Is there a valid reason for a pony bottle

[grf88]

Gotta push those limits!

Hard core scuba diver!

I would call doing a CESA from any more than 30 feet or so pushing the limits, not diving to recreational depths with redundancy which also can be hardly considered hard core. I also understand that it would take professional deprogramming to have you change your mind so I will not bother to try.

 

[doctormike]

These are not sudden gas losses, they are sudden leaks. Even using a small aluminum 50 as in the video I posted, you would have enough time to make an ascent and still breathe on the way up.

81 seconds for an AL80 with 3000 PSI to empty, as per the test at Advanced Diver magazine. That's about 1 CUF/second.

Let's take a common scenario - you are at 80 feet at the end of your dive, ready to ascend, at NDL=0. Your tank has 1000 PSI, so about 27 CUF. That's 27 seconds to empty.

You want to ascend with that nitrogen load at 175 FPM? Not me.

Let's use the data that you feel makes your case better, from the guys at the Lake Hickory Scuba Marina. 50 CUF in 3 minutes. So 0.3 CUF/second. AL80 at 80 feet, 1000 PSI=27 CUF. 90 seconds to empty, so a 53 FPM ascent, with no safety stop.

Even assuming that the Advanced Diver data is wrong and the Lake Hickory guys are the NEDU of North Carolina, you are making the case for an N2 loaded ascent at nearly twice the widely accepted safe ascent rate for the past 20 years, AND for blowing off the safety stop. And even THAT is assuming that you INSTANTLY figure out what is happening and start your ascent.

You want to do this why?

For my dives, by the time I am at 50 cu feet of gas left, I'm already at or near the anchor and could ascend at any time. That's only if the leak occurs near the end of the dive. Any time earlier, I would be able to make an even slower ascent.

For my dives, I dive from the shore, so there is no reason why anyone would need a dive boat...

 

[MaxBottomtime]

81 seconds for an AL80 with 3000 PSI to empty, as per the test at Advanced Diver magazine. That's about 1 CUF/second.

Let's take a common scenario - you are at 80 feet at the end of your dive, ready to ascend, at NDL=0. Your tank has 1000 PSI, so about 27 CUF. That's 27 seconds to empty.

You want to ascent with that nitrogen load at 175 FPM? Not me.

Let's use the data that you feel makes your case better, from the guys at the Lake Hickory Scuba Marina. 50 CUF in 3 minutes. So 0.3 CUF/second. AL80 at 80 feet, 1000 PSI=27 CUF. 90 seconds to empty, so a 53 FPM ascent, with no safety stop.

Even assuming that the Advanced Diver data is wrong and the Lake Hickory guys are the NEDU of North Carolina, you are making the case for an N2 loaded ascent at nearly twice the widely accepted safe ascent rate for the past 20 years, AND for blowing off the safety stop. And even THAT is assuming that you INSTANTLY figure out what is happening and start your ascent.

You want to do this why?



For my dives, I dive from the shore, so there is no reason why anyone would need a dive boat...

You are assuming a worst case scenario only, but let's go with that. 60 per minute was fine for decades before the training agencies made things even more conservative. If for some unknown reason my low pressure hose blew and I was unable to pinch it or feather my valve I would ascend at whatever rate would get me to the surface. I and thousands more dived for years before anyone heard of a safety stop. If I was making a dive to my ndl I would either be using doubles or it would be a long, shallow dive. I would not be at 80 feet on a single tank with no ndl. I try not to put myself in situations where I would need a buddy or a redundant tank to escape.
Also, that 0.3 CUF/second is from an aluminum 80 at 80 feet. I wouldn't be staying at 80 feet, so the remaining air would last a bit longer. Either way, I'm not going to place myself in a situation like that.

 

[doctormike]

You are assuming a worst case scenario only, but let's go with that. 60 per minute was fine for decades before the training agencies made things even more conservative. If for some unknown reason my low pressure hose blew and I was unable to pinch it or feather my valve I would ascend at whatever rate would get me to the surface. I and thousands more dived for years before anyone heard of a safety stop. If I was making a dive to my ndl I would either be using doubles or it would be a long, shallow dive. I would not be at 80 feet on a single tank with no ndl. I try not to put myself in situations where I would need a buddy or a redundant tank to escape.
Also, that 0.3 CUF/second is from an aluminum 80 at 80 feet. I wouldn't be staying at 80 feet, so the remaining air would last a bit longer. Either way, I'm not going to place myself in a situation like that.

0.3 CUF/s was from your video. AL50 drained in 3 minutes. 50 CUF / 180 seconds = 0.3 CUF/s. In a swimming pool.

Unlike a free flowing second stage, which loses gas faster as ambient pressure increases, a cut LP hose loses air at the same rate in shallow and deeper water, at least in the 0 - 232 FFW ranged tested in the study I quoted.

But fine. Your plan seems to be to hope that the Advanced Diver numbers are wrong because you want to prove that a pony bottle is unnecessary, and to just ascend loaded with N2 at 60 FPS with no safety stop.

Hey, if 60 FPM with no safety stop was fine for decades, is that what you do now? If not, why not?

Having spent time in a chamber, I prefer to always be able to make a safe ascent...

 

[MaxBottomtime]

But fine. Your plan seems to be to hope that the Advanced Diver numbers are wrong because you want to prove that a pony bottle is unnecessary, and to just ascend loaded with N2 at 60 FPS with no safety stop.

I never said a pony was unnecessary. You and a couple of others in this thread have been lashing out at anyone with a different opinion and misstating facts. If you want to use a pony bottle, go ahead. I choose not to because I don't put myself in situations where one would be needed. I'd rather avoid trouble than carry more gear "just in case".

