Doubles?

[liuk3]

Yes, that's snow ... but it wasn't too bad. We dress for it ...

Wow! That's pretty cool.

 

[halocline]

Worst case scenario you have a manifold failure or are unable to operate the isolation valve for whatever reason.
With isolated doubles no action is required by the user to preserve half their gas, unlike manifolded doubles.

This does not explain how a single failure in manifold doubles could result in the loss of all your gas. If the isolator failed, you just couldn't isolate in the event of an additional failure. If any other single failure occurred you could use the isolator to save the gas in one tank. It takes two failures to lose all the gas, just like independent doubles. Or am I missing something?

The main benefit of the manifold is to retain access to the gas in both tanks in the event of a reg failure. With independent doubles if you lose a reg, you lose the gas in that tank. Since regs are MUCH more likely to fail (freeflow) than a tank valve, this is a pretty big safety advantage. Another big advantage is that you automatically breathe down the tanks evenly, which means you will never mistakenly empty a tank and lose redundancy.

The fact that there are a couple of additional o-rings in the manifold is essentially meaningless. Each joint in the manifold is sealed by either double or triple o-rings. That means ALL the o-rings on a particular joint must fail for the manifold to leak.

 

[DA Aquamaster]

Matt is correct. In the event you had a burst disc failure, you would have to be able to isolate to prevent you form losing all your gas. So unless you also have an isolator failure, or are in a restriction that prevents you from reaching your isolator valve, it is a non issue.

Which is to say JDMerk is also correct as if you have the same burst disc failure in independent doubles, no action is required, so if you are in a restriction, etc and can't reach the isolator, you are covered even.

Both systems make sense in different circumstances.

I have never heard of a real life manifold failure where the center bar or related o-rings catastrophically failed so that is even less of an issue.

 

[DA Aquamaster]

Do you guys realize that the OP is a 15 year old high school student with somewhere between 0 and 24 dives and you're arguing about whether he'd be better off with 216 or 260 Cu Ft of gas on his 100+ pound rig?

Terry

Having been 16 and survived doing incredibly stupid stuff in cars and airplanes at that age, having used firearms from about age 8, and having run with scissors for most of my life, I'll ask if you realize there are a whole lot of things that a 15 year old could do that are a lot more dangerous and irresponsible than diving doubles?

For example, I'd rather see him spend $500-$800 on doubles than to spend the same amount of money on crack.

So a 15 years old sees diving as adventurous and wants to dive doubles. Great! We need a lot more of that not less and I'd encourage more people to encourage such obviously rampant irresponsibility in our youth - because it is a lot healthier than most of the alternatives.

There is some irony here as at 15 I would not have wanted to carry 140 pounds of tanks, wing, regs and plate - and a far lesser load of 85 pounds about killed me in OCS at age 22, but oddly enough I strap on that 140 pounds on virtually every dive at age 44 and think nothing of it.

 

[BabyDuck]

heh - so does his chubby girlfriend!

 

[MXGratefulDiver]

Do you guys realize that the OP is a 15 year old high school student with somewhere between 0 and 24 dives and you're arguing about whether he'd be better off with 216 or 260 Cu Ft of gas on his 100+ pound rig?

Terry

Of course ... and once we've got him into the biggest set of doubles he can carry, we're gonna send him to the "Carrying Three Regulators" thread ...

... Bob (Grateful Diver)

 

[Kevin Carlisle]

Of course ... and once we've got him into the biggest set of doubles he can carry, we're gonna send him to the "Carrying Three Regulators" thread ...

... Bob (Grateful Diver)

LOL.. now that was just mean..

 

[DevonDiver]

I was wondering about doubles. I'm Just OW.........I know the dangers of diving so don't tell me not to do It.....

Excuse me far saying this....but as an OW diver, how can you profess to "know the dangers of diving".

You know what has been taught to you...and at OW level, that is the basics...just what you need to know to enable you to smootch around a dive site no deeper than 18m, using standard recreational equipment and nothing more.....

You were trained on single cylinder...so dive on a single cylinder.

You want to dive on doubles....then train to dive on doubles.

If you don't see that there is a difference (or increased dangers) of diving with doubles, then it only reinforces my point that you need training....then you would be educated on those new dangers along with the skills and drills you need to offset them.

 

[Web Monkey]

Of course ... and once we've got him into the biggest set of doubles he can carry, we're gonna send him to the "Carrying Three Regulators" thread ..

It's a little sad that even new divers think that all diving has to involve large amounts of gas and equipment. I think it's one of the unfortunate side-effects of unlimited information availability on the internet.

Some of my happiest dives have been hanging out in a sunny spot in about 30' with nothing but a single tank, a reg and a wetsuit, watching the fish in the grass.

Terry

 

[DA Aquamaster]

Some of my happiest dives have been hanging out in a sunny spot in about 30' with nothing but a single tank, a reg and a wetsuit, watching the fish in the grass.

I said the same thing...before I discovered doubles, offshore wrecks, caverns and caves.

It does not in any way reduce the beauty of hanging out at 30 ft watching the fish in the grass, but it does greatly expand the range where you can find and experience the beauty diving offers.