max depth with an 80 cuft. tank

[AfterDark]

Do your rock bottom math, you can use an 80 but you sure don't get a whole lot of gas to use, or that you should use.

Assuming both divers have a sac rate of 1 cu ft and are diving at 100 ft where one diver has a catastrophic loss of gas.

- You would need 8 cuft at 100 ft assuming 1 minute to resolve a situation
- 10 cu ft from 100-50 ft assuming an ascent rate of 30 ft per minute which is 1.66 minutes needed.
- Assuming minimum deco from here you need 17.57 cu ft and a ascent to the surface totaling 5 minutes

This means you need 1420 psi in a AL80 to reach the surface in the event of a catastrophic gas failure of your buddys gas. So your turn pressure probably needs to be 1600-1700 because I don't think you can breath your tank down to 0.

I hope I did my math correctly, but I'm sure someone will point it out if I didn't.

I can make up a dive where I go to 100' swim around for 10 min without anything going wrong and surface with air to spare. I mean as long as were making things up.

 

[Superlyte27]

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)?

 

[UCFKnightDiver]

I can make up a dive where I go to 100' swim around for 10 min without anything going wrong and surface with air to spare. I mean as long as were making things up.

You do understand what rock bottom is right? The amount of gas it would take you and a buddy to get to the surface if one diver had a catastrophic gas failure AND you observed proper ascent speeds and saftey stops.

 

[Cave Diver]

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.

I would challenge the premise that "most of us" could make that ascent on a single breath of air.

 

[Superlyte27]

The average scuba diver, in average shape and decent health can make it. I didn't choose 100' arbitrarily. I've seen it done from much deeper. Try it next time you're at 100'. Take a deep breath at 100', leave the regulator in your mouth, but exhale during the entire length of your ascent. Make haste, this isn't a sight seeing ascent. Pretend you're really out of air...safely. I wouldn't steer you wrong.

 

[drbill]

Of course this assumes you have just taken a deep breath prior to catastrophic loss of gas in your tank. I had my Al 80 fail three minutes into a dive after I exhaled at about 75 ft. It was not easy to get to the surface (since I did ascend at just 60 ft/min).

With an Al 80 and a 19 cu ft pony bottle I limit myself to 150 ft.

 

[Diver Tim]

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?

Possible? Perhaps. My first choice in the event something goes wrong? No. I'll do my rock bottom calculations and dive accordingly, thank you.

 

[MXGratefulDiver]

The average scuba diver, in average shape and decent health can make it. I didn't choose 100' arbitrarily. I've seen it done from much deeper. Try it next time you're at 100'. Take a deep breath at 100', leave the regulator in your mouth, but exhale during the entire length of your ascent. Make haste, this isn't a sight seeing ascent. Pretend you're really out of air...safely. I wouldn't steer you wrong.

There is ... of course ... a HUGE difference between doing something in practice and having to do it in a real emergency. Most of that difference involves what happens to your physiology as a result of your mental state ... in other words ... STRESS!

WRT a 100-ft emergency ascent ... perhaps the average scuba diver, in average shape and decent health can make it ... IF they remain mentally calm and physically relaxed.

I contend that the average diver would not do so in a real OOA emergency ... because the average diver has never really had to deal with a real emergency, and likely has an inflated opinion of their own ability to deal with one.

Necessity may be the mother of invention, but reality will be the father who beats the crap out of you when you most need to deal with it ... this is why DM courses involve stupid exercises whose only purpose is to train you how to remain calm in a crisis ...

... Bob (Grateful Diver)

 

[David_57]

From 100ft theoretically maybe in a real situation not a chance

 

[Superlyte27]

I guess it depends on the mental stability of the Diver. Dive long enough and often enough, and everything that can go wrong will go wrong. Plan well enough, and you should never have to find out. Unfortunately, I've been diving alot longer than pony bottles have been popular.

And yes, I have had it happen to me, just after I exhaled. I sucked the air out of my BC and swam for the surface hard.

Early in my diving career, I tried to think of everything that could go wrong, and given that event, how would I overcome it. When those events happened in real life, it didn't take alot of thought to make the solution a reality.

When you are spearfishing with power heads 100' in Daytona, generally for our group of people, it's a solo endeavor. For several reasons. Someone can make sure the boat doesn't get stolen while I'm down. And, I'd rather the risk of no air, than somebody shoot me with a .357 underwater.

I still don't own a pony bottle. I dive a Single LP 95 spearfishing. It's DIN, so that takes away a little risk. And my regulators are kept in top condition. Sure, a HP hose could burst. I've had that happen too, but I know how to respond to these crisis, because I experienced most of them. Is a pony bottle safer? Absolutely! But for me, at 100', it's just not necessary.