pony bottles

[fire_diver]

This is the reality of pony bottles: when used by new divers, they provide a sense of security that makes the need to master skills less urgent and that tends to allow bad habits to propagate.

Wow, just like diving with a buddy, or with a group, or even with a divemaster provides a "sense of security". Hmmmm, maybe we should eliminate diving with others all together. Don't want to feel too secure underwater.

Along with providing a marginal bit of extra air, they encourage divers to take extra risks, counter-balancing whatever safety benefit they might have.

Marginal huh? So all ponys are nothing more than 1.5 spareair I guess. I never thought of 25% of my starting back-gas for emergency situations as "marginal" before. Thanks for opening my eyes.

They also require a modicum of skill to handle and that task loading also interferes with a new divers focus and learning ability.

Really? You mean, like taking 2 lbs of lead fom my left (where the pony is), and placing it on my right? Wow. that was hard. I don't know if any of the dumb newbies can handle that. Or maybe you were talking USING it. Lets see, pony reg is on my LEFT, away from any other regs I might use during the normal course of my dive.... "hey, somethings wrong. I better grab my octo. Crap, no air from it either. grab pony reg, place in mouth, breath. AHHHHH, thats better. I better signal my buddy and start my normal ascent." Yep, WAY to complicated to teach a newbie how to do that either.

Finally, for every problem that a pony bottle is supposed to solve, there is almost always a better answer and that is what divers, especially new divers, should be learning and practicing.

So tell us, oh sage of the sea, what the answer is. What is the OOA answer that is so much better than carrying a calculated amount of emergency air with it's own, seperate container, and seperate reg, and seperate gauge?

FD

 

[Darnold9999]

Always interesting seeing others decision processes.

I sling a 13cf pony and dive with it every dive. Is this enough gas to get me out of any emergency. Nope - no amount of gas will do that. It is however enough to bail from any dive I have done to date. However I could also CESA from all of those dives so that has always been my back pocket option, and one I am quite comfortable with. The pony adds a layer of safety on top of CESA as I can come up more slowly and it has added two or three minutes to my bottom time to solve a problem that I might otherwise not have had. Is it significantly safer than a single tank - not really, in the dives that I do it just adds an ability to bail at a more relaxed pace.

Are there options that are much safer, yes. Would I routinely dive doubles, no - I can barely carry a single tank and the lead I need to dive dry. But never say never. H valve is not available most places I travel - not going to bother. Will I carry a larger tank - 40 etc. Surface weight and space in the car becomes an issue so again, no.

However this is all in prep for solo diving - with a buddy they are carrying my backup gas so I never carried a pony at all until I started solo. Solo, I have no backup gas what I have is bailout gas only. At any point in the dive the pony will get me to the surface and give me, worst case, two maybe three minutes to solve a problem. If I need longer than that I am toast.

Risky yes, but not as risky as a single tank and I can live with that risk. I don't think that a larger tank - doubles, 40 etc. really add that much(in a non overhead environment - overhead is a completely different discussion). If the problem that prevents you from getting to the surface AND has killed your main supply can't be solved in a minute or two, likely adding more gas is just going to delay the inevitable.

My thoughts at this point in time - will see what more time and experience brings.

 

[ClayJar]

MikeFerrara: I understand your points in post #44, and they are good points. (I'd heard about the breathing stages first idea before, and it made perfect sense.)

The way I carry my pony (front, left, shoulder to hip), it is less susceptible to damage than my main supply, at least marginally (and only taking into account the type of diving I do). That said, although I make it a point to verify everything (breathe the reg, watch the full-size SPG, etc), I understand and must accomodate the possibility of failure. If I have a pony failure, it could as easily happen during an emergency as during a test. I have to be capable of dealing with that.

I have a pony for one reason and one reason only, and that reason is to allow for a "normal" ascent in the event of a backgas failure. If I go on the pony, the dive is over just as absolutely as if I had lost all gas, I just get to ascend more slowly. Perhaps it's overkill to have a pony just in case, when the whole point of it is to use it when I could make the surface without it, but that is what I wanted. I would be quite remiss, however, if I were to consider it failure-proof. It's a safety net which gives me a chance to lessen the impact of a failure.

Of course, there are many types of diving where a pony (as such) would be completely worthless. If I wouldn't plan the dive without a pony, I would be three kinds of fool to use the pony as misguided justification for doing the dive. There are obviously dives which cannot be planned without redundancy (doubles, twins, stages, or what-have-you), and without adequate training, planning, experience, and gear, I will certainly not be going anywhere near there.

 

[Web Monkey]

My opposition to pony bottles comes after several decades of diving and a desire to see others avoid some of the mistakes I've seen - and made. If you have a history of running out of air, no amount of extra air is going to solve your problem. Period. Divers like Ice9 need to address the root question - why are they running out of air? What is it about their skills, plan, attitude, and decision making capabilities that led them to be in a situation where they ran out of air? Adding more air to the equation only means they will be that much deeper or farther in when the run out the next time and that is not an improvement.

I've never run out of air (or even come close), but still bring a pony.

Aside from a little extra drag, nobody has ever come up with a valid reason why an extra 30' of air is a bad thing.

Think of it as independant doubles with non-equal tanks.

Terry

 

[Web Monkey]

Here is where you're wrong. A pony should NEVER, NEVER, NEVER be part of any gas plan. It's part of an escape plan. To say it's part of a gas plan, says it's going to be used to extend bottom time. Jeff was also making a joke. Since when is a first stage failure a saftware problem? Before you claim it doesn't happen, it happened to one of our SB members a week or so ago.

While not common, first stage failures do happen, and generally aren't subtle and generally involve big chunks of metal flying around. Other times the first stage is fine, but someone sucked the tank dry a month ago, it became contaminated and now there's gunk clogging the valve.

