Testing a Spare Air

[markmud]

Where do you get that idea from? Don't know about you but you but I can swim the length of a 40' I ground pool and back on one breath. Add a half dozen breaths provided by a 3ff cylinder and that's another 40-50' easy.

Hi Caruso,

I think Toairishuman qualified his point correctly. "...most people..." probably could not do a deep recreational ascent on 3cf and have gas left over. They would probably make it most of the way and then have to CESA from 20 or 30 fsw. Better than noth'n, right?

I have a feeling that you and I are in decent physical condition with good vital capacity, most are not.

Pony on Bro!
markm

 

[caruso]

A person should be required to swim the length of a 40' pool twice on one breath before they are allowed to purchase a Spare Air.

 

[markmud]

A person should be required to swim the length of a 40' pool twice on one breath before they are allowed to purchase a Spare Air.

I am way too libertarian for that. All Scuba Police Special Agents should be fired without being eligible for unemployment benefits. Dive and let dive... dealing with different styles of diving.

I think a better course of action is for you and I to avoid diving with them unless there is a paid DM or instructor in charge of their safety.

Pony on bro,
markm

 

[johndiver999]

Where do you get that idea from? Don't know about you but you but I can swim the length of a 40' I ground pool and back on one breath. Add a half dozen breaths provided by a 3ff cylinder and that's another 40-50' easy.

He referenced a deep recreational dive. I'm not sure if that should be interpreted as 100 ft or 130 feet, but arguing that certain divers are more fit and need less air to ascend has limited applicability. I personally would be uncomfortable with just 3 cu-ft and looking at a 100 ft ascent while having a decent load of nitrogen, but this is a gross generalization and who knows if it translates to anyone else?

In any case, it is more useful to specifically state an assumed air consumption rate, depth, ascent rate, delay in beginning the ascent and the performance of a safety stop (or not) and then it becomes a relatively straight forward math problem, rather than a discussion of swimming abilities or fitness.

If needed, I can use my BC and fins to ascend a lot faster than I can swim horizontally in a pool in a bathing suit, but that is not my planned solution to a potential out of air emergency.

 

[markmud]

He referenced a deep recreational dive. I'm not sure if that should be interpreted as 100 ft or 130 feet, but arguing that certain divers are more fit and need less air to ascend has limited applicability. I personally would be uncomfortable with just 3 cu-ft and looking at a 100 ft ascent while having a decent load of nitrogen, but this is a gross generalization and who knows if it translates to anyone else?

In any case, it is more useful to specifically state an assumed air consumption rate, depth, ascent rate, delay in beginning the ascent and the performance of a safety stop (or not) and then it becomes a relatively straight forward math problem, rather than a discussion of swimming abilities or fitness.

If needed, I can use my BC and fins to ascend a lot faster than I can swim horizontally in a pool in a bathing suit, but that is not my planned solution to a potential out of air emergency.

Hi Johndiver999,

I like your response better than mine!

You wrote: "If needed, I can use my BC and fins to ascend a lot faster than I can swim horizontally in a pool in a bathing suit, but that is not my planned solution to a potential out of air emergency."

How will you use your BCD in an OOA situation without a pony? Even with a pony, you will need to manually inflate your BC.

Did I miss something? I think you mean ascending with no pony faster than you can swim horizontally by using your BC.

What is your planned solution to OOA?

thanks,
markm

 

[scubadada]

He referenced a deep recreational dive. I'm not sure if that should be interpreted as 100 ft or 130 feet, but arguing that certain divers are more fit and need less air to ascend has limited applicability. I personally would be uncomfortable with just 3 cu-ft and looking at a 100 ft ascent while having a decent load of nitrogen, but this is a gross generalization and who knows if it translates to anyone else?

In any case, it is more useful to specifically state an assumed air consumption rate, depth, ascent rate, delay in beginning the ascent and the performance of a safety stop (or not) and then it becomes a relatively straight forward math problem, rather than a discussion of swimming abilities or fitness.

If needed, I can use my BC and fins to ascend a lot faster than I can swim horizontally in a pool in a bathing suit, but that is not my planned solution to a potential out of air emergency.

I use a minute at depth, a normal ascent, and a safety stop, at twice my average RMV. From 130 feet, that's 16.4 cf. So, I may not need a minute at depth, I could ascend faster, I could skip the safety stop, and perhaps my RMV would not be twice normal. That's all a built in safety factor when I'm carrying my 19 cf pony.

 

[Marie13]

I got curious about the costs of it. I just looked up the cost of a Spare Air. $380 for a 6cft package!

Compare with -

19cft pony - $146 with valve

Above prices off DRIS’ website

Chances are someone has a spare reg they could use or could pick a used one up for not that much. Plus reg could be repurposed for something else. You can make your own stage kit for not that much.

 

[Saboteur]

Thanks for the detailed scenarios.
I never understand why so many folks hate on the Spare Air. As you said, it does what it says it does. Once you accept it is not a pony bottle, and is not a direct replacement for a pony bottle, you can focus on what it does do.

In fact, last year I switched from my 3cf bottle to a 1.7cf bottle. No, it is absolutely not as useful as the 3cf version. But since finding a place to clip the 1.7 is far easier and less intrusive than attaching the 3, I decided to opt for the smaller size that actually gets wet rather than stick with the larger, better size that pretty much stays dry at all times. Took me a while to realize that and accept it, rather than repeatedly vowing to change my behavior next time.

I've read all the arguments against them about not having enough capacity for you to stop and analyze the situation, ascend at the proper rate and do safety stop....all with heightened air consumption. I think one use of the Spare Air or any other small cylinder bailout can provide is enough air to get you to a distant or inattentive buddy in a small compact package.

 

[markmud]

I got curious about the costs of it. I just looked up the cost of a Spare Air. $380 for a 6cft package!

Compare with -

19cft pony - $146 with valve

Above prices off DRIS’ website

Chances are someone has a spare reg they could use or could pick a used one up for not that much. Plus reg could be repurposed for something else. You can make your own stage kit for not that much.

High Marie13,

I agree with you. Below are links to Liesurepro.

A 6cf with regulator and button gauge is $330.00. A 13cf is $20.00 more.

Oceanic Alpha 7 SP5 Regulator
Catalina Pony Bottle Tanks, Yellow with Pro Valve
Highland Millworks Mini Tech Gauge

Plenty of other options out there beyond spare air.

markm

 

[JackD342]

My bottom line on the Spare Air is that is best for the recreational vacation diver that has never used a pony bottle, never intends to use a pony bottle with another 1st and 2nd stage, but wants to add an extra margin of error to their dive plan.

Here is a chart I created a while back to illustrate the benefits and the limitations of a Spare Air.
I start by taking the Submersible Systems statements regarding "estimated number of breaths at the surface" at face value, so that I have a less than arbitrary starting point. (57 for 3cf, 30 for 1.7cf) From there it is basic math, using formulas in Excel.
As an example, a 3cf Spare Air providing 57 breaths at the surface equates to 14 breaths at 100ft.
If that diver immediately starts an ascent to the surface when OOA, at a constant "ideal" rate that finishes at the surface with the last breath, no more and no less, then the 3cf would provide 23 breaths for the ascent.
Addendum: Spare Air surface breaths cited are based on 1.5L/breath.

Yes, there several assumptions and variables, but this provides a reference for the limit of what is possible under the best of circumstances. Probably anything less than ideal = less capacity.