Anybody come across this thing yet? All in one pony bottle.

[kelemvor]

As an aside, I note that nobody has said anything about having to do a bottom swim before starting the ascent. It's all well and good to only need 8 cu-ft to get to the surface, but a lot of my dives would first require getting back to an anchor line before starting the ascent. Another reason I would not personally spend money on a cylinder smaller than a 30. Actually, I wouldn't spend money on one smaller than a 40. But, I do have a 30 because I basically got it for free with a deco reg I bought.

It's an interesting point. I figure if I'm having to use my emergency gas supply then a bottom swim is out of the question. In my mind if I switch, I expect to be moving vertically almost immediately. From my perspective even one of those puny 3cuft spare air tanks might be enough. Maybe not, but I'm highly confident that 13 will get the job done with gas to spare..

I want it to be small enough that it won't be a hassle. If it becomes a hassle, I'll end up leaving it at home where it won't do anyone but the LDS who sold it any good. I know myself and I know if it is a hassle it won't go anywhere.

 

[stuartv]

A dive that requires a horizontal swim before a safe ascent can be made is not a recreational dive.

I guess it's a grey area. A NC wreck dive does not have anything to prevent you from going straight to the surface. In that sense, a bottom swim is not required. But, it is HIGHLY advisable (usually) to get back to the anchor line before beginning the ascent. A 5 minute (more or less) free ascent could result in hitting the surface pretty far from the boat, depending on the conditions (i.e. current). Even if they see you, you could still be out of sight before the boat is free to unhook and come looking for you.

I would still class it as a recreational dive. But, if I were carrying a pony bottle, I would want it to be big enough to accommodate getting back to the anchor line before beginning an ascent. Someone who goes OOA and also isn't prepared to get back to the anchor line before ascending probably is not well suited to be drifting off into the blue for 30 minutes to an hour. You could make the case they shouldn't be doing that dive at all. That's fine with me. But, telling them they're fine with an AL13 as a pony doesn't seem so "fine" to me. Saying "that's not a recreational dive" also doesn't make sense to me.

 

[stuartv]

It's an interesting point. I figure if I'm having to use my emergency gas supply then a bottom swim is out of the question.

All I can say is that if I were taking redundant gas on a NC wreck dive, I would absolutely plan my redundant gas to be enough to get me back to the anchor line. It makes no sense to me at all to carry redundant gas and have it NOT be enough to do that.

Of course, the reality is that most folks on the NC rec boats I've been on were diving a single tank with no redundant gas at all. I guess that's what buddies are for.... And I suppose we should all recall that being a gas hog and actually using all your air is not the only way a diver can end up needing a pony or a buddy's gas. Even someone with a SAC of 0.25 could have a tank O-ring blow out.

Which reminds me. I was diving in NC last year. My buddy was using my steel 100s and diving sidemount. I had just gotten them back from hydro. He got back on the boat from a dive, set his tanks in the rack behind his bench seat and grabbed one of them by the valve to rotate the tank a little bit. When he did, the valve actually turned in the tank! I just happened to be talking to him at the time and saw it happen with my own eyes. I guess the shop that did the hydro didn't torque the valves back into the tanks properly. That could have easily turned into a mid-dive tank valve blow out....

 

[mi000ke]

Regarding my earlier post about slinging a 13 cf pony:

Context: All my dives have been and will be non-solo recreational boat dives in warm, high visibility, low current Caribbean waters where we are usually doing an underwater loop that never goes very far from the boat, plus the occasional shore dive out to a reef and back. My max depth is generally about 100’ as I am almost always on EAN32 and I give myself a few feet of safety factor. My normal SAC rate is about .45 cf/min. I can (have done) CESA from about 50’ if needed. I have two herniated discs/sciatica and want/need to minimize the amount of weight I carry out of water. (Btw, diving is incredibly therapeutic for my back.) I have never seen anyone else on one of my dives carry a pony, but it gives me a little peace of mind.

Calculation:
At 100’ for one minute to get sorted out: .45 x 4 x 1 = 1.8 cf
Ascend from 100’ (4 atm) to 15’ (1.5 atm) at 30 fpm  2.75 ave atm x .45 cf/min x 85’/30 fpm = 3.5 cf
Safety stop at 15 ‘ (1.5 atm) for 3 minutes: 1.5 atm x .45 cf/min x 3 min = 2 cf
Ascend to surface: 1.25 ave atm x .45 cf/min x 15’/30 fpm = .3 cf
Total air consumption: 7.6 cf

If I speed up my ascent to, say, 45 fpm then we are talking 6.3 cf
If I eliminate the safety stop we are talking 4.3 cf

I am comfortable that a 13 cf will do the job for me if for some reason I become OOA. Plus I don’t want to carry the extra 3 lb of a 19 cf.

 

[stuartv]

If you HAVE to switch to your pony, how confident are you that your SAC is going to still be at 0.45?

 

[The Chairman]

ScubaBoard Groupthink #21: "The right size pony cylinder for most recreational divers is 40 cubic feet."

If you're going to sling a bottle, an AL40 is just as easy as a 19 or a 30. I have the other two and I'll break them out for a diver's first attempt slinging a bottle, but I have a lot of 40s and I can use one dive after dive after dive.

My normal SAC rate is about .45 cf/min. I

Run out of air and watch it jump to 4 or 5 times normal. That 4.3 to 6.3 just became 21.5 to 31.5 cf if you can't get your breathing under control.

You must travel with larger suitcases than I do. A 19 fits very nicely into my luggage, no way could I squeeze an AL40 in there

I don't travel with tanks. It's easier to rent a 40 with a reg on site.

 

[The Chairman]

BTW, I have simply passed off my bottle to a low air diver before. We were on the down line doing a safety stop and they got that wild eyed look. Clippy, clippy and they swam away without me having to baby sit them.

 

[JohnN]

If you're going to sling a bottle, an AL40 is just as easy as a 19 or a 30. I have the other two and I'll break them out for a diver's first attempt slinging a bottle, but I have a lot of 40s and I can use one dive after dive after dive.

You must travel with larger suitcases than I do. A 19 fits very nicely into my luggage, no way could I squeeze an AL40 in there

 

[stuartv]

Run out of air and watch it jump to 4 or 5 times normal. That 4.3 to 6.3 just became 21.5 to 31.5 cf if you can't get your breathing under control.

Not to mention what it will do to your gas consumption if you went with a "budget" reg for your pony and it "don't breathe so good."

 

[The Chairman]

Not to mention what it will do to your gas consumption if you went with a "budget" reg for your pony and it "don't breathe so good."

Or that silly bite me valve.