AL40 for redundancy diving single tank on deeper dives.

[Scubatude]

There is no reason not to sling a redundant supply. Personally, I would not use anything less then a AL40, but that is just me. I would not use it to extend my dive, as stated above, but I would use it....on every dive. I stress time and again the importance of training. Something that is used only in an emergency will not be handled with the same expertise as devices that are used often. If you feel more comfortable with a slung tank, do so.....then deploy it on your safety stops or other safe, shallow place and get very comfortable with it's use.

 

[luscioman]

I think based on what you are saying you need to find what works for you and your wife. On a post like this you will probably get 10+ different opinions. They are not right or wrong just different based on peoples preferences and experience. You have a lot of options for this. Are you both going to sling an extra tank? What size? Also I know a lot of people with your type of concern that have gone with a 19CF on an attachment to their main tank so that it doesn't get in the way.

 

[boulderjohn]

Yes, it defeats the redundancy purpose if you use the pony to extend your dive. But why is that all they should be used for? That is pretty dogmatic. Why not use a pony for extra gas?

If I used my pony at all during a dive other than an emergency it would be used as a stage bottle, use a third and stow it so that you can "exit" on the other two thirds.

You can't see me as I type, but my tongue is firmly in my cheek.

You have to differentiate between a stage bottle and a pony bottle. A stage bottle is used to add to the amount of gas used during a dive. A pony bottle is used to provide a redundant air source in the case of an emergency. They both come in different sizes with differing amounts of gas. They look and work exactly the same, but they have those very different functions, and should not be confused. When you put one on before a dive, make sure you tell the bottle what it will be used for on that dive so it knows.

Let's say you have pre-planned the dive carefully and decided that the amount of gas in your main tank is not sufficient to allow you to be sure you can do the planned dive, so you decide to carry a 40 cubic foot stage bottle to provide a bit more gas. You begin the dive on the stage bottle, breathe say 1/4 of it, and then switch to your primary tank. At that point, you wish you had brought along a pony bottle for redundancy in case of emergency. What you should do is take the pony bottle off and set it down for a few seconds, or simply hold it out in front of you. Wave a hand over it and say, "You are now a pony bottle!" Clip it back on, and you are all set.

 

[gcarter]

You can't see me as I type, but my tongue is firmly in my cheek.

You have to differentiate between a stage bottle and a pony bottle. A stage bottle is used to add to the amount of gas used during a dive. A pony bottle is used to provide a redundant air source in the case of an emergency. They both come in different sizes with differing amounts of gas. They look and work exactly the same, but they have those very different functions, and should not be confused. When you put one on before a dive, make sure you tell the bottle what it will be used for on that dive so it knows.

Let's say you have pre-planned the dive carefully and decided that the amount of gas in your main tank is not sufficient to allow you to be sure you can do the planned dive, so you decide to carry a 40 cubic foot stage bottle to provide a bit more gas. You begin the dive on the stage bottle, breathe say 1/4 of it, and then switch to your primary tank. At that point, you wish you had brought along a pony bottle for redundancy in case of emergency. What you should do is take the pony bottle off and set it down for a few seconds, or simply hold it out in front of you. Wave a hand over it and say, "You are now a pony bottle!" Clip it back on, and you are all set.

Should the bottle not have a say in that? It should be able to choose and self-identify. Who are you or I to tell it what it can be?

What is this, the dark ages?

 

[Basking Ridge Diver]

I use a 19 cu ft. I learned on 40 cu ft for the solo class. I do a lot of solo and shore dives. For me - I found my RMV/SAC and used that to determine my needs.
For those advocating 40's are you only boat diving and are you pushing 40's because you use them on every dive?
A 40 to me is too bulky and overkill ' ymmv.

 

[Scubatude]

I advocate an AL40 for several reasons. The number one reason is that I believe you should train with what you will use. If you train and practice with an AL19 and only use an AL40 for deeper dives, you will not be well trained and practiced with the AL40. The AL40 provides enough gas to handle an emergency underwater, and make a slow safe ascent with stops as needed from recreational NDL limits.

