Should we get pony bottles?

[lindenbruce]

Okay, if you want a redundant air supply as an added safety margin with minimal expense and you guys are always close to each other during your dives, then I would go with an AL40 in a sling configuration. You wont even feel that size tank during your dives and is easy as pie to handle. Just practice exchanging the tank in shallow water so you guys can get than down pat.

If you are looking for more air and not worried about redundancy then go with a larger main tank if they are available. B.

 

[Jim Lapenta]

Yep, sling it. It also lessens the chance of you losing gas if the second gets bumped and you don't notice it. I like having the handle right under my left hand all the time as well. Makes a nice resting spot for it . A slung bottle is also more boat friendly as one mounted on the tank probably won't fit in the tank holders of most boats.

 

[SanDiegoSidemount]

You already have the long hoses and are good buddies, those in my opinion are the most important starting points. Your safety margin with 2 air supplies and 4 good regulators between you is already pretty good.

I had a similar set of concerns as you about redundancy and extra air, especially when I became more diligent about Rock Bottom gas management, and playing out all the "what ifs" in my mind. My solution was to reconfigure so that I dive double side mount AL80s. (I use a UTD Z-System with LP manifold, which always gives me a working necklace and long hose.)

My most frequent buddies -- my wife and son -- dive back mount singles, so I'm responsible for carrying our redundancy/safety margin. I'm fine with that: it's surprisingly easy to carry side mount doubles, and it is probably more streamlined and better balanced than the combo of a back mount single + pony bottle.

 

[rx7diver]

This reminds me of another thread where TS&M (I think it was) posted some calculations for a buddy pair with one failed gas system (e.g.: regulator malfunction, blown o-ring) needing to air-share on ascent from great depth (let's say 120 feet?) at a safe rate, while stressed with higher-than-usual SAC rate, and do safety stops, after getting together and past the confusion of 'what's going on' at depth, on the remainder of air in just one tank.

Drrich,

I don't think this (http://www.scubaboard.com/forums/ba.../377545-gas-planning-example.html#post5831222) is the thread to which you refer, but it (including the "Rock Bottom" link supplied in one of the posts) might prove helpful to the OP. I know I, myself, learned quite a bit from this long-ago thread.

Safe Diving,

rx7diver

 

[Michael Guerrero]

In single tank I always sling a pony. 30 cu ft is probably enough, but a 40 is more versatile. It's redundancy and self-reliance. I definitely recommend slinging as apposed to mounted on the AL80. You have the spg and valve handle in front of you, so you can just charge it and turn it off. You can hand it off as well.

 

[phoenix31tt]

Thanks will check out The link



Can a pony be slung with a standard rear inflate BC?.. slinging a single tank is seeming like a nice compromise to have that redundancy between us...


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[je76]

Yes a pony bottle is a good idea for a number of reasons but I always think of two simple rules with a little story to back the second one up.

1) At any time you should be ready to finish your dive alone. A pony bottle offers a redundancy, is generally easy to carry and can be quite effective if you train with it. That doesn't mean you should take it to the absurd and carry a 80cf bottle or some other crazy amount of redundancy but a nice single back up is helpful.

2) You don't know what you don't know. That bottle may be the solution to problems you haven't even thought of yet.

I recently had a slow leak that I couldn't hear through my hood. I was diving 85fsw with manifolded 100s, dry suit, hood, gun, canister light etc etc I was separated from my teammate at depth. I decided to ascend as I was close to deco and hadn't planned on it. Fussed with gear at 65' at on point (3-5m) and when I continued up but I noticing I was consuming gas a little faster than normal. I did not have a deco obligation so I could ascend whenever I wanted BUT I had a slow leak that I couldn't hear it (had a hood on). The leak was apparently increasing in intensity as I came shallower. At the 15' mark I knew I was leaking but couldn't hear it. The leak had been slow enough to sort of mask itself.

Point is had I needed the extra gas to get me to the surface or if I accidentally had deco for some reason I may have had a much bigger problem that a 30cf could have easily solved in absence of my buddy. I can hang around 10 minutes at 15' with 30cf bottle.

Invest, train with it and carry it.

 

[Max Speed]

@max speed.. If I get one for me then the best option would be to sling so I can hand off?


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Slinging is best for me. IMHO if you're going to mount to your primary tank the valve can be hard to reach and setup is a hassle.



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[lamarpaulski]

If one pony bottle wouldn't the air hog of the buddy pair be the one to carry as most likely to be OOA ?

 

[WhiteSands]

Hi there!
I've been down this path myself and I eventually found answers that I'm currently very happy with. My answer as to whether or not to get the pony bottle is no.

My buddy is my redundant system. What we need are good protocols and good training, not slapped on equipment to circumvent the former two.

Divers run out of air because of poor gas management doctrine, rusty skills, sub-optimal equipment, poor situational awareness, poor team positioning and in very rare cases, equipment malfunction. I'll briefly go through each.

Poor gas management doctrine - E.g. I was taught to start my ascend at 50 bar. But is this good doctrine? Ascending at 50 bar from 30m requires very different amounts of gas from ascending from 10m. Is ascending from 30m with 50bar enough to share with my buddy if his regulator starts freeflowing uncontrollably at that point? Is there enough air to do your safety stops properly so you don't get bent? Clearly the answer is no. This is not a good doctrine. Much better is the concept of Rock Bottom taught by some agencies such as GUE/UTD.

Rusty skills - when was the last time me & my buddy practice our air share drills? Are we able to still do them under stress quickly and smoothly? Have we done it so many times its ingrained in muscle memory? It's a good idea to devote half a dive out of every dive trip to just go through the drills. Doesn't take a lot of time.

Sub-optimal equipment - it's common to see the backup octopus dragging on the sandy seabed on many divers. When it's needed and the OOA diver puts it in his mouth, he's going to choke. I think you already have this settled by using the longhose/necklace.

Poor situational awareness - Not checking the gauge ever 5-10mins, not checking on buddy every minute or less, devoting too much attention to equipment or photography or fighting to control buoyancy, all these takes away a divers attention to other needed things.

Poor team positioning - Not descending together, not swimming together, not ascending together, buddy too far when an emergency occurs

Equipment malfunction - With good protocols & training, it'll take a very rare event of having both diver's equipment malfunction at the same time to create a life-threatening emergency. Mitigate it by not servicing your regs at the same time for e.g., in case the servicing job was not done properly.

Check out GUE Fundamentals, where all this is covered, no point trying to reinvent the wheel.