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aka Chimp 1 or Mavis...
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Discussion Starter · #1 ·
Following on from the recent thread about twinset advice and the information forthcoming about Indies vs manifolds, I would like to ask some questions about Indies diving. I ask this because I do not dive them, but to be able to criticise something, you must be able to understand that thing which you are criticising rather than blindly argue!

So, my questions are:

1. Reg setup on Indies - 2 to 4 regs. Which and why? Can you explain wing and suit inflation sources too?
2. Equivalent of Min Gas for Indies. How do you know what gas pressure you need to turn the dive. Eg dive of 30m for 30mins with twin 12s. Is this the limiting factor when planning Indies dives?
3. Explain what happens with a failure of a single reg on a diver ie OOA drill for Indies. Double failures aren't something expected but OOA on the remaining cylinder might be. Linked to point 2.
4. If people dive solo with indies, can they explain their gas planning too as I believe that this would provide the most limiting scenario regarding 'Min Gas'.
5. Do you dive stages with Indies?

This is truely meant as a 'I don't understand why' post so please explain :)
 

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The smell of freshly turned delrin is more powerfu
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I dont know mate :)

but I have a question too.

when does diving a single become dangerous. I do mean a single with no other gas source. no pony no stage no nothing

I ask for all the same reasons you ask about indies.


David
 

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aka Chimp 1 or Mavis...
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Discussion Starter · #3 ·
I dont know mate :)

but I have a question too.

when does diving a single become dangerous. I do mean a single with no other gas source. no pony no stage no nothing

I ask for all the same reasons you ask about indies.


David
When you can't do the dive with a buddy and the gas you have! Min Gas for singles gives you a very good indication at what point this happens.
 

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A short fat well off crap cave diver. Likes wrecks
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I dont know mate :)

but I have a question too.

when does diving a single become dangerous. I do mean a single with no other gas source. no pony no stage no nothing

David

As soon as you get in the water.


ATB

Mark Chase
 
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Resident 'Jawling Man' and 'Graunching Specialist'
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Following on from the recent thread about twinset advice and the information forthcoming about Indies vs manifolds, I would like to ask some questions about Indies diving. I ask this because I do not dive them, but to be able to criticise something, you must be able to understand that thing which you are criticising rather than blindly argue!

So, my questions are:

1. Reg setup on Indies - 2 to 4 regs. Which and why? Can you explain wing and suit inflation sources too?
2. Equivalent of Min Gas for Indies. How do you know what gas pressure you need to turn the dive. Eg dive of 30m for 30mins with twin 12s. Is this the limiting factor when planning Indies dives?
3. Explain what happens with a failure of a single reg on a diver ie OOA drill for Indies. Double failures aren't something expected but OOA on the remaining cylinder might be. Linked to point 2.
4. If people dive solo with indies, can they explain their gas planning too as I believe that this would provide the most limiting scenario regarding 'Min Gas'.
5. Do you dive stages with Indies?

This is truely meant as a 'I don't understand why' post so please explain :)
Hi mate. I started off life on indies and still use them abroad. On balance I decided manifolds are slightly superior overall and moved on to them (and sinc eon to a CCR) but my 2p:

1. 2 Regs. If diving with a similarly equipped buddy you would never need any more than this - if he has two failures you give him your backup, with three failures you would end up buddy breathing off a very limited supply (you'd have more with a manifold) but this is exceedingly unlikely.

2. I used rule of thirds exactly as you would for a twinset - ie given a starting pressure of 210 breathe first side to 140, swap to other, when this hits 140 turn for home. If you have a failure you still have one complete side of 2/3 for your exit. Modify this according to the complexity of the dive ie rule of fourths etc but always ensure that at all points of the dive you have enough on EACH side to get you home. Again your buddy would be doing the same and so it still takes 3 failures before this becomes an issue.

3. Failure - turn it off and swap to backup. If it is fixable turn it back on. No different to manifold although a manifold SHOULD leave you with more gas in MOST (but NOT all) failure situations. Rememeber a manifold has MORE failure points than an indie set even though it gives you more "tools" to sort out these failures.

4. I think this is covered but basically the same. I firmly believe that ALL solo dives should be done on indies not on manifolds cause with manifolds you have (very rare) potentiallly unfixable failures that could leave you totoally OOG.

5. Yes.
 

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Hi Gloc.

As a reletive (to many on this site) newcomer to the world of twins I hope this answers some of the questions as to how I do the Indie thang… Not a definitive answer though as others (with more experience) may do things differently.

1. I use the 2 reg set up. I chose this as (as you said) otherwise you’d have regs coming out of my ears! I did once try the 4 reg set up and it was a nightmare! Regs everywhere!!! Short hose off my left post, long hose off my right.

Wing and suit inflation hose routing I run the same as you guys. Wing inflator off right post, drysuit hose off left post.

