Weight-integrated BCD with trim pockets and positive buoyancy?

[seeker242]

OK, I will play.

All that sounds great! Although, I would imagine thinking that rationally, under water in an emergency, would be more difficult than sitting at a computer. Also, I thought ponies were scared of the water? My sister's pony doesn't like the water at all!

 

[RJP]

Also, I thought ponies were scared of the water?

Common misconception.

 

[stuartv]

BTW Stuart, an aluminum 80 is only ~2 lb negative when full.

Right. And +4.4 when empty. So, it's a 6 # swing from full to empty, right?

Stuart, your posts are usually thoughtful, if a bit long. And I do admire the thoroughness with which you examine many concepts in diving, not being willing to just accept things on face value.

But this should not be posted in a forum where new divers are looking for advice. It is a very dangerous suggestion.

Yes, by completely dumping a full AL80, you will drop 6 lbs of negative buoyancy - I'm assuming that the scenario that you envision would involve less gas than that. It would be extremely unusual for a diver to be unable to swim up their rig due to wing failure where 2-4 lbs will make the difference. And in that very rare situation, we are almost certainly talking about a new diver, who should be the last person to think about dumping breathing gas as ballast.

Also, remember that intentionally free-flowing a regulator at depth can cause it to stick open, which can completely empty an 80 in less than 3 minutes.

This is a recipe for a panic spiral and a disaster. Don't do it. Even as a "last ditch effort", better to sit on the bottom, breathe and think things through - you will either find a buddy to help or eventually get rid of that gas weight anyway...

Thank you, doctormike. And that is why I listed as last, for a self-sufficient diver. After you've sat on the bottom and thought things through and your buddy is nowhere to be seen and you are not able to swim your rig up with its current weight, is it better to consider dumping gas while swimming up - if you can? Or ditch your weights and end up corking? If the answer really is "just sit there for however long it takes to breathe the tank down", okay. I can see that that is certainly a better way to get rid of gas than just freeflowing a 2nd stage - if circumstances permit it. To that point, since we're talking about a BC failure, what about dumping gas using the LPI (presuming it's the bladder that has the problem)? Will that freeflow the way a 2nd stage would?

Obviously, if you have a safety sausage, SMB, or lift bag, inflating that would be the way to go in this example. But, the context is new divers and I'm not sure how many new divers have those or would be likely to have training on using one at depth. I certainly never got any training on that kind of thing at all, in OW.

I'm not trying to dispute your points. I am asking your opinion as a more experienced diver.

And also I posted because as a new diver myself, I really have hated being talked down to and as if I'm just not smart enough to be told a full and complete answer. So, I will do my best to avoid doing that to other people.

ps. No, I specifically identified the worst case scenario, so I was envisioning only possibly needing to do this if the tank was full (or nearly so). So, potentially 5 - 6 pounds of "help" in getting off the bottom.

 

[RJP]

And also I posted because as a new diver myself, I really have hated being talked down to and as if I'm just not smart enough to be told a full and complete answer. So, I will do my best to avoid doing that to other people.

To be clear, the suggestion to drain one's tank as a way to ditch ballast and gain buoyancy is not "part of a full and complete answer" but rather it is a bad, bad, bad, idea. The suggestion, particularly in a forum for new divers, is dangerous and irresponsible.

The idea is so far beyond "worst-case scenario" that no diver should allocate even a single brain cell to storage of the suggestion.

 

[archer1960]

What Archer said. If you're wearing a wetsuit, it will probably provide enough buoyancy to get positive, if you ditch enough weight. A dry suit definitely would.

...

Also, if that worst case scenario really did come to pass and your BC is completely useless, you can hold down the purge button on your octo to dump air. The more air you dump, the lighter your tank will get, also helping you to swim up. Wasting air in an emergency situation may sound counterintuitive, but the option is still something to keep in mind. EDIT: As a LAST resort!

The next thing working in your favor is that a 100% failure of your BC is pretty darn unlikely (according to what I've read). If it does have a failure, it will most likely still hold some air - just not as much as it's supposed to. So, it will still give you some lift, in most failure scenarios. Especially if you maintain some self-awareness and can orient your body to keep the hole in the BC at the lowest point.

The last thing working in your favor (if you're striving to be a self-sufficient diver) is that you should have a buddy who can help you get to the surface, if your BC really does have a complete failure.

This (the bolded part) is a bit silly. Instead of dumping air, why not just use it trying to swim up, or getting just a little air into your BC by figuring out where the hole is and keeping it facing down? Or even into your wet suit by purging your octo into a sleeve?