 

[doctormike]

I never said a pony was unnecessary. You and a couple of others in this thread have been lashing out at anyone with a different opinion and misstating facts. If you want to use a pony bottle, go ahead. I choose not to because I don't put myself in situations where one would be needed. I'd rather avoid trouble than carry more gear "just in case".

I don't think that I'm "lashing out". It's a conversation. Anyone can leave it at any time if they get bored or offended. I still think that it's interesting, which is why I'm bothering to type this.

New divers read these threads, so that's why I'm making these points. Not everyone dives in the same environment. Sorry if I misunderstood, but it sure seemed like you were taking issue with the idea that a redundant gas source was helpful, as a general rule, based on the very specific type of diving that you do.

Of course, there are many types of dives where a pony bottle would be ridiculous, and other types of dives where it would be woefully inadequate. If you are going to significantly limit your N2 loading and ascend after using 1/3 of your tank, then yes, a pony bottle would be less helpful.

I'm really kind of surprised that this is so controversial. If I went to the CCR forum and said that I don't need bailout because I take good care of my equipment and I meticulously pack my scrubber, I don't think that it would go over well. Is OC gear really so bulletproof that a redundant gas supply is simply superfluous?

Remember, stuff happens fast in emergencies, and the best trained people often panic and forget their training and contingency plans.

 

[CWK]

You and a couple of others in this thread have been lashing out at anyone with a different opinion and misstating facts.

I've attached my log from 13 October last year so that I do not misstate facts.

I remember that it was a beautiful morning for diving. We jumped in calm waters and I spot a couple of eagle rays so I drop to about 30m to video them. They are at 1:25 in the following video. You can see from the video that conditions were calm.
At some point quite early in the dive the current starts to pick up. It was probably about a medium current when I hook into the reef at about 12mins.

By 21 mins the current had become strong. It was blowing onto a ridge so I decide to go over the ridge to take shelter behind. That's what that first spike in the dive profile is about.

At about 23 mins, I see my buddy drifting off in the current, so I unhook to go to her. By the time I reach her, she has things under control and we both drop back down to the reef. My buddy told me later that her reef hook had ripped out at the BC end. That's what the second shallower spike is about.

At 26:30 we are at a depth of 21m and I checked air pressure. I had 65 bar left and my buddy had about 75 bar. I would normally start ascent when I reach 50 bar, but I decided to be more conservative on this dive and signaled to end the dive.

At 27:30 we had ascended to 15m when the washing machine struck. We were first driven down to 28m, and we fought our way up to 13m. A second down phase drove us to 32m. Thankfully we were able to fight our way to the surface. Having broken the washing machine's grip, we went back down to 5m to do our safety. I ended the dive with 17 bar. It could well have been ZERO.

A washing machine can strike anytime including at the end of a dive when you are already low on air. Don't assume that you can get to your buddy in a washing machine. Even if you can get to your buddy as I was able to do, he or she may not have much air left in the tank to share. An octopus in such a situation may be of little use. I suspect that attempting a CESA in a washing machine will result in the ultimate life changing experience.

There were a couple of lessons that I took away from this dive. One was that I needed to carry a larger pony.

 

[johndiver999]

Choosing to limit your dives to shallow water and staying far from the ndl is perfectly defensible; prohibiting other people from using safety equipment that they feel is warranted, is quite different. If a bail out bottle enhances a diver’s enjoyment and allows them to relax and better enjoy their dive, I see few reasons to prohibit its use.

 

[CWK]

By sheer coincidence, I took delivery of my new and larger pony today. It was ordered last October when I decided that I wanted to carry a larger pony and it took a couple of months to get to Malaysia.

It’s a gift from a grateful buddy who says that I saved her life in October last year. It may well save my life one day.

 

[KenGordon]

View attachment 497131

I've attached my log from 13 October last year so that I do not misstate facts.

I remember that it was a beautiful morning for diving. We jumped in calm waters and I spot a couple of eagle rays so I drop to about 30m to video them. They are at 1:25 in the following video. You can see from the video that conditions were calm.
At some point quite early in the dive the current starts to pick up. It was probably about a medium current when I hook into the reef at about 12mins.

By 21 mins the current had become strong. It was blowing onto a ridge so I decide to go over the ridge to take shelter behind. That's what that first spike in the dive profile is about.

At about 23 mins, I see my buddy drifting off in the current, so I unhook to go to her. By the time I reach her, she has things under control and we both drop back down to the reef. My buddy told me later that her reef hook had ripped out at the BC end. That's what the second shallower spike is about.

At 26:30 we are at a depth of 21m and I checked air pressure. I had 65 bar left and my buddy had about 75 bar. I would normally start ascent when I reach 50 bar, but I decided to be more conservative on this dive and signaled to end the dive.

At 27:30 we had ascended to 15m when the washing machine struck. We were first driven down to 28m, and we fought our way up to 13m. A second down phase drove us to 32m. Thankfully we were able to fight our way to the surface. Having broken the washing machine's grip, we went back down to 5m to do our safety. I ended the dive with 17 bar. It could well have been ZERO.

A washing machine can strike anytime including at the end of a dive when you are already low on air. Don't assume that you can get to your buddy in a washing machine. Even if you can get to your buddy as I was able to do, he or she may not have much air left in the tank to share. An octopus in such a situation may be of little use. I suspect that attempting a CESA in a washing machine will result in the ultimate life changing experience.

There were a couple of lessons that I took away from this dive. One was that I needed to carry a larger pony.

Or, take more gas, or leave the bottom with a reasonable contingency. The way you talk about ‘the washing machine’ makes it sound like a known hazard so being delayed in your ascent is a forseable risk and ought to be factored into your plan.