max depth with an 80 cuft. tank

[miketsp]

..snip..

Assuming both divers have a sac rate of 1 cu ft

..snip..

This seems pretty pessimistic for divers venturing below 80ft.

My SAC on a calm drift is around 0.3, on a typical reef dive around 0.4 and the worst cases I found in my log, fighting current all the time around 0.7.

This is only slightly better than the averages reported on SB in various polls
example:
http://www.scubaboard.com/forums/basic-scuba-discussions/296993-sac-rate.html

and I'm just a little better than the average among the groups of (fairly experienced) divers I normally travel with.

While I can imagine a momentary SAC increase following an OOA while you get on to your buddy's spare, I just can't imagine consuming 1 cu ft/min for the whole 7.66 minutes of scenario you sketched out.

The number of situations that will give you a true OOA are very few, the only ones that come to mind are a blown cylinder neck ring or a missing internal cylinder valve tube allowing dirt to enter and block the tank valve while diving inverted.
Practically all the other situations that I've ever seen will allow you to get at the remaining gas even if it means breathing off the cylinder. (I'm excluding actually running out of gas through incompetence!)
Even when I experienced a blown 1st stage o-ring/tank valve I was able to breathe off the reg for a good couple of minutes.

So we all know that Murphy's out to get us and yes, I could just have a blown neck ring at exactly the critical moment when I'm about to start my ascent, but heck I could also get injured seriously with about the same probability in a lot of other sports.

The dive tables I carry in my BC have rock bottoms previously calculated and penciled in based on just under 0.5 for myself and my buddy. The resulting figures let me (and my buddy) enjoy a lot of safe diving on AL80s below 80ft.

 

[miketsp]

so what do you do when a HP hose blows and you are solo at 100 feet with no poony bottle?

Simple, continue the dive, if you really want you can breathe off it.
The HP hose has a pin-hole limiter and we were taught to do this in training.

We were taught to cut the HP hose instead of the LP hose in case of a total 2nd stage failure and no spare.
The LP hose will of course give a much higher flow rate.
Unless the LP hose is broken actually at the valve just kink it to control the flow.

 

[UCFKnightDiver]

This seems pretty pessimistic for divers venturing below 80ft.

My SAC on a calm drift is around 0.3, on a typical reef dive around 0.4 and the worst cases I found in my log, fighting current all the time around 0.7.

This is only slightly better than the averages reported on SB in various polls
example:
http://www.scubaboard.com/forums/basic-scuba-discussions/296993-sac-rate.html

and I'm just a little better than the average among the groups of (fairly experienced) divers I normally travel with.

While I can imagine a momentary SAC increase following an OOA while you get on to your buddy's spare, I just can't imagine consuming 1 cu ft/min for the whole 7.66 minutes of scenario you sketched out.

The number of situations that will give you a true OOA are very few, the only ones that come to mind are a blown cylinder neck ring or a missing internal cylinder valve tube allowing dirt to enter and block the tank valve while diving inverted.
Practically all the other situations that I've ever seen will allow you to get at the remaining gas even if it means breathing off the cylinder. (I'm excluding actually running out of gas through incompetence!)
Even when I experienced a blown 1st stage o-ring/tank valve I was able to breathe off the reg for a good couple of minutes.

So we all know that Murphy's out to get us and yes, I could just have a blown neck ring at exactly the critical moment when I'm about to start my ascent, but heck I could also get injured seriously with about the same probability in a lot of other sports.

The dive tables I carry in my BC have rock bottoms previously calculated and penciled in based on just under 0.5 for myself and my buddy. The resulting figures let me (and my buddy) enjoy a lot of safe diving on AL80s below 80ft.

It was just a figure to use in planning, also keep in mind your sac rate may/probably will be elevated, and also not everyone's sac rate is great, thus I used 1 cu ft which I agree is pretty conservative but *shrugs* I usually don't use 1 cuft in planing either but on the forums I figured it was prudent.

 

[wedivebc]

so what do you do when a HP hose blows and you are solo at 100 feet with no poony bottle?

You have about 10 minutes to make it to the surface. HP hose does not flow much air since most regs use a pinhole oricice for the HP port

 

[PfcAJ]

10 mins, assuming the tank was full.

 

[Superlyte27]

so what do you do when a HP hose blows and you are solo at 100 feet with no poony bottle?

Okay, earlier today... I became a little bit torn on exactly how much info to present. You see, there's PADI's guidelines and then there's our experience. For instance, today in class I watched the ascent of 60'/minute on PADI's DVD. I chuckled a bit.

Guys, if you are 100' and an HP hose blows with no pony and no buddy. It's simple. Head for the surface. It's a no brainer.

 

[Superlyte27]

You have about 10 minutes to make it to the surface. HP hose does not flow much air since most regs use a pinhole oricice for the HP port

This is correct. But, the HP hose I lost recently was an o-ring failure. I lost 1k air in less than a minute.

 

[dktexas54]

You guys do realize that for most of us. We can make a free ascent in open water from 100' to the surface on a single breath right? The navy does it even deeper than that.

Do the math. The average lungs in a adult male hold 5 liters of air. Every thirty three feet that amount of oxygen is doubled as you ascend. You can exhale the entire ascent and never run out, if you do it right.

Am I telling secrets no one knows (or shouldn't know)?

Far be it for me to question your experience with over 5,000 dives. You have obviously done things correct to still be here. My thread was started to help those of us much less experienced than you learn from those on SB. I can't imagine a new diver with 10 dives in lakes going to 100' and in an emergency, figuring it out and ahhing appropriately to the surface. Many fellow divers probably tried what you say is possible, but it did not work out for them. I urge you to share your knowledge so the young divers reading this thread will think and perhaps remember what was posted here and say how it saved their life one day! That would be a blessing for us all. :kiss2:

 

[AfterDark]

Oh, so we don't drown but now we're bent?

Are you telling me to get bent? Who's we? I dive alone. Over 1900 dives with over 1300 hours bottom never bent. Doing something right I suppose.

 

[dumpsterDiver]

This is correct. But, the HP hose I lost recently was an o-ring failure. I lost 1k air in less than a minute.

Wow, that definitely gives us some insight into the situation.