I've noticed a lot of negative talk about independent doubles. I'm curious as to why all the negative talk about independents.
Independent Doubles
- Thread starter Divesherpa
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There's nothing wrong with independent doubles, but there are advantages of using a manifold that are lost with independents. You still have advantages over a single tank.
As Walter sez, there's nothing "wrong" with 'em. But there are no advantages in their use over manifolded doubles unless you require side mount, and lots of disadvantages.
That said, I do have my independent double rig that I carry to places where all I can get are rental 80's...
Rick
That said, I do have my independent double rig that I carry to places where all I can get are rental 80's...
Rick
OP
How about specific problems with independents over manifold doubles?
I'm asking this question to find out some actual physical reasons not to dive independents. As I dive independents most of the time, I have a vested interest in someone disproving my reasoning for diving independents.
I'm asking this question to find out some actual physical reasons not to dive independents. As I dive independents most of the time, I have a vested interest in someone disproving my reasoning for diving independents.
In the event of a regulator failure you only have access to the air in one tank. With a manifild, you shut down one valve and access the air from both tanks with the remaining regulator. Diving independent doubles is similar (but not exactly like) to diving a single with a very large pony.
A manifold set up gives you all the advantages (except, as Rick pointed out, side mount) of independents and adds the ability to breath air from both tanks if one regulator fails. The manifold is clearly a better method for most instances.
Isolated vs non islolated manifold is less clear.
A manifold set up gives you all the advantages (except, as Rick pointed out, side mount) of independents and adds the ability to breath air from both tanks if one regulator fails. The manifold is clearly a better method for most instances.
Isolated vs non islolated manifold is less clear.
All evolve from the fact that you can't access all the air from either regulator.
(1) Gas management: To safely manage the gas you have to switch regs at least once, and you really ought to switch twice. And that's only on the way to your first third. You still need one more switch coming out. Are you going to use two long hoses so you can stick with the procedure of donating the reg you're breathing, or are you going to have to remember which one you're breathing, which one to donate? Just making sure you're always associating the correct SPG with the correct reg is a pain in the tail.
(2) Fewer options - a simple free-flow, the most common regulator failure mode, costs you all the air in its associated tank. If you're diving thirds (maybe you shouldn't go all the way to thirds on independents - I don't - I should say I "wouldn't" - so far I've restricted my independent doubles use to open water) and lose a tank just as you hit thirds on tank 2, you have just enough gas to get out with no delays, and nothing left for the excitement... this is not good. If for some reason your buddy needs any of your air, you're both dead.
(3) More failure points - two HP hoses vice one.
Rick
(1) Gas management: To safely manage the gas you have to switch regs at least once, and you really ought to switch twice. And that's only on the way to your first third. You still need one more switch coming out. Are you going to use two long hoses so you can stick with the procedure of donating the reg you're breathing, or are you going to have to remember which one you're breathing, which one to donate? Just making sure you're always associating the correct SPG with the correct reg is a pain in the tail.
(2) Fewer options - a simple free-flow, the most common regulator failure mode, costs you all the air in its associated tank. If you're diving thirds (maybe you shouldn't go all the way to thirds on independents - I don't - I should say I "wouldn't" - so far I've restricted my independent doubles use to open water) and lose a tank just as you hit thirds on tank 2, you have just enough gas to get out with no delays, and nothing left for the excitement... this is not good. If for some reason your buddy needs any of your air, you're both dead.
(3) More failure points - two HP hoses vice one.
Rick
OP
On the subject of gas switches, if you can't handle gas switches, should you really be in a cave?
No.
Should you arbitrarily increase the number of gas switches and therefore your task loading due to a perceived advantage of independent doubles?
No.
Roak
Originally posted by Divesherpa
On the subject of gas switches, if you can't handle gas switches, should you really be in a cave?
---------------------------------
Just because you can doesn't mean you should.
In technical diving we are into minimizing risk. Every failure point you can eliminate, both in equipment and in procedure, lowers the risk of a life-threatening problem. Finding the right balance, the safest balance between redundancy and minimal failure points is the trick. Independent doubles add failure points and reduce redundancy all in one fell swoop.
Is that smart?
Only if you must use independents (side mount) does it make any sense.
Rick
On the subject of gas switches, if you can't handle gas switches, should you really be in a cave?
---------------------------------
Just because you can doesn't mean you should.
In technical diving we are into minimizing risk. Every failure point you can eliminate, both in equipment and in procedure, lowers the risk of a life-threatening problem. Finding the right balance, the safest balance between redundancy and minimal failure points is the trick. Independent doubles add failure points and reduce redundancy all in one fell swoop.
Is that smart?
Only if you must use independents (side mount) does it make any sense.
Rick
OP
Although I'm starting to sidemount more and more, I still dive back mount about 1/2 the time. I actually prefer sidemount, but that's a different thread. The reasons listed so far are 1) complexity of gas switching, 2)addition of ?failure points.
On the subject of gas switching, if you do it every day, it's like brushing your teeth and not swallowing toothpaste. It is more complicated at first, but with repetition, becomes second nature. The failure points I can concede.
The advantage of independents are not numerous, there is only one. One failure can not possibly exhaust your entire gas supply. All the people who I know that dive independents with 2 exceptions dive them for that reason.
Plain and simple, independents give the diver the ability to self rescue without ever(almost never)needing to breathe their buddies gas, which lends itself to solo diving as well. I see the DIR people sneering, but that what friendly debate is all about.
Some more reasons why independents are so bad would be helpful, as I sincerely want to know what you guys dislike so much about independents.
Rick, out of curiosity, what situation prompts diving double (al) 80's?
On the subject of gas switching, if you do it every day, it's like brushing your teeth and not swallowing toothpaste. It is more complicated at first, but with repetition, becomes second nature. The failure points I can concede.
The advantage of independents are not numerous, there is only one. One failure can not possibly exhaust your entire gas supply. All the people who I know that dive independents with 2 exceptions dive them for that reason.
Plain and simple, independents give the diver the ability to self rescue without ever(almost never)needing to breathe their buddies gas, which lends itself to solo diving as well. I see the DIR people sneering, but that what friendly debate is all about.
Some more reasons why independents are so bad would be helpful, as I sincerely want to know what you guys dislike so much about independents.
Rick, out of curiosity, what situation prompts diving double (al) 80's?
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