Twin Tanks

Is diving with twin tanks different from diving with single tank (does it need a course) or it is just the same but more air?

gehadoski:

Is diving with twin tanks different from diving with single tank (does it need a course) or it is just the same but more air?

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Well without knowing exactly what tanks you want to double up and what tanks your currently diving, I'll go out on a limb and say, yes, it is very different. You don't need a course but you should have another expierenced diver (with doubles) to help.

You need to work on trim and diving overweighted thoughout most of the dive. You'll need to learn the valve shutdown procedures. (One of the reasons to have doubles) And the last part is that you really could use someone who know's to go along on your first few dives to ensure you don't hurt yourself in the learning process. ascents and descents are more involved when greatly overwieghted.

Mind you, in my case I went from either an Al 80 or Steel 120 to double 104's. Basically from 20-30lbs lead to none

Mike

thanks alot you were very helpful, sorry cause I didn't meantion that I am talking about duoble 12 liters of compressed air.

Yes, I would say it is very diffrent. My singles felt like a Ferrari and my doubles more like a minivan!

gehadoski:

Is diving with twin tanks different from diving with single tank (does it need a course) or it is just the same but more air?

Click to expand...

I'll second what the others said about the few extra skills you need but I'll add that I find double 12's easier/more comfortable to swim in than a large single (steel) tank. Part of it has to do with the tanks themselves; the tanks are thinner and closer to your back and don't pull you over as much when tilt. Part of it has to do with the fact that the bp/wing is much more stable feeling on your back than a stab-jacket is. Part of it has to do with what feels to me like less drag so the whole thing, even though larger goes faster than a stab-jacket and large tank and part of it has to do with the fact that you only need minimal (if any) extra weight so it doesn't feel as heavy under water because there's nothing hanging around your middle.

The surprising thing is how long it takes to vent the bladder. A stab-jacket has some disadvantages but it vents WAY faster than a moderate/largish wing. That means, just like when you learn to dive a dry suit, anticipation is key to keeping buoyancy control....especially when you start.

R..

The main difference I noticed between a single 80 and double 80's is the weight, slow response to mainain bouancy, slower than shooting air in a wing with a single, takes a little longer to "respond".

I'd suggest finding someone local that has experience wtih doubles so they can show you the ins and outs, I have 3 dives in on my doubles and started making changes after the first dive and taking good advice from people that have been there done that.

I did enough reserach and talked to enough people on scuba board I went into doubles with no problems, however my local peeps are helping me "tweak" the setup

I'd been diving solo in 20-30ft of water in a lake, since I can easily freedive my drysuit to 40. I started reading about solo diving redundant systems, and decided more air and an extra regulator on a twin manifold I had laying around would be a good way to go. It doesn't drive like an SUV as much as it feels like pushing one. A standard fin and kick at a standard pace will move you along at about 6 inches per kick (with no current).

The real beauty is that I'm now exploring places that I'd never seen before, well beyond the horizontal range any other diver would have. Its turning all the old dive spots into new adventures.

I don't have enough experience to be anything close to an expert, but I do have a couple of pieces of advice. Have at least 65lbs of lift for a BC. If your going to be in the current, it better be a drift dive, a crawl dive (extra, extra weight), or aided by a scooter. I've got a scooter in mind that is fast enough to fight the current, but without overdriving the headlights in the murky Puget Sound, make sure the batteries handle longer dives, and you can stay warm for two hours. Chill'n leads to cramp'n, especially when your push'n twins (sounds like childbirth - sorry )

Most divers that die, drown from running out of air. Its nice to have a nearly 1.5 to two hour dive, and return with nearly 1000 PSI. One of the dive shops even filled me up for one tank charge fee, since I had so much left over!

Really think about getting a lot of buoyancy. I'm thinking 85-90lbs of lift on a wing would be better. I want to be able to use the wing like an inner tube and have a chance of swimming back to shore against a light current. Diss the equipment and swim, if your life depends on making back to a boat of shore. A current is going to win against the twin.

Doubles eh? Hell, it's all I can do to get off the bench with one tank let alone two.

It depends on how you set them up and intend to use them:

Isolated Manifold. You need training on how and when to conduct
'shut-downs'. This isn't required for recreational diving, but has the benefit of giving you redundancy as well as increased volume.

Independant Tanks. You can dive the twinset with both tanks unconnected. Some basic advice and practice on how to 'balance' your consumption between cylinders will allow you to use them in the most safe manner, to give an element of redundancy.

Manifolded (Non-Isolated). You can dive the twinset as though it was one big cylinder. No specific operating procedures required. Obviously larger volume than a single tank, but no benefit of having a redundant gas supply in the event of emergency.

Other than that, you would certainly benefit from some training or mentoring about how to most efficiently configure (set-up) and dive with (finning technique, trim, buoyancy) the twinset.

I had 4 AL80 I wasn't using, and another SB member suggested I double up a set. It's a cool learning experience. But IMHO I needed another experienced diver to show me how everything goes. It takes some getting used to jumping off a dock with all that stuff on. I do want to get steel tanks instead of AL.