Twin cylinders??

[kemahdiver]

Oh yeah, and on the steel tank front, you have quite a few options. 100 cf are great tanks and similar in size to Al 80s. The LP 108s are larger in size, and many shops will overfill them, giving you somewhere in the neighborhood of 120 cf. The HP 117s will give you a nice bit of gas filled to their nominal rating. Both the 108 & 117s are thicker tanks (8" in diameter compared to 7.25" for Al 80s). The HP 120's are slimmer tanks (same diameter as Al 80), but are long. They really tend to be too long for divers under 6'.

Thanks for the replies Ryan. Different tanks and more diving sound like the most logical remedies.

 

[kemahdiver]

Been there, lived that. My air consumption has improved somewhat but I have a higher basal metabolic rate than most people, due to muscle mass, and I'm always going to use more air.



Here's what I do:

- For local dives where I can bring my own cylinders, I typically dive a single HP120. That gives me slightly more run time than most people with AL80s.
- On local dives where that isn't enough air or where I'll be diving solo at depths greater than about 25 feet, I dive a twinset. I have one pair of LP72 twins, and two pairs of HP100 twins, and I have the parts to make up an HP120 twinset from my fleet of HP120 singles.
- While traveling I seek out operators who offer larger cylinders. For example, in Cozumel I use Aldora, who offer HP120s, and in the keys Conch republic offers HP100s. Most operators have at least something larger than an AL80 they will let you use if you ask, but too often it's an AL100 that is short filled to 90 cf, and that's not enough for me to keep up with most divers.

To be clear, when I'm speaking of a twinset, I'm talking about manifolded, banded doubles, that attach to the BC with two bolts.

My BC will allow me to dive independent doubles, which can be mounted ad hoc using cam bands. I've done this experimentally. Since there is no manifold, you have to switch back and forth between regulators, and have two SPGs. I might try it if I want to make a long dive in some place where AL80s are the only thing available.

While I have not asked, it is my perception that few dive boats will permit doubles unless you are on a trip that mainly caters to technical divers, and have a technical certification of some kind. They complicate cylinder handling and tend to lead to longer dives that complicate scheduling.



I dive a DSS backplate and wing. I have separate wings for singles and doubles. I believe this is the most common arrangement for people who dive twins.

2air--great information. Thanks. Think I'll spend more time looking for operators with larger cylinders. Nice to know there are some out there.

 

[kemahdiver]

Pm sent.

We use bm doubles all the time on our boat. Not a big deal for us, although we really need to raise our tank brackets a bit so that they can fit on the rack like all the single tanks.

Responded to your PM. Might have to come see y'all soon.

 

[kemahdiver]

Well the two main multi-task setups are back mounted doubles or sidemounted tanks. Before we delve into that I'd like to echo what has been stated in this thread, as you gain more experience your SAC rate will get better. New divers are often under insulated and overweighted, a combination that can kill efficiency. Also effective breathing underwater is very different from aerobic breathing or from playing a wind instrument. If you take big gulping deep breaths you'll not utilize all the o2 in the breath before you exhale it . Try to stick in the range of 33% full lungs to 80% full lungs. You probably also do more arm and body movement than you realize as a new diver.

Backounted doubles is typically two tanks of the same size connected by an isolator manifold and worn on the back. The manifolds mean either reg breathes out of both tanks, giving you a double sized air supply.

Sidemounted doubles involve slinging one tank on each side of your body, each with independent regulators. This will double you total volume but each tank is independent as opposed to backounted doubles.

Blac-Thanks for the helpful info.

 

[kemahdiver]

No - you get to a certain point and you will go through MORE air with higher capacity tanks - especially twins. Just keep diving and work on relaxing and exhaling almost completely. You may be breathing off the top of your lungs and not getting rid of abnormal amounts of C02 in your blood which just triggers another breathing cycle

Good to know. Thanks for the response.

 

[Mustard Dave]

I would try to address the cause of the high SAC before going as extreme as twins. Twins are great though, because as well as the extra capacity, you benefit from redundancy (but you should seek appropriate training to take advantage of this aspect). Over here in the UK, they are quite common, even in recreational circles; cold water and poor vis can often equal freeflows and buddy separation. Most twinset divers on recreational trips will just use half (or whatever) for the first dive, and save the rest for the second; this saves no end of faff when the others are tripping over each other on a rocking boat trying to swap cylinders for the second dive.

A couple of people have mentioned a backplate and wing. The BP&W vs. jacket debate often crops up and causes much debate, but I am a big fan. I got a BP&W when I went to twins and I will never go back. If you just want twins as a great big single tank, it is less of a problem, but to gain the full benefit (which requires you to be able to reach the valves), a BP and simple one-piece webbing harness is the answer. The BP will also take a single cylinder But you may need a single tank adapter (simple and inexpensive) and possibly a smaller wing. Some jacket BCDs will take twins, but I have never seen a setup I like the look of.

A downside of switching between singles and twins is that the reg configuration differs. On twins, you'll have a first stage on each cylinder valve and one of your second stages connected to each first stage. If you cannot get a twinset, you'll have to either reconfigure your regs, keep a separate set for singles, or use a H-valve or Y-valve (if you can actually find one).

