Is a 6cf pony bottle good enough as a back up?

[Scared Silly]

While I like math - the calculations are really just theoretical. Try this experiment - with all your gear on, swim 100 yards on the surface without stopping, (i.e. get your breathing rate up) shove yer pony in yer mouth and descend to 15' and swim horizontally for 2 minutes, then swim down at an angle so you descend at 30' per minute until you run out of air. That might give you an idea of how well yer bottle will work.

For me a 6 cuft bottle is for wing inflation or keeping martinis nicely chilled .

 

[bigrich954rr]

i just bought a steel hp120 now trying to pick a back up. guess ill have to see the size of the 19
I played around with 2cf bottels while in the Marines they seemed to have lasted ok but we didnt go deep with them,

 

[AbyssalPlains]

For me a 6 cuft bottle is for wing inflation or keeping martinis nicely chilled .

I'm intrigued - how do you use a gas cylinder to chill a drink?

 

[AbyssalPlains]

i just bought a steel hp120 now trying to pick a back up. guess ill have to see the size of the 19
I played around with 2cf bottels while in the Marines they seemed to have lasted ok but we didnt go deep with them,

The best backup for a 120 would be an H valve, no? Why carry around another tank with that big of a primary? For no-decompression diving, I can't think of a scenario in which one could empty a 120 tank without going well into deco. If we are talking deco diving, then why bother with a single tank in the first place? I'd go doubles in that case.

 

[616fun]

IMO a 6 is too small for a backup. 19s aren't bad, but for a similar cost you can pick up a 40 and it's a much more versatile cylinder. If you decide to extend you diving it's a great deco capacity.

Take it from a guy that sold a 19 a few yearsnafter he bought it. Just get the 40.

 

[4sak3n]

I'm intrigued - how do you use a gas cylinder to chill a drink?

Adiabatic cooling.

Edit: to be more precise the air cools as it leaves your cylinder due to the decrease in pressure. This cool air can suck the heat out of a drink thereby cooling it. It is the same principle that freezes regulators into an open position when diving in very cold water.

 

[Darnold9999]

The size of the pony that will work for you depends on the amount of risk you are willing to take on.

6 cf will get you to the surface from 100 feet. You will have no time at depth to solve a problem, and you will be skipping most if not all of your safety stop depending on your ascent rate, but as someone pointed out it is significantly safer than a CESA which is what you will be doing if you don't have it and your buddy is unavailable. But there is 0 margin for error and probably carries a false sense of security. It is what I use in clear tropical water - diving solo but I am aware that it only solves a very limited number of problems and if something not on that list happens - I won't be coming back (the risk I am willing to take on). I am also rarely at 100 feet, most of my diving in that environment is at 50 - 80 feet and I am entirely comfortable doing a CESA from that depth.

A 40 will allow you lots of time to solve a problem at depth, do a leasurly ascent, safety stop and then some. If you are diving where the entanglement risk is high, even that much gas might not be enough. There is always some problem that you might need to solve that will take more gas than you have. We all take that risk every time we dive. Fortunately mostly the risk is extremely small.

You have to decide what problems you are trying to address, how much time you want to spend at depth resolving those problems, what kind of ascent rate you are comfortable with and how long a safety stop you want to do. Once you know the answers to all of these questions you will have your answer. Without your answers to these questions everyone is just giving their opinions based on their own answers.

 

[dumpsterDiver]

The size of the pony that will work for you depends on the amount of risk you are willing to take on.

6 cf will get you to the surface from 100 feet. You will have no time at depth to solve a problem, and you will be skipping most if not all of your safety stop depending on your ascent rate, but as someone pointed out it is significantly safer than a CESA which is what you will be doing if you don't have it and your buddy is unavailable. But there is 0 margin for error and probably carries a false sense of security. It is what I use in clear tropical water - diving solo but I am aware that it only solves a very limited number of problems and if something not on that list happens - I won't be coming back (the risk I am willing to take on). I am also rarely at 100 feet, most of my diving in that environment is at 50 - 80 feet and I am entirely comfortable doing a CESA from that depth.

A 40 will allow you lots of time to solve a problem at depth, do a leasurly ascent, safety stop and then some. If you are diving where the entanglement risk is high, even that much gas might not be enough. There is always some problem that you might need to solve that will take more gas than you have. We all take that risk every time we dive. Fortunately mostly the risk is extremely small.

You have to decide what problems you are trying to address, how much time you want to spend at depth resolving those problems, what kind of ascent rate you are comfortable with and how long a safety stop you want to do. Once you know the answers to all of these questions you will have your answer. Without your answers to these questions everyone is just giving their opinions based on their own answers.

Excellent post! another component of the decision is how much extra weight and drag are you willing to endure for a particular redundant function. A 6 cu-ft tank may be too small for many people (and the utility that they expect to derive from it), but it does has one huge advantage.. It is so light and small that you hardly know it is there when diving. Back mounted, out of the way, with a necklace and it just doesn't get in the way. Someties i dive 149 cu-ft single steel tank and ANY reduction in weight is beneficial to my comfort on the boat.

I Trained my 10-yr olds to dive with 6-cuft pony bottle and they have fully adaptered to the configuration. The youngest is now 12 and I generally keep him abouve 80 feet or so and the tiny pony seems to suit him well.

 

[drdaddy]

No. Why are you even asking this?
6cf is kinda like "snair air" - it sets you up to thinking it will help you, but in the end it's useless.

19cf is minimum from 100ft
13cf is minimum for 50 ft
6cf is minimum for snorkeling

 

[dumpsterDiver]

No. Why are you even asking this?
6cf is kinda like "snair air" - it sets you up to thinking it will help you, but in the end it's useless.

19cf is minimum from 100ft
13cf is minimum for 50 ft
6cf is minimum for snorkeling

Didn't know snorkeling HAD a minimum pony bottle specified for the activity.... Is that in one of then new dive manuals?