losing weights / uncontrolled ascent

[PfcAJ]

Disregard

 

[whitefang21]

Exhale - open that air way

 

[DiverRtNY]

---------- Post added October 15th, 2014 at 02:04 PM ----------




Folks - this is the "Advanced Scuba Discussions" forum. I'd suggest that a discussion of remedial Open Water topics properly belongs in "New To Diving" or "Basic Scuba Discussion." The discussion of "what do do if you're in deco" between divers that don't have enough dives/certs between them to qualify for a Deco course is likely to end up in the "Incidents and Accidents" forum eventually - especially if the best advice offered is "stay down and come up with a plan."

I don't think you need to take a DECO CLASS to happen to fall into deco. Not to say that should be a planned event but if does happen (where your computer tells you that you went into a deco UNINTENTIONALLY and there is any issue with an "unctrolled ascent", like Hedgehog is referring to, I think a game plan to have rather than shooting to the surface and hope it works out is not a bad idea. Shake your head as you may but perhaps give some insight to the NON DECO CLASS taking poster rather than saying "he's screwed". I think the overall safety of diving is planning for anything and everything to happen and ensuring you are mentally prepared for these possibilities. Such as "what do I do w/ an uncontrolled ascent due to losing all my weight?" I see you are an experienced diver of 500-999 dives with 10x's as many posts as dives so fill my sponge brain with knowledge and insight.
:blinking:

 

[Adobo]

I have a diverite transpac BC.

The weights are in pockets which are velcro'ed and then have a clip which secures them further. But Assuming somehow, magically these weights fell off and I started heading rapidly up towards the top.


What would I want to do in that situation ? I use about ten pounds of weight, total.

Trying to sort this out through the internet seems like a recipe for a lot of unnecessary trial and error. Even if you get the right information, digesting it and putting it into action is not necessarily simple. And that assumes that #1, you are getting the right info from the internet and #2, you can extract it from the rest of the information that is less useful.

One suggestion is for you to read up on a concept called "balanced rig". Once you get the gist of this concept, you might find that you are carrying more weight than you need or even if you have the right weight, you might find that you have no need for ditchable weight. So I would suggest that you start there.

Finally, there is a lot of talk about deco and so on. Without knowing you or the diving you are doing but knowing that you have minimal dive experience at this point, I would just take that deco stuff out of the equation. The assumption in your open water training is that at any point on the dive, you will have the option to make a direct (though very controlled) ascent to the surface. If finding yourself in a state where you have a deco obligation is possible, then the question is not going to be, what do you do if your weights fall out? The question will be, how do you plan and execute your dives so that you are diving within the constraints of your open water training.

---------- Post added October 23rd, 2014 at 11:06 AM ----------

---------- Post added October 15th, 2014 at 02:04 PM ----------

I don't think you need to take a DECO CLASS to happen to fall into deco. Not to say that should be a planned event but if does happen (where your computer tells you that you went into a deco UNINTENTIONALLY and there is any issue with an "unctrolled ascent", like Hedgehog is referring to, I think a game plan to have rather than shooting to the surface and hope it works out is not a bad idea.

Can you walk me through an example of someone finding accidentally finding themselves in deco?

Also, assuming that you have your weighting strategy worked out, what do you do if you find yourself in deco? Do you stay down and do the deco? If so, at what depth? And for how long? And what happens if while doing your deco, you or your dive buddy have a gas emergency?

 

[DiverRtNY]

Can you walk me through an example of someone finding accidentally finding themselves in deco?

Also, assuming that you have your weighting strategy worked out, what do you do if you find yourself in deco? Do you stay down and do the deco? If so, at what depth? And for how long? And what happens if while doing your deco, you or your dive buddy have a gas emergency?

Perhaps it was a computer error... or perhaps is was a misconception/ misinterpretation on my part but recently came back from COZ and during 2nd dive I was around 50' and 55 minutes and comp and computer "beeped" to inform me I was "in deco" (perhaps not but that what it said). Long story short it required me to "deco" (computer terms) for 9 minutes before the comp would then go into the basic 3 minutes 15' safety stop. Was this an accidental deco? I assumed so. Never happened before but that's not saying much. No one else in my dive party had this requirement and I know my comp was more liberal than a couple others I was with but that was about it. Wasn't going to argue with what the comp wanted and wasn't about to let the comp go into "deactivation" mode for future dives.
As far as what to do if I find myself in second question... If history repeats itself... I don't foresee needing a "requirement" much longer than the example above (whatever you want to interpret that example as because I just followed what computer was recommending). I haven't been formally trained in regards to doing any diving with doubles or stage tanks or whatever that would require a 60' 30' 20' 10' deco stops for a prolonged period requiring different gas mixes but I assume if their was an out of air emergency for myself or my buddy and i was doing a staged deco then I hope I would have my buddy to share air with or at least more than one redundancy with regs and stage bottles on my person or at a stage that would be accessible. or a Pony. If all this failed (myself and dive buddy's redundancy)... and staged bottles were not accessible... and emergency air hanging wasn't placed below the boat then i'd probably be hanging out in a post in incidents and accidents.
But if it was for what I assume was an accidental deco from my original example (9 minutes because my computer said so)I would burrow air from my buddy and if that failed I would rip the gills out of a nearby shark and take a Darwinism approach or just go to the surface ( but prefer to follow my computer's recommendation).
My answer to your original question, as far as "can you give me an example" was a legit response and any input as to what that clearly was would be appreciated. Second answer to you 2nd example wasn't intended to come off as a smart ass answer but just vibing off your interpreted tone that was received... if it was a legitimate open ended question then I would say one needs to reassess their approach to advanced diving that can/should involve an expected prolonged deco. I would have been a dead diver statistic (recreational single tank air diver) way before even thinking about my needed deco.

