beginning with doubles

[AlaskaDiver]

im not sure but i dont think i would have a problem here. i am 6'3" 295lbs and play football so the issue of hauling them around and in/out of the water wouldnt be a big one i dont think.

Carry my tanks too!!

 

[TSandM]

It's not that it's any harder to swim around with double tanks on your back. It's just that an isolation manifold introduces a bunch more failure points, and unless you can manage your valves, it's a net negative rather than a positive. Doing valve shutdowns without losing buoyancy control takes some work.

My husband and I both took the route of establishing excellent buoyancy and trim under task loading BEFORE adding doubles, and the transition was pretty easy. On the other hand, I watched a friend switch to doubles before he had his issues in a single tank worked out, and I think he struggled a lot longer to get the doubles dialed in.

 

[tstormdiver]

I had well over 100 dives before I did my first dive in doubles,.... & it was a disaster. Long story short, I wasn't prepared for the negative buoyancy of 2 steel tanks on my back & got into an uncontrolled descent, that I finally got under control at about 95ft (5ft off the bottom). After about 2 dozen dives in them so far, I'm still on the learning curve, but getting better each time. Last time I dove them, I was with a very experienced cave diver & he had me try some barrel rolls. Got through them without too much struggle, but they are a pair of beasts to handle at times. MY confidence level is slowly building, but I'm now very cautious about the circumstances I 'm going to dive in them, before I do (AKA, lesson learned about pushing limits in new equipment). I'm hoping this summer to get with my technical instructor & start learning some of the fundamentals (right now, he just wants me to get used to them & be able to control them).

 

[limeyx]

I'm trying to remember. I think Jacques Cousteau had a set of these. They sorta looked like 3 40's hooked up together.

I saw a guy locally (at Casino Point on Catalina Island) with triple 40's once.
Very odd. No isolator, I think maybe only one 1st stage ?

 

[Blackwood]

It's not that it's any harder to swim around with double tanks on your back. It's just that an isolation manifold introduces a bunch more failure points, and unless you can manage your valves, it's a net negative rather than a positive. Doing valve shutdowns without losing buoyancy control takes some work.

If manifolded, he can treat them like singles (abort on one failure) until he's managed to get solid enough to add valve tasks (that doing so totally defeats the purpose notwithstanding)

 

[TSandM]

If manifolded, he can treat them like singles (abort on one failure) until he's managed to get solid enough to add valve tasks (that doing so totally defeats the purpose notwithstanding)

That's true, but then he's got all the extra failure points of a isolation manifold setup, but none of the advantages.

I suspect, however, that quite a few of us did a few dives in doubles getting our balance before we even started playing with the valves

 

[Walter]

They must be tiny tanks!

Yep.

It's just that an isolation manifold introduces a bunch more failure points

True, which is one reason I use a manifold without an isolation valve.

Doing valve shutdowns without losing buoyancy control takes some work.

Any new skill takes some work.

I saw a guy locally (at Casino Point on Catalina Island) with triple 40's once.
Very odd. No isolator, I think maybe only one 1st stage ?

Sounds about right.

 

[jim T.]

It's not just the weight though. It's balance. On shore dives, with doubles, you may find yourself limited by climbing over rocks, logs, etc. or having to go up and down a reasonably steep sandy path in a bank, etc. Once you start falling over in doubles you're usually going all the way! On a boat...? One big lurch and over you go if your buddy isn't around to steady you. You're going to have near/over 100lbs. of stuff on you with doubles.

Starting with a backplate and singles wing as opposed to a jacket b.c is a definite plus though!

I waited until at least 50 dives to try doubles (and that's probably earlier than most)
and I was very glad that I got confident with a singles rig lst. Going into accidental deco time wasn't a problem for me (due to all that extra gas) because I'm the paranoid/neurotic type anyway and always watched (watch) my depth and time like a hawk, but for a new diver it would be relatively easy to forget-if you're not the paranoid/neurotic type.

Learning your SAC rate and how fast you actually go through a single tank on various dives under various circumstances will give you a much better idea of how long your air will last and you'll probably go diving (if shore diving) a lot more often and to more varied sites.

I agree that doubles are steadier underwater than a single which is easier to "roll" with, but that's only after you're somewhat used to them. Definitely get a mentor or two who regularly dives doubles to show you the ropes. Do not try them yourself at lst. It IS easy to turn turtle, end up head down, etc. especially while figuring out where your trim weight should go, etc.

If you can pick up both rigs at a really attractive price that's great, but I would recommend waiting on diving doubles for now. Later, you'll be glad to have a singles rig too for easier (lazier) shore dives. I've got about 45 dives on my HP 100s and I'm still getting the feel of them although I'm pretty comfortable with them now.

You only need that much gas if you're going deep, need the redundancy, are going purposely into decompression time or overhead environments like wrecks, caves, etc. which of course is a very dangerous thing without the proper training and should of course,definitely not be done as a beginner.

 

[limeyx]

Yep.



True, which is one reason I use a manifold without an isolation valve.



Any new skill takes some work.



Sounds about right.

I could be wrong, but doesn't the isolated manifold only introduce a failure of the isolator itself compared to a non-iso manifold ?

So there is then no advantage to the non-iso version as you always lose all the gas in both tanks with a failure that an isolator could help with ?

compared to independent doubles/sidemount I could see some real pluses and minuses but I dont see the benefit of a manifold with no isolator -- what am I missing ? Where does it help ?

 

[Colliam7]

when i say set up for doubles and singles i mean that one bp/w has doubles on it now and another has a single on it now. and everything needed would be coming with both rigs. i may pick them up to save for a later date and just play around with them in my pool for awhile while im refining my skills.

A good idea, if they are reasonably priced. That's why I tried to separate the two potential issues (buying the gear vs diving early on with doubles) in my original post. If the gear purchase is a good deal, go for it. I like diving doubles. Like most of those on SB I started later in my diving experience (my first doubles dive was #150). But, I doubled up some HP steel 120s and took them to a quarry, then on an ocean (boat) dive wet, then on another dry, and found they were fairly straightforward to dive. (Then I started tec which wasn't as straightforward.) Knowing what I know now, I probably would have started down the doubles path sooner, not as an exclusive diving rig, but in addition to singles. One perceived challenge of doubles is that many start with them at the same time they begin tec training, and we therefore tend to associate doubles with tec diving, which probably isn't appropriate. Tec IS a task loaded environment, but the doubles are only one small piece of that. So, if you can carry them and afford them and start with them in a prudent manner (your pool sounds like a good idea), why not?