doubles worth it???

[Xman]

Its ok, the penny has finally dropped and I understand what you are getting at. It certainly gives you much more flexibility on how you use that availble gas, and gives you the opportunity to do a first dive requiring a greater amount of gas.

You are quite right about the regulator failure. I was having "a moment".

 

[mweitz]

LOL, your post is what I should have said! Sometimes I have trouble explaining! Yeah, you have more options.

I know 7 or 8 people that dive recreationally with doubles. All like them and probably half will move onto technical diving.

Mark

 

[TX101]

I dive doubles (or twins as we call them) and have done since about dive #45 or so. I usually dive them no matter what sort of dive I'm doing because I don't have a STA and my wing is a doubles only wing, means if I dive a singe I have to move back to my stab jacket. This keeps everything consistient between "rec" & "tech" dives.

I agree with most of the comments here - get some experience before you start thinking about doubles, etc. The good thing about a single is it has some inbuilt "saftey" in terms of DCS. That is, usually your air consumption is so high when you start that you could not stay down long enough to get DCS even if you tried.

The only thing I really disagree with is the cost. It's really not that much more expensive! If you have the ability to do two dives a day with your current rig (ie. you own 2 cylinders so you can do 2 boat dives without having to return for refills), all you need is another 1st stage, some twinning bands, and an isolation manifold. Even if you only own 1 cylinder currently, you just need to buy a second cylinder... (and you dont even need to buy a valve, since you get that with the manifold kit).

Compare that with buying a pony - where you have to buy another cylinder, another full reg (1st and 2nd stage), spg and mounting rig. It's not a whole lot more - especially since there isn't much price difference between a 3ltr and 12ltr.

 

[mempilot]

I think his point is that you aren't leaving gas back on the boat. That 500psi and it's associated cubic feet go with you on the second dive and can be used in the reserve calculations.

Whilst I agree with most of your post, I don't agree with number two (quoted above).
If you save a 500PSI reserve in your doubles at the end of the second dive, then this is no different to saving 500PSI in each tank if used seperately. The 500PSI in the manifolded doubles = twice the actual gas that 500PSI is in a single tank.
If you mean that you will go lower than 500PSI in the manifolded doubles, then you are defeating the point of the redundancy.
This is the confusion that arises when you discuss PSI(or BAR/mPa) as though it is a measure of gas volume. It is entirely dependant (as you know already I'm sure) on the internal volume of the specific cylinder/s being discussed.

 

[Wijbrandus]

Doesn't your reserve supply requirement drop as you move to shallower depths? Wouldn't that allow you to plan a second dive on what was the "reserve" for your first (deeper) dive?

From the plans I've seen for people's "rock bottom" calculations, I could make quite a nice set of dives. If you just used the margin of difference between the reserve requirement of the first dive and the second dive, you could make a great 40' dive, for example.

I've never used doubles, but this is the impression I have. Am I all wet?

 

[MXGratefulDiver]

Remember that with singles you leave the reserve from your first dive on shore. With doubles you take that same reserve with you on the second dive.

... Bob (Grateful Diver)