AL40 for redundancy diving single tank on deeper dives.

[BenjaminF]

Your best back up air source is your buddy. But your buddy needs to be competent and willing to help in OOA situations.

And remember to refer to them as your "dive buddy", and not as a "mobile backup air tank". It helps keep the dive slightly more fight free...

 

[guyharrisonphoto]

I'll weigh in with another perspective. It seems that much of this discussion assumes AL 80 tanks (as these are what is for rent everywhere). When my wife and I recreational deep (90' or below) we rent big tanks (100s or 120s). Thus, as individuals, we each are "carrying" a 19 or 40 cf "pony" With this built-in cushion, we have the same protection against going OOA as even the largest pony would give, without the need for extra gear, and manipulating it at depth or messing with it when gearing up. If there was an unexpected equipment failure for one of us, we would have the extra 20 or 40 cf cushion in the other's tank to get to the surface.

I recognize that big tanks are not available for rent everywhere, but where we dive it is our regular option.

This does not give redundancy, only extra capacity, but gear redundancy is what your buddy/team is for.

If I had to regularly deep dive with insta-buddies and could not get big tanks, I would get a 19 cf pony as a personal emergency reserve for any dive deeper than 90'.

 

[stuartv]

we have the same protection against going OOA as even the largest pony would give.

I don't believe that is true. If you blow out the tank valve O-ring on an 80, your pony will still take care of you, even if your buddy happens to not be close by. Having your buddy use a bigger tank is more protection than having your buddy using an 80. But, it's not the SAME as carrying a pony.

You might discount this failure as so unlikely that you wouldn't plan a contingency for it. Or you might dive on the basis that your buddy will always be there to help.

But, if it's the former, well, I got my own tanks back from VIP recently. I let a buddy use them. We were out on a charter boat and he got back on the boat from a dive. He put his tank in the rack behind his bench and attempted to turn the tank in its spot by grabbing the valve. The valve turned on the tank. We both looked at each other with WTF written all over our faces. Apparently, the VIP inspector didn't put the valves back on the tanks very tightly. The point being, if I were renting tanks, I definitely would not want to just assume that my tank will never have a catastrophic loss of air.

I think the best idea is to be totally self-reliant AND be the best buddy you can be. If you and your buddy both do that, then you should complete every dive in good shape.

The experience definitely has made me start thinking about carrying a pony bottle on deep(ish) single tank dives.

 

[guyharrisonphoto]

Hi Stuart, I think I qualified later in my post that we have the same gas capacity as pony divers with regard to preventing going OOA, but not the same redundancy of equipment n the event of failure.. We rely on our buddy system for redundant equipment in the event of equipment failure, and the buddy's bigger tank for gas to surface. Personally, we don't want extra weight, extra bulk, extra complexity, reduced streamlining, and extra stuff to manipulate, which is why I have so far resisted a pony, when I can get the same benefit with good buddy practice and a little bigger tank.

 

[rjack321]

OK, I'll bite: why not clip the AL40 to your right side? That's where I had it when carrying two stage bottles. Should I have carried both on the left side?

After using both a button gauge and a 6" rubber hose with a gauge, I like the compactness of the button, but found it easier to read the gauge on a short hose. Probably just my lousy eyesight.

Less than 100 dives and carrying 2 stages??

Right side stages are a royal pain to route the 2nd stage hose (compared the the left which conveniently goes behind your neck)

 

[dberry]

Less than 100 dives and carrying 2 stages??

Right side stages are a royal pain to route the 2nd stage hose (compared the the left which conveniently goes behind your neck)

LOL, no, that's not my average weekend diving kit, and I only slung two tanks on one deep dive. It was in a deco procedures / wreck class, and one was for deco and the other wasn't a really a stage, it was a 72cf as redundant air supply for contingencies (same as backgas), since my RMV really sucked during the class. FWIW, I wasn't draining doubled LP85s on one dive - we were double-dipping, two dives without fresh tanks, and it seemed like a good idea to leave some air in the tanks at the end

That was one of the biggest surprises - whether due to stress, excitement, dealing with back mount doubles for the first time, or all of the above, my SAC/RMV was running almost *double* what I had been used to with single tank back mount.

I'll be getting my own doubles set and will be getting comfortable diving it in fairly shallow water for a long time before doing any deco dives.

 

[rjack321]

In doubles you ought to have a long hose and the right sided stages will conflict with that too.

The only time a cylinder goes on the right is sidemount...

 

[dberry]

In doubles you ought to have a long hose and the right sided stages will conflict with that too.

The only time a cylinder goes on the right is sidemount...

Tell that to the instructor, who isn't a fan of long hoses for wreck diving. I'm in no position to argue with either him or you!

 

[rjack321]

Tell that to the instructor, who isn't a fan of long hoses for wreck diving. I'm in no position to argue with either him or you!

welcome back to 1990!!!

 

[rongoodman]

Is the instructor in favor of 95# OMS wings too?