 

[scubadada]

This topic has been debated many times, to each their own. I would take the time to calculate the amount of gas needed to conservatively ascend from your deepest dives. I use a minute at depth, 30 ft/min ascent, 3 min SS, all at twice your average RMV. A 19 cf pony is what I use on all my solo dives. I sling it on the left. I have a full size SPG and leave the pony on for the dive. I could easily see if I was losing any gas. My cylinder is 1 pound negative, I take a pound off the left side. I think that covers all the usual questions regarding a pony

 

[uncfnp]

I advocate an AL40 for several reasons. The number one reason is that I believe you should train with what you will use. If you train and practice with an AL19 and only use an AL40 for deeper dives, you will not be well trained and practiced with the AL40. The AL40 provides enough gas to handle an emergency underwater, and make a slow safe ascent with stops as needed from recreational NDL limits.

Unless carrying my O2 I don't carry anything larger than a 19. But I am curious, what special training does a 40 cf pony require that a 13 does not?

 

[BoltSnap]

As a general rule using the pony to extend dives creates complacency and is poor form from a dive planning perspective.


That said, I would consider/do use the pony in certain situations take can be dive or site specific.

I sling a 40 so obviously not all of these scenarios work well with smaller bottles

1. I have used a pony to stay shallow under the water after a dive has been turned so that I wouldn't have to surface swim. Mostly in situations where the site is benign and it looks like my tanks might end around the 200-300 psi so I'll switch to a pony when back gas is 500 so I don't need to rush out of the water/surface. I still have plenty of back gas and gas in the pony.

2. If I have a half full tank and am going to be doing a shallow no current shore dive or work on the platforms at Dutch at 25'. I have brought that pony and treated it like a stage bottle so I wouldn't have to spend money to fill up a tank that is still half full.

3. Similar to point #1. A buddy of mine wanted to make a deep push into the back of Dutch Springs. I had a HP100. He had an LP108 and a slightly better SAC rate. We planned that when I got low I would switch to the pony. This was a little bit different than #1 bc it was treated more like a stage bottle and I was breathing it for longer at deeper depths.

In my mind, general rules if you are going to use the pony to extend the dive
1. Benign dive conditions--lakes, quarries, shallow shore dives, areas where you can safely surface and swim to the exit. Would never plan on using it if you are doing a wreck in the ocean to many unexpected things can happen

2. Only needs to be deployed after you have turned the dive-It is not the "hey let me drain my tanks and then deploy my pony and decide to swim back" like a J valve. It is in situations where you could surface if you needed to and/or you could finish the dive, but it would mean the tank were a very low on PSI and the pony will be used to conserve back gas PSI and allow you to enjoy the end of the dive and not rush.

3. You have buddies-Using the pony could be a planned part of the dive or just a precaution, but either way you have other divers as a redundancy.

I wouldn't expect everyone to agree with the above and the examples given are really for being used with a bigger bottle--I recommend at least a AL 30,preferably a AL 40.

Some people might consider the above poor gas planning, but I don't think I completely agree with that. There is no deco in these dives and there is no hard set game plan. You say you are going to go see X or try to find Y, depth with be around Z, but its never 100% exact. Only the final destination is set, enjoy the journey.

Terrible advice indeed.

 

[Bigeclipse]

I think we all know that it only takes a moment of inattention or distraction. It is not a perfect world and neither is the buddy system. If a buddy team feels safer with personal redundancy, that is a self reliant diver and it will only add to the safety of the team. Is it necessary? That is for the team to decide.

I agree with this. My dive buddy is pretty attentive but there have been times I tried to get his attention signaling and banging my tank (he was 6 feet away) and yet he didn't notice for a brief moment (few seconds?) but still, if I was completely out of air I would not want to be frantically trying to signal my buddy...etc. It is nice to know I can simply reach down to the pony and put that reg in my mouth. Then go get my buddy to start our ascent.