Pony or twin - what's safer, better...

[^*^BATMAN^*^]

Could you please explain this :06:

he means that if you are diving to the DIR type of diving(i think, im not sure if this is true) that you have a regulator on either valve, so if you have a freeflow, you can turn off one tank, but because the tanks are connected beneath the valves, you have access to both tanks through on reg.

http://www.bitz.fsnet.co.uk/images/isomanifold.jpg

as you can see here, the DIN valve is above the connection between the two tanks, if you dont quite understand, maby someone else can provide a more easily readable explination.

P.S- about isolating the tanks, i dont know what could happen to the tank, but hte valve in the center of the manifold is so you can isolate the tanks so they are seperate

 

[tamorgen]

Not to contribute to the flame, but I think what is better really depends on your situation. I think the arguement for twin tanks is very strong, in fact, I dive twin tanks myself sometimes. However, twins are not suited for all types of diving, or all dive centers to be more precise. My dive shop in Columbia, MD is very conservative for the most part. There are a few rebreather divers, but almost no one who shows much interest in any sort of tech diving. When I dive with them, I tend to dive with a pony, because that's what is accepted. Some of the instructors and trip leaders frown upon twins simply because they believe its "tech".

Of course the other disadvantage to doubles is cost. To begin with, if you dive twin, you are most likely going to have steel cylinders, which are much more expensive than AL anyway. Then you have to buy the manifold and bands to connect the tanks. You also need two first stage regs and at least one second stage for each. You can easily spend $2000 + on a twin cylinder setup at $400 a tank, plus the regs & manifold.

Pony bottles are significantly cheaper. Even a steel 20 l tank is less than $200. AL are usually less than $100. You can also through on a cheap reg on a pony and not be too worried, unless you are careless and start using your pony bottle as your reserve supply. You don't need a high performance regulator to simply accend out of an out of air/equipment malfunction. A simple sherwood piston reg is fine for this application. All told, I can't see why anyone would spend more than $500 on a pony setup, unless they are a tech diver and insist only on the $1000 titanium regs for all of their cylinders.

Just my $0.02. Feel free to correct me if any one feels my comments are wrong.

 

[MechDiver]

When I dive with them, I tend to dive with a pony, because that's what is accepted. Some of the instructors and trip leaders frown upon twins simply because they believe its "tech".

It sounds like you need to find a shop that knows its the 21st century, and a new bunch of dive buddies.

Doubles may indeed imply tec, but they are not tec by themselves, that takes much more. Tell your buddies safety and common sense should overrule ignorance.

MD

 

[tamorgen]

MechDiver, I agree almost entirely. They are behind the times a bit, and there are other scuba shops in my area who criticize them for being that way. They just don't like to take risks. The dive shop owner from what I'm hearing is finally trying to get certified as a "Advanced Nitrox" instructor by TDI, but that is as far as he wants to go. Unfortunatley, to do any sort of tec diving in my area, I have to travel about an hour and a half to the one store in my area that even participates in PADI's new tech program. I wish I had another option, but there's little I can do to change my stores mind aside from becoming a tec instructor myself and getting the owner to recognize the rewards of more technical diving.

 

[idratherbediving]

i dive doubles and dont consider myself a tech diver , yet. i am fascinated by "tech" diving and when i feel i am ready to spend the money on the gear and training, i will pursue it. right now, however, i still see the benefit of diving doubles. i dont have to change tanks after a nice long dive and should i have an equipment malfunction, i dont have to stress and immediatly abort a dive.
just my 2cents.

 

[MyDiveLog]

It's more a question of the right tool for the job. I don't do decompression diving or especially deep diving, so don't find the need for doubles. I use a 19 cubic foot pony bottle when solo diving or doing any diving below 100'...just thinking of lugging doubles on a beach dive makes my back hurt.

If you are doing mostly boat diving, deep diving, decompression diving, etc. then doubles probably make sense.

BTW, the issue for me isn't the one-time cost, but rather the hassle of lugging the darn things around! ... My $0.02 worth.

 

[MechDiver]

Unfortunatley, to do any sort of tec diving in my area, I have to travel about an hour and a half to the one store in my area that even participates in PADI's new tech program. I wish I had another option, but there's little I can do to change my stores mind aside from becoming a tec instructor myself and getting the owner to recognize the rewards of more technical diving.

Tech PADI is an oxymoron.

I had to drive 5 hours each way to take my tech training so I'm afraid I don't have any sympathy for only 1 1/2 hours. There are far better choices, IMO, for tech training. Have you checked the IANTD or TDI websites for instructors in your area?

MD

 

[6474286]

"The alternate air supply" required for some reasons/organisations seems to be a must. The question appears immediately : add 4liters pony or switch to twin (even 2x8liters) ? I am tending to ss backplate and IMHO twin would be better. What do You think ? Any ideas, pros ?

Personally, I would recommend the twin set over the Pony bottle. I very rarely use anything less than a double 12 when Diving, and I have two underlyin reasons for this:

The first is the obvious safety factor, basically the more segregated air you have the better; the one thing you can never have too much of is air!

Secondly; I find diving with a double set more comfortable underwater; you are nicely balanced!

Hope this helps!

Paul

 

[6474286]

P.S- about isolating the tanks, i dont know what could happen to the tank, but hte valve in the center of the manifold is so you can isolate the tanks so they are seperate

With regards to Isolating the Tanks; it is possible for teh O ring in a tank to rupture or burst, thus causing a very quick loss of air. By being able to isolate the tanks, you can keep 1/2 of your air in such a circumstance!

Paul

 

[DA Aquamaster]

Another alternative to a pony or manifolded doubles would be independent doubles secured with a set of "travel" bands.

You have the same basic set up as a pony except you add an SPG to your "pony" reg. Independent dobles give you the option of using both tanks and managing the air in thirds (with 2 reg switches during the dive) or on shorter rec dives of using one tank with the other along as sort of a "super pony".

It actually works better than a pony for dive travel as you don't need to carry the pony with you. At the destination just strap on both your tanks for the two tank trip and go to it. In a rec situation, the 500 psi or so left in one tank after the first dive becomes the "pony" for the second dive.

In cold water they also offer some advantage as well as they are isolated and with proper gas management you do not need to take any action to preserve enough air to safely end the dive at any point if one of the regs freeflows. It's a good idea to shut the frozen reg off, but your life does not depend on having to do it.