 

[Adobo]

But if it was for what I assume was an accidental deco from my original example (9 minutes because my computer said so)I would burrow air from my buddy and if that failed I would rip the gills out of a nearby shark and take a Darwinism approach or just go to the surface ( but prefer to follow my computer's recommendation).
My answer to your original question, as far as "can you give me an example" was a legit response and any input as to what that clearly was would be appreciated. Second answer to you 2nd example wasn't intended to come off as a smart ass answer but just vibing off your interpreted tone that was received... if it was a legitimate open ended question then I would say one needs to reassess their approach to advanced diving that can/should involve an expected prolonged deco. I would have been a dead diver statistic (recreational single tank air diver) way before even thinking about my needed deco.

The context of my questions to you were around the original post. The original post was, how to manage weights (ditchable or otherwise) so that one doesn't find himself rocketing to the surface should the dithable weights ditch themselves. This question is being asked by a seemingly new diver.

To introduce the concept of deco as a factor in this process is really introducing something that should be irrelevant for this and other new divers. If as a new diver, you run the risk of "finding yourself in deco", then what you want to do is figure out how you found yourself in that situation in the first place. And learn how to dive so that you are within the constraints of your training. With what little info you gave, my guess is that you did not plan your dive or you did not dive your plan.

The second question is really to re-inforce the first point. Once you are diving profiles that mandate some sort of deco, you need more than random circumstances to make sure you can complete the dive. What if you are at 50 ft with 600psi in your Al80 and your computer tells you to do a 3 minute stop? Do you have enough gas? What if at this time, your buddy signals OOA to you? Do you share gas and go to the surface or do you share gas and complete the stop as recommended by your computer?

You have two choices in this area - one is to dive in a way that the surface is always a viable direct option. two is to plan the dive such that a certain amount of deco is acceptable and then bring the sufficient resources so that you can safely complete the dive. In either case, better planning is required than "finding myself with a deco obligation". At any rate, the answer here is not to factor deco obligations when figuring out proper weighting but rather separate the two problems and address them both appropriately.

 

[DiverRtNY]

Well said ADOBO... I took the OP and blew it up into a snake pit mentioning terms such as "accidental deco" which can easily be taken into something more than I assumed... that was my fault. Not sure where I went wrong with my experience of having my comp tell me I put myself into a deco time (9 minutes). I was with a dive op with 5 other divers besides myself. Our first dive was all done within the same confines and others had longer bottom time then myself but my comp alone gave me the notification of the 9 " deco time. I play ignorance as not diving an individual plan outside of the plan the DM and the group decided on the boat prior to the dive. My only thought is that while doing our surface interval at a beach I was floating around the surface with my watch on. Did I submerge enough to interrupt my surface interval and disrupt the computations? Perhaps, but reviewing the computer log didn't display any interruptions but I don't know and still don't know...

 

[TSandM]

Although not entirely relevant to the original post, there are some good things to talk about in this deco stuff.

Adobo implies that you can't go into "accidental" deco, and he is making a point. When you did this second dive in Cozumel, it seems pretty clear that you didn't plug the briefed depth into your computer's dive planning function, to see what kind of no-deco time the computer would allow you, so you could anticipate having to ascend before you looked at the gauge and realized you no longer were allowed to. In addition, it seems an unavoidable deduction that you weren't monitoring your no-deco time very well, or you would have seen it ticking down and requested to get shallower before you ran out of time.

You can't count on the divemaster's computer (or whatever he is using) to match the output from yours. Decompression is not an exact science, but rather an exercise in mathematical modeling of nitrogen dynamics in the body. There are different models, and they make different assumptions, and result in different answers. This is what people mean when they talk about "conservative" or "liberal" computers -- conservative computers use an algorithm to compute nitrogen loading and offgassing that results in shorter no-deco times than liberal computers do. The differences can be substantial. I remember looking at a table in Lippmann and Miller that compared no-deco times from various models, and noting that, at one depth, they varied by eleven minutes. This means that a person using the conservative model would run out of no-deco time eleven minutes before anybody else in the group.

