double tank equipment

[agilis]

Here is what I know about the reef tank hobby - it is the only recreational activity that I know of that has just as much people posing as "experts" as scuba. And just like scuba, they drop names and drop their years of experience as if that gives credibility to their arguments. And just like scuba, they resort to logical fallacies to support their arguments.

Despite your ad hominem attacks, I am not particularly motivated to illustrate for you what you clearly refuse to see. But to humor you, I will give you just one example. You state:


If that diver puts together a set of double 130s, fills it with 32% and wants to dive this rig to 100ft (30 meters) in the ocean while wearing his 7mm farmer john. Is this a good idea or a bad idea? What are the gotchas for this dive? It's not a hypothetical. I've watched someone do this.

P.S. My only experience with triple, quadruple and quintuple (is that how you say five?) tanks is using stages and deco bottles with backmount doubles. These configurations are not that uncommon in tech and cave diving. I have no experience in sidemount, independent doubles or the convoluted set ups that world record depth divers use.

Anyway, my position on it is this, someone who doesn't have knowledge and is wanting to do dives that require 3, 4 or 5 tanks, it is absolutely imperative that the diver get proper training.

You failed to give an example. What you described was a hypothetical situation, not a basic principle, an important skill that any certified diver should possess.

In your example there are a number of issues that might present problems, including the implications of the gas mix, potential for exceeding ND limits, especially with that much gas, possible buoyancy issues, all sorts of things. This is not relevant to what I wrote. You might just as well have thrown in other irrelevancies, like the possibility that the purely hypothetical dive was at night in freezing cold water in a current with a powerful down draft at the edge of a drop off where terrorist frogmen armed with sharp bamboo stakes stalk any diver with more than one tank because such a configuration is an affront to the Goddess Iemanja, and that the diver, though fully certified, was suffering from senile dementia and had just consumed an entire pepperoni pizza before entering the water and was using a bowling ball as his primary weight system.

Hypothetical examples are infinitely expandable and cannot substitute for technical analysis.

Eng is dead. He was never famous. There are, in addition to scuba and reef aquaculture, many areas of recreational activity in which people pose as experts and drop names.

"Dropping their years of experience" would be counterproductive, though, since doing so would diminish the pretentious affectation of the poseur who was attempting to impress others. Adding, not dropping years, I would have thought. Another logical fallacy?

Why stop at quintuple tanks? I wonder what you think about the possibility of carrying a bag filled with 30 or 40 Spare Airs to be used sequentially? See any problems? Would further training be in order?

 

[Adobo]

You failed to give an example. What you described was a hypothetical situation, not a basic principle, an important skill that any certified diver should possess.

In your example there are a number of issues that might present problems, including the implications of the gas mix, potential for exceeding ND limits, especially with that much gas, possible buoyancy issues, all sorts of things. This is not relevant to what I wrote. You might just as well have thrown in other irrelevancies, like the possibility that the purely hypothetical dive was at night in freezing cold water in a current with a powerful down draft at the edge of a drop off where terrorist frogmen armed with sharp bamboo stakes stalk any diver with more than one tank because such a configuration is an affront to the Goddess Iemanja, and that the diver, though fully certified, was suffering from senile dementia and had just consumed an entire pepperoni pizza before entering the water and was using a bowling ball as his primary weight system.

Hypothetical examples are infinitely expandable and cannot substitute for technical analysis.

That's all fine and dandy except its not a hypothetical. I watched a guy do it.

Why stop at quintuple tanks? I wonder what you think about the possibility of carrying a bag filled with 30 or 40 Spare Airs to be used sequentially? See any problems? Would further training be in order?

What? You are the one who asked about 3, 4 and 5 tanks. Which by the way, anyone who is doing any kind of technical diving and a huge portion of people doing cave diving are using at least 3 tanks. Its not that unusual.

 

[agilis]

That's all fine and dandy except its not a hypothetical. I watched a guy do it.

And I've watched people leap into the water without a mask, with a closed valve, all sorts of idiocy. These are all individual aberrations, and cannot be used as examples illuminating more fundamental issues. One can just as easily point out the divers who died from lack of air at Dahab while attempting long deep dives with only a single tank as examples of the dangers inherent in single tank diving.

