Pony Bottle / Stage Bottle / Decompression Bottle. What's the difference?

[tursiops]

Again, I have no dog in this fight.... just playing devil's advocate. To address the first point... I presented how I read his post, only @broncobowsher can definitively tell us what he meant.

I guess you can read it any way you want, but what he said clearly involved getting two people to the surface.

That reserve is there for reasons like having to share air at the last second at the bottom and get someone to the surface.

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Also, a downstream second will function all the way down to ambient pressure... it will just get harder to draw the further below intermediate pressure you go.

Yes, usually, with balanced gear....but recreational dive boats do not know what kind of gear you have, so must assume the worst.

To address the second.... By that reasoning, the 500 psi on the boat rule common in recreational diving leaves zero reserve, and in the scenario I presented (starting my ascent to reach the boat at 500 psi) if you approached me OOA, then you would assume you are SOL?

I don't understand your question. The OOG diver might be SOL, but I'm not. How much gas do I have, what is the situation, when did I leave the bottom, do I need a safety stop? Too many hypotheticals. Here is a question for you: how do you know when to leave the bottom so you get back on the boat with 500 psi?

 

[James79]

I guess you can read it any way you want, but what he said clearly involved getting two people to the surface.

I does, but the I believe reserve is being applied to one person (the recipient) while the gas owner is using the planned gas. Again, only he can chime in to clarify for certain what he meant.

Yes, usually, with balanced gear....but recreational dive boats do not know what kind of gear you have, so must assume the worst.

ALL downstream seconds will function all the way down to ambient, not just balanced ones and not just usually. And upstream seconds are getting vanishingly rare (I also honestly do not know their behavior below design IP). A first stage uses the IP to close the valve, so at tank pressures below IP setting the first stage remains open. So it isn't an assume the worst in that regard.

I don't understand your question. The OOG diver might be SOL, but I'm not. How much gas do I have, what is the situation, when did I leave the bottom, do I need a safety stop? Too many hypotheticals. Here is a question for you: how do you know when to leave the bottom so you get back on the boat with 500 psi?

To clarify, I should have phrased it as you (general "you", as an OOG diver, not you specifically). As to knowing when to leave the bottom... that is gas management. I know my SAC/RMV (pick your teminology), I know my ascent rate, I know my depth. I plan the gas needed to surface (with safety stop if needed), add 500, and that is my depart the bottom minimum. That is not addressing turn points/pressures for navigating away from the boat and back, etc., but in an emergency the big gas supply in the sky will give us all we need for the surface swim to the boat if needed.
To the original point... if that 500 extra psi (13cf) reserve will suffice for the OOG diver on my alternate, why wouldn't handing the same OOG diver a 13cf pony get him to the surface? Or if I had a catastrophic gas failure (plugged dip tube for example), wouldn't that 13cf pony still be viable for me?
Respectfully,
James

 

[tursiops]

I does, but the I believe reserve is being applied to one person (the recipient) while the gas owner is using the planned gas. Again, only he can chime in to clarify for certain what he meant.

ALL downstream seconds will function all the way down to ambient, not just balanced ones and not just usually. And upstream seconds are getting vanishingly rare (I also honestly do not know their behavior below design IP). A first stage uses the IP to close the valve, so at tank pressures below IP setting the first stage remains open. So it isn't an assume the worst in that regard.

To clarify, I should have phrased it as you (general "you", as an OOG diver, not you specifically). As to knowing when to leave the bottom... that is gas management. I know my SAC/RMV (pick your teminology), I know my ascent rate, I know my depth. I plan the gas needed to surface (with safety stop if needed), add 500, and that is my depart the bottom minimum. That is not addressing turn points/pressures for navigating away from the boat and back, etc., but in an emergency the big gas supply in the sky will give us all we need for the surface swim to the boat if needed.
To the original point... if that 500 extra psi (13cf) reserve will suffice for the OOG diver on my alternate, why wouldn't handing the same OOG diver a 13cf pony get him to the surface? Or if I had a catastrophic gas failure (plugged dip tube for example), wouldn't that 13cf pony still be viable for me?
Respectfully,
James

Sorry, I do not understand what your point is. The purpose of carrying the pony is if you lose your gas supply. A 13 will barely suffice, if all goes well. That 13 is not for someone else, it is for me. Yes, you can give it to an OOG diver, but then you have no backup if you lose your gas, or the dip tube clogs, or whatever. So are you saying that if I leave the bottom with 1000, I can be at the surface with 500? But if someone is OOG, I must leave the bottom at 1500 so we each have 500? Or are you saying that you'll use that last 500 to get the OOG diver to the surface and get back on the boat with zero? Or what?

 

[James79]

Sorry, I do not understand what your point is. The purpose of carrying the pony is if you lose your gas supply. A 13 will barely suffice, if all goes well. That 13 is not for someone else, it is for me. Yes, you can give it to an OOG diver, but then you have no backup if you lose your gas, or the dip tube clogs, or whatever. So are you saying that if I leave the bottom with 1000, I can be at the surface with 500? But if someone is OOG, I must leave the bottom at 1500 so we each have 500? Or are you saying that you'll use that last 500 to get the OOG diver to the surface and get back on the boat with zero? Or what?

