How to configure independent doubles

[Tanto]

I believe that the huge flow rate of the Jet is due to the second stage, as a simple comparison with the Cyklon will show (they share the first stage).
Anyway, flow rate and breathing effort are entirely different things, in most situations.
A fit, well trained and relaxed tech diver at 300 ft breathing hi helium mixes in the correct position (horizontal body, face partially tilted up) will probably breathe half cubic foot per minute * 10 atmospheres = 5 cubic foot per minute, any reg will provide that, cracking and inhaling efforts will be the only things he will notice, so any second stage with a good venturi and a good adjustment knob will do.
So in a "safety" perspective, DAA reasoning seems absolutely flawless to me.

 

[Manos]

I compare diving indep. doubles with driving a motorcycle on one wheel. Looks cool but at the end of the day is a suicide.

Manos
www.dir.cy.net

 

[MikeFerrara]

Manos once bubbled...
I compare diving indep. doubles with driving a motorcycle on one wheel. Looks cool but at the end of the day is a suicide.

Manos
www.dir.cy.net

While I dive manifolded doubles (probably for the same reasons you do) I don't think independant doubles, sidemount for instance, is suicide.

If I was going to dive independants I'd sidemount em. No sense in having to carry both at one or suffering the larger profile when they don't need to be straped together. A sidemount diver I know swears that your valves belong in your arm pits. LOL

 

[ew1usnr]

Two other adavantages of independent doubles are:
1. It makes unscrewing the valve for a VIP quick and easy.
2. It saves money because you don't have to buy a manifold.

 

[Duncan Price]

MikeFerrara once bubbled...


While I dive manifolded doubles (probably for the same reasons you do) I don't think independant doubles, sidemount for instance, is suicide.

If I was going to dive independants I'd sidemount em. No sense in having to carry both at one or suffering the larger profile when they don't need to be straped together. A sidemount diver I know swears that your valves belong in your arm pits. LOL

I think that being able to lose all your gas at once is suicide. With independents (sidemount or backmount) you can only dump half your gas. With a manifold you do have the potential to isolate a rogue regulator and still have access to all your gas (providing you've got some left). Furthermore you can share gas more easily - though with independents gas sharing is a last resort since you should still have one funtional set. I'd say its pretty evenly balanced between independents and manifolds for safety.

Arguments are made for increased task loading with independents but I say that its not the big deal that people make out. Many European cave divers employ independents (including quad rigs) because they can be broken down easily for transport.

I prefer sidemounts due to the lower profile and ease of reaching your valves. Besides, backmounts don't fit most of the places I go.

Duncan

 

[dvas]

Hi,
as a part of my ANDI tek certification (I am trimix certified), I was teached to dive independent tanks. The main point behind it to have two totally independent systems, and with using the 1/3 rule, there is always 1/3 of the whole gas available...
If you need more info, I'll be glad to provide.

Sasha

 

[toodles]

This is so great to hear.

Cheers to all on the board that have thought through the
advantages of diving independants.

I believe most divers do not dive independants because
they were told not to by their instructor or books.

It would appear that most have not been given ALL the
information with DIFFERENT scenarios.

I understand I am in the minority and others will dive differently,
however in my travels I have found that it seems more divers
dive independants in countries outside the USA.

Why?

 

[Duncan Price]

toodles once bubbled...
Why?

The dual outlet isolation manifold was invented in the US and its adoption has spread from there. As with any configuration, each has its merits and demerits. Often the favourable case it put for one option whereas only the drawbacks of the alternatives are promoted. I know of some (cave) divers who use a manifold but dive with the isolator closed (effectively independants) when they happen to be operating alone - sort of the "best" (?) of both worlds.

I would advise against mixing a team of divers using independants and manifolds.

Duncan

 

[ew1usnr]

toodles once bubbled...
I believe most divers do not dive independants because
they were told not to by their instructor or books.

I was REQUIRED to have a two-valve manifold in order to get my cave certification.

I also dive with side mounts and do not have any difficulty monitoring the air in two tanks. I watch the gauges of course, but the tanks themselves remind me to keep them even. If I don't they will float me sideways.

The manifold keeps things simpler because there is only one gauge to watch. But, I don't think that the manifold is more safe.

I don't sidemount all the time because back mounting lets me wear bigger tanks plus stage bottles.

 

[dennisgrimm]

Is ANDI the only agency that teaches how to dive either independants or manifold safely?

Does every other agency say "independats suck" and not explain why?

Of the people that trash independats, who has actually tried diving in this configuration for an extended period of time?

I am interested in hearing from people that have dove both for more than a couple of dives about their experiences.

I have heard from too many people that repeat what they have read without trying it themslefs. [To this someone could respond "I have read that jumping off a bridge is a bad idea, that does not mean I am going to try it." Don't tell me that. Diving independants a couple of times is not 99.98% certain to kill you.]