Which then raises the question of what you do in that situation. You are "in deco", and nobody else is . . . What does this mean? Are you going to get DCS and nobody else will? Are you going to be the safe one, and everybody ELSE will have problems? The answer is that all the models currently being used seem to result in a very low incidence of DCS for divers in the recreational range, which suggests, of course, that the conservative models may be excessively so. But it all depends on risk tolerance (and probably on individual factors that we don't even know for ourselves, especially at the beginning).

My husband teaches a class called "Techreational Diving", which is a distinctive specialty that he wrote. The basis for the class is that there is no bright line between recreational and technical diving. As the dives get deeper, further from the surface and further into nitrogen loading, the desirability of a direct ascent -- let alone an inadvertent and incompletely controlled one, as might occur from the loss of weights -- becomes less and less. With those dives, it's more and more advisable to do advance planning, and also to contemplate one's equipment setup and ask some hard questions about reducing the risk of even relatively improbable events, like the loss of weights. For example, one might tolerate a Velcro weight retention system when doing shallow, warm water diving, but the same system would be intolerable if doing deeper wrecks in the Great Lakes.

 

[boulderjohn]

What I've read suggests that it's better to have enough ditchable weight to ensure you can make a buoyant ascent rather than putting too much weight in non-ditchable pockets. Ensure that you have positive buoyancy with an empty BCD after releasing your ditchable weight.

So how much ditchable weight does a recreational diver need to perform a buoyant ascent in the event of an OOA emergency?

Let's look at the weight check process used to determine proper weighting. The diver at the surface empties the BCD while holding a normal breath and not kicking. The diver should float at eye level. If the diver does this with a full tank, it is sometimes (not always) recommended that they diver add a few pounds to allow for the loss of the weight of the air during the dive--usually about 6 pounds if you drain the tank completely. Some people argue with good reason that doing a weight check like this at the beginning of the dive includes enough trapped air in the BCD and wet suit to make compensating for the loss of the weight of the air unnecessary. Another factor that may call for some extra weight is wet suit compression for those wearing lots of neoprene.

To sum that up, in most cases a properly weighted diver with an empty tank should have a hard time staying below the surface without dropping any weight at all. If the diver is only a little overweighted, as would be the case with a thick wet suit, only a tiny amount of weight would need to be released to initiate a buoyant ascent, and if the diver has any ability to kick upwards at all, even that should be unnecessary.

For that reason, many people argue that the worst case scenario would only require the diver to have ditchable weight equal to the amount of air in the tank so that a buoyant ascent could be made in the nearly unthinkable event of a catastrophic emergency requiring a buoyant ascent with an empty BCD at the beginning of the dive with the tank still full. Those events don't happen often.

 

[dumpsterDiver]

So how much ditchable weight does a recreational diver need to perform a buoyant ascent in the event of an OOA emergency?

Let's look at the weight check process used to determine proper weighting. The diver at the surface empties the BCD while holding a normal breath and not kicking. The diver should float at eye level. If the diver does this with a full tank, it is sometimes (not always) recommended that they diver add a few pounds to allow for the loss of the weight of the air during the dive--usually about 6 pounds if you drain the tank completely. Some people argue with good reason that doing a weight check like this at the beginning of the dive includes enough trapped air in the BCD and wet suit to make compensating for the loss of the weight of the air unnecessary. Another factor that may call for some extra weight is wet suit compression for those wearing lots of neoprene.

To sum that up, in most cases a properly weighted diver with an empty tank should have a hard time staying below the surface without dropping any weight at all. If the diver is only a little overweighted, as would be the case with a thick wet suit, only a tiny amount of weight would need to be released to initiate a buoyant ascent, and if the diver has any ability to kick upwards at all, even that should be unnecessary.

For that reason, many people argue that the worst case scenario would only require the diver to have ditchable weight equal to the amount of air in the tank so that a buoyant ascent could be made in the nearly unthinkable event of a catastrophic emergency requiring a buoyant ascent with an empty BCD at the beginning of the dive with the tank still full. Those events don't happen often.

I am surprised an instructor would give such inaccurate information. A diver with a thick wetsuit at depth can drop 15 or 20 lbs EASILY and remain neutral. I remember about 20 plus years ago, I was scuba diving in some springs/caverns in about 80 feet. Both my buddy and I took our 12-15 lb weight belts off and laid them on top of a prominent rock feature and went further back and in. It is nice to be able to dive with no lead and no air in the bc and still use a thick suit.

When we came back our belts were GONE! I was particularly pissed because the belt was my first belt, I had owned it for like 20 years or something. We saw no divers and there were no divers around, but I figured pretty quick a diver must have taken them.

So we ascend and ask my GF (who was hanging out), did you see any divers come out a few minutes ago, yeah those young guys leaving right now in that car. I run over and DEMAND our belts back. The two guys might have had a clue about how close they currently were to getting their butts kicked. They said, oh you mean these belts (that they burried at the bottom of their truck under all their other gear). We got the belts back

Suit compression can be much. much more density swing than the air in a single Tank!!!