When does "Gas Management" get taught?

[vkalia]

That is not the issue. The issue is when something goes wrong at the worst possible moment (50 bar or 70 bar), do you have the gas left to solve the problem, collect your wits and get out of dodge. The point is that before the emergency you are watching your gas and you never let it go below 70 bar at depth and therefore you have more margin of safety than the diver who lets their gas get down to 50 bar at depth, at the moment that the emergency occurs.

Unless I misunderstood what you are saying, it seems to me that the problem you are not describing is not so much as when to head up, but adhering to that limit.

If you have people who simply forget to come up at 50 or 70 bar without having an emergency occur, then you have a whole different issue in executing a safe dive.

Yep indeed.

I'm driven by the probabilities of large numbers. Your sample size, and any one single divers sample size, no matter how experienced or prolific of an instructor, is simply miniscule compared with the entire sample of all divers across the world. Something that you would not expect to see once in your life could be expected to happen once every year in a sample size 100 times as large as what you have contact with.

Again, I agree with this - and my hats off to you for also realizing this. It is precisely b/c of this that I take a contrarian position on some of these commonly held nuggets of diver wisdom - not necessarily b/c I personally disagree with them, but b/c I can see there being a possibility of someone with exposure to a larger sample size being in a better position than me to make a call. Who would that be? Well, RSTC and the other diving agencies, for one. A simple application of Occam's razor, combined with the fact that virtually every aspect of recreational diving has been tried/tested by lawsuits leads me to conclude that maybe, just maybe, the training standards arent as lousy as people make them out to me. Could they be better? Fer sure. Are they crap? Not a chance.

Vandit

 

[vkalia]

The problem is when you're at 100 fsw/30msw+ and one buddy hits 50bar/700psi and at that moment the other guys regulator starts to free-flow and drain his tank. Heartbeats race, SAC rates increase and perceptions narrow. Both divers task-focus on dealing with the free-flowing regulator at depth. Eventually the other guys tank is drained and they're trying to sort out the OOA. Hoses get caught and minor CFs ensue because they're rushed, maybe they have buoyancy issues and drop down to 120 fsw. Now they're down to 25 bar or so in a single tank. The team starts out swimming towards the bow of the ship at depth because they're task-focused on finding the upline and not on simply getting off the bottom (this is a super-common mistake) and they run out of gas completely at 80 fsw and both of them CESA and hope they don't embolize or get bent. This is really entirely plausible

Let's just agree to disagree on this. I agree that better training to handle situations like this is always nice to have, but this isnt exactly a huge problem in the dive world.

And also, you keep on trying to claim that we're trying to make it too difficult and really I'm fine with "don't go below 50 bar and don't go below 20msw/60fsw" as a rule for BOW divers. But for AOW divers diving to 100 fsw, they need to be aware of the basic physics that they'll be consuming gas at a faster rate the deeper they go, and that the "50 bar" rule needs to be modified the deeper they go. If they can't handle gas management at even that most rudimentary of levels then they simply have no business going deeper than 60 fsw.

This echoes my sentiments exactly.

Vandit

 

[vkalia]

I would say (shock horror) that it's not necessarily that 100% level trim is so vitally important, but to borrow someone else's words, (and kind of echoing what Jason says) It's more about being able to control your position in the water. Which may be horizontal, or may be some other orientation (preferrably not touching the bottom/destroyin the coral).

Amen. This is called being a thinking diver, and figuring out what is best from first principles.

A lot of sheeple seem to think that trim means always being perfectly horizontal, regardless of whether it is needed or not, just because they saw it on the <insert tech training agency of choice here> video.

V.

 

[StSomewhere]

I love these posts. The nerve of people to actually plan to have enough gas to cover a normal ascent in the event a buddy loses his gas.... :33:

It seems like I just read a post about a bunch of divers with poor gas management being scattered about on the Grove when the current picked up, I'd be most of them initially planned to be back on board with 500 psi before the brown stuff hit the whirling blades...

Back to RB concepts, the way I learned it you calculate RB for 100' as one number (given tank size and the team's SAC rates), if you do a multilevel dive up to 50' then your RB number changes. So just like you can use a multilevel dive and depth averaging or a dive computer or whatever to extend your bottom time, it also allows you to recalculate your RB, which is as significant to me as the MDL time. So its a concept thats applicable to multilevel dives as well as square profiles.

