As you inflate it, while holding onto it, it will pull you up by your hands. Hold tight!
3.d. Continue to inflate it, while holding onto it, until you achieve neutral buoyancy.
3.e. As you ascend, vent a little bit of gas out as the gas expands, so you maintain neutral buoyancy.

Keep the bag or SMB mostly rolled-up (with the bag's inflate valve and the dump valve both readily accessible), and held tightly in your hand(s), and only a breath or two of gas should be adequate to keep you from plummeting down. If not, add another breath or two.

The only downside to this is that now you don't have a bag to shoot to the surface to alert the boat. However, if you're diving in a team then someone else should have a bag to shoot. If you're diving solo, get two bags/SMBs.

This is really quite easy. I am half-asleep, though, so I perhaps I haven't explained it articulately enough. If you're confused, I'll try again tomorrow.

Thank you this makes sense. I do carry 2 lift bags a 25lb on but ring for general use and a 75lb with a dump for emergencies rolled up and bungied to bottom of my BP. I do intend to practice this so becomes second nature.

---------- Post added March 24th, 2014 at 08:40 PM ----------

A clarification: Besides not diving deeper than recreational limits, are you also not exceeding your "No Deco" times (however you may calculate them)? There is, obviously, a vast difference in how you approach the question of handling an equipment failure at 72' depth between having no deco obligation and needing to execute one or more deco stops correctly on your way back to the surface.

Not exceeding depth or no decompression limits

---------- Post added March 24th, 2014 at 08:43 PM ----------

Did you happen to look up the lift calculator in the BCD equipment section?. It works pretty good, just make sure you go to the end of the sticky thread and get the latest link.
http://www.scubaboard.com/forums/bu...ems/158370-ultimate-wing-lift-calculator.html

I used the spreadsheet not sure if I have every thing in right. Here was the results

	surface	decent	depth	depth	safety stop	surface
	swim	full	full	empty	empty	swim
Result table	predive	20	60	60	10	postdive
Above Water	-10.0	0.0	0.0	0.0	0.0	-10.0
Suit	35.0	21.9	12.5	12.5	26.9	35.0
Tank(s)	-10.0	-10.0	-10.0	0.0	0.0	0.0
Non-Buoyant Gear	-10.0	-10.0	-10.0	-10.0	-10.0	-10.0
Required Lead	-17.0	-17.0	-17.0	-17.0	-17.0	-17.0
Rig	-20.0	-20.0	-20.0	-10.0	-10.0	-10.0
Total	-12.0	-15.1	-24.5	-14.5	-0.1	-2.0
Wing Failure and Ditch	5.0	1.9	-7.5	2.5	16.9	15.0