 

[dumpsterDiver]

Yeah sit on the bottom absorb as much nitogen as possible and when the tank is almost MT. Shoot for the surface.... I will have to try that next time.

---------- Post added September 15th, 2015 at 05:57 PM ----------

What Archer said. If you're wearing a wetsuit, it will probably provide enough buoyancy to get positive, if you ditch enough weight. A dry suit definitely would.

However, the more important thing to know is that, generally, the experienced and knowledgeable divers on here (not that I am one of those, mind you - I've just read this multiple times) say that there is no Recreational diving scenario where you should ever need to ditch weights at all (other than possibly when you're on the surface, to maintain positive buoyancy). If you are weighted properly and have a BC or wing of the right lift capacity, the wing will be able to lift you off the bottom. If you were to have a complete, 100% totally catastrophic failure of your BC or wing, then you should be able to swim yourself up to the surface. That latter depends on the presumption that you are properly weighted. If you are carrying 10 # of weight more than what you actually need, then you might not be able to swim it up and so would need to be able to ditch some.

The idea of being properly weighted, again, for recreational diving, ranges from diving in just a pair of shorts with an AL80 in salt water, to diving in a 7mm suit with a single steel tank in fresh water. With shorts and an AL80, "correct" weighting would yield little or no weights at all - and you should be able to swim that up from any depth. With a 7mm suit and a steel tank, you might have a fair amount of weight on to be able to sink that 7mm suit. And, at depth, the suit will compress, losing buoyancy. At the deepest recreational depths, a thick wetsuit could compress enough to lose somewhere around 75% of its buoyancy. If you're at the start of your dive, your tank is full and so it is the most negative that it's going to be. So, if you had a complete BC or wing failure, at 130' (the max depth for recreational diving), right at the start of your dive, that would be your worst case. At that point, you would be negatively buoyant by the amount your suit compressed plus the weight of the gas in your cylinder (e.g. for an AL80, 5 to 6 pounds). Fortunately, if you had that worst case scenario, there would be a couple of things working in your favor. One, you would not have to swim up very far for your suit to start decompressing and regaining some of its buoyancy. If you were, for example, 20 pounds negative at 130', you would not have to swim that 20 pounds all the way to the surface. Remember, because we're assuming you're correctly weighted, that means when you get to 15', you should be neutral with an almost empty tank and an empty BC. That means, with a full AL80, at 15' you'll only be 5 - 6 # negative. So, in this example, you'll gradually go from 20 # negative to 5 # negative as you swim up.

The problem you always have to keep in mind is if you are correctly weighted and you drop weights when you are 100' down (and wearing a wetsuit that is compressed because of the depth), as you ascend your wetsuit is going to become more positively buoyant and (again, if you were correctly weighted to begin with) you are going to become positively buoyant overall (unless you have a full tank and only ditched 5 or less pounds) and end up corking right to the surface, possibly inducing Decompression Sickness due to a too-rapid ascent.

Also, if that worst case scenario really did come to pass and your BC is completely useless, you can hold down the purge button on your octo to dump air. The more air you dump, the lighter your tank will get, also helping you to swim up. Wasting air in an emergency situation may sound counterintuitive, but the option is still something to keep in mind. EDIT: As a LAST resort!

The next thing working in your favor is that a 100% failure of your BC is pretty darn unlikely (according to what I've read). If it does have a failure, it will most likely still hold some air - just not as much as it's supposed to. So, it will still give you some lift, in most failure scenarios. Especially if you maintain some self-awareness and can orient your body to keep the hole in the BC at the lowest point.

The last thing working in your favor (if you're striving to be a self-sufficient diver) is that you should have a buddy who can help you get to the surface, if your BC really does have a complete failure.

Wow so much of this is plain wrong... If you have a thick 7 mm suit with double layer over chest and maybe a hooded vest too, you will loose around 20 lbs of buoyancy at depth,, possibly more. I know I will lose over 25 lbs..

Have you ever tried to swim up 20 lbs negative while wearing a scuba tank? I doubt most people are physically capable of doing that.

Ditching lead does not necessarily result in "corking", but i am not sure what that means exactly. A diver using the proper technique can offset considerable bouyancy and can control an ascent rate to 60 fpm for most or all of the ascent with a reasonable amount of excess lift... 15 lbs should be controllable for most people.

Dumping air and absorbing nitrogen is not a good idea... Hell i would say take several deep breaths and ditch the whole tank and just swim up if your rig is just way too heavy and you have no choice..better than purging air on the bottom.


