Help with which pony?

[RDRINK25]

I have moved to wanting redundant air when we dive at least 60'. When I say we I mean my wife and I. It all started when when we got our deep diver cert last year I purchased a 30ft pony and used a old Atomic z2 that I upgraded from for a reg. I use a good bit of air on dives and usually am the first one too surface so I felt the 30 was a good fit if needed. I have only used it on dives to 90' or more and was thinking on getting a 6' and 13' pony with another reg setup. My logic is that my 5'0 wife who barley ever evens breathe underwatrer can have one as well. If we go deep she will use the 13 and I the 30 but if we stay at 60 or so I will take the 13 and her the 6. Is my logic wrong? What am I missing with this thinking? I know the cons about safe buddy practice and fully understand it. This is for true redundancy. We are both Padi Master divers if that matters too anyone.

 

[dumpsterDiver]

I use a 6 cu-ft down past 100 feet. If your wife stays around 60 or so, that is more than enough air to make a direct ascent.

 

[NAM001]

Why are you using a pony for normal breathing air. the pony should be for emergency use. If you need more air then perhaps a larger tank may be a better way to go.

 

[ScubaInChicago]

Have you thought about using a small set of doubles? It also gives you a second 1st stage, addition volume of usable gas, carry less weight, and in most cases can add to better trim in the water.

 

[GCullen94]

+1 for double small tanks for the reasons said above.
72's can be found on craigslist for next to nothing.
If you do go with the pony, I'd give your wife the 13, its not that much bigger and the average female sac rate is .4, stressed would be .75-1. which from 60 feet would only use around 3.2 CF but thats without a safety stop. Most dives to 60 that would go ooa are also bordering on NDC times, if its a multi day dive trip then that safety stop could make a difference on getting bent or not. It's actually a little scary on how little we know about repetitive dives and DCS. Personally I'd rather sling a 13 and go or better yet, small set of doubles.

 

[uncfnp]

My Sac rate is .4 so a 13 cf should get me safely to the surface from 100 feet with an eight min safety stop for a close to NDL with plenty of air to spare (could possible do it twice if I can stay calm and not explode my Sac). I have a 13. Even with his higher Sac Eric can make it to the surface from 100 with an adequate safety stop as well with a 13 but a 19 would give a little extra margin but he too went with the 13 cf. We only plan to use them for OOA and not prolong our dives. I don't see the need for you each to have 2 sizes. There is not that much size difference between the 6 and 13 in my opinion. I would recommend a 13 for your wife for all dive depths and possible a 19 for you but it may be helpful if you knew you Sac. I like consistency in equipment so that is why I prefer to use the same tank each dive.

 

[DevonDiver]

Decide the level of redundancy you desire:

1) CESA Bottle - something tiny like a 'Spare Air' - good only for a few breaths during an emergency out-of-air ascent. Little leeway for any delays or problems with the ascent.

2) Ascent Bottle - A small capacity 'pony' with regulator. Enough gas to get you to the surface in a controlled manner, including safety stops. The volume will be dictated by your air consumption. Rock Bottom (single diver) is a good method for calculating this.

3) 1/3rd Redundancy - Providing a full 1/3rd gas redundancy via larger pony bottle. Pony cylinder size equates to 1/2 of your main cylinder (i.e. 40cuft if you dive with an AL80). This covers all potential contingencies and is particularly suitable for recreational deep or overhead environment diving; such as that offered by PADI Deep Diver or Wreck Diver recommended dive limits. If combined with 'rule-of-thirds' on the primary cylinder, the diver now has a full 50% reserve, half of which is independent.

4) Full Redundancy - Doubling your total gas volume by using two primary cylinders; either back-mount or sidemount, independent or using an isolator manifold. Provides access to a full spectrum of effective gas management solutions, extended dive times and emergency protocols.

 

[dumpsterDiver]

My Sac rate is .4 so a 13 cf should get me safely to the surface from 100 feet with an eight min safety stop for a close to NDL with plenty of air to spare (could possible do it twice if I can stay calm and not explode my Sac). I have a 13. Even with his higher Sac Eric can make it to the surface from 100 with an adequate safety stop as well with a 13 but a 19 would give a little extra margin but he too went with the 13 cf. We only plan to use them for OOA and not prolong our dives. I don't see the need for you each to have 2 sizes. There is not that much size difference between the 6 and 13 in my opinion. I would recommend a 13 for your wife for all dive depths and possible a 19 for you but it may be helpful if you knew you Sac. I like consistency in equipment so that is why I prefer to use the same tank each dive.

I see a big difference in a 6 and a 13 cu-ft tank. a 6 has negligible weight and the reduced diameter makes it have imperceptible drag..not so for the 13.... as for other comments... the guy asks about a 6 cu-ft tank to reduce weight and he is told to buy doubles.. crazy

 

[uncfnp]

I see a big difference in a 6 and a 13 cu-ft tank. a 6 has negligible weight and the reduced diameter makes it have imperceptible drag..not so for the 13.... as for other comments... the guy asks about a 6 cu-ft tank to reduce weight and he is told to buy doubles.. crazy

I see what you are saying but for me personally, unless you are talking about Spare Air, by the time you add 1st and second stage and gauge, the weight/size of the 6 vs 13 is negligible so I chose to go with double the air for, to me, minimal increased weight and drag.

 

[Kharon]

With a SAC of 0.31 and a dive factor of 1.5 a 6 cf would give me 5 minutes of gas for ascent and a 3-5 minute safety stop from 60 feet. That's cutting it pretty close for me. I take a 13 cf on every dive. I recently got a 27 cf for deep dives because the 13 cf from 130' gives me only 5.7 minutes - doable with a minimal safety stop if nothing goes wrong. I consider the 13 cf good down to 90'. Below that I feel safer with a bit more redundant, independant air.