Bailout Bottle Test

[Spectre]

I see uses for spare air..... kayaking, freediving maybe... but -definately- not scuba. There are so much better ways to handle the situation at... what... $100 more? In my case I was upgrading my reg anyway, so a pony bottle was actually -less- then spare air.

It's funny you mention that Rodale's article. I flipped through that mag the other weekend, read the article on ascents by John Francis, and thought... hey... rodales has somethin' pretty good. I then flipped forward a few pages and saw that there wasn't a shift in the universe, they managed to balance it out to be at their typical level of quality.

And yes... I don't trust -anything- in Rodales that involves products.

 

[Snowbear]

What are the use cases where people actually have used pony bottles or spair air?

Here's one
http://www.scubaboard.com/showthread.php?s=&threadid=16008

 

[geraldp]

The following recommendations are for a diver in control
13 cuft is adequate for about 80 fsw, 19 cuft about 100, and 30 cuft for about 130.. someone with a higher RMV would have to adjust these sizes.

Hmmm. I read the Rodales article and decided to go for a pony bottle. I figured if the Rodales's diver could do an emergency ascent from 132 feet with a 6 cu.ft. bail-out bottle then a 13 cu. ft. pony would be about right. I just picked it up yesterday. I wish I had read your post. I suspect a 19 cuft bottle wouldn't have been that much more.

As other posters have said, there's lots of reasons to get a pony/bail-out bottle. The one experience I had was when a buddy simply ran short on air on a 90 foot dive in Cozumel. He hadn't been monitoring his SPG. He was down to about 300psi when he started his ascent, and he had to share air at the safety stop. No harm, but the DM yelled at him for at least 15 minutes when surfaced. If I ever did anything that stupid I figured I could at least draw from my pony and thus save my self a razzing from everybody else on the boat (especially the DM).

Jerry

 

[padiscubapro]

Hmmm. I read the Rodales article and decided to go for a pony bottle. I figured if the Rodales's diver could do an emergency ascent from 132 feet with a 6 cu.ft. bail-out bottle then a 13 cu. ft. pony would be about right. I just picked it up yesterday. I wish I had read your post. I suspect a 19 cuft bottle wouldn't have been that much more.

As other posters have said, there's lots of reasons to get a pony/bail-out bottle. The one experience I had was when a buddy simply ran short on air on a 90 foot dive in Cozumel. He hadn't been monitoring his SPG. He was down to about 300psi when he started his ascent, and he had to share air at the safety stop. No harm, but the DM yelled at him for at least 15 minutes when surfaced. If I ever did anything that stupid I figured I could at least draw from my pony and thus save my self a razzing from everybody else on the boat (especially the DM).

Jerry

When you start to dive in a drysuit,, a 6 cuft bottle is the perfect size for an independent drysuit inflation system..

 

[-hh]

The real argument to have here I think isn't over the math of how much air you use at a given depth, but in accident analysis.

Accident analysis does play a part, in determining what are the most likely scenarios in which the capability would be needed...basic variables like depth, time spent on bottom, deco obligation, etc.

The "math" really is nothing more than an implimentation of the contingency planning process. It plays its part based on the establishment of reasonable estimates of the contributing variables so that the capability can be "sized". Afterall, if size wasn't somehow an issue, then we would simply all carry doubles.

Here's a post I made a few days ago...

Saw it the first time. Overall, the things I noticed were the bottom times: the first had zero time which is clearly excessively liberal, whereas the second had 3 minutes which is quite conservative for such contingency planning.

I can agree with the two illustrated ascent rates as well as adding in a safety stop, as my philosophy is that you plan for a safety stop, even though it might be aborted because of higher consumption rates elsewhere.

IMO, your 1.5 SAC is reasonable for an experienced diver (IMO this was the factor that wasn't adequately considered in Rodale's "test", as it explains the optimism in their reported values). Even though its ~3x my nominal SAC which would probably make it a reasonable starting point for estimating my increase in SAC due to stress from an OOA type event, it still however some risk, because if we refer to sources such as the USN Diving Manual, we can find that under very heavy labor, a diver's SAC can actually be as high as 3-4 ft^3/min! But we must make some compromises in our conservatism somewhere.

