AL40 for redundancy diving single tank on deeper dives.

[scubadada]

I was going to disagree and argue with Bigeclipse and his experience of less than 100 dives, but, instead, I will agree with the replies from boulderjohn.

In my post, #27, I stated exactly how I calculate my gas needs and why I use a 19 cf pony for solo recreational diving. My SRMV for the last 742 dives is 0.37 +/- 0.04 (mean +/- SD) cf/min. I have never come close to doubling my RMV, even in the coldest, darkest, most challenging, anxiety producing situation. However, I do use twice my average RMV for making my gas requirement calculations for my redundant air source. And, of course, if push came to shove, some or all of the ascent could be quicker and the SS could be skipped, this is recreational diving. To each their own, in my case it's based on reasonable experience and a conservative calculation rather than internet second guessing.

 

[The Chairman]

I think pony bottles are great if used for what they are meant to be used for and that is emergencies.

OK, where is this rule written? I've heard it said before, and I've actually believed this for a while myself, but I no longer feel this way. This is especially true when the "pony" is a 40cf bottle.

 

[Reku]

Any do's or donts? when getting tanks or rigging the bottles.

I realize my previous answer completely ignored your questions. Sorry.


Use a stage kit to mount it onto your body using D rings (if possible).

Get a Luxfer 40cf if you can - characteristics in the water are good.

How you use the bottle is going to be up to you. I am not the one diving - you are.

As others have said a properly configured bottle shouldn't be awkward. You'll have to figure out how to make that happen.

I can't tell you how to dive I can only point you in a direction. Good Luck.

 

[boulderjohn]

OK, where is this rule written? I've heard it said before, and I've actually believed this for a while myself, but I no longer feel this way. This is especially true when the "pony" is a 40cf bottle.

I wrote a tongue in cheek post a while ago on this topic, but I think I will expand it a little here with a description of an unlikely but viable dive plan for a dive at recreational depths.

On this dive, Tom is going to use a single tank for back gas. His calculations indicate that he will likely go into deco a little on his planned dive, maybe 10 minutes at most using the same gas he is breathing at depth. He is trained and certified for this. He wants to make sure he has both redundancy and plenty of gas for the dive. His gas calculations tell him he should have enough gas to complete his mission in the single tank for the dive, but not as much as he would like to hold in reserve, and, of course, that single tank does not .provide redundancy. Here is the dive he plans and executes:

1. He starts the dive carrying and breathing from an AL 40 stage bottle with the same mix in the primary tank. He breathes it for about a third, giving him that extra gas he needed for a reserve and leaving him with about 27 cubic feet in the AL 40. He switches to back gas. He now no longer needs a stage bottle.
2. He continues the dive with an AL 40 with 27 cubic feet in it as a pony bottle. This will give him both redundancy and all the gas he needs for an emergency, even if that emergency takes place after he has gone into deco.
3. At the end of the planned dive, he does indeed have the expected deco to do--essentially an extended safety stop. He ascends breathing his back gas, which still has that planned reserve. The pony bottle that was there for emergencies was not needed, as is almost always true for pony bottles.
4. When he reaches the required stop depth, his unneeded pony bottle becomes a decompression bottle. He switches to it in order to retain more back gas and thus increase the value of the redundancy.

On Tom's dive, he always had enough gas for the dive, he always had redundancy, and he always had an adequate reserve in case of emergency. He carried a stage bottle at one point, a pony bottle at another point, and a deco bottle at another point--all in the same vessel.

 

[Doby45]

I wrote a tongue in cheek post a while ago on this topic, but I think I will expand it a little here with a description of an unlikely but viable dive plan for a dive at recreational depths.

On this dive, Tom is going to use a single tank for back gas. His calculations indicate that he will likely go into deco a little on his planned dive, maybe 10 minutes at most using the same gas he is breathing at depth. He is trained and certified for this. He wants to make sure he has both redundancy and plenty of gas for the dive. His gas calculations tell him he should have enough gas to complete his mission in the single tank for the dive, but not as much as he would like to hold in reserve, and, of course, that single tank does not .provide redundancy. Here is the dive he plans and executes:

1. He starts the dive carrying and breathing from an AL 40 stage bottle with the same mix in the primary tank. He breathes it for about a third, giving him that extra gas he needed for a reserve and leaving him with about 27 cubic feet in the AL 40. He switches to back gas. He now no longer needs a stage bottle.
2. He continues the dive with an AL 40 with 27 cubic feet in it as a pony bottle. This will give him both redundancy and all the gas he needs for an emergency, even if that emergency takes place after he has gone into deco.
3. At the end of the planned dive, he does indeed have the expected deco to do--essentially an extended safety stop. He ascends breathing his back gas, which still has that planned reserve. The pony bottle that was there for emergencies was not needed, as is almost always true for pony bottles.
4. When he reaches the required stop depth, his unneeded pony bottle becomes a decompression bottle. He switches to it in order to retain more back gas and thus increase the value of the redundancy.

On Tom's dive, he always had enough gas for the dive, he always had redundancy, and he always had an adequate reserve in case of emergency. He carried a stage bottle at one point, a pony bottle at another point, and a deco bottle at another point--all in the same vessel.

Exactly what I was saying too, thanks John..

 

[WarrenZ]

Bigeclipse said: ↑
I think pony bottles are great if used for what they are meant to be used for and that is emergencies.

OK, where is this rule written? I've heard it said before, and I've actually believed this for a while myself, but I no longer feel this way. This is especially true when the "pony" is a 40cf bottle.

I thought this was stamped on the bottom of every ponybottle, stage tanks dont have anything stamped there. Now you know the difference between a pony and a stage.

I carry a 19 because it is just for redundancy If I was looking to extend a dive I would be carrying something bigger or not rely on the 19 for redundancy.

 

[gypsyjim]

A properly slung AL40 should not feel awkward ... one of the nice things about the tank is that it tends to ride butt-light, and as such pretty much disappears under your arm. I use one often, both for solo and for some buddy diving, and the only time I ever even notice it's there is when I'm trying to get low to the ground to get a picture ... at which point I have to remember to reach over and lift the top end of the tank up a bit so it doesn't dig into the bottom as I get below those last few inches off the bottom.

... Bob (Grateful Diver)

New shoes, or a wedding band can feel a bit awkward at first, until you become more adjusted to them with experience.
I have only used a pony the one time, when the laws of NYS mandated redundancy in orde to obtain permission to dove the Radeaux. I'm certaincertain that I could, will become accustomed to the 40, with more experience.

 

[Jack Hammer]

[
Can you give us an example where a diver is using it as "a crutch for many to compensate for poor gas management skills"?

Looks like you've already found examples

 

[uncfnp]

Looks like you've already found examples

Not really. I have read examples of alternative gas planning but not poor gas management. Which post(s) are you referring too?

 

[mainedvr]

Thanks for all the input, what I was looking for is some input on rigging, DYI, buy it like Diverite stage set up, size of bottles and material and maybe the boyancy characteristics, even the length of hose. I was thinking something comfortable to donate but not so long that when I hand over the bottle to my partner or the OOA recipient they have a bunch of hose to deal with. I do realize there are man schools of thought and I respect each individual. My wife and I do so much different types of diving we will decide when we want to take it or not, just like hearing what others are doing and will definitely make our decision for our self.

Thanks again.