Considering that I have not yet learned how to extract oxygen from seawater, a pony is a second chance in case something bad happens.

I understand that my buddy should have my backup gas, but it's nicer if I have my own. Regardless of what anybody says, it still makes me happy to have an extra 10 or 15 minutes of air sitting right in front of me.

Terry

 

[ClayJar]

"No rule of thirds? That may be relevant when diving with a buddy as a source of redundant gas in case of gear failure at depth, although there are many cases where other gas plans are more applicable."

Not trying to throw stones, but I would love to hear the specifics of a situation where the rule of thirds is not relevant. I'm assuming that you never plan on taking any technical training.

MikeFerrara described some situations well. Diving quarries, springs, lakes, and rivers, I and my buddies often have plans which call for ascending anywhere. When you can throw a baseball from one side of the dive site to the other, there's not much point in being pedantic about ascending precisely where you descended.

(With our normal ring-around-the-quarry dive at one site, you start on the floor and basically ascend site to site around the quarry, with the sites at the end of the dive being around 15-20 feet deep. Normal things like "turn pressure" make no sense for that profile, and even rock-bottom is a moving target, as you can hit rock-bottom on the floor and be hundreds of PSI above rock-bottom by the next [shallower] site on the tour. For that dive, we have a set of checkpoints and pressures, and as long as we have excess gas above that plan, we can continue. If someday one of us is hoovering like there's no tomorrow and we hit one of the checkpoint pressures, we'll simply skip the next tour site and ascend to the next target level in order to be well on the side of excess gas.)

As for your assumption that I never plan on taking any technical training, I currently have no desire to enter that arena, however, I am constantly striving to pick up new information from all aspects of diving. I also make it a point to grok the concepts so that I will know where and when they apply. (Chemical engineering taught me well that understanding principles and equations is not enough; one must also understand their application.)

 

[sbushong]

That seems reasonable. The reason I mentioned technical training is that you will NOT have the option to toss out the rule of thirds in any sort of technical training program. For those who want to progress to technical side of the house, it makes sense to follow generally accepted technical diving practices early on. Otherwise, it is like trying to reinvent the wheel.

 

[Doc Intrepid]

So tell us, oh sage of the sea, what the answer is. What is the OOA answer that is so much better than carrying a calculated amount of emergency air with it's own, seperate container, and seperate reg, and seperate gauge?

Magic 8-Ball says:

"Don't go OOA in the first place."

"Turn the dive at a reasonable time or psi limit."

"Plan to be back at the boat with a gas reserve."

"Check gauges, yours + buddies to track consumption."

Those sorts of fundamental answers shouldn't be too complicated for new divers to grasp either.

Or, you could forget all about planning and execution and situational awareness, and drop $400+ on a bottle & regulator plus annual costs of VIPs/stickers and reg maintenance...so you have spare gas around and you don't need to do all that other unnecessary stuff...

 

[ClayJar]

Ah, I follow you now. (Fortunately for me, should I ever go down that path, I've worked for the government [public schools] long enough that I have no problem following any rule set where necessary, although many of ours are far more arbitrary than the logically-derived rule-of-thirds and its ilk. )

Incidentally, Doc, you forgot the kicker:

"Never have gear failures."

(I always get hung up on that one when I'm working on planning and theoretical situations.)

 

[robzr]

I looked at your calc page, but I don't agree with it's results. Ive run the calcs many times, and many times more explaining it to others, and your results show WAY more CF of gas needed than what I come up with. Care to explain your equations?

FD

Hi... the default parameters are very conservative (re: use a lot of gas), so you really need to review each one in order to get an accurate estimate. Examples:

- defaults to 30 seconds of initial bottom (non-moving) time - usually folks don't include this when calculating, so feel free to set it to zero, or give it a number you feel more accurately represents how long it will take you to start moving up once you switch to the pony. Since this time is spent at maximum depth, it has a very high DCR (Depth Compensated Rate) due to the water pressure, and therefore adds a significant amount of used gas to the totals.

- The RMV (SAC) rate was chosen to be 50% higher than that of the median scubaboard diver as explained in footnote #1. That means 50% higher air consumption than the reported median (.50 cfm)

- The excertion factor is yet another safety margin, which defaults to, again, another 50% of air usage. Feel free to turn this safety margin off if you think you would maintain your average RMV rate during a (possibly panic'd) ascent.

- Many folks are going to calculate at a ascent rate of 60 fpm all the way up, with no safety stop. If you are comfortable allocating only this margin to yourself during an emergency ascent, feel free to set those parameters to 0.

If you still have questions about the results, set "Show Every Breath" to "Yes", and you can follow the fairly simple math. Basically, you take the RMV rate, multiply it by the excertion factor, compensate for depth (atmospheres of pressure based on water density & depth), and you end up with the DCR (Depth Compensated Rate). Divide by breaths per minute and you have the surface volume of gas used in each breath. Factor in your ascent rate to figure your depth change, and there you have it.

By adjusting parameters, you can show someone making it up from 120 ft on a spare air:

http://cemu.org/scuba/ponycalc.php?...ge=60&verbose=1&excertion_rate=1.0&density=33

Or you can model that guy who guzzles 2.8 cfm and can't make it up from 132 ft on a 19 cf tank:

http://cemu.org/scuba/ponycalc.php?...ge=60&verbose=0&excertion_rate=1.0&density=33

and everything in between... The problem with these one-off calculations that people do (like when Scubadiving magazine shows someone safely making it up from 132 ft on a 6cf tank) is that it doesn't allow for any of these parameters which very HUGELY according to the situation and the diver.

Rob