2. I tend to use the rule of thirds in my gas planning. A third to get down and do whatever I’m doing, a third to get back, and a third incase of emergencies. I think the only difference is that these thirds are managed independently so….
a. Breath a third off reg 1,
b. then reg 2 for a third and turn the dive, stick with reg 2 for another third,
c. then switch back to reg 1
I do it this way so that on much of the bottom phase of the dive I’m on my short hose and have my long ready for donation if needed. During ascent I will still have air available to allow me to switch to short hose and donate long.

3. If a single reg fails I would have the choice of either ascending whilst breathing off the failed reg if possible until that one is OOA then change to other reg,
OR
Switch to good reg and could shut down the offending post and make ascent.

4. I’ve only been solo on a couple of drift dives… Not my regular choice for diving.

5. Yep, I have a 7lt steel.


I’m far from a DIR / GUE knocker. I see the benefits of pretty much the whole system and the level of training (judging from the skill of DIR divers I’ve seen) is great. I don't rule out taking more from that system in the future (who knows, I may even do some courses in the future (if / when I move to a manifolded system))
 

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The smell of freshly turned delrin is more powerfu
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As soon as you get in the water.
so you only dive solo then I guess.... or the team is diving solo and just dont know it yet....


Gloc question is a fair one. still hopping to get a real answer. I thought mine was too.

the reason for question. Indies and diving a 15 and a pony could on some dives be called simlar. but if I was diving indies I would feel a lot safer than diving with just a pony. But 15 and a stage... is this not the same while it might not be the first choice. If I found something worth spending more time underwater before you jump to full sat diving other options might be sought.

:)

so back to op question.....

David
 

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A short fat well off crap cave diver. Likes wrecks
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15,343 Posts
Following on from the recent thread about twinset advice and the information forthcoming about Indies vs manifolds, I would like to ask some questions about Indies diving. I ask this because I do not dive them, but to be able to criticise something, you must be able to understand that thing which you are criticising rather than blindly argue!

So, my questions are:

1. Reg setup on Indies - 2 to 4 regs. Which and why? Can you explain wing and suit inflation sources too?
One reg on each cylinder otherwise it gets silly. Suit on one tank wing on the other. The los of one tank then does not cause total loss of boyancy control.

2. Equivalent of Min Gas for Indies. How do you know what gas pressure you need to turn the dive. Eg dive of 30m for 30mins with twin 12s. Is this the limiting factor when planning Indies dives?
The reserve is enough gas in any one tank to get you safely to the surface.


3. Explain what happens with a failure of a single reg on a diver ie OOA drill for Indies. Double failures aren't something expected but OOA on the remaining cylinder might be. Linked to point 2.
You swap to the other tank and if you can you shut down the failed tank. If you cant you just let it empty its self as your ascending on your second tank.


4. If people dive solo with indies, can they explain their gas planning too as I believe that this would provide the most limiting scenario regarding 'Min Gas'.

Reserve is enough gas in either tank to get you to the surface or the next available gas source safely?? Thats it.

5. Do you dive stages with Indies?
Sure why not.


This is truely meant as a 'I don't understand why' post so please explain :)

Indis for me are for when i cant get a proper twinset. For some its a safe way to dive because they cant shut down but i dont agree with this argument at all. A slob knob or a buddy is a better option.


Me on indi12s which enabled me to do some deep dives in Egypt





ATB

Mark Chase
 

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2. I tend to use the rule of thirds in my gas planning. A third to get down and do whatever I’m doing, a third to get back, and a third incase of emergencies. I think the only difference is that these thirds are managed independently so….

a. Breath a third off reg 1,

b. then reg 2 for a third and turn the dive, stick with reg 2 for another third,

c. then switch back to reg 1

I do it this way so that on much of the bottom phase of the dive I’m on my short hose and have my long ready for donation if needed. During ascent I will still have air available to allow me to switch to short hose and donate long.



3. If a single reg fails I would have the choice of either ascending whilst breathing off the failed reg if possible until that one is OOA then change to other reg, OR Switch to good reg and could shut down the offending post and make ascent.

4. I’ve only been solo on a couple of drift dives… Not my regular choice for diving.
Can we put some figures on that? It appears with that plan that you can - in the worst scenario - be left with only 1 third gas to ascend.

Let's assume a SCR of 15 lpm and using twin 12s on a 30 metre dive. Gas fill pressure of 210 (it's easy for 3rds and about what I get when hot filled jumping in to cold water!)

60 lpm which is 5 bar per minute on a single 12. So with 70 bar in cylinder A to play with, if we say that descent takes 2 minutes, you have 12 minutes before you switch regs to cylinder B. A further 14 minutes later you turn the dive with one third gas in cylinder B and two thirds in cylinder A.