Many operators will say only single tank diving. doubles screws their planning up big time.

I am not disputing what you are saying (I have heard this before), but it seems an odd attitude. Where applicable, the skipper or dive manager will give a maximum run time; this applies to all divers, regardless of how much gas they can carry. In this litigious society, I'd be interested in how a dive operator would talk their way out in the event of an OOG accident where they had refused to let the victim use a rig that offered an independent gas source.

 

[azstinger11]

Yup, here with the military from AZ hence the handle.

I'm not sure your diving conditions but if your dive boat doesn't offer steel tanks, just look at local dive shops and rent them separately from the dive boat. Most of the dive boats I like would only do AL80s or LP steels, but more than a few of the dive shops had steel HP tanks for rent (that was back in San Diego, haven't rented gear here in Wichita in a longgg time)

 

[KenGordon]

After taking/implementing all the tips and strategies for efficiently consuming air, I have concluded that I just suck a lot of air. Dive trips are frustrating because I have to terminate my dives much earlier than the rest of the group.
This has led me to believe the best fix is to dive with two tanks. However, during the relatively few dives that I have been on, I have never seen anyone diving with two tanks nor have I heard any dive shops suggest/offer twin tank capabilities.
So my question for the operators and experienced divers out there is: How foolish is the thought of diving each dive with a two-tank set up? Too impractical?

All thoughts, pros and cons, are appreciated.

Info. gathered here will likely drive my new BC purchase in a couple weeks. Looking at the Zeagle Ranger (twin-cylinder capable) or the Zeagle Halo (jacket style which I still prefer).

Thoughts on these BCs also welcomed.

Thanks to all in advance for your input

J.R.

The first thing is to be relaxed in the water. However, even a relaxed parent is going to use more gas than their child.

The main decider would be where you are diving.

For the sort of warm water destinations where the AL80 is the norm I would suggest diving a normal single setup but with an additional AL80 as a bottom stage. Keep two second stages on your main rig, start breathing from the stage. If you can get away with using only half the tank then you can make it last two dives which might help,logistics. Use a camband to hold the rigging on and all you need is an extra regulator. Make sure your BCD has substantial D rings on the shoulder and waist (or somewhere similar) or just get a backplate and wingback setup.
For shallow dives where gas is not the minuting factor you can leave the stage on the boat.

Mostly these destinations have a hard time supplying larger cylinders.

If diving your own kit a the home, or in a place where big singles are available then go with those. The extra hassle and weight of multiple cylinders will make your air consumption worse to begin with.

Much typical SB rubbish was spoken above about needing lots (4?) of twinsets. Actually if you ignore fashion and use indie twins you gain a huge advantage of being able to swap out one
cylinder between dives. This is very common here in the UK.

The main skill you need is planning. Given your higher SAC and the requirement for gas to donate who much do you need at the start of the dive? How much will be left at the end and in which cylinders? Will that be useful for another dive? Plan that dive and see.

You will also need to be patient with the dive ops you use. Talk to them early.

 

[HantsDiver]

I would suggest diving a normal single setup but with an additional AL80 as a bottom stage. Keep two second stages on your main rig, start breathing from the stage

Yes. I'm sure having an ali80 stage would be fantastic for someone with less than 50 dives. I really can't understand why most people wait until they are doing mixed gas dives with lots of deco before using the biggest stage possible.

Much typical SB rubbish was spoken above about needing lots (4?) of twinsets.

I always recommend multiple twin sets to new divers... As does everyone else on here.

Actually if you ignore fashion and use indie twins you gain a huge advantage of being able to swap out one
cylinder between dives

Who wants to start loosening bands and playing around like that on a boat??? I can't think of anything worst. He'd be better of using sidemount. And I don't even like sidemount.

This is very common here in the UK.

I've never seen someone taking their twindies apart to swap in a full bottle. Ever. And I've dived all over the UK and on lots of boats.

 

[KenGordon]

Using a bcd with twining bands (which are cam bands, not metal) or something like the Ap TekWing it is as easy to swap out one of a pair or indies as it is to change a single. Three people in my club (about half of those using twinsets) do this. If the first dive is halfway serious then it means you have enough gas for a proper second dive. With a more fashionable manifolded twinset you would have to decant from a third cylinder. That is what I used to do (now I dive a JJ).

An Ali 80 is actually the easiest stage to dive if you can stand up to get in the water. In the water it is almost not there, especially once it has been breathed down a bit. When completely empty it is a pain so if using half for one dive and half for another it might be best to use a weight on the cam band holding the rigging.

As regards needing to be all trained up like a mixed gas diver. Well what risk is that training mostly about? Breathing the wrong gas, and also swapping stages in case of loss of deco gas. Given just a bottom stage those are not an issue. Sure get someone to give some training, intro to tech would be appropriate, as some of the kit configuration is best demonstrated in person.

I am trying to make a practical suggestion which might really work in the places where cylinder choices are non existent. Clearly improving his SAC is the best course but some people cannot match a fit young woman for gas.