Optimal Pony Bottle Size for Failure at 100ft?

[scubadada]

...IIRC, I wrote up and posted an example here a long time ago that suggests that an Al 30 is sufficient for returning from a 130 fsw recreational dive at maximum NDL ...

The luxury of knowing your average RMV. From 130 ft, after a min at depth, a normal ascent, and a 3 min SS, at twice my average RMV, I use 16 cu ft. That's why I dive a 19 cu ft pony.

For a no stop dive, the SS could be skipped. If push came to shove, the ascent could probably be a little shorter.

 

[sod kamus]

You might get by with a 19 for 100 feet, but why not just go to a 40 (or 30) on the theory you may want to dive deeper and don't want to get another bottle?

Can't say for others, but for me, the answer is because I don't want to drag a 40 all over the ocean on a rec dive that I'm probably never gonna need...and if I did need it it's 3x more gas than I'd need...it's excess weight and bulk to have to drag along on a dive.
When diving becomes work, then it isn't a hobby anymore.
Dragging cylinders around is OK for tech divers, oil rig divers, or research divers. They get paid to do it. I'm a sight-seeing diver. Less is more.

It's like fueling an airplane. When you fly from Raleigh to Atlanta, you don't put 20,000 lbs of fuel in your aircraft. You calculate that you'll need 2000 lbs of fuel to fly from Raleigh to Atlanta and you put 2000 lbs of fuel in the tank plus bingo. You don't need enough fuel to fly to London, so filling the tank is "excess baggage" and is more dangerous.

"You might get by with a 19 for 100 feet..."
In an emergency situation Sir, "getting by" is good enough. The goal is to get back on the boat alive, not to get back on the boat with excess gas.

When I was in Iraq, I carried 210 rounds and an Army Ranger, basic combat load. Could I have carried 1000? Sure. But it was excess baggage, excess bulk and weight, and simply not needed for the mission in front of me.

Unless youre doing something in excess of rec diving or to depths beyond "sight seeing", then carrying 40 cu ft of gas is simply making more work for yourself with no increase in benefit for your labor.

Just my opinion. If I'm four minutes from topside, I don't need 20 minutes of gas.

Notice how a fire extinguisher in most aircraft or boats or armored vehicles isn't a 20 lb fire extinguisher? More isn't always better. The purpose of a fire extinguisher on a plane or boat is to get you out. A 4 lbs fire extinguisher will accomplish that without the excess weight and mass.

I'm a trained believer of the "Take what you need for the mission, not what you want for the mission" philosophy.

Other may prefer to lug a 40 on a dive for a "pony" bottle, and that's OK. I'm just not doing it. The dive becomes too much like work then.

 

[sod kamus]

If you know you can not calm down doing a leisurely 3- minute ascent, then perhaps you should take a larger pony, so you can do the safety stop.

I'm comfortable with a 6 cu-ft at that depth.

You can't either.

There's a lot of difference in a drill and a real-world OOA emergency. I've trained at Bragg in the shoot house, probably fired 50,000 rounds in scenarios during my career. You can practice shot drills 10,000 times. When you're on the street in combat, your heart is racing, your breath is rapid, your head is throbbing. Humans generally can't control their bio reactions like that no matter how much you train.

We've had shooters who have been thru so many scenarios in the shoot house that they get carpel tunnel in their gun hand from so many shoot drills. Yet when they get in combat, they biochemically react like everyone else does. You can't remove the panic, you control the panic. I think your gas consumption will increase when your brain knows it's a real-deal regardless of how much you've trained before hand.

And I don't consider a safety stop a mandatory. I skip them all the time (yeah I know, bash me). Bad habit I know, but I can skip the safety stop from 100' and have no noticeable after effects. In a real-deal, my goal would be to get back to the surface alive, not mess around at 15 feet on a safety stop for five minutes. The goal of any real-deal scenario is to "arrive alive". If that means breaking a few of PADI's rules, then I don't care.

I don't doubt you can do it with a 6 cu ft pony. That's certainly reasonable for drill training. I chose the 19 cu ft because for the trade-off in weight/size, 6 cu ft just wasn't that much smaller than 19 cu ft for the extra amount of gas the 19 cu ft offers me.

Now as soon as they make a pony in 19 cu ft dimensions that will hold 40 cu ft of gas, then I'm running to the store to give them my money.

 

[rx7diver]

... There's a lot of difference in a drill and a real-world OOA emergency. I've trained at Bragg in the shoot house, probably fired 50,000 rounds in scenarios during my career. You can practice shot drills 10,000 times. When you're on the street in combat, your heart is racing, your breath is rapid, your head is throbbing. Humans generally can't control their bio reactions like that no matter how much you train. ...

Recreational dives, correct? Suppose your (primary) first stage on your back tank ceases to deliver air. Then you put your pony bottle 2nd stage in your mouth, turn your pony bottle on, purge your pony bottle 2nd stage, breathe, signal your buddy, and begin your ascent with your buddy. Easy-peasy.

Retrace the route you took to get where you are, if you're able, if you've planned for this (i.e., if your pony bottle has sufficient capacity for this).

There is no inordinate stress introduced--this is not combat!

rx7diver

 

[JonnieB]

Optimal Pony Bottle Size for Failure at 100ft?

I dive with a 19 cu ft. I've drilled with it and at 100' it will give me about 10 minutes of air. Some self-proclaimed "experts" say that's too small, and I'm better off without it. My logic is, if I'm in a situation where I need to switch to the pony, I'm coming home now, so that's all I need to reach the surface from 100'. My pony is a get-to-the-surface bottle, not a bottom-time-extender bottle or a deco bottle.

