Down deep...things to remember

[Chaseh]

I like the guardrail analogy. You can make similar arguments about many forms of safety equipment in life. I've been down over a hundrew times with a hung air source and I've never seen it used, the dives are planned and followed.

Funniest thing I saw was one hung in Belize at a manditory stop after a deep drop into the Blue Hole. The stop had the added entertainment of a shark feeding from the boat, and we loved watching the reef and bulls swarm around us as we were parked in the sand. I don't know if I would have liked to make a quick dash for the can of air.

 

[OneBrightGator]

Interesting... because I would consider the reserve my buddy and I plan into our gas management as the guardrail, because most likely if you blow through that you're done six ways to Sunday. I suppose you could consider a hang tank as a second guardrail behind the first, because if you've got enough steam to blow through the first the second probably ain't gonna save your *** either.

 

[Snowbear]

I like the guardrail analogy.

Me too!! Gator's guardrail analogy is pretty Bright

 

[OneBrightGator]

Well, I've been Bright all my life

 

[OE2X]

Why hang a tank if it's unnecessary? Those of you who advocate it all say that you haven't seen it be used. That this tank isn't put into the gas plan. So it's unnecessary? Right?

So I assume your gas plan is rock bottom or thirds for your buddy or team. If this is the case a free flowing reg, burst o-ring, etc... is very easily resolved. You go to your buddies back gas. You know the gas that you figured into your gas plan topside before the dive for just such and occurance. You plan each dive based on that every time you go diving. Doesn't matter whether it's a shore dive or a boat dive. Don't you always plan a contingency reserve of gas into your buddies and your own tank?

Why then do you need a hang tank?

Does Murphy join you right when you get to the line where the tank is clipped off?

What happens if you are 200' horizontally away and 80' below the hang tank with a one knot current pushing you away from the line? How do you get back to the tank now that Murphy has become part of your team? You don't.

To me the solution is simple: You use your buddies back gas which you planned for, make your ascent doing your planned stops and somewhere around 30' you blow a bag so that the captain of the dive boat can follow you. You surface no worse for wear and in no danger of taking a hit.

Maybe you folks like redundancy. That's a good arguement. But how many of you dive a single tank with a Y valve and two first stages? I'm guessing that like most of the rest of us you are either diving a single with one first stage and two regs or you are diving doubles in a standard configuration. How many of you carry pony bottles for backup? Maybe you just like having the hang bottle because you don't feel that you can trust your buddy to stick to the dive/gas plan? Can you honestly make that swim back to and then ascend the line in time to get to hang bottle all by yourself?
I know I couldn't. That's why I'll stay right near my buddy until we get back on the boat.

Plan your dive and dive your plan.

 

[OE2X]

In fact, the most likely scenario for the tank to come in handy would be if your reg free-flows. Obviously you try to stop it. If you do, great, if not, not so great. In either case you will be down a bit on air. If it is a significant amount, or if you were at the end of your dive you may not be able to make it to the surface, but more likely you may be forced to blow off your safety stops and/or ascend a bit more quickly than you would like. I would much rather be able to make my way to the line, get to the tank, and do my safety stop then skip them and risk DCS.

Kestrell

You've dropped down the line to 100' and have been swiming away from it (at a reasonable pace) for 6 minutes. There is no current at all. You are still well within NDL. Your reg goes into free-flow.
What do you do?


You spend one minute and can't fix it.
What do you do?

 

[QuoVadis]

It's just a safety issue only to be used in an EMERGENCY when a drop tank may mean the difference between life and death. The best ones are never used...but SOME OF US don't have THOSE KIND OF EMERGENCIES ON THEIR BOAT!!! They can magically plan for ANY UNFORESEEN emergency...that is impossible to do. Can you get to the tank? Will it be in use by someone else? Who knows but at least give the diver a chance. No I have never been on a dive where one is in use but if given the choice I would say "hang one"!

 

[OneBrightGator]

There's a difference between unforeseen and unplanned for.

As far as my gas plan goes, I've accounted for about every possible emergency situation, a hang tank will not save me from those that I haven't accounted for (aliens, killer whale attack, rapture, etc.)

 

[QuoVadis]

There's a difference between unforeseen and unplanned for.

As far as my gas plan goes, I've accounted for about every possible emergency situation, a hang tank will not save me from those that I haven't accounted for (aliens, killer whale attack, rapture, etc.)

I see your point. Nothing beats good planning and nothing should. It's just an extra safety precaution in my view. Nothing wrong with that.

 

[Uncle Pug]

They can magically plan for ANY UNFORESEEN emergency...that is impossible to do.

... and it isn't impossible... it is simply planning.

There are somethings that truly can't be foreseen but it isn't wise to then conclude that modes of failure cannot be anticiplated and appropriate mitigation planned.

Try to identify the things that could conceivably go wrong. Determine the likelyhood that one (or more) might occur. Plan an appropriate mitigation for those that you can.

Several years ago a recently restored Boeing 307 Stratoliner ditched into Elliot Bay near Salty's resturant on Alki in Seattle. No one was injured but it ruined the restoration of that historic and extremely rare aircraft. Was this unforeseen? Yes. Should it have been anticipated as a possibility and an appropriate amount of fuel have been carried? Yes.

Where the Stratoliner ditched is called Cove One and it is a popular dive training site for OW classes. (Fortunately there were no divers in the water when the plane ditched.) Would this incident be classified as unforeseen from a diver's perspective? Yes. Should it be anticipated as a possibility (it has already happened once remember) and steps taken to mitigate? No... the possibility is there... but it is very very remote even though planes fly overhead all the time.