Using a twin cylinder?tanks. .

[Karel26]

I konw to alot of people this my be a stupid qeustion,
but i have been taught that only clever people ask qeustions. .


I have always been curiouse about the twin cylinder. .
When will one use twin cylinders to dive and what are the
benifits if one only has a certain time to dive in the
decompresion limts. . Are there courses that one need
to be able to do a twin dive. .

I am not sure but my logic tell me that it sounds to
be some what technical. .

I will ask more questions during the tread if i learn more
about it. .

Thank you. .

Live to dive and dive to live. . . . :burnout:

 

[tstormdiver]

People ( a lot of, but not necessarily all,techncial divers) dive twin cylinders for many reasons. Among the top reasons are for additional air (longer bottom times), that may very well include decompression diving & also for redundancy (2 air sources is better than 1 in an emergency where coming to the surface may not be an option). There are many configurations that twin cyliners can be set up in (back mount, side mount or even no mount). I dive back mounted double cylinders with an isolator manifold. As a student learning to cave dive, I use my double cylinders for a combination of both longer bottom time & redundancy of my air source, if needed. I would be certain that there are courses available to learn to dive double cylinders, I learned personally, by diving with experienced technical divers who have a lot of experience with doubles. Kind of a mentoring process. One thing I will say (at least for me) is that learning to dive double cylinders was like learning to dive for the first time all over again. Your balance, trim & buoyancy is completely different. I took me a little over a year to get comfortable diving doubles. I'm sure there are those who take to it with very little issues; not so in my case. Diving doubles, while not incredibly hard, is different & should be approached in a methodical manner.

 

[Diver0001]

The above is how I see it too

- larger capacity
- redundancy

In terms of capacity, two tanks generally provide more stability than one large tank. For example a twin 50 will probably feel more stable in the water than a single 100. In any event that's my experience.

One point about redundancy. All of the redundancy in the world won't help you if you can't use it... if you can't reach the valves, if you don't practice shut downs, etc. I see lots of people diving with twin cylinders who would be just as well off with one, for this reason.

Unlike Tammy, my experience in making the change was immediate. The twins felt perfect from the first moment I had them in the water and I never looked back. In fact, now I use my twins all the time. I still have a single-tank set but I only use it for teaching because the shop makes me (er... "strongly recommends") wearing what the students are wearing.

R..

 

[Karel26]

Okay longer dive time can work. . My qeustion though now
is that i am very blessed, i can use a 10liter cylinder and do
my full dive, even at 66 to 72 feet in can do my whole dive
then most of the times the dm will say that its time out we
must acsent. .

So then i will use most of the other air for for a deco stop
or how will it help me by ussing twins? ?

 

[Diver0001]

The way it sounds it probably won't help you to use twins. A 10 litre tank isn't prone to being unstable and since you don't need the extra air then I can't see any benefit for you in that way.

Redundancy is a separate issue but I would assume that you're diving within the NDL's with a buddy so in a sense your buddy is your redundancy. If you're not diving over the NDL's, solo or in (semi) over-head environments then the extra redundancy beyond what your buddy offers isn't really needed.

That said, I'm curious. What, exactly, prompted you to ask this question?

R..

 

[DA Aquamaster]

My conversion to doubles was similar to Diver0001's - a non event rewarded with increased stability. I also started with double steel 50's which were popular in the 70's due to great stability, so that no doubt helped.

I don't currently own a single tank - unless you count stage bottles or single tanks set up for twin tank side mount diving.

For a decade or so I dove independent doubles cylinders. (two back mounted single tanks not connected with a manifold). It offerred 100% redundancy as well as extra gas on deep dives. I switched to manifolded doubles when I started Cave diving, and I am currently switching to side mount diving.

All my diving is in doubles. If I am cave diving I am using doubles for the extra gas (2 hour or so bottom times) and the extra redundancy (maybe 2000' back in a cave is a bad place to lose all your gas. In that regard the need for doubles is driven by technical diving requirements.

However on local quarry dives, I dive the same configuration (for practice mostly) but do both dives on the same set of tanks and still have a very healthy reserve. In that regard there is some economy in just setting up your gear once.

The same is true on North Carolina Wreck dives in the 80-120' range. I set my gear up at the dock, due the first dive using no more than half the gas (not an issue as even with double 100's that will be enough to getme into perhaps 10 minutes of deco) and then use the remaining gas for the second dive, again with an ample reserve. That approach saves me from ever messing with my gear and changing tanks on the boat.

Side mount diving involves useing independent doubles clipped to your sides. It offers great stability and comfort (once the bugs are worked out) and gas management is the same as with independent doubles, but it is not as ammenable to boat diving as back mounted doubles or a single tank.

For solo diving, some form of redundant doubles makes a great deal of sense and is in my opinion preferrabel to using a pony bottle.

 

[Sas]

Yea I didn't find it difficult to swap either - at least in the water, still getting used to lugging that weight around above water . The first half an hour was uncomfortable but after that it just clicked. I think if you are very comfortable in a single tank the swap should not be hard. I notice that I have more drag when moving around (I got 12L twins) but that just makes me move a little slower.

Personally, the reason why I switched to twins was predominantly redundancy for decompression dives, cavern dives (some sites require twin tanks) and also solo diving. The dives I am starting to do now I could do fairly easily on a single tank and have in the past but with a pony for emergencies, but decided to get my own gear this time instead of always borrowing off friends . I am sure capacity will come into it later on when I start doing longer deep dives but that is a while away.

 

[TSandM]

I'd say, if you're happy with a single tank and you can do the dives you want to do with one (and they're dives within no-decompression limits, and outside of overhead environments) there's no reason to go to twins. Twins are heavy to haul around and many boats aren't set up for them. They're also expensive to fill, because even if you use only a single tank's worth of gas, the shop is likely to charge you twice as much to fill them.

Doubles are a tool. I dive them because I dive caves and I dive outside no-deco limits, and I dive them more often than I do those particular dives simply because hauling them around is good to maintain my strength. But I'm always happy to dive a single tank when it is reasonable to do so.

 

[tstormdiver]

Yea I didn't find it difficult to swap either - at least in the water, still getting used to lugging that weight around above water .

Maybe I'm just different . I tend to struggle with new things. In a way (for me) a good thing. When I have to fight to get where I want to be, I never forget the lessons learned. It's both a blessing & a curse, I guess.

 

[DaleC]

I hear you Tammy. While switching to doubles didn't cause me any undue hardship, diving and photography has caused me revert to new diver status. If I am trying to shoot video I am a mess in the water (or rather, the water I am in is a mess)