Pony vs. Doubles -- Philosophical Difference?

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[TSandM]

I think where the "philosophical" difference comes in is not how a pony works in contradistinction to doubled tanks. It's where the pony is used. A pony bottle is used to render the diver gas-independent from his buddy or buddies, when the diver is using a single tank -- i.e. for low-risk dives in recreational depths. This is the opposite of the team diving approach, where one's emergency gas is on a teammate's back. In the world of diving as a team, doubles are used where gas loss puts the TEAM at risk -- in other words, in higher risk environments like deeper dives and overheads.

Of course, a lot of people who own doubled tanks use them in other circumstances for a variety of reasons -- see DAA's post above. I dive mine a lot because I need to, to keep strong and stay in practice for the cave diving I can only do at intervals. But I also use doubles when I'm diving with someone I can't regard as a full teammate, and if I didn't have doubles, I'd probably use a slung tank in that circumstance.

 

[IceBergSlim]

Diving with a pony is diving with independent doubles. You have two tanks where either one can become worse than useless at any time and there is not much you can do about it. But, since you are in theory diving recreationally, it should not amount to too much of a problem.

(And assuming the pony has gas in it, is turned on and you did not breathe it down by accident and is in no way a part of your gas plan)

While I feel most ponies are carried for decoration they can be useful in some cases. Still, I am of the ilk that "if you think you need a pony you should get doubles".

In general the doubles are sounder as they have just as much "redundancy" but you can isolate them and save your gas if you have a problem. But, as said before, they are far too heavy in many cases and generally a pain in the ass to deal with as I can totally understand not wanting to use them at all.

Still, doubles can be had in some very small sizes. I do know of a few people that enjoy the safety of tiny doubles without the weight of large tanks and the bulk of a pony.

 

[Blackwood]

I think if you made a poll you'd find that the vast majority of ScubaBoard members feel that ponies should only be used in emergencies (in other words: carry them, but don't use them to extend dive time).

Double tanks, on the other hand, are frequently used to increase dive time.

That's the biggest philosophical difference I can come up with.

 

[Dive-aholic]

I'll use a pony on dives deeper than 80' when I'm off somewhere in the tropics where I can't get a set of doubles and I'm only doing recreational dives. Otherwise it's doubles/sidemount.

 

[Pimdiver]

I saw a video demonstration of a Spare Aire 3.0 recently and they tested it for number of breaths at ~60 feet. I've read quite a bit on here about the concept and understand the doubts, but what of it's use as nothing more than a rec (open water only) device for self rescue?

 

[UCFKnightDiver]

at 66 ft you have 1/3 of the gas you originally had at the surface to breath so of a 3 cuft spare air you have 1 cuft to breath, assuming your sac rate in an emergeny is 1cuft per minute, you have one minute at that depth to breath... will that really be enough air assuming you do a saftey stop. The only thing I think a spare air would be good for would be a CESA aid.

 

[Pimdiver]

Spare Air Scuba Safety Tank: Underwater Test Dive

Interesting

 

[DaleC]

Ding! ding! ding! I think Blackwood gets the prize.

That would be a very valid philosophical difference. The rest are practical reasons IMO and practicality is in the eye of the beholder.
I rec dive, part of the time solo. There is no reason for me to go out and buy double tanks, a double wing, the isolator manifold etc... just so I can enjoy redundancy. The pony is an emergency air supply, that's all. If one is extending dive times it becomes a stage bottle, which is another philosophical discussion altogether

Here's a question though. Supposing someone does the first dive using half the doubles air, and then does a second dive using the last half. If something then goes wrong during the latter part of the second dive - where's the redundancy (aside from your buddy)?

 

[IndySCUBA]

Here's a question though. Supposing someone does the first dive using half the doubles air, and then does a second dive using the last half. If something then goes wrong during the latter part of the second dive - where's the redundancy (aside from your buddy)?

By utilizing the rule of thirds. If on your second dive you are stating out with 1800 psi your turn pressure would be 1200 psi and should leave 600 psi in reserve.