I have personally experienced two total BC failures and seen another one... all in the last 6-8 years and I have probably seen other failures as well. If the corrugated hose rips, if a tie wrap fails, if an OPV valve at the top fails, if the dump mechansim fails and falls off....if the OPV spring rusts and fails... this was so common there was a big recall for that one several years ago... ALL of these scenarios can and have resulted in a total loss of buoyancy..

The total failure is not that common, but it would be wise to have a plan to SURVIVE a total BC failure.. which may include a lift bag, a smb with a dump valve on it, a redundant BC bladder, a dry suit, ditching ballast, climbing up a wall, climbing up an anchor line or even just swimming up may all work in certain situations...Talking about these types of potential responses is way more practical than some of the ideas you floated and they make a hell of a lot more sense than assuming the BC will never take a dump or will retain some level of functionality.

 

[Centrals]

To be clear, the suggestion to drain one's tank as a way to ditch ballast and gain buoyancy is not "part of a full and complete answer" but rather it is a bad, bad, bad, idea. The suggestion, particularly in a forum for new divers, is dangerous and irresponsible.

The idea is so far beyond "worst-case scenario" that no diver should allocate even a single brain cell to storage of the suggestion.

It is NEVER an option!
I have came across plenty dangerous and strange suggestions over last 19yrs. By suggesting ditching breathing gas so as to lose weight is by far the most......I can't think of any word which is allowed to type.
No one die from having too much gas! This is the only exception.

 

[jringold]

Wow! Interesting discussion. I’m pretty new (at least I’m low mileage and was only driven by a little old lady to church on Sunday…) but I have never even considered the possibility of a total BCD failure. The academics of the discussion are pretty interesting. But in practicality I just don’t see if you are properly weighted starting out (or even a little heavy) that this would be a huge issue.

All that being said though, from an application standpoint, my BCD is similar. I have a ScubaPro GlideX. It has the integrated weights as well as the rear non-dump-able trim pockets. After several attempts I found that I need 16 pounds in SW to be slightly negative and that if I put 1 pound in each trim pocket and 7 in each integrated pocket, then I’m trimmed well with the least possible weight at a position where I cannot get it.

While I haven’t actually tried it yet (but this will be on my list for my next dive) I’m pretty sure that if I ditched the 14 pounds with every bit of air out of my BC, I would have no problem getting to the surface – I don’t think it would even take a lot of kicking.

I know that I’m stating the obvious to most, but looking at the OP I did want to comment on the practicalitiy of the trim pockets the fact that I think if you keep the min in them, you wont have an issue.

 

[archer1960]

...

Have you ever tried to swim up 20 lbs negative while wearing a scuba tank? I doubt most people are physically capable of doing that.

...

I haven't, but I intend to if the opportunity presents itself (good conditions, a good buddy to help if necessary, etc). However, I think I could. When I was in lifeguard training, I had to hold a 10 lb weight out of the water with both hands, using just my leg kicks, with no fins, for several minutes (I don't remember exactly how many minutes). I was 20 years younger back then, but haven't lost all that much thanks to a lot of hiking and bicycling. I think I could bring up 20 lb of negative buoyancy from the bottom with fins on my feet and my hands helping, without too much difficulty. I'd be tired and sucking air big time, but I think I could get it high enough that my wetsuit would start helping, and it would get progressively easier as I went up.

 

[dumpsterDiver]

I haven't, but I intend to if the opportunity presents itself (good conditions, a good buddy to help if necessary, etc). However, I think I could. When I was in lifeguard training, I had to hold a 10 lb weight out of the water with both hands, using just my leg kicks, with no fins, for several minutes (I don't remember exactly how many minutes). I was 20 years younger back then, but haven't lost all that much thanks to a lot of hiking and bicycling. I think I could bring up 20 lb of negative buoyancy from the bottom with fins on my feet and my hands helping, without too much difficulty. I'd be tired and sucking air big time, but I think I could get it high enough that my wetsuit would start helping, and it would get progressively easier as I went up.

Perhaps you can do it. I probably can as well (with my big freedive fins)... but the reality of the situation is that you don't want to depend on total brute strength to muscle your way out of emergencies. I have done it several times and you learn from them and say.. "well I am NOT going to do that again". Take 20 lbs of extra lead on a belt and swim with it for 2 minutes suspended in the water column... your air consumption will go through the roof, IF you can even do it.

The take home message is NOT how strong of a swimmer you are, but rather how you can ditch enough ballast so you can make it to the surface with out too much trouble. I had a whole thread a while ago on a BC failure and how i handled it with a thick wetsuit on in 80 ft.

Can't seem to find it now.. ...oh yeah, I am banned from the accidents and incidents section... so I can't see any of my old posts there.. that is the problem I think..