In OW, introduce &#8216;rock bottom&#8217; type calculations by working an example using an al80, from 100&#8217; with an elevated SAC. I haven&#8217;t worked through the calculations, but let&#8217;s assume for the moment that it comes out to 800 psi. Point out that this calculation is for an al80, and must be recalculated for different tanks. Give the example as a handout for future reference. For the remainder of the class emphasize &#8216;leaving the bottom with 800 psi&#8217; rather than the old &#8216;be on the surface with 500 psi.&#8217; Now the OW students have a simple number that will serve in the vast majority of dives, but have also been exposed to the logic and calculations. My approach assumes that the new divers are unlikely to encounter anything other than an al80. In my limited experience, I&#8217;ve seen that it&#8217;s really hard to rent anything else. If the new diver ends up with something else (say they go out and buy a different size tank) they have at least been exposed to the logic and calculations, and have the handout to reference.

I think that's an outstanding idea. So outstanding, in fact as Ted points out, that that's what we did (and then some!) in my Essentials class. The main thing IMO is to know how the number is calculated in addition to having a rule of thumb or a chart or whatever with the numbers precalculated.

 

[Lightning Fish]

... The team starts out swimming towards the bow of the ship at depth because they're task-focused on finding the upline and not on simply getting off the bottom (this is a super-common mistake) and they run out of gas completely at 80 fsw and both of them CESA and hope they don't embolize or get bent. ....

Instead of finding the upline, shoot a bag. But that begs the question, how long does it take to shoot a bag and is it a reasonable course of action? (serious question)

Jersey line - is that where you tie off to the wreck and then ascend? Being tied off gives you a reference line for the ascent and you won't be blown off the wreck?

Cheers,
Bill.

 

[Doc Intrepid]

Instead of finding the upline, shoot a bag. But that begs the question, how long does it take to shoot a bag and is it a reasonable course of action? (serious question)

You can shoot a bag and may have to, it only takes about a minute or two. Doing so, however, is significantly more problematic in some areas than making sure you get back to the upline. This is because some wrecks are located in shipping lanes. Very large ocean vessels may not see your SMB and may not be able to change course if they did. Depending on time of day, wind, weather, rain/mist/fog, velocity of currents, other parameters, you may surface a great distance from your charter boat and/or may not be spotted. Best bet is to be technically proficient enough to make it back to the upline or don't do the dive.

Jersey line - is that where you tie off to the wreck and then ascend? Being tied off gives you a reference line for the ascent and you won't be blown off the wreck?

Yes. This method is preferred by many east coast charter captains who take divers to wrecks in shipping lanes. Their rationale is that despite weather, fog, wind, anchor failure, whatever, they will always be able to navigate back to the wreck - it is programmed into their navigation systems. If they can always find the wreck, and you are tethered to the wreck, they will find you. If you are not, well...every year for the last few years along the eastern seaboard at least one diver has either not surfaced or drifted off and not been located after an air/sea search. They simply are never seen again.

Your call.

I'll plan so that whatever happens I've enough time to find the upline.

That's one reason why gas management when wreck diving 70 miles offshore is important.

[/HIJACK]

 

[cornfed]

That's one reason why gas management when wreck diving 70 miles offshore is important.

But... oh, nevermind...

 

[Lightning Fish]

You can shoot a bag and may have to, it only takes about a minute or two. Doing so, however, is significantly more problematic in some areas than making sure you get back to the upline. ...
<snip>
....to navigate back to the wreck - it is programmed into their navigation systems. If they can always find the wreck, and you are tethered to the wreck, they will find you. If you are not, well...every year for the last few years along the eastern seaboard at least one diver has either not surfaced or drifted off and not been located after an air/sea search. They simply are never seen again.

Your call.

I'll plan so that whatever happens I've enough time to find the upline.

That's one reason why gas management when wreck diving 70 miles offshore is important.

[/HIJACK]

Thanks Doc. (Though I wouldn't consider it a full hijack. I think, as Lamont demonstrated in his post, being aware of your gas supply (gas management) has to be considered when problem solving.)

Bill.

 

[limeyx]

Amen. This is called being a thinking diver, and figuring out what is best from first principles.

A lot of sheeple seem to think that trim means always being perfectly horizontal, regardless of whether it is needed or not, just because they saw it on the <insert tech training agency of choice here> video.

V.

Well, the words I "Borrowed" were from a GUE instructor, so I can't take all the credit!
That said, I am horizontal (or the best impression I can do) as much as I can. The exceptions are when I want to take a video or photo up toward the surface, or some other minor issue, but 99% of the time I like to get as horizontal as possible including ascent and descent.

 

[caseybird]

OK, we have our divers, 70 miles offshore, lost on a wreck in poor viz and current, in the shipping lanes in fog, and these fricking guys don't have redundant air? Rock bottom calcs are not going to solve thier problems.
Leave the bottom at 800 psi. That's good advice.