Should I switch to BP/W?

[BabyDuck]

"If you don't have data, then all you have is an opinion".
-hh

i can see that. ok, i'll be one data point.

my deepest dives (to 120 for about 15 min - don't have my log here but that's close) did not require adding air to my bc, nor finning or sculling to hover. i know i can swim up what i tote, because i do.

i also know that one person's experiences do not constitute 'proof'. in fact, i hate when commercials say 'clinically proven...' since the correct term imo is 'clinically shown', but that's a whole 'nother discussion!

 

[GreenDiverDown]

Then what's your definition of a balanced rig?

I'll give you my definition, albeit a very brief one. The best description that I have found was in a Quest Journal several years ago... and that article was three pages long.

The term "balanced" refers to balancing the weighting requirements for the lightest and the heaviest part of a dive or... the end and the beginning of a dive. A balanced rig is "balanced" so that the diver is heavy enough that at the end of the dive he can maintain neutral buoyancy for the appropriate shallow stops yet light enough that at the beginning of the dive he can swim up his rig from the bottom in the event of a complete failure of his BC.

A balanced rig does NOT preclude the use of ditchable weight and in some circumstances ditchable weight may indeed be required. A balanced rig also assumes appropriate choices of cylinders and thermal protection. It can be quite difficult to achieve a balanced rig and for some it may be impossible for it also assumes a fit diver with reasonable weighting requirements.

The appropriate use of this rig must include other considerations, as well. This is what I meant when I referred to the "big picture" in an earlier post. For instance, the safe use of a balanced rig must include a team or buddy approach. Likewise, its use assumes that problems at depth should be solved at depth.

Consider the oft mentioned ultimate emergency... the sudden OOG situation. The last resort, buoyant emergency ascent taught by most agencies is not an option with a balanced rig as there is never a need for such a measure. In such a situation, the diver's buddy... not the surface... is the answer.

Now, certainly, one can point out the dangers of this approach. You made a very good point that those divers switching from a standard BC to a BP/wing combo are at special risk. This is why the safe use of a balanced rig must be done as part of a larger more encompassing approach or system. To do so requires some training or at least some serious consideration coupled with significant practice and experience. Those divers without such training or experience are best warned not to rely on this method.

True, and the basic "problem" here goes back to an old Engineer's adage: "If you don't have data, then all you have is an opinion".

I'm not sure what you mean. The only thing that I was trying to say was that setting up a balanced rig requires getting in the water and experimenting a bit. Can you hold your stops? Can you swim up your rig? The diver answers these questions not with an equation but by experimentation. Jeff doesn't need to know the amount of thrust that he can generate. He just needs to get in the water and try it. If he can't, then he needs to make some adjustments.

I don't think there is one. As far as I'm concerned, if you have to cut off your gear, it had better have been because it was entrapped in a wreck or something: a diver who fails to configure his gear with sufficient ditchable weight deserves to die in it - - assuming that his stupidity doesn't increase my insurance rates or in any other way inconvenience my diving.

I do not believe that removing one's gear to swim to the surface should ever be considered. I mentioned the alien thing only because "never" is such a strong word. I suppose one could come up with some situation where that might have to be done... but it would be a rare set of circumstances, indeed.

Even when teaching basic open water I emphasize to my students that this is not an option. The reg stays in the mouth. Where the reg goes so must the rest of the rig.

Its normal topic creep.

Ah... the crotch strap thing. When the topic came up none of the balanced rig divers suggested that everyone should wear their weight belt under the crotch strap. You again make a very good argument that this can be a significant danger and most divers would be wise to heed your warning. Nevertheless, there are some of us that safely wear it in this position.

In view of what I have described above, can you see that for some of us there is never a need to instantly drop a belt. Should the worse happen, we go to our team mate or buddy for gas. We dive in such a manner that our buddy can and is relied on for our redundant gas supply. The surface is not an immediate goal. At this point, having secured gas from our buddy, a controlled ascent or exit becomes the priority.

Thanks. I'm physically a righty, but I'm left-eye dominant, which is a strength for photography as well as Design, but it does make it a royal nuisance to shooting weapons.

Your Galapagos shots suggest that you have an artistic flair and a photographic eye. Very nice!

I also looked through your "stroke" folder. I see that you keep some interesting company.

FWIW, I'd like to see the flammage on this thread subside...

I hope that you haven't felt flamed on my account. Much of what you say makes sense and applies well to the average diver. It's obvious that this ain't your first rodeo and that you know a thing or two about diving. I think that if you give some consideration to the system as a whole, however, you can see that a balanced rig... and even a weightbelt under the crotch strap approach... can be a safe option for some.

 

[-hh]

i can see that. ok, i'll be one data point.

my deepest dives (to 120 for about 15 min - don't have my log here but that's close) did not require adding air to my bc, nor finning or sculling to hover.

Okay, but is this with a completely empty BC?

Personally, I suspect not: I would say that your BC can't be empty, particularly at the beginning of the dive, since you're effectively saying that you're neutrally buoyant at depth, but there's ~5lbs of mass in your tank in the beginning of your dive that you're planning on consuming during the dive that has to be compensated somehow for you to be neutrally buoyant.

