Pony vs. Doubles -- Philosophical Difference?

[Gilldiver]

Pony tanks, doubles, stage tanks, side mount, etc. are all tools in your tool box. No one system will be correct for every dive. You should pick and choose what you need for each dive.

Even rule of 1/3rds is over kill for a simple shallow dives such as places like the pier in Bonaire or screwing around in a shallow non-overhead (real or deco) area.

Look at your dive plan and select the correct tools for that plan.

But if you use a pony, make sure that you can tell the difference between your main 2nd stage(s) and the one from the pony by feel, sight, smell etc. I have seen too many near misses, and a few body recoveries, due to going deep on the pony instead of the main tanks by mistake.

As for those who say they will not dive a pony, would they dive a stage bottle? Tell me the diffrence beside the way it may be slung.

 

[Peter Guy]

BTW, what generated the question is that I do work with some people who have been "critical" of me for diving in doubles but who, themselves dive with a pony and/or have no problems of diving with someone with a pony. (OK, maybe it is ME to which they object and not the doubles -- but.....)

So that is why the question regarding a "philosophical" difference between the two.

Also, in my case, perhaps the "philosophical" difference is that diving doubles means a hog rig (or at least BP/W) (BP/W-Hog = arrogant tech diver who doesn't "look like us") while a pony can be dived with a "traditional" single-tank BCD.

 

[Lucy's Diver]

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)?

You still have the ability to shut down a defective regulator (the whole thing) with access to all your remaining gas, or to isolate the problematic tank if that doesn't do it, leaving you with half of what's left. Assuming proper operator input, you are thus always carrying, at a minimum, a pony with half of what's left.

 

[UCFKnightDiver]

Ill be a devils advocate here, I have never heard of this happening, but what if your manifold on your doubles failed, in this line of thinking, a pony bottle would be more redundant and safer.

 

[String]

Ill be a devils advocate here, I have never heard of this happening, but what if your manifold on your doubles failed, in this line of thinking, a pony bottle would be more redundant and safer.

Or independent twins used a lot here by cave divers for that very reason.

 

[DaleC]

I'll play devils advocate for discussion sake (although I think both systems are valid) and will leave some of the more inflamitory statements aside.

You have two tanks where either one can become worse than useless at any time

How can a single tank become any more "worse than useless" than a double. If one thinks along DIR/Hog lines a doubles set up has more failure points than a single tank set up.

And assuming the pony has gas in it, is turned on and you did not breathe it down by accident

and assuming the doubles have gas in, both posts are turned on etc... You are confusing diving skills with equipment and assuming that someone who uses a pony will have less skills than someone who uses doubles. In fact, someone with good skills will be just as safe while someone with poor skills is worse off with doubles in an true emergency as identifying and isolating valves you can't see is far more complex under stress than working a pony you can see (but I won't defend poor skills to far down the path).

and is in no way a part of your gas plan

My pony is part of my gas plan (Unless you mean part of the gas one plans to breath on a routine dive which I do agree with). It is part of my emergency air source supply, along with reserve back gas.

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.

Depends what you isolate doesn't it? If you isolate a second stage, yes, you have access to both tanks but if you shut down a stem valve you've lost that whole side in which case they are just as redundant, not more sound.

Here's a real problem, not of doubles themselves, but of their common usage, that I have seen. I alluded to it in my most recent previous post; multiple dives on doubles.

If you can follow my reasoning:

A doubles diver entering the water on the second dive (assuming they used half their back gas on the first dive) having as much back gas as I do on a single tank but I also have a 30cu.ft. pony.
When the sh-t hits it on the last part of the second dive the doubles diver has little back gas to work with (this is what I meant by where's the redundant air source). They become buddy dependant for meaningful redundant gas or have to be diving a very conservative profile. The question is whether buddy dependance is more sound than self sufficiency? A safe diver would, of course, dive the conservative gas plan but I don't always see that in practice. I see doubles divers diving the same profiles as single/pony divers.


Here's another way to look at it:

..........................Doubles diver...................Single + pony diver
First dive..............80 + 80 (160)cu.ft. ..........80 + 30 (110)cu.ft.
Second dive..........40 + 40 (80)cu.ft. ............80 + 30 (110)cu.ft.

This has nothing to do with whether one is a good buddy, team player etc... or not. just with the actual state one finds themselves in. Each person has to decide whether they will ever experience buddy seperation at a critical time and what position they want to find themselves in when/if it happens. On the first dive both systems provide good coverage but on the second dive the doubles diver has to plan a shorter dive, not lose their buddy or push the safety envelope.

I want to be the fly on the wall on a boat charter when the doubles diver tells the single/pony diver they want to dive to the rule of thirds instead of halves.

It would be the correct thing to do but I wonder if ego's would interfere with common sense.
PS. A soloist on the second dive with doubles would be at even more risk IMO.

 

[Lucy's Diver]

If I jump in the water for a second or third dive with doubles when I think I might have any kind of gas issue in an emergency (i.e. if my dive buddy in a fresh single has as much or more gas than me for example) I will clip on a small (19) pony. Now I have triple redundancy.

But I am also (normally) diving double 120s with a buddy swapping off single 100s. I would likely be diving singles as well, but I get all the gas filled doubles and ponies I want for free, but only single 80s, nothing bigger.

But also consider that a doubles diver is still getting in the water on the second dive with more air than his single diver buddy - even assuming equal SAC. They get out of the water with, say 500 or 800 PSI left in their "first" tank. The singles diver leaves what he didn't breath int he first dive on the boat, the guy in doubles takes it with him.

 

[mwilding]

If you use exactly half of your gas on the first dive, you better not be planning a second dive of equal depth and duration.

Let's simplify your model and assume it is a pair of twins diving the two set-ups on a standard recreational boat dive.

At the end of the dive, the singles diver will have 500psi or 13 1/3 cuft of gas left in his tank. He then leaves that gas on the boat for dive number two and starts with a fresh 80 at 3000 psi. At the end of dive 2, he has another 500psi in the tank as his safety margin.

On the other hand, the doubles diver uses the same 66 2/3 cuft of gas on his first dive and surfaces with 93 1/3 cu ft or 1750 psi. at the end of dive 2, he surfaces with 26 2/3 cu ft of gas in his tanks at approximately 500 psi.

Bottom line: without getting into complicated gas management issues that I have no clue about (especially when talking about two buddies with different tanks and different SACs) the diver using doubles ends the second dive with more gas in reserve that the singles diver (ALL ELSE BEING EQUAL)

 

[micklock]

This spring I removed the isolation valve from my doubles and went to independent doubles. I already had a third tank, I used as a single with a pony, so I can swap the emptier tank for a full one the second dive. I don't dive deco or cave but most of my dives are solo. If I get into deeper wreck and deco I will double up some hp100s with a manifold so I can still have accsess to air in both tanks. The best part about independent tanks is it's easy to break them down and take them to the lds for fills.

 

[dkktsunami]

In recreational diving, by my way of thinking, the pony bottle is used (hopefully never) only for emergency ascent for equipment problems and should never be used to extend the dive. It is not "extra air" but is more like a seat belt in your car - you put it on but hope to never use it.