I will add some comments here, not as a Mod Post, but as a user.
The OP's original question was answered, back in May/June. He has not participated in the thread since then, and has moved on to several other, quite interesting and worthwhile, questions posed in other forums.
I am intrigued that in recent posts there seems to be assertions of 'dogma', and taking of dogmatic positions, in this thread. Frankly, reading through the entire thread, I think the sources of those assertions reside on both sides of the, shall we say, 'argument'. OK, we know it should be a 'discussion', right?
Perhaps, it might be more useful, if we wish to continue to discuss this thread - long after the OP has left the discussion - to look at where we can agree, and to articulate, in a reasonably dispassionate way, our reasons for disagreement, where that is the case.
Is a pony bottle, or backmounted manifolded doubles, or sidemounted independent doubles, a 'better' or 'best' approach to carrying a redundant air supply? My answer, would be, in fact my answer is, 'it depends'. I suspect most would not disagree. I dive a pony for certain dives - deep (>60 fgeet) recreational dives, for example, or for Public Safety diving, where it is a team requirement. A slung 30-40 cf pony is reasonably easy to manage, for me at least. But, my personal favorite rig to provide redundant gas supply is a set of double, backmounted AL 80s. The rig is reasonably light (even consiodering my knees and shoulders), it trims out very nicely, etc. But, there are times / circumstances where that rig may be impractical - some boats don't accomodate manifolded doubles very well, and I don't particularly fancy a long walk in backmounted doubles to a shore to water entry, over uneven terrain. As an aside, can new divers learn to dive initially with backmounted doubles? Of course they can. Let's give new divers at least some credit for intelligence, and competence! Is it the most conveneient approach in the context of instruction? Maybe not. Can new divers learn to dive initially with a slung pony? Of course they can! Can new divers learn to dive initially with sidemounted doubles? Of course they can. Now, there are practical equipment issues. I have a class of 6 OW students. Which is easiest for ME - providing 6 single cylinders, or 6 pony bottles, or 6 sets of doubles? I have no problem putting a newly certified diver in the pool with a set of BM doubles, so they can learn how to use them. Frankly, I don't have to deal with possibly confusing second stage issues. But, it is also a bit easier to teach them good dive planning, and how to use their single cylinder - correctly.
Is it appropriate to encourage divers to plan EVERY dive? My answer would be, yes. No one is saying that we have to have an 'Andrea Doria', technical dive approach to planning every dive. But, as I just said to 6 OW students this past weekend, 'you should plan EVERY dive', to some extent. And, you should have at least some idea of what YOUR gas consumption is, even if that idea is simply ordinal - i.e. 'I use a lot of gas' vs 'I don't use a lot of gas'. Sure, the intensity of planning may vary according to the dive, but there should be some element of 'planning' every time you go in the water - What are we going to do? How deep are we going to go? What will be out turn-around / cut-off points? That process has absolutely NOTHING to do with a specific certifying agency, by the way. EVERY credentialing agency that I am aware of would endorse that concept (even if some / many diver certified through that agency don'ty seem to do it).
I suspect that many of us have certain practices that we think are 'better'. For example, I think that a 'primary donate' gas sharing system is better than a secondary donate system, in the event of an out of air situation. I have very specific reasons for that belief, which have nothing to do with any agency through which I have been trained or credentialed. That belief is also what I share with divers with whom I work. And, I readily admit it is not what I teach at first in Open Water (at least not yet
).. Secondary donate is not 'bad', it just isn't as good - in my opinion - as primary donate. But, if divers I work with don't agree, no problem. I also believe that the DAN diving accident data show that 'interruption of the gas supply', in some form, is the numerically most common source of diver accidents / deaths. And, it is also my conclusion from those same data that the most common cause of gas supply interruptions is diver error, not equipment failure. So, I also conclude that I should put emphasis on dive planning and gas management in my treaching. But, I also acknowledge that equipment failure may occur. Now, that is what I have concluded - thus far. If additional data become available, that might cause me to view things differently, I am very willing to consider those data.
If someone disagrees with my beliefs, I don't look for MY perceptions of possible biases in their personality, or their training, or their agency affiliation, or their age. I look to understand their reasoning. I would encourage those involved in this discussion to do the same. By the way, it just might be that an important step in that process is to also look at OUR own biases, and personality, and training, and agency affiliation, etc. Just a thought..
