Recreational doubles

[Bob DBF]

A small twinset without an isolation valve is effectively no different from a large, flat single tank, albeit with two 1st stages.

I use old j-valve steel 72 twins in the same manor, one set can only have one first stage, the other can use two. With the twinset I have 14 or more cuft more than my 120, depending on the fill. Used them more before I got the 120's since I dive wet and I can only stay warm for so long.


Bob

 

[rivers]

Those of my clubmates who like them claim that a small twinset balances much better on their back than a single tank rig does. A small twinset without an isolation valve is effectively no different from a large, flat single tank, albeit with two 1st stages.

I prefer singles because it makes it possible to swap tanks between dives. Those twins hold only 50% more gas than one of my singles, so if you don't have a compressor available, you're basically limited to one and a half decent dive during a day outing. Besides, a broken down singles rig with two tanks is easier to stow under the benches in my boat.

Tech doubles are, as I've said, usually D12x232 around here, and although they provide enough gas for two good no-stop dives, they're no fun to schlep from the car to the boat, or to carry down to the water on shore dives. And since larger tanks means more buoyancy, the total weight of your rig and your weight belt increases with increasing tank volume

Tank length and the ability to get 300 bar fills are the common reasons i hear.

I personally use D12x232 for 99% of my diving. I don't have an issue lugging them around. I use a single for pool and shore (sea) dives only.

 

[JohnnyC]

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.

 

[Storker]

I personally use D12x232 for 99% of my diving. I don't have an issue lugging them around. I use a single for pool and shore (sea) dives only.

That's interesting. I've seen a few people with a D12x232 for tech dives and a D8.5x232 for rec bimbles, but I haven't seen anyone with a tech twinset and a singles rig.

De gustibus etcetera, I guess

I guess the issue of getting 300 bar fills depends on where you dive. I've never had any problems with that, but unless you fill from a bank you have to cool the tank properly and top it up to get a real 300 bar fill. If I don't do that, I won't have more than around 270 bar when I've set up my rig.

 

[Rhone Man]

Why aren't more divers using this set up?

Doubles are fricking heavy and awkward above the surface. I have a set of Al 80 doubles that I bought for tec diving but now that I am older I only ever use (a) if I have nothing else with gas in it, or (b) if I plan on doing a particularly long dive. And every time I do it I bitch and moan about lugging the extra weight to my car, to the dock, onto the boat, etc., etc. Doubles are one of those bits of gear that, cool factor or not, you kind of need a reason for.

 

[drmwc]

My apporach is similar to River's - I use twin 12s for most of my diving. However, I'll move to single tank for rib diving, as well as shore diving and pool stuff. Twinsets are useable on a rib, but a single is more straighforward.

 

[2airishuman]

Why aren't more divers using this set up? I would think improving on the center of gravity and having a lower profile is great for every aspect in diving.

What are the pros and cons when using recreational doubles?

Thanks in advance
Frank G

The main disadvantage is cost. Today's price at DGX for a LP50 twinset including bands and manifold is $709. Today's price at DGX for a single FX-100 is $338. The twinset is also slightly heavier in tank weight alone, and the valves and bands contribute further to dry weight on land. LP50s are slightly buoyant when empty so you'll be carrying more lead also.

At least in North America, there aren't any new cylinders other than the LP50 that are readily available that are well suited for recreational doubles (aka "tiny doubles"). FX-71s will work if you can find them and find 6.7" bands, but they're on the big and heavy side, with a pair weighing more than a single FX-149. LP72s, as suggested upthread, are several pounds heavier than FX-71s.

There aren't any dive charters around here and relatively few dive shops. I bring my air, often enough for several days of diving. I emptied three 120s, an 85, and twin 100s my recent trip to Lake Pactola, and brought back a fourth unused 120,. The nearest dive shop was a 3 hour drive away. I see the costs of getting enough LP50s to do dives like that as being prohibitive.

Another fact to consider is that you do need a BP/W setup and have to choose the wing carefully. I don't believe there are any wings made specifically for the purpose. Usually people use a large singles wing, I believe, but that can't be ideal. Part of the wing can't expand because it's stuck between the backplate and the cylinders.

 

[rivers]

That's interesting. I've seen a few people with a D12x232 for tech dives and a D8.5x232 for rec bimbles, but I haven't seen anyone with a tech twinset and a singles rig.

De gustibus etcetera, I guess

I guess the issue of getting 300 bar fills depends on where you dive. I've never had any problems with that, but unless you fill from a bank you have to cool the tank properly and top it up to get a real 300 bar fill. If I don't do that, I won't have more than around 270 bar when I've set up my rig.

I can't justify a second twinset. In the off chance I'm in a single, I'm either DMing in the pool and use a school cylinder and reg set, or I've gone for a shore dive and borrowed a single from a friend (and spent 5 minutes converting my regs). I think I did 2 days of shore diving last year, I might do 2 days this year.

 

[Agility]

you have to have both tanks of a twinset hydroed which elevates the cost of ownership, all the same I love my Double 8.5l rig for recreational diving and might sell my Double 12 because of its weight. not enough deep dives to justify keeping them

 

[Z Gear]

Hey thanks every one for answering my question on the pro and cons of having a double set up.

I have to think about this one a bit because I really do like some of the advantages you guys brought up.
On the same note I definitely do realize the disadvantages of having one of these.

As for myself what I really like on the advantages from what I have gathered is the not only is are the tank closer to you and helps with the center of gravity. Not only is it lower profile, But tank length is much shorter! That actually is a big deal for my wife. She has to put that aluminum 80 all the way down to avoid hitting her head. She really does not like that at all.

Ideally one way to reduce the weight factor would be to switch over to a dry suit vs my 7 mm (less lead to carry) this might help overall when going the double set up.

I do realize the cost is going to be more for the maintenance of both tanks but what about the BC. But another main cost is going to have to be getting another BCD for this set up.

I wish my LDS had this available to rent out. I would think it is a good option for people to consider and really look at when trying to figure out what gear is best for them,.

Thanks all for your inputs

Frank G
www.zgearinc.com