How many non-tech divers carry a pony bottle?

[Chris Bangs]

A redundant air supply is the ONLY reliable emergency air source. Period! I always dive with one unless I do not plan to go deeper than 30ft.

 

[tracy_from_oz]

Yes I have a pony bottle/redundant air source. There is actually 2 I own. A 6 cft and a 30 cft. I am not a tech diver as of yet but am looking into that area of diving.

You can travel with them, dive with them and rely first and foremost on yourself.

I like a lot of other people do not have a regular dive buddy so I dont see the problem with having them especially on deeper dives.

 

[Meng_Tze]

After my human dive buddy aborted and left me 4 out of 4 dives at 90-120 feet, I have ordered from the LDS, a nice little 6 cu ft yellow buddy, filled with Nitrox-- so offgassing will be enhanced--just to get me up if my primary regulator malfunctions. NOT to prolong bottom time (6 cu ft wouldn't do that much anyhow).

Not picking on anyone in particular, but I have seen several posts where people mention a 6cft bottle. I suggest that proper calculations are done of gas consumption to get you from say 100ft up. Keep in mind the following things: SAC, RMV (increased rate due to stress), ascent speed, depth, stop times (if you want to plan a minimum), time to start ascending etc.

You will find that even with an average (non-adjusted RMV) 6cft is not going to last.

 

[MikeFerrara]

One example would be entering and traveling with the flow in a cave. The OW analogy would having to travel out with the current and return against it.

Overhead means just that, any place where its either impossible or not wise to directly surface. It also can include diving in active boat channels for that matter.

When diving an overhead, 3rds is the most liberal gas plan used. Low flow, no flow or siphon conditions or any of a hundred other things is cause to reserve more gas.

Regardless of where you set that turn pressure, the idea is to have at least twice as much gas as you will need to exit so that two divers can get out on it. In a strong siphon this could be a LOT of gas.

 

[highlandfarmwv]

Gosh, I hope I didn't make a mistake with that size. My dive instructor siad the 3cf wouldn't be enough for a safety stop, but the 6 cuft was... Do you all think one could get up from 100 ft depth andhave a 3 minsafety stop with the 6 cu ft Nitrox? I use air very sparingly, if that is significant. Thanks.

 

[do it easy]

Do you all think one could get up from 100 ft depth andhave a 3 minsafety stop with the 6 cu ft Nitrox?

In a word- NO. I would try breathing it at the surface and see how long it lasts. Then remember that at 100' you will you the gas 4 times faster.

This post is pretty good (from this thread)

This might be helpful

Lamont wrote up a short essay that will get your propeller spinning.

 

[tropicaledit]

I have 25 dives under me. I carry a pony. It's strapped to my side. A quick reponse is, 2nd air supply cant hurt, only help. I try to be very conservative. I've also been doing relatively shallow (15') beach dives with it. I hope I never NEED it. But I use it and practice with it.

Best

 

[Meng_Tze]

Gosh, I hope I didn't make a mistake with that size. My dive instructor siad the 3cf wouldn't be enough for a safety stop, but the 6 cuft was... Do you all think one could get up from 100 ft depth andhave a 3 minsafety stop with the 6 cu ft Nitrox? I use air very sparingly, if that is significant. Thanks.

I wrote this to someone else (edited for clarity), but since the question was asked directly, here goes my rough take... and bear in mind that we are talking about an emergency. No safety stop, quick (direct ascend) to surface.

Lets assume:
30m (100ft).
SAC = 0.7 cf/min
ATA= 4
Takes about 3 mins to get to surface (10m/min====fast)

1min at 4 ATA (30m to 20m) = 4* 0.7=2.8 cft
1 min at 3 ATA (20m-10m) = 3*0.7=2.1 cft
1 min at 2 ATA (10m-surface) = 2*0.7=1.4 cft.

total of 6.3 cft needed for ascend alone...... And this is at exact times disregarding increased RMV (increased work rate, increased breathing rate).

You have NO time to mess around, have to head up at the set speed and keep breathing as you did on the surface and it already runs short of gas...

If on top of that you are IN the wreck, bad vis, need to shoot a SMB bacause of current, drift.... add more gas needed.

You may want to consider a larger pony, there is no margin in 6cft.....

This is for illustration only and I advise everyone to do their own calculations based on what they feel is the safety they need. This illustration highlights only that a 6cft bottle does not cover the ascent itself, let alone any added time/gas one may need.

Of course if I made a mistake, wrong assumption, I look forward to a correction.

 

[ArcticDiver]

As we all know, house fires are extremely rare. You're much more likely to have a car accident, therefore, having smoke detectors in your house is a bad idea.

Nope. Still doesn't work for me.

The problems of equipment failure and those of "human problems" or entanglement are orthogonal. While one would be served well by addressing all factors, I see nothing egregiously wrong with addressing the low-hanging fruit of equipment failure.

Most of my dives have been in open water with vis anywhere from decent to great. I do not do penetration diving. The dive sites rarely have any discernable current at all. The odds of my finding a way to entangle myself are quite slim, indeed. As for "human problems", I have no idea what that's supposed to mean, but I'll just say that if I'm a healthy, fit, well-hydrated, properly trained, experienced diver diving conservative profiles at depths where narcosis is unlikely for a diver in said condition, I don't know why having some extra gas in case of equipment failure would be such a bad idea.

You have gone to great pains to contort my post. Clearly I have never advocated not carrying extra gas. In fact, mine, and several other folks' posts, have said that the minimal amounts of extra gas pony users carry is more false security than anything.

It is the false sense of security provided by the pony that is the primary fault with its' use. Most of the arguments for a pony contemplate an equipment failure and an immediate ascent to the surface. In fact, an equipment failure is extremely rare and should not be the primary consideration.

On the other hand many human and environmental factors fairly often extend dives beyond what is planned. Such things as current change, entanglement, searching for a mislaid buddy, narcossis, finding that "perfect" image at the end of the dive, etc are not unusual.

So, to me and others, once a diver decides their diving circumstances demand extra gas it is time to go the whole route, not see just how little extra gas they can carry and get away with it.

After all that is what this whole argument boils down to: Just how much extra gas should I carry once I decide a single tank isn't enough? One school of thought is to carry the minumum amount of extra gas they can rationalize; a pony. The other school of thought is to just add a second tank like the first and effectively double the amount of available gas. Seems to me the logic of the second group is superior to the pony folks.

 

[highlandfarmwv]

What is the next size up from a 6cuft? Seeing how it is Sunday and the LDS is closed. I'm trying to go as small as possible and still be useful. I photograph with every dive, and am trying to hold down clutter. Thank you, Meng Tze for working out the figures.