Emergency bailout strategies for recreational diving

[Centrals]

The price you must pay includes the inconvenience of periodically reaching back to open and reclose the isolation valve to equalize cylinders, greater hassle breaking them back down to singles, and introducing two potential failure points on the valve (where the plug or isolation valve install) compared to a dedicated K-Valve. Both methods allow using the second cylinder as a hard reserve… sort of a higher volume and much more reliable J-Valve.

Side-mounting would eliminate the inconvenience of reaching back.
BTW, I am not side-mounted trained.
Given choice, i would prefer a twin set with manifold than a single.

 

[Centrals]

Double posted

 

[Akimbo]

Side-mounting would eliminate the inconvenience of reaching back…

Sidemount is an option for a pony bottle, but that quoted paragraph was describing the tradeoff using manifolded doubles with an isolation valve and the progressive equalization technique.

 

[Akimbo]

...Akimbo, your points about chambers are interesting as I remember my "slap the head" moment of understanding the context that USN tables were used. Most of those dives had a chamber on station and there was an acceptable risk of DCS symptoms developing - they expected it...

Good point, but there is another factor in the Navy tables that compensates in our favor -- the square or working diver's profile. Navy tables, and the way the vast majority of dive stats were collected, are based on the diver spending virtually their entire bottom time within a few feet of their maximum depth. A recreational diver's meandering profile often results in a significant percentage of their bottom time being much shallower than their max. That is huge and helps explain how the Navy's high acceptable hit rate had been lower in recreational diving for so many decades. The advantage is becoming increasingly academic now that computers credit us for that profile.

My current thinking has me using the RGBM algorithm at my age. I still use Navy tables for the reality check, but the computer hasn't been so far off that I didn't trust it... yet anyway. Statistically I am so far overdue for my first mandatory chamber ride it is confusing -- recreational or commercial.

 

[DaleC]

Great point about the profiles Akimbo. I'm going to remember that for further discussions.

I'm quite interested in progressive equalization and wouldn't mind hearing how you set up your rig (where your spg is mounted particularily) and the way points for equalization/surfacing you use.

"I am so far overdue for my first mandatory chamber ride it is confusing — recreational of commercial."

No use complaining about good luck

 

[rx7diver]

Statistically I am so far overdue for my first mandatory chamber ride ...

Akimbo,

You're probably tongue-in-cheeking here, since theoretical probabilities don't work this way. In fact, depending on how you believe probabilities should be interpreted, the fact that someone has completed 100 (say) non-repetitive dives without incidence of DCS suggests his likelihood of experiencing DCS in his next 100 (say) non-repetitive dives either (1) hasn't changed or (2) has actually decreased. Theoretically, of course. AOTBE. A lot of divers don't understand/appreciate this.

Okay, now back to the OP's topic ...

Safe Diving,

Ronald

 

[Akimbo]

Great point about the profiles Akimbo. I'm going to remember that for further discussions…

Don't forget the rest of the downside. All male, physically fit (though nothing like SEALs), mostly 20-35 years old, good health verified by an annual diving physical, and diving supervisors that don't hesitate to bump them to the next table if conditions suggest it. There are (were?) alcohol issues that probably favor sport divers.

… I'm quite interested in progressive equalization and wouldn't mind hearing how you set up your rig (where your spg is mounted particularily) and the way points for equalization/surfacing you use. …

Here are some links to previous posts:
Post 41:
http://www.scubaboard.com/forums/ad...ly-reach-doubles-valves-help.html#post6011977

Post 34, SPG use
http://www.scubaboard.com/forums/ta...-isolation-manifold-question.html#post6090785

Progressive Equalization without redundant regulators
http://www.scubaboard.com/forums/tanks-valves-bands/394714-custom-manifolds.html

Way-points vary from “leave bottom now” on the first equalization to 6-7 equalizations depending on the conditions and dive profile. I may also plan for the first equalization at half full if I am shooting for something closer to the rule of thirds. I gave an example in Post 41 I probably use more than most.

… "I am so far overdue for my first mandatory chamber ride it is confusing -- recreational of commercial."
No use complaining about good luck

Not exactly complaining. Fortunate genetics maybe, lucky certainly, good looking definitely not, good living… not so much. I think somewhere between concerned and scared is more accurate. I think I will keep my DAN insurance paid.

 

[Akimbo]

…You're probably tongue-in-cheeking here, since theoretical probabilities don't work this way. In fact, depending on how you believe probabilities should be interpreted, the fact that someone has completed 100 (say) non-repetitive dives without incidence of DCS suggests his likelihood of experiencing DCS in his next 100 (say) non-repetitive dives either (1) hasn't changed or (2) has actually decreased. Theoretically, of course. AOTBE. A lot of divers don't understand/appreciate this….

Good point. Partly tongue-in-cheek and partly accepting reality.

• I am a geezer now
• Have made enough dives to possibly alter my physiology :shocked2:
• I often make repetitive dives beyond recreational limits where tables and algorithms have less data and more variables to support conclusions
• The denominator (number of dives) has gotten large enough that a lot of statistical variables might apply — probably not in my favor
• Sometimes, your number is up and it’s time to pay for that chamber ride instead of getting paid for it. :depressed:

However, I really like option 2, “has actually decreased”

BTW, AOTBW???

 

[rx7diver]

BTW, AOTBW???

AOTBE = "All Other Things Being Equal," which means "provided nothing substantive has changed."

 

[RonFrank]

I use a CF19 as a bail out bottle when I'm diving solo or deep. Not as nice as doubles, but it gets you to the surface with a SS. That works for me. I have not needed it but its nice to have when you run across those same Ocean buddies.