Spare air VS pony? Why?

[Charlie99]

hambleto once bubbled...
I can see that it is a viable option for equipment failure, but wouldn’t proper planning, training, maintenance, and practice prevent normal OOA situations that are described on their website?

As far as taking it on airplanes for travel... would they allow that now?

I agree that the spare air idea is a good one. However, more and more I think about it, I am probably going to get myself and my GF a 20cf pony for each of us. Although I am very curious as to how I could travel with that. I am going to have to do a search and see what I come up with.

You are deluding yourself if you believe that proper maintenance eliminates the possibility of equipment failure. Reduces it, yes. Eliminates the possibility; no.

FAA regs say the cylinder needs to be less than some low pressure, 41psi IIRC. On a practical basis, it's better to remove the valve completely since the airline has no reason to believe your claim as to what the pressure it.

In spite of my playing devil's advocate in my previous post, I recommend that you hold off on getting a pony for a while. The real solution to having a good redundant air source is to have a good, trusted buddy close by. For non-overhead dives down to the 100ish sort of depths I'm content with the backup of my buddies air.

You might also practice ESA a few times and learn how to do it properly. I've done nice slow ESAs from 85' and 90' --- the key is to keep your airway open and let the excess air bubble out rather than humming, going aaaah, or blowing bubbles.

The spare air has a very narrow range of applications where it's useful, but at the same time, it's not the horrible, dangerous thing that many make it out to be.

---------------------------

I occassionally see Spare Airs on dive boats. Usually I casually ask the diver "how much air; how long does it last?".

The last diver promptly answered "2.7 cu ft. At least 10 or 15 breaths at depth". Others have been completely clueless.

Like any tool, it can used or abused.

 

[dc4bs]

hambleto once bubbled...
Charlie99, those are all viable reasons for the spare air. If I can ask a question though, is that 3cf of air, just 3cf of air that you are taking out of your primary? I can see that it is a viable option for equipment failure, but wouldn?t proper planning, training, maintenance, and practice prevent normal OOA situations that are described on their website?

As far as taking it on airplanes for travel... would they allow that now? I have to take my shoes of to get through the security at an airport. I am sure if they saw that in my bag I would probably be naked in a back room getting a body cavity search!

I agree that the spare air idea is a good one. However, more and more I think about it, I am probably going to get myself and my GF a 20cf pony for each of us. Although I am very curious as to how I could travel with that. I am going to have to do a search and see what I come up with.

Hi

I have taken 40cf ponys on airplanes several times. Just completely drain the tank and then carefully remove the valve and put it in a clean ziplock bag and wrap it in bubblewrap. Don't touch anything from the threads down, especially if you have the pony cleaned for nitrox.

VERY IMPORTATNT: Get a clean plastic "screw in plug" ffrom a diveshop if you don't have the plug that came with the new tank (pre-vavle installation) so you won't get anything in the tank while traveling.

If the pony is nitrox clean, then once you get home, consider having the tank cleaned again if you have the least doubt that it could have gotten anything in it or that the "local" fill stations might not have been quite "up to par".

I pad the tank with my wetsuit and put it in the bottom of my biggest suitcase with the valve and my fins nested in the clothes towords the top.

2nd suitcase or UNMARKED divebag contains the rest of the dive gear. You don't want to travel with your gear in a duffel with a big SCUBA logo on the side... It just might "dissapear" enroute...

 

[String]

Taking the information off the manufacturers site for the "300" version.

200 bar pressure

0.42l water capacity

Gives a total of 84l air.

Assume a diver under a high stress situation could use up to 25l/minute at the surface.

Ok, thats 3.3 minutes of air at the surface.

Lets take that down to 10m (30ft).

You're looking at only about 90 seconds air.

Right. Something happens at 20m (65ft)

Down to about 1 minute of air.

100ft (30m). Oh dear, 48 seconds.

If you're tangled at depth it'll take a lot more than that to free.

Even given the lower consumption as you rise through the water column you havent got much time.