FWIW, here's another analysis; it was done around a decade ago:

http://scifi.squawk.com/scuba.html#PONY_HOWMUCH

Note that it uses 60ft/min ascent rates throughout, and assumes only 30 seconds on the bottom ("bottom stop").

If we don't want to do the detailed math, we can make a very rough re-estimate for today's 30ft/min ascent rate by taking any value on the left side and multiplying it by 1.7 The result is an approximation of what the calculated value would be for a profile of 30sec@bottom, 30fpm ascent and this chart's perscribed standard safety stop (3min@15ft@half SAC). It pretty much confirms that you're going to need a SAC well under 0.5 to get up from 80fsw on a Spare Air...my swag is that 0.35-0.40 is what would be required.



-hh

 

[geraldp]

When you start to dive in a drysuit,, a 6 cuft bottle is the perfect size for an independent drysuit inflation system..

I just bought my first drysuit last weekend, in fact. Now that I have a 13 cu ft pony I'll probably use that for its intended purpose. I do have a 6 cu ft alu. bottle that I had bought for paintball It's rated to 3000 psi... Maybe I should look into converting that into an Argon bottle for drysuit inflation.

 

[CJ_Albertson]

...
Here's a post I made a few days ago though in the last pony/spair air argument thread which has a couple of tables of gas consumption to reach the surface from a given depth, given some different assumptions:

http://www.scubaboard.com/showpost.php?p=553252&postcount=265

I just read your calculations. Question: Could you not acend from 10 feet using zero air? At 60fps it is only 10 seconds.

There is likey some depth (20ft??) where most divers would have a
good chance of making a swimming acent with zero air. To prevent
drowining you only need to get to that depth not all the way to
the surface.


I'm not on one side of this argument or the other. I think it's
claer thar any reserve air supply is better then none and more
is better then a little

 

[-hh]

(sorry for the delay...business trip)

I just read your calculations. Question: Could you not acend from 10 feet using zero air? At 60fps it is only 10 seconds.

Yes, but the shallower you are, the more likely and dangerous a breath-hold is for an Embolism risk.

There is likey some depth (20ft??) where most divers would have a good chance of making a swimming acent with zero air. To prevent drowining you only need to get to that depth not all the way to the surface.

Yes, but since the purpose of this exercise is to figure out if "A" is better than "B" and at what trade-offs, the working question is what product will get you _all_ the way to the surface and with the least NDL violations. As such, stuff like running out at 10fsw but surviving anyway are trademarked as "Bad Ideas" when we're in the contingency planning stage.

In other words, it may happen out in the Real World, but to plan for a second failure such as this is a horribly bad thing to actually plan to occur.

I'm not on one side of this argument or the other. I think it's claerer thar any reserve air supply is better then none and more is better then a little

Most of my perspective boils down to the question of if you're going to spend some money to address this risk, how much capability does X number of dollars really buy. In this context, two bottles at the same price point (and "all other factors generally equal") should generally favor the bigger capacity bottle.

Another way to look at this same basic problem is to accept each system for what its limits are, and with the perspective of all competing products, then subjectively declare what its value is worth in the overall scheme of the total marketplace. For example, by this method it is my personal opinion a Spare Air is only worth ~$50. As such, its not that a SA is ultimately "good" or "bad"...its merely overpriced, so I would say that it is poor value!


-hh

 

[crpntr133]

But a lot of folks buy a pony bottle then never use it, because if you go on a trip, it you must disassemble it to fly with it, and its added weight. Would probably be better to have something lightweight and be willing to carry it, than to carry nothing because of the inconvenience.

Happy diving.

Haven't read this entire post word for word so pardon me if I missed the following information.
With the new restrictions with flying, you can't take a pony bottle. Even disassembled TSA doesn't allow them anymore. I don't know about a SA but I would think it would fall into the same catagory.

 

[spog]

Haven't read this entire post word for word so pardon me if I missed the following information.
With the new restrictions with flying, you can't take a pony bottle. Even disassembled TSA doesn't allow them anymore. I don't know about a SA but I would think it would fall into the same catagory.

But that's only for the States.

Move to the rest of the world and they're a bit more sensible. I spoke to China Air in HK and they told me that if I wanted to take a tank on their planes, I should call the cargo dept to arrange for it to be inspected (to check it is empty) before checking in.

spog

PS I don't hear PADI campaigning on your behalf about this.