FWIW, please keep in mind that I'm asking for what one's net buoyancy would be if you were to have a BC bladder failure.

For example, for me, at the start of a dive, I'm going to have a -4lb tank, -4lb weightings, -2lb UW camera, +4lb wetsuit buoyancy (at surface) which nets out to zero at the surface when the air's gone (+2 -4 -2 +4 = 0) . However, at depth at the beginning of a dive, worst case is to assume zero from this particular warmwater wetsuit, so before adding air to the BC, I'm at -4 -4 -2 = -10lbs. If I had a BC failure, I'd have to swim up against -10lbs negative buoyancy, but if I were to ditch the UW camera and weights, this drops to -2lbs negative to swim up against. By these numbers, I'll become non-negative somewhere between 2500-2000psi, depending on how much actual residual buoyancy this tired wetsuit has at whatever depth.


-hh

 

[dherbman]

For example, for me, at the start of a dive, I'm going to have a -4lb tank, -4lb weightings, -2lb UW camera, +4lb wetsuit buoyancy (at surface) which nets out to zero at the surface when the air's gone (+2 -4 -2 +4 = 0) .

-hh

What about the buoyancy of other air spaces?

 

[BabyDuck]

Okay, but is this with a completely empty BC?

-hh

sorry, i wasn't clear.

yep, empty wing, checked by hand for any air bubble.

once again, only my experience. not intended to be generalized to anyone else.

 

[MXGratefulDiver]

FWIW, I'd like to see the flammage on this thread subside (I don't like hitting the "Report to Moderator" button) and get elements of this discussion tangent answered: I'm personally very interested to see if Bob can learn from NAUI as to precisely why their training did a literal 180 on this particular over-vs-under element, or if its a training void (I'm very much hoping that the answer's not that Bob has not been following standards). If it has indeed changed, I'm very interesting to hear what their logic is for justifying the change. There might be a case to be made, but the DAN reports frequency with which dead divers are found still wearing their weightbelt is a sobering statistic that doesn't go away with hand-waving.


-hh

Well now ... if you'd like to see the flammage subside, I suggest you stop provoking it. How DARE you suggest I'm not following standards? Are you a NAUI instructor? Do you have a clue what's actually in the NAUI S & P? I suspect not. Nor am I interested in defending my instructional practices over the internet.

You're quick to make offensive statements to and about others ... then you complain when someone says something back you don't like! I salute your cajones.

Now, let's discuss those "facts" of yours.

If you want to "learn from history" you need to look at not just the “facts”, but what those facts are really telling you. Furthermore, you need to investigate ALL the facts … not just the ones that support your case.

I’m won't argue that people sometimes die with their ditchable weight still in place … clearly that happens. But the fact ... in and of itself ... doesn’t really say anything about what caused the diver to die, or whether their death might have been prevented by ditching the weight. Nor does it address the efficacy of one method of doing so versus another.

You have to look at each accident from a larger perspective. And in order to do so you have to ask more questions. Some relevant questions to ask would be …

- What type of equipment was the diver wearing? Do the statistics support a theory that one method is inherently safer than another? My bet would be most of these incidents involved divers wearing a standard BCD that didn’t include a crotch strap … therefore the protocol question isn’t a factor.

- How many of those divers lost consciousness before they died? In other words, was the fact that the diver was wearing weights when found even a mitigating factor? My bet here is a statistically significant percentage would not have been in a condition to release their weights at the time ... and that unrelated physical factors such as heart attack, seizure, or other medical conditions prevented them from doing so.

- How many of those divers died due to being in a state of panic … which precludes the ability for rational thought? In other words, were they in such a mental state that equipment configuration didn't matter ... they were not rational enough to follow even the simplest protocol? As I'm sure you're aware, a panicked diver doesn't stop, think, and act ... they are beyond rational thought, so even the simplest protocol becomes irrelevent unless someone is there to intervene on their behalf.

Without giving thought to these and other circumstances, you really have no idea whether their ability to release ditchable weight had any bearing whatsoever on the outcome of these accidents. And without that knowledge you’re not “learning from history” at all … you’re simply cherry-picking facts on an as-needed basis to support what you’re already inclined to believe. There really isn’t any learning involved in that approach. Nor is it a rational way to develop a safety protocol.

To respond directly to your statement that I am perhaps not teaching to protocol, the NAUI Standard and Procedures manual does not address this specific topic at all ... not in terms of a hard and fast rule that says "you will teach this, then this, then this at the level you seem to feel that it should. Nor should it, given the variations of commonly-used dive gear such as weight-and-trim systems, integrated-weight BCD's and other forms of ditchable weight.

... Bob (Grateful Diver)

 

[-hh]

A balanced rig does NOT preclude the use of ditchable weight and in some circumstances ditchable weight may indeed be required.

Thanks for this important clarifiaction: the definitions I've seen haven't gone into any significant discussion about the process by which to identify what amount of ditchable weight is appropriate.

A balanced rig also assumes appropriate choices of cylinders and thermal protection.