All diving is technical diving, and unless you are being paid or being compensated in some way, all diving is also recreational.

Back in the late 70s, I used three tanks when I dived with my twin 40s and a redundant 10cf pony. Purely recreational. The same with a stage bottle on a few deep wreck dives when I was much younger.

 

[Storker]

Yeah, its terrible that people overreact and are so eager to tell others that they are going to die. Could you point me to where anyone did that on this thread?

I'll confess to resorting to a bit of hyperbole. However, look at what started this discussion:

there is a lot more to "doubles" than how many spgs……...

That really depends on the reason for using doubles, doesn't it?

Why do you encourage irresponsible behavior?

That's my beef, right there. And the reason for me resorting to a bit of hyperbole, which IMO wasn't way out of line compared to the arguments I reacted to.

Anyway, as I've said before, I'll leave the discussion.

 

[Adobo]

But according to what Agilis said, there is no difference. If a thick wetsuit diver used a single 130cuft tank to dive to 100 feet they would encounter the same issues of compression and lost buoyancy, only to a lesser degree. They still have to consider their weight vs available lift.

Come on, man. Try to be fair at least. This is what I was responding to:

Weighting properly for doubles is largely a matter of achieving proper buoyancy with tank(s) filled, and anticipating the difference when tank(s) are down to whatever minimum is applicable. Again, this is absolutely basic stuff, and no one should be certified without that skill and knowledge.

agilis is stating that weighting for doubles is a function of achieving proper buoyancy with tanks filled and anticipating the buoyancy characteristics of the tanks when they are at minimum gas for the dive.

If I am to be generous, I would say that agilis meant to include the notion of suit compression as part of "proper buoyancy". I would also say that agilis meant to include the notion of gas choice as part of proper buoyancy (recreational trimix being lighter than nitrox). And finally, I would say that the questioning the motives for this kind of dive is somehow implied even though it is not explicitly stated.

That would be incredibly generous on my part to assume that agilis meant all that.

But how do I get around the last statement? That the concept of proper buoyancy, gas choice (or more importantly gas properties as it relates to weight) and being aware enough to judge the wisdom of this kind of a dive - all being basic stuff that any certified diver should have this knowledge?

All you have to do is to look around in scubaboard's new, basic, and advanced forums to see that clearly, not many divers possess this "basic" knowledge.

---------- Post added June 18th, 2015 at 09:46 AM ----------

And I've watched people leap into the water without a mask, with a closed valve, all sorts of idiocy. These are all individual aberrations, and cannot be used as examples illuminating more fundamental issues. One can just as easily point out the divers who died from lack of air at Dahab while attempting long deep dives with only a single tank as examples of the dangers inherent in single tank diving.

All diving is technical diving, and unless you are being paid or being compensated in some way, all diving is also recreational.

Back in the late 70s, I used three tanks when I dived with my twin 40s and a redundant 10cf pony. Purely recreational. The same with a stage bottle on a few deep wreck dives when I was much younger.

I don't mean to sound antagonistic but I feel like I am having a conversation with someone who has attention deficit disorder.

 

[agilis]

Come on, man. Try to be fair at least. This is what I was responding to:



agilis is stating that weighting for doubles is a function of achieving proper buoyancy with tanks filled and anticipating the buoyancy characteristics of the tanks when they are at minimum gas for the dive.

If I am to be generous, I would say that agilis meant to include the notion of suit compression as part of "proper buoyancy". I would also say that agilis meant to include the notion of gas choice as part of proper buoyancy (recreational trimix being lighter than nitrox). And finally, I would say that the questioning the motives for this kind of dive is somehow implied even though it is not explicitly stated.

That would be incredibly generous on my part to assume that agilis meant all that.

But how do I get around the last statement? That the concept of proper buoyancy, gas choice (or more importantly gas properties as it relates to weight) and being aware enough to judge the wisdom of this kind of a dive - all being basic stuff that any certified diver should have this knowledge?

All you have to do is to look around in scubaboard's new, basic, and advanced forums to see that clearly, not many divers possess this "basic" knowledge.

Thanks for your generosity, but it really was not needed.