Ascent rate assumed to be about 10m/minute (most tables want this). Whoops, from 30m you're out of time.

From 20m you're out of time

From 10m you're just about OK.



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Lets look at the "original" version:

0.28l @ 200bar giving 56l in total.

Again assuming 25SLM rate, thats 2.25mins surface.

1.1 minute at 10m

45 seconds at 20m

30 seconds at 30m

Taking standard ascent rates into it if you have to get up on spare air theres a very high chance you'll get bent giving the speed in which you'll need to come up.

------

Lets do the same maths for a 3l / 232bar pony

696l of air in total. At 25SLM thats 27 MINUTES at the surface.

Near 14minutes at 10m

Near 9 minutes at 20m

Near 7 minutes at 30m

Now this is enough to ascend normally and complete (short) stops if neccesary, at the very least perform a decent safety stop.

The cost is slightly LESS than a spare air.

---


From those figures spare air might be of use if you're snorkelling, otherwise not.

For that money a poney is a FAR better invention.

Things like spare air were developed to give flight crews a few seconds to evacuate crashed aircraft, NOT for them to go scuba diving with.

A small redundant air source such as a pony is IMHO a great idea. A stupidly small resource that doesnt carry enough to get you to the surface even from shallow dives however is a waste of money.

7 minutes or 30 seconds for the same price. I know which id prefer under 100ft of water.

Note:- its 0130am so my maths could be totally wrong.

 

[drbill]

I have several friends (and two occasional buddies) who dive with Spare Air instead of a pony. I tried to get them to see the benefits of a pony (cost, easy fills, ability to do slow ascent and safety stop, etc.) before they purchased them. They prefer the Spare Air over the pony. Why? Simply because it is so small and inobtrusive.

My mileage does vary. I use a 13 cu. ft. pony.

Dr. Bill

 

[GQMedic]

Pony bottle... The "why" is: "More air"! And that speaks for it's self.

 

[hambleto]

In this case, more is clearly better. Thank you. The math shows it all.
Ben


Although a spare air looks like a cool pool toy.

 

[jviehe]

Now, lets do the math with no Spare Air (1.5cu or 3cu).

Ok, at the surface you have 0cu.

so at 33ft, you have 0cu, which you can go through in 0 secs.

ok, 130ft, 0cu, 0secs to breathe, you're dead.

I rest my case. In an emergency a 3 cuft SA is enough to get you from 130ft to the surface. Its been done.

 

[String]

jviehe once bubbled...
I rest my case. In an emergency a 3 cuft SA is enough to get you from 130ft to the surface. Its been done.

However for less money you can get a 3l pony and have 6 times as much air which not only will it get you to the surface, will enable you to get there without getting bent.

I cant see why anyone would pay more money for a vastly inferior solution.

 

[drbill]

Hambleto- I agree 100% with Charlie99, especially after my recent incident. My reg had been rebuilt 4-5 weeks earlier and my tank VIP+'ed a few weeks after that. Despite this regular maintenance, the system failed to deliver air at 70 ft. No one has discovered the reason although debris in the tank (from a fill?) is suspected.

Dr. Bill

 

[Boogie711]

I rest my case. In an emergency a 3 cuft SA is enough to get you from 130ft to the surface. Its been done.

Remind me to never use YOU for a lawyer if that's called resting your case.

You know what else has been done? Divers have embolized (sp?) because they held their breath on a free ascent from depth. Divers have been bent, too... is that a good thing? I mean, after all, it's been done and some are still alive, right???

Or put another way:

I'm going to wear a piece of string instead of a seatbelt tonight. In an accident, a piece of string will keep you inside. It's been done.

I'm going to snowboard this winter using only a cafeteria tray in my boxershorts. That's all I need to get downhill. It's been done.

I'm going to rock-climb without ropes or a safety harness. In an emergency, I just need to hang unto a tree branch, that will keep me alive. It's been done.


Need I continue? Or do I "rest my case?"