Which alludes to the "no steels with wetsuits" rule. What this really boils down to is that the general balancing of steel tanks is negative buoyancy, which reduces the amount of ditchable weight (all other factors equal). When this is stacked with the loss of buoyancy at depth due to wetsuit compression, the system can lack sufficient ditchable weight to be able to swim up against. Even my warmwater rig using an AL80 manifests this with a mere 3mm suit whenever I'm deep enough to have less than 2lbs of residual buoyancy remaining in the suit.


It can be quite difficult to achieve a balanced rig and for some it may be impossible for it also assumes a fit diver with reasonable weighting requirements.

Consider the oft mentioned ultimate emergency... the sudden OOG situation. The last resort, buoyant emergency ascent taught by most agencies is not an option with a balanced rig as there is never a need for such a measure. In such a situation, the diver's buddy... not the surface... is the answer.

Now, certainly, one can point out the dangers of this approach.

Sure. one major contributing factor element with this particular contingency plan's setup is its reliance on the buddy in its reliability chain.

For example, because I carry an UW camera, I can be very non-attentive to my buddy, and this factor needs to be included into the dive contingency plan for me/my buddy. As such, it can reasonably then be expected to lead to a different conclusion as to what procedures are most appropriate for that type of subset of diving.

You made a very good point that those divers switching from a standard BC to a BP/wing combo are at special risk.

Yup.

This is why the safe use of a balanced rig must be done as part of a larger more encompassing approach or system.

That larger system is Risk Management. Having formal training or experience with Fault Tree Analysis techniques can be helpful here.

For example, it is understandable why a snorkel is a "useless" piece of equipment for a cave diver - - but just because that's an appropriate conclusion for their environment does not mean that this applies to all (eg, OW) environments.

True, and the basic "problem" here goes back to an old Engineer's adage: "If you don't have data, then all you have is an opinion".

I'm not sure what you mean. The only thing that I was trying to say was that setting up a balanced rig requires getting in the water and experimenting a bit.

Sure. Getting in the water and conducting an experiment to see what you can/can't do is gathering data.

(in geekish engineering terms, its "direct evidence testing"). The degree of formality approprite for such data collection depends on the application, the implications of coming up with the wrong answer, and the customer's risk tolerance for errors.

I do not believe that removing one's gear to swim to the surface should ever be considered. I mentioned the alien thing only because "never" is such a strong word. I suppose one could come up with some situation where that might have to be done... but it would be a rare set of circumstances, indeed.

Yes, it is a "hopefully never, ever". Not unlike breathing off of a BC.

... the crotch strap thing. When the topic came up none of the balanced rig divers suggested that everyone should wear their weight belt under the crotch strap. You again make a very good argument that this can be a significant danger and most divers would be wise to heed your warning. Nevertheless, there are some of us that safely wear it in this position.

IMO, its an acceptable trade-off to wear it under for when you're diving in a strong overhead environment. But that is pretty far removed from OW-I certification.


(Other stuff)

Your Galapagos shots suggest that you have an artistic flair and a photographic eye. Very nice!

I also looked through your "stroke" folder. I see that you keep some interesting company.

Thanks. Insfoar as the denizens of rec.scuba, I have some free webspace that I donate; Jason O'Rourke (had some excellent pages on the Ikelite disposable housing) previously was the donor. I've not most most of these rabble-rousers, but their SB reputation for being a rough crowd is a bit overstated; those that I have met & dived with are pretty nice and down-to-earth folks.

I hope that you haven't felt flamed on my account. Much of what you say makes sense and applies well to the average diver. It's obvious that this ain't your first rodeo and that you know a thing or two about diving. I think that if you give some consideration to the system as a whole, however, you can see that a balanced rig... and even a weightbelt under the crotch strap approach... can be a safe option for some.

I agree that there's plenty of lattitude for variation in protocols...and insofar as WB donning vs rig balancing, I see them as independent variables. My concern after mentioning it here was with the suggestion that 'WB under' is supposedly now the preferred configuration for everyone, including rank OW novices.


-hh

 

[-hh]

sorry, i wasn't clear.

yep, empty wing, checked by hand for any air bubble.

But doesn't this then mean that you're around +6lbs positive at the end of said dive?


-hh

 

[JeffG]

Thanks for this important clarifiaction: the definitions I've seen haven't gone into any significant discussion about the process by which to identify what amount of ditchable weight is appropriate.

Rule of thumb is ditchable ~= the weight of gas. That way if it fails at the start, ditch weight and then you should be able to swim up still be able to control yourself. At the end of the dive, you shouldn't have to ditch at all.

Most warm water trips with Al 80's are balanced to begin with. Unless you are grossly overweighted you should always be able to swim up your rig.

Usually, the only time you get a very unbalanced rig is when using thick wetsuits with big tanks.

 

[GreenDiverDown]

Rule of thumb is ditchable ~= the weight of gas. That way if it fails at the start, ditch weight and then you should be able to swim up still be able to control yourself. At the end of the dive, you shouldn't have to ditch at all.

Exactly. Pair that with the need for a drysuit and you're stylin'.