Running your BCD / Dry suit off your Pony?

[divingbuddy]

I saw a diver with an argon bottle for dry suit inflation with an extra LPI on his left stage bottle. In the event that he lost the gas in the argon bottle, he could attach the inflator to the nitrox in his stage bottle. When not needed, the LPI was securely held against the stage bottle. I thought it was a decent idea....Cheers!

 

[utdivermatt]

Maybe its just me, but this seems like alot of worth for next to nothing. Diving a basic profile of going down to my deepest point, and working my way up, I put air in my wing once. On the surface, I can fill up my wing with 3-4 breaths. That is almost entirely full, and enough to keep me way up on the surface. I dont add anywhere near that much underwater... Id go flying. That seems like we are talking a psi in the single digits, much less 300-500. That is looking at 1/5th of your breathable gas in a standard AL 80. If you use that much air in your BC during a dive, youve relying on it way too much. You have lungs for a reason.

 

[all4scuba05]

Of course, if the "pony" is dedicated to suit inflation (with air, argon, etc) and doesn't have a second stage for breathing, then the gas planning isn't relevant... so long as it doesn't mean you're going without a redundant breathing gas when you need one.

In other words, an ADDITIONAL small tank used for just for inflation may not be a bad idea.

my thoughts exactly

 

[Captain12Pk]

Let's keep in mind, a pony bottle is a redundant air source used to get a diver safely to the surface in the case of primary gas failure. If you use any amount of your redundant air to inflate your wing, BC, drysuit, whatever, you are gambling with your redundancy. In which case, why have it at all?
Now, if a little additional bottom time is the goal, may I suggest possibly using a slightly larger primary tank?

 

[shadragon]

Now, if a little additional bottom time is the goal, may I suggest possibly using a slightly larger primary tank?

I would like to be clear I never intended this approach to increase bottom time. I asked only to see if safety could be improved by increasing the available gas to hand in the main tank. As I said, I have no idea how much air is used in a BC or Dry suit and the guesses since the original post are just that, guesses. I am not proposing this method. I am not asking someone try it. I asked the question to see if it had been considered in the past. Please do not read anything into it beyond being a mental exercise...

Not everyone can increase their tank size and in an emergency there are times you will never have enough air.

Cheers.

 

[all4scuba05]

Let's say a diver doesn't believe in ponies for redundant air. He depends on his team diver for redundant air. So now this same diver decides to buy a pony and use it strictly for drysuit and BC. How can that be considered wasting you backup air? It isn't. Some folks use the word "pony" to signify "bailout". Others use it to signify "smaller slung bottle". Whatever. If a diver wants to use that bottle strictly for drysuit and/or BC, and depend on his buddy's backgas as his backup, then so be it. Not everyone dives the same depth, style, conditions, caves, ets....

 

[AzAtty]

What you're seeing is likely a 6cu ft argon bottle, not a pony bottle. A lot of the people who use argon bottles are diving trimix instead of air or nitrox. Trimix has helium in it, and it conducts heat away from your body faster than air. Consequently, inflating your suit with trimix cools you faster than desirable. Argon is denser than trimix and has been adopted by trimix divers as a preferred suit gas because, as the theory goes, the denser the gas, the better insulator it is. As noted above, that hypothesis is up for debate.

 

[ClayJar]

Okay, here's one for you. I ask this not because I intend to do it, but merely in the interest of physics:

If Argon is so good because of its higher "molecular" weight (which is a misnomer, as its a noble gas and therefore monoatomic), why doesn't anyone use CO2 instead? CO2 is 44 grams per mole, while Argon is only 40 grams per mole. (Air is somewhere around 29 grams per mole, and I didn't run the numbers for any trimix blends.)

Last time I had my CO2 cylinders filled, it cost around a quarter of what I've seen Argon listed for, and you can fit a lot in a small cylinder, as it does that whole liquid state thing. Naturally, it would require a submersible regulator that could properly handle a liquid state, which may be a rather significant hangup, and the cylinders and valves are not compatible with standard air or argon regs (for rather obvious reasons), but if you were just interested in molecular weight and cost, you really can't beat CO2, eh?

(This is also thinking about it completely ignorant of any potential transdermal absorption of CO2, but no need to get all physiological about a physics musing, eh?)

 

[Captain12Pk]

Sorry Shad,
I guess I misunderstood. When you said " ... but you would have more gas to breathe from your main bottle" it seemed to me you were thinking you could gain more bottom time by sacrificing your redundancy. That's why I said " if a little additional bottom time is the goal, may I suggest possibly using a slightly larger primary tank?"
My mistake ... won't happen again.

 

[Darin]

Okay, here's one for you. I ask this not because I intend to do it, but merely in the interest of physics:

If Argon is so good because of its higher "molecular" weight (which is a misnomer, as its a noble gas and therefore monoatomic), why doesn't anyone use CO2 instead? CO2 is 44 grams per mole, while Argon is only 40 grams per mole. (Air is somewhere around 29 grams per mole, and I didn't run the numbers for any trimix blends.)

Last time I had my CO2 cylinders filled, it cost around a quarter of what I've seen Argon listed for, and you can fit a lot in a small cylinder, as it does that whole liquid state thing. Naturally, it would require a submersible regulator that could properly handle a liquid state, which may be a rather significant hangup, and the cylinders and valves are not compatible with standard air or argon regs (for rather obvious reasons), but if you were just interested in molecular weight and cost, you really can't beat CO2, eh?

(This is also thinking about it completely ignorant of any potential transdermal absorption of CO2, but no need to get all physiological about a physics musing, eh?)

If you can wrap your head around the physics, this does a good job...

http://www.decompression.org/maiken/Why_Argon.htm

Darin