I'm just not the guy whose going to drag a 30 or 40 cu ft bottle around on a recreational dive with me. At 100" or less, I just don't need 20 minutes of air to "get home" in an emergency. At 100', the surface is less than 4 minutes away at a safe ascent rate. From 100' I can surface, and do a safety stop on my pony during drills. I figure in a "real" emergency situation that safety stop air would be used up by increased breathing rate, so I obviously would skip the safety stop in a real OOA emergency.

Dragging a 30 or 40 cu ft deco bottle around as a pony bottle for recreational diving is like using a .30-06 for squirrel hunting IMO. But to each his own.

Agree...anyone who says you need a bigger pony for non-deco recreational diving are also the ones who insist on surfacing with 1/3 of a tank and ending a dive and starting up from depth with enough air for two divers sharing air from 30 meters!

 

[johndiver999]

You can't either.

There's a lot of difference in a drill and a real-world OOA emergency. I've trained at Bragg in the shoot house, probably fired 50,000 rounds in scenarios during my career. You can practice shot drills 10,000 times. When you're on the street in combat, your heart is racing, your breath is rapid, your head is throbbing. Humans generally can't control their bio reactions like that no matter how much you train.

We've had shooters who have been thru so many scenarios in the shoot house that they get carpel tunnel in their gun hand from so many shoot drills. Yet when they get in combat, they biochemically react like everyone else does. You can't remove the panic, you control the panic. I think your gas consumption will increase when your brain knows it's a real-deal regardless of how much you've trained before hand.

And I don't consider a safety stop a mandatory. I skip them all the time (yeah I know, bash me). Bad habit I know, but I can skip the safety stop from 100' and have no noticeable after effects. In a real-deal, my goal would be to get back to the surface alive, not mess around at 15 feet on a safety stop for five minutes. The goal of any real-deal scenario is to "arrive alive". If that means breaking a few of PADI's rules, then I don't care.

I don't doubt you can do it with a 6 cu ft pony. That's certainly reasonable for drill training. I chose the 19 cu ft because for the trade-off in weight/size, 6 cu ft just wasn't that much smaller than 19 cu ft for the extra amount of gas the 19 cu ft offers me.

Now as soon as they make a pony in 19 cu ft dimensions that will hold 40 cu ft of gas, then I'm running to the store to give them my money.

You know you, I know me. Coming up from 100 feet for 3 minutes on a pony will not freak me out and I WILL control my respiration rate unless there is some exertion involved.

As a matter of fact, I once stupidly ran completely out at 130 ft, solo, while sprinting after a fish which had a spear shaft in it. I was terribly out of breathe from the chase and then it got hard to breathe, right as I grabbed the fish. I switched to the 6 cuft pony and started up. I knew I had to slow my breathing and as I got 15 feet off the bottom, my pole spear fell out and fell to the floor. I sure wished I had a bigger pony (like a 13) on that dive, or I would have turned around and grabbed it. Instead, I ascended, totally bummed about the lost pole spear.

Switching to a pony bottle at 100 feet is not some sort of death defying stunt, if you are well trained, practiced and - making many thousands of freedives might help a little too. LOL

I've had much scarier things happen at 100 feet than simply having to switch to a back up.

You honestly don't sound like you are very comfortable underwater with the analogies you draw and the supposition that training is ineffective.

 

[MidOH]

I could have switched to a pony during discover scuba.

Come on, it's the easiest thing you can do underwater.

 

[sod kamus]

turn your pony bottle on

My pony is already on when I go into the water.

Been diving for 36 years, Sir. First duty station was Bragg where I was sent to Key West to the Army Special Forces Underwater Operations School right out of Benning . If that's a "new inexperienced diver" in your judgement, you're my hero.

"There is no inordinate stress introduced". That hasn't been my experience. I've seen five incidents over the years in recreational diving, all minor things that were controllable situations, in all three the diver(s) did panic. In two of the incidents two divers drowned in each incident. In the last case, the entire incident was recorded on one of the drowned diver's mask-mounted GoPro. Both divers in the later incident were PADI Master Divers with decades of diving experience, were accomplished spearfishers, and "should have" handled the relatively simple emergency with ease. They didn't react in the GoPro video under simple stress the way lucid divers do in a training drill emergency.

I suppose it depends on the individual diver. I would think a tech diver or experienced diver wouldn't panic, but you always have increased bio functions. There's uncontrolled panic and controlled panic. You'll keep your head in the later, but you will still have increased heart rate, increased breathing rate, increased blood pressure, and hypersensitivity which will lead to increased gas consumption. As soon as the adrenaline hits your brain, you don't have any control over your biostate functions; you manage them.

I was a the barracks bombing in Dhahran in 1991 that killed over 100 soldiers. Despite some of the most elite training the Army has to offer, there was still hyper vigilance and increased bio function during that event. Humans are hard-wired like that.

 

[JonnieB]

If you know you can not calm down doing a leisurely 3- minute ascent, then perhaps you should take a larger pony, so you can do the safety stop.

I'm comfortable with a 6 cu-ft at that depth.

You do know that ALL recreational divers are by definition "no decompression" dives; meaning the diver always has direct access to the surface with no stop required, right?

 

[sod kamus]

Missouri Divers....they got all them opinions, they just ain't got no ocean!

LOL

Just picking on you Brother.