Octo bungee logic?

[stuartv]

I'm about to take my OW class. I've been studying up on equipment to educate myself for future purchases.

One of the things I've seen recommended often is a BP/W setup with an octo on a short hose and a bungee necklace to hold the octo just below the diver's chin. In an OOA situation, the diver donates their primary 2nd stage and uses the octo for themselves.

Fine. But... The intuitive reasoning for having an octo seems twofold. One, so that you have a spare for your buddy, in case of OOA. And, two, so that you have a spare in case your primary fails.

So, that leaves me wondering why it would be okay to put the octo on a hose so short that it makes it difficult to share? What if you have a primary failure at the same time your buddy is OOA? Why not mitigate this risk (no matter how unlikely it is) by having the octo on a longer hose?

I realize that this scenario is probably considered so unlikely as to be considered not worth accommodating in your gear setup (otherwise, people wouldn't use the short hose for the octo). But, is it really? Or, I mean, am I interpreting all this correctly? Do second stages just NOT fail while in use? I.e. SO unlikely that you don't really allow for it? Or just so unlikely to happen at the same time as a buddy OOA?

My own experience in life suggests that a more likely time for equipment to fail is when you change how you're using it. So, intuitively, I would expect a second stage failure to be more likely when you start sharing it than for it to fail when you're just using it by yourself. I mean, just thinking about why that might happen, I could imagine being in cold water and starting to draw twice as much air through the second stage which seems like it would increase the chances of ice forming somewhere in the second stage. Or who knows what other reason. All this imagining and supposing is based on my knowledge of physics and book-learning about diving - not diving experience. Which is why I'm asking this question (above).

I did also read that it's not unusual for solo divers to dive with no octo and a pony bottle. Given that the diver could be too deep to safely use a pony bottle of 100% O2, I take that to mean that, essentially, second stage failure is simply not considered likely enough to worry about at all?

Thanks for any insight y'all can share.

 

[rivers]

Are you diving with three second stages?

 

[diver 85]

I use my octo(on a longer hose vs my primary) bungeed below my neck------IF a buddy 'needs my octo', I just pop it off the bungee loop & donate it, to him/her buddy(OR as wookie just described, if he/she 'steals' "MY" regulator--I know right where my 'other one' is, all nice & clean)......ie------I use my 'neck bungee' to simply 'hold' my octo in place below my chin, basically centered in my upper chest area....................

.EDIT----please note though, 75%+ of the time I dive solo--most 'buddies' don't like to follow a slow 'picture taker'---OR---my buddy is a 'fellow picture taker' & wants no part of my fins/body in their frame---
& vice versa,.lol.............,So, what I'm saying is most of the time my octo is for me/myself/ & I--this may affect the way you think of my octo situation......

 

[Wookie]

I dive with three second stages, have for thousands of dives.

An out of air diver is most likely to come after the regulator you have in your mouth, as they know it works, and it's got the air turned on. Real life isn't like OW class. The OOA diver will not get on their knees, give you a big OOA signal, and wait for you to pass them your reg. They will come from behind at light speed, rip your reg out of your mouth and take a big deep breath. if your octo is bungeed to your neck, you know where it is, you don't really need a hand to get it to your mouth, or at least I don't, tuck your chin, nudge the octo, and slip it in. Clear and purge while you're checking that your new best buddy is OK, and start your ascent. Even if you use a hand to help you slip it in, you can still grab the shoulder strap of your new friend and keep them from bolting with you. Or, you can fumble around looking for the thing that might have come out of it's holder, is full of sand, schmutz, and bristle worms, purge said schmutz, and find out that your new best friend has dragged you up from 100 feet to 20 feet before you know it.

I am a solo diver and instructor. I dive with a pony and octo. The pony isn't a deco bottle, as in, it isn't filled with oxygen, it's filled with gas appropriate for the dive. Usually 32%. If I need a deco gas, I'm likely in doubles with deco bottles.

Don't mix your terminologies. A pony is a smaller bottle with first and second stage and gage for emergency use if your main gas supply becomes unusable. A deco bottle is usually a slung bottle with an enriched O2 content for deco (or enhanced safety stop), usually requiring an advanced cert (Deco Procedures and Advanced Nitrox) to use. A stage bottle is a bottle filled with a deco or bottom mix that may be dropped off on the way into the dive (usually a cave or wreck) and "staged" for the return trip.

 

[Dhboner]

The additional hose length and potential for entanglement is the greater risk than the "simultaneous buddy out of air/primary regulator failure" scenario. Additionally, most divers who practice the DIR philosophy will never encounter an out of air situation...there is simply no excuse. Finally, your scenario also underscores why diving in a three man team is safer than the traditional buddy system.

 

[Lorenzoid]

Just BTW, but along the lines of terminology, I believe most people who dive with this configuration refer to the bungeed reg on the short hose as their "secondary" or "backup" rather than an "octopus" or "octo." The diver considers both of his regs to be equally functional.

 

[rhwestfall]

nicely put Frank.

To the OP, keep in mind, there are equipment configurations that change based on the dive conditions. If proper dive protocols are followed, air supply issues, for the most part, should be only an inconvenience that halts the current dive.