Things like neoprene suit compression and the slight variations in gas density are so basic and so obvious that they do not require mentioning. Of course I was fully aware of these issues. They have nothing to do with the single/double tank issue whatsoever. They are the kind of things that might seem arcane or impressive to someone new to diving physics, but they are things learned during basic diving classroom training. Not mixed gasses for me, since we didn't have that option when I was certified 40 years ago, but it was mentioned the first day of classroom training when I got my Nitrox card.

I learned about suit compression before I was certified, from experience. I noticed I became overweighted around 25 meters. This was a problem in the days before BCs. I asked other divers, and they explained. When I was certified in 1972 it was mentioned before we ever got near the water.

The wisdom of such a dive? Are you kidding?

Actually, you do sound like a kid. You seem to have regarded at least one of your posts as if it were a written question in a certification class. "Oh, but you left out not holding your breath during while ascending. And what about putting on your weight belt last? Integrated weights? You didn't mention a check to see if the drop mechanism is functional before every dive."

 

[Adobo]

Thanks for your generosity, but it really was not needed.

Things like neoprene suit compression and the slight variations in gas density are so basic and so obvious that they do not require mentioning. Of course I was fully aware of these issues. They have nothing to do with the single/double tank issue whatsoever. They are the kind of things that might seem arcane or impressive to someone new to diving physics, but they are things learned during basic diving classroom training. Not mixed gasses for me, since we didn't have that option when I was certified 40 years ago, but it was mentioned the first day of classroom training when I got my Nitrox card.

The wisdom of such a dive? Are you kidding?

Actually, you do sound like a kid. You seem to have regarded at least one of your posts as if it were a written question in a certification class. "Oh, but you left out not holding your breath during while ascending. And what about putting on your weight belt last? Integrated weights? You didn't mention a check to see if the drop mechanism is functional before every dive."

That's all fine and dandy that you were certified when Moses was walking on earth and you were Cousteau's mentor and that mixed gas is for new age whimp divers. I get it already.

The thing is, its not about you. Read the original post. And check to see what forum you are in. This stuff is not common or known to divers certified you know, in the modern age. We can only assume that level of knowledge based on the original question and based on the forum we are in. For us to do otherwise is, as Tobin put it, irresponsible.

 

[cool_hardware52]

That really depends on the reason for using doubles, doesn't it?

Q. What exactly do we know about the OP's motives or intentions or level of knowledge?

A. Nothing.

Yet you are willing to suggest he and others should proceed without competent training.

That fit's my definition of irresponsible, yesterday, today, and for the foreseeable future.

Tobin

 

[Adobo]

I don't mean to sound antagonistic, but I feel like I'm having a conversation with an adolescent suffering from assburgers.

Your remarks about my age are a sad commentary on your moral construct. Do you really think any of that indoor Plunbing/Couteau stuff was clever?

I agree that there is a lot of misinformation and lack of accuracy surfacing in various posts. One need look no further than your amateurish stuff.

Actually, you do sound like a kid.

I think the reality is that you are out of facts, very short on practical information with only moderate experience and bereft of any logical consistency. A formalistic zombie with the zeal of a convert.

Writing that everything is incorrect without any specificity suggests a limited knowledge base and a tiny mind.

Honestly, I am at a loss. I mean, I never brought up dates, age, experience or anything else. You did. You made reference to how long you have been diving and your reef tank from 1984 and your certification from 1972. And then you get sensitive when I exaggerate about how long you have been diving.

I don't particularly care how long someone has been certified or how many dives they have or anything else. They either make sense or they don't. But one thing that is a red flag for me is when a person sprinkles in pot shots at my character, intelligence, my motives. I mean, if I had a tiny mind as you suggest and bereft of logical consistency and was a formalistic zombie (whatever the heck that is), is that sophisticated name calling really necessary? And I won't even mention assburgers. I'll just assume that you meant Aspergers and weren't looking for another clever way to take a pot shot.

Its just scuba talk on a forum.

 

[cool_hardware52]

I did not. Re-read my initial post, this time for comprehension:

I've already listed, in detail, what would be missing from a standard "rec cert" that most responsible divers would consider important to the safe use and operation of doubles.

Do you need me to repeat the list *again*?

You continue to ignore this, as necessary to fit your rather odd view that doubles are no different from a single cylinder.

One more time

Q. What are the risks of too much training?

Q. What are the risks of too little?

Tobin