40cf too big for pony?

[caruso]

This is not a good idea nor is it the point in a pony bail out.....

A bail out is NOT to be calculated into your breathing gas. It is to be used as a redundant air source and for contingency purposes

I hear and read this quite often. No one ever gives a reason other than "That's what we were taught". Carrying around a pony bottle and never using it to extend a dive is a waste of effort and perfectly good breathing gas.

Pony or planned gas, use it to its fullest. If you plan your dives and then, like holy crap, dive that plan,,,you have or should have figured the extra gas into your contingencies. A wise man once told me, use it however the mission or dive dictates. I have planned my 30 cu ft tank into many of my dives as a dual purpose. However that is how I see it and I'm sticking to it!! Whatever you do, someone, some where, will tell you it's wrong. Enjoy your dives, my theory!

Agreed. I use my pony primarily as a backup/bailout but have dipped into it to extend more than one dive, and carrying a pony allows me to draw more gas from my main tank since I don't need to keep any gas in the main tank as a backup. It means longer and usually more enjoyable dives every time (NDLs not withstanding). If I surface with more than 50 psi in my main tank, it's a waste as far as I'm concerned. I've still got more gas than divers who surface with 750 psi in their main tank and I've got the extra safety of redundancy.

 

[Dirty-Dog]

I hear and read this quite often. No one ever gives a reason other than "That's what we were taught". Carrying around a pony bottle and never using it to extend a dive is a waste of effort and perfectly good breathing gas.

It's mostly just a matter of terminology. The term "pony bottle" isn't typically used to mean "any extra tank" so much as it's used as a synonym for a bail out bottle.
If I'm doing a solo dive and clip on an extra tank to provide some redundancy, that's a pony bottle.
If I'm a hoover (I am...) and clip on an extra tank, then it's diving doubles. I do pretty much every dive in doubles.
If I'm doing a deep dive and clip on an extra tank with high O2 to accelerate deco, that's a deco bottle.
If I'm doing a long dive and clip on two or three extra tanks, those are bottom gas, or deco gas, or travel gas (depending on the dive and the gases in those tanks).
Words have meaning, and if we don't all use the same meaning then communication gets really difficult. And to most divers, "pony bottle" means "oh ****" gas.

Note that I'm not saying you shouldn't use that bottle to extend your dive (so long as you're not doing something foolish like going into unplanned deco). I'm saying that if you're using the tank as part of your gas planning and intend to use it, then you're diving doubles.

 

[sh0ck1999]

Using as an emergency pony only. Draining your main then going to your pony as part of the "plan" doesnt sound safe nor smart.in that case you have a stage not a pony , correct? if i wanted more gas id move to doubles or side mount. im currently happy with my hp120 but if i find people to do more wreck diving with i may move that direction. but im currently content diving local lakes and in a few months is ice diving season

 

[caruso]

Using as an emergency pony only. Draining your main then going to your pony as part of the "plan" doesnt sound safe nor smart.

I don't see anyone talking about "draining their main tank then going to their pony".

I "drain my main tank" down to about 300 lbs prior to beginning an ascent (that's an average, more or less depending on depth), usually end up with about 250 at my safety stop and 50 psi after my safety stop. The pony isn't actually "used" to extend the dive, the dive is extended because little to no reserve is kept in the main tank, because the pony IS the reserve. On rare occasion when I've gone to the pony I have done it long before I get anywhere close to draining the main tank, because when I switch to the pony, now the main tank is the backup and I'd want at least 750 psi in there prior to starting an ascent from depth.

 

[Fibonacci]

Have a look at the diver in this video (from 5:15 to 5:27) taken at Truk lagoon a few years ago:

The diver was well out of his comfort zone diving the wrecks and was burning through air rapidly.
The 'solution' was to strap on a pony and switch to that after the primary tank was emptied!

Pretty sure that is a 40cu ft size... and poorly mounted transversely.
He was unused to the extra width and could be heard clanging around hatchways inside the wrecks... and is clearly in distress about buoyancy as he exits.

A better solution IMO would have been to take him aside and run over the basics of conserving air consumption on a single tank and a few skills checks vs task loading an already stressed diver with a large pony.

 

[caruso]

The 'solution' was to strap on a pony and switch to that after the primary tank was emptied!

He's doing it wrong.

 

[doctormike]

As Dirty-Dog mentioned, the same piece of gear gets a different name depending on what you are using it for.

OC backup? Pony bottle
CCR backup? Bailout
Rich mix for accelerated deco? Deco bottle
Part of your overall gas plan? Stage bottle

It's not unreasonable for someone with a high SAC rate (especially when diving with a buddy with a lower SAC rate) to just bring along a pony as a stage bottle. It is the same gas planning as if you were using a larger tank, but it also gives you some degree of redundancy. And some dive locations may not have 100s or 120s available for rent, but they may be able to give you a 40 to sling.

Sure, if it's part of your gas plan then you no longer have the full tank volume available as your redundant gas supply, but not everyone dives with a redundant gas supply. So the basic fact that you are including it in your gas plan isn't automatically bad technique.

Most people using a 40 as a stage bottle breathe from it at the beginning, leave some gas in it so that it can act as a (smaller) redundant gas supply later in the dive, and then switch to their back gas. Apart from the fact that it's a 40 instead of an 80, this is functionally similar to sidemount diving.

Of course, if you are diving in conditions that make a decent sized alternate gas supply necessary (physical or virtual overhead), then you need to account for that with true redundancy.

 

[flyboy08]

What if your diving with Ean32 on your back and your stage bottle is 21%?

 

[doctormike]

What if your diving with Ean32 on your back and your stage bottle is 21%?

Not sure why you would plan it that way, but then I guess you would just have to remember to change the mix in your dive computer when you switched to your back gas, just the same as with any other gas switch.

 

[flyboy08]

Not sure why you would plan it that way, but then I guess you would just have to remember to change the mix in your dive computer when you switched to your back gas, just the same as with any other gas switch.

Just bought a Pony....never dove with one. I assume I can fill it with Ean as well?