Going from the premise that we are supposed to be on the boat with 500 psi (13cf) as a reserve, then if you are about to start your ascent with 1000 psi (notional number) to surface with 500, and then your buddy goes OOG. That is the worst case timing for the gas plan. My point was that if that 500 psi on the boat reserve doesn't work in this scenario, then it is an invalid reserve to start with (whistling in the dark). If it is sufficient in that scenario, the 13cf in a pony for yourself is a valid reserve to get you to the surface when your primary reg set quits giving air (OOG, catastrophic equipment fail, etc.). I carry a pony not just for me, but as needed. If I was solo (only one second stage on my solo set), and an OOG diver approached me, he is getting my pony and we are both headed up. I guess I just don't see the pony in as concrete of terms as some.... to me it is an available gas supply, meant for emergency use only. My emergency, or someone else's, doesn't matter to me. If a stranger approached me out of gas, and needed my pony.... he ended my dive, but he's alive to feel bad about it so it's still a win.
I do feel that we are starting to talk past each other... regardless, I appreciate the discourse and thought that it's provoked.
Respectfully,
James

 

[tursiops]

My confusion is still there.
Do you think a 13 is an adequate size? Apparently not, you said you carry a 19. Ok, fine. Is there more to be said than this?

 

[broncobowsher]

Going from the premise that we are supposed to be on the boat with 500 psi (13cf) as a reserve, then if you are about to start your ascent with 1000 psi (notional number) to surface with 500, and then your buddy goes OOG. That is the worst case timing for the gas plan. My point was that if that 500 psi on the boat reserve doesn't work in this scenario, then it is an invalid reserve to start with (whistling in the dark). If it is sufficient in that scenario, the 13cf in a pony for yourself is a valid reserve to get you to the surface when your primary reg set quits giving air (OOG, catastrophic equipment fail, etc.). I carry a pony not just for me, but as needed. If I was solo (only one second stage on my solo set), and an OOG diver approached me, he is getting my pony and we are both headed up. I guess I just don't see the pony in as concrete of terms as some.... to me it is an available gas supply, meant for emergency use only. My emergency, or someone else's, doesn't matter to me. If a stranger approached me out of gas, and needed my pony.... he ended my dive, but he's alive to feel bad about it so it's still a win.
I do feel that we are starting to talk past each other... regardless, I appreciate the discourse and thought that it's provoked.
Respectfully,
James

That sounds like my thoughts.

The numbers are off, but for the sake of simple simplicity got with it...
Do a dive, go down, do whatever, plan to head up when you hit 1000. Planning to burn 500 for the ascent. (I really don't see how you could burn that much air on a direct ascent, but go with it). At that point you get someone else out of air and need to share. You are now going to double your gas consumption as you are splitting what air you have left. Actually putting that reserve to use. You should be able to get yourself and someone else both safely to the surface. You had the 13 CF for yourself (the planned 1000 to 500 drop) and 13 CF for someone else (the 500 to 0 drop). If that 13 CF plan doesn't work then the 500 PSI to reach the deck isn't the correct plan. You should be able to safely surface from any recreational dive with less than a 500 PSI drop, thus a 13 CF should be enough to get any single person to the surface in any recreational dive. Are you going to do the 100 yard swim at depth then go up the anchor line? No, you go to the surface and do a surface swim. IF you are on the last of your air you don't screw around at the bottom anymore, go up.

13 CF will get any recreational diver safely to the surface. Add additional requirements (cave, overhead, deco) and you are no longer in the recreational world and you need to plan better.

Will larger work, sure it will. 19 CF? If that was what was available when getting a pony, so what. Got a deal on it, good. But to say you need more than 13 CF for a recreational dive just doesn't add up. Or all the training we have had for decades is completely wrong.

 

[Jack Hammer]

13cf is more than enough to rocket up uncontrolled on your own as quick as possible from depth. Which, by the way, is a great plan if you don't mind getting bent or having lung and ear barotrauma.

 

[Edward3c]

I just wonder how many who carry a pony (substitute your preferred word) have regularly practiced changing over to it at depth and going to the surface. I do it at least once a year from 30m.

 

[James79]

13cf is more than enough to rocket up uncontrolled on your own as quick as possible from depth. Which, by the way, is a great plan if you don't mind getting bent or having lung and ear barotrauma.

I am an air hog at .75cf RMV... at 120ft (deeper than I normally dive) an ascent at 30ft/min takes 4 minutes. Average pressure is 3 ATM. That takes 9 cf to get to the surface, leaving 4 cf for safety margin or an abbreviated safety stop. At 1cf RMV, it is 12 cf to the surface with no safety stop. To me that is not an "rocket up uncontrolled as quick as possible from depth."
I carry an AL19 when I carry a pony, for reasons of my own... but I don't see a need to hammer others who make a different choice or imply that they are going to get bent because they don't dive the way I do.
Respectfully,
James

 

[James79]

My confusion is still there.
Do you think a 13 is an adequate size? Apparently not, you said you carry a 19. Ok, fine. Is there more to be said than this?

For most of the diving I do, 6cf would be adequate.... Me owning a 19 is due to factors that include more than just the diving.
I believe we have reached the point of "agree to disagree" and "dive and let dive."
I genuinely do thank you for the debate and discussion on the subject.
Respectfully,
James