Realistically, if you want 100% safe, stay at home on the couch (but even then, a meteor may smash into your house).....

 

[grf88]

On a dive trip last year my bungeed second stage hose started leaking and I replaced it with a longer hose that I had with me. On the very next dive my son's first stage diaphragm failed in high current and after giving him my primary I went for my bungeed reg. Unfortunately the current had flipped longer hose over my head and the reg was now upside down causing my first breaths to be mostly water. Not fun in an emergency situation.

 

[TSandM]

A friend of mine refers to "Little House on the Prairie" scenarios. I never watched the show, but apparently the episodes often involved cascading catastrophes, almost beyond credibility. It's easy to construct LHOP scenarios in diving (and technical classes are often composed of them). But the reality is that major failures are uncommon, and cascading failures are extremely rare, IF the first problem is competently handled. Trying to build an equipment configuration that can handle anything can result in a setup of such complexity that the likelihood of a problem has actually been INCREASED.

In medicine, I say my job is to consider the worst possibility, and the most likely ones. The worst possibility in diving (or the only true emergency, as my friend Diver0001 says) is that someone has nothing to breathe. Set your kit up to deal with that well, which the long hose/bungled backup arrangement does. Then consider functionality in the more common settings: Freeflow? Switch to backup. Lost regulator? Switch to backup and locate lost primary. Broken or lost mouthpiece? Switch to backup. Easy!

If you lose a mouthpiece at the same time your only buddy runs out of gas, you are having a very bad day. I wouldn't arrange my gear to try to optimize my response to a one-in-a-million chance.

 

[Dirty-Dog]

I'm about to take my OW class. I've been studying up on equipment to educate myself for future purchases.

One of the things I've seen recommended often is a BP/W setup with an octo on a short hose and a bungee necklace to hold the octo just below the diver's chin. In an OOA situation, the diver donates their primary 2nd stage and uses the octo for themselves.

Fine. But... The intuitive reasoning for having an octo seems twofold. One, so that you have a spare for your buddy, in case of OOA. And, two, so that you have a spare in case your primary fails.

So, that leaves me wondering why it would be okay to put the octo on a hose so short that it makes it difficult to share? What if you have a primary failure at the same time your buddy is OOA? Why not mitigate this risk (no matter how unlikely it is) by having the octo on a longer hose?

I realize that this scenario is probably considered so unlikely as to be considered not worth accommodating in your gear setup (otherwise, people wouldn't use the short hose for the octo). But, is it really? Or, I mean, am I interpreting all this correctly? Do second stages just NOT fail while in use? I.e. SO unlikely that you don't really allow for it? Or just so unlikely to happen at the same time as a buddy OOA?

My own experience in life suggests that a more likely time for equipment to fail is when you change how you're using it. So, intuitively, I would expect a second stage failure to be more likely when you start sharing it than for it to fail when you're just using it by yourself. I mean, just thinking about why that might happen, I could imagine being in cold water and starting to draw twice as much air through the second stage which seems like it would increase the chances of ice forming somewhere in the second stage. Or who knows what other reason. All this imagining and supposing is based on my knowledge of physics and book-learning about diving - not diving experience. Which is why I'm asking this question (above).

You're overthinking it. The odds of a simultaneous OOA and primary reg failure are so miniscule as to not be worth bothering yourself with.

I think most OW student are still taught to donate the backup reg, and if that is your training, then it's probably not a good idea to have it on a necklace. On the other hand, the hose on most necklaced backup regs isn't really any shorter than the inflator hose, which is where you will find the backup reg for those who use Air II-type backup regs. If I absolutely needed to share my necklaced backup reg, I could. A good yank and I could pull it out of the necklace. Or I could slip it over my head. Or I could cut the bungee.

You're going to find that most people who have their backup reg on a necklace are using some variant of tech configuration. For example, their primary reg will likely be on a long hose, anywhere from 5-7' long. And they will be donating IT, not their backup. The idea here is to give the OOA (an stressed) diver a reg that you bot know is both (1) working and (2) has air. You, as the less stressed diver, then pop in your backup. Air sharing in this manner is quite unlike air sharing on a short hose (by short I mean normal rec diving length) and requires different training.

I did also read that it's not unusual for solo divers to dive with no octo and a pony bottle. Given that the diver could be too deep to safely use a pony bottle of 100% O2, I take that to mean that, essentially, second stage failure is simply not considered likely enough to worry about at all?

Thanks for any insight y'all can share.

You're confusing a pony bottle and a deco bottle. Deco gas might have any concentration of O2, up to 100%, depending on the depth at which the plan calls for switching to that tank. A pony bottle for a solo dive will likely be filled with good old air. Also, keep in mind that a pony bottle is not used to extend the dive. It's a bailout bottle in case your primary system fails. That's why they're used by solo divers. They provide a redundant reg AND a redundant gas supply.

One last thing. Second stage regulators are designed to fail in the open position. This means that the vast majority of failures will result in a free flow. You can breath from a free flowing regulator just fine.