Recreational doubles

[Eric Sedletzky]

Doubles are a pain in the ass for basic recreational dives. For tech yes, when you need the gas, but a set of small doubles for basic dives to me is not the most streamlined setup on many levels. First, it's an extra reg set unless you just use one post. That's two regs in for service. As has been mentioned, two hydros, extra weight, top heaviness because of the manifold and twin first stages which affects trim and has to be accounted for, more drag underwater, a pain to hike from the car to the beach/boat/pier/ and back, and at my lds at least, they charge for two tanks for a fill even if it's just a top up.
That's why they make big singles these days, so we don't have to use doubles or triples anymore like they used to back when all tanks were small.

 

[JohnnyC]

A set of little doubles is much more convenient for me. I already own and use the regs for OC tec dives so it's not like it's costing my anything extra. A full set of doubles is less streamlined, but 50's sit closer to your back than a large single, they're wider so it's basically a trade off. Sure, two hydros, but quite a few people own more than one tank anyway. It's not like they're a pain in the ass, they're not really that heavy, and it doesn't screw your trim up any more than a large single will. You trim for what you have, so it's not an issue. I trim the same whether I'm in a single, doubles, tiny doubles, or a rebreather, because they're all adjusted so that my trim is the same.

I guess I just don't have the issues you have with a set of small doubles.

 

[Eric Sedletzky]

A set of little doubles is much more convenient for me. I already own and use the regs for OC tec dives so it's not like it's costing my anything extra. A full set of doubles is less streamlined, but 50's sit closer to your back than a large single, they're wider so it's basically a trade off. Sure, two hydros, but quite a few people own more than one tank anyway. It's not like they're a pain in the ass, they're not really that heavy, and it doesn't screw your trim up any more than a large single will. You trim for what you have, so it's not an issue. I trim the same whether I'm in a single, doubles, tiny doubles, or a rebreather, because they're all adjusted so that my trim is the same.

I guess I just don't have the issues you have with a set of small doubles.

The smallest doubles I've used are twin 72's which are fairly small but not as small as some.
I guess some of it has to do with body height. I'm fairly tall so a single 120/130 is fine, I have plenty of height to deal with the longest tanks. The 72's gave a little more gas, but in my case I never really took advantage of it because I dive wet and get too cold anyway. Shorter stubbier tanks would be silly for me in a set of doubles, but might be the answer for someone short that needs more gas that can't handle a single large cylinder.
But thanks for your views regardless, that's what's great about diving, all the different gear and viewpoints. There's different gear and methods for a reason because we're all different and have different needs and goals.

 

[The Laconic]

I'm actually about to buy a set of LP50 doubles for recreational dives. Same regs and more gas than a single AL80/11L. Even more if overfilled to 3000psi/200 bar. Bring along another tank to transfill from and you can easily get 2 dives out of the whole getup, have the redundancy of twins, no dealing with multiple reg configurations, easy to lug around.

I'm thinking about this myself. I've never worn a set of doubles (although I cave dive, I was trained on sidemount), and was looking for something to start messing around with, which would be useful on either solo dives, or on effectively-solo (i.e. instabuddied) dives, or on deeper recreational lake dives where I could use a bit more gas anyway, and I wouldn't say boo to the redundancy. A pair of LP50s looks pretty sweet. Incidentally, in the course of my googling I discovered it's what Chatterton uses on rec dives--just an interesting data point here.

NB I'm having trouble following a lot of this thread, because I don't know offhand the imperial equivalents of the metrically-described cylinders...

 

[Aquavelvet]

I'm a fan of double LP steel 72s for deeper recreational dives. They are lower profile than an FX117, and are easier to manage than a single tank + pony bottle for redundancy. I don't notice increased drag, but I'm not trying to set any speed records either.

 

[2airishuman]

I use a FX-100 twinset for some dives and an HP120 and pony for others. It's taken a good deal of experimenting but I finally have the pony bottle trimmed out just right and am happy with that combination. It's not a twinset, to be sure, but provides a degree of redundancy appropriate for many dives. The combination is considerably lighter than a pair of LP72s, and carries the same amount of gas.

 

[Imla]

Anything wrong with using 10LX300B in double setup?

They are too heavy. They weight too much to carry, are too negative to safely negotiate, and they are too top heavy to trim/balance out.

Considering the D12 232Bar will give you just about the same amount of usable gas, less load to carry, and they are less negative in the water with the weight at a lower point than the 10L 300Bars, it is an easy choice.

 

[stuartv]

I was assuming that the 7 mm wet suit would add a significant amount of buoyancy compared to a dry suit. Is this not correct?

I have no idea just guessing.
Frank G

I think you've got it backwards. A dry suit, even with no under garments, would be more buoyant than a 7mm, for most divers. A dry suit simply presents more volume in the water. If it didn't, it was be just about as snug on your as a wet suit.

 

[boulderjohn]

I do not normally use doubles for recreational dives, but I have done it in the past for training purposes--I was training for technical diving while doing recreational dives. I thought i would point out a minor advantage for doubles that has not been considered.

Let's say you are doing a two tank dive off of a boat, the first to about 80 feet and the second to about 50 feet. You are doing it with two separate AL 80 tanks, each filled to 3,000 PSI. You plan for a gas reserve that includes enough gas for you to reach the surface and also deal with an emergency, including an OOA buddy. You will need to make sure you have enough reserve in each tank, and you will need a bit more for the 80 foot dive. You will end the day with a reserve of unused gas in each tank.

Let's say you are doing the same two tank dive off of a boat, the first to about 80 feet and the second to about 50 feet, but this time you are doing it with double AL 80 tanks, each filled to 3,000 PSI. For the first dive, you really only have to have a vague notion of when you should ascend to have enough gas for the second dive, and you don't need to calculate anything extra for an emergency, since you will have plenty. of gas. For the second dive, all the gas you have left from the first dive is there for you to use, including the gas that would have been your reserve if you had done the first dive on a single tank. That could mean an additional 700 PSI or more.

Thus, by diving doubles, you effectively get more usable gas.

 

[BoltSnap]

They are too heavy. They weight too much to carry, are too negative to safely negotiate, and they are too top heavy to trim/balance out.

Considering the D12 232Bar will give you just about the same amount of usable gas, less load to carry, and they are less negative in the water with the weight at a lower point than the 10L 300Bars, it is an easy choice.

Thanks!!


What about the 12LX300B in Doubles? Do you use them (assuming filling to 300B isn't an issue).