We try to plan for worst case scenario. If you lose cylinder A at this point, do you have sufficent gas in cylinder B to get to the surface? (I won't ask you if you can get you plus a buddy up on the gas that you have left as this would require two simultaneous major failures)

If you have been prompt and accurate in your switching, you have 70 bar in a single 12. If your breathing rate does not alter at all (which is unlikely if you have just lost two thirds of the gas that you thought would be available to you) you have roughly 10 minutes of gas left to play with. Depends what gas mix you are diving as to whether you would have to miss any deco to ascend safely.

I have to say that I have considered gas management abroad with two independant cylinders - but configured as a stage and one back tank. In this scenario I'd breath the stage down completely leaving back gas (with the two regs it provides) available for ascent plus sharing. I find the management issues interesting and worthy of consideration.
 

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A short fat well off crap cave diver. Likes wrecks
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so you only dive solo then I guess.... or the team is diving solo and just dont know it yet....


Gloc question is a fair one. still hopping to get a real answer. I thought mine was too.

the reason for question. Indies and diving a 15 and a pony could on some dives be called simlar. but if I was diving indies I would feel a lot safer than diving with just a pony. But 15 and a stage... is this not the same while it might not be the first choice. If I found something worth spending more time underwater before you jump to full sat diving other options might be sought.

:)

so back to op question.....

David


This is a real answer. If you don't accept the truth of it then thats up to you.

The most unreliable piece of equipment in the water is the buddie. Whilst DIR GUE and best M8s who have dived together for years may or may not offer a comfort zone in the buddy diving death trap, the fact is diver separation and subsequent out of air death is all too common. If your diving with a stranger or with someone who you have never been is a serious high stress situation with, then your playing Russian roulette.

The majority of single tank divers do not have the necessary skills, ability, confidence and most of all experience to carry out a successfully emergency OOA.

Personally I would never let my child dive without a redundant air supply and the skill to use it or at least me as a buddy. I have seen buddied with and experienced so many totally useless buddies in my 19 years as a diver I wouldn't trust anyone i haven't had a lot of diving experience with.

If you come back and tell me how your buddie is amazing and highly skilled and would lay down his life for you in an emergency well thats just fine, but its just covering up for poor diver preparation in my mind.

Diving with the ability to self help doesn't mean solo diving, it means taking responsibility for your own life.


If you want a different answer then a single tank is suitable for diving to a max depth of 18m where the diver stands a reasonable chance of ascending directly to the surface on a single breath. Assuming that is the diver got a good single breath before the tank ran out.

ATB

Mark Chase
 

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Can we put some figures on that? It appears with that plan that you can - in the worst scenario - be left with only 1 third gas to ascend.

Let's assume a SCR of 15 lpm and using twin 12s on a 30 metre dive. Gas fill pressure of 210 (it's easy for 3rds and about what I get when hot filled jumping in to cold water!)

60 lpm which is 5 bar per minute on a single 12. So with 70 bar in cylinder A to play with, if we say that descent takes 2 minutes, you have 12 minutes before you switch regs to cylinder B. A further 14 minutes later you turn the dive with one third gas in cylinder B and two thirds in cylinder A.

We try to plan for worst case scenario. If you lose cylinder A at this point, do you have sufficent gas in cylinder B to get to the surface? (I won't ask you if you can get you plus a buddy up on the gas that you have left as this would require two simultaneous major failures)

If you have been prompt and accurate in your switching, you have 70 bar in a single 12. If your breathing rate does not alter at all (which is unlikely if you have just lost two thirds of the gas that you thought would be available to you) you have roughly 10 minutes of gas left to play with. Depends what gas mix you are diving as to whether you would have to miss any deco to ascend safely.

I have to say that I have considered gas management abroad with two independant cylinders - but configured as a stage and one back tank. In this scenario I'd breath the stage down completely leaving back gas (with the two regs it provides) available for ascent plus sharing. I find the management issues interesting and worthy of consideration.
Good to get some tangible numbers on the issue. Thanks Clare.

Worse case scenario does leave things in a potentially tricky situation of having to miss some deco... Very worthwhile keeping that in mind.

Of course this scenario does also involve losing your buddy and their ability to donate a reg though.
 

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A short fat well off crap cave diver. Likes wrecks
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Can we put some figures on that? It appears with that plan that you can - in the worst scenario - be left with only 1 third gas to ascend.

Let's assume a SCR of 15 lpm and using twin 12s on a 30 metre dive. Gas fill pressure of 210 (it's easy for 3rds and about what I get when hot filled jumping in to cold water!)

60 lpm which is 5 bar per minute on a single 12. So with 70 bar in cylinder A to play with, if we say that descent takes 2 minutes, you have 12 minutes before you switch regs to cylinder B. A further 14 minutes later you turn the dive with one third gas in cylinder B and two thirds in cylinder A.

We try to plan for worst case scenario. If you lose cylinder A at this point, do you have sufficent gas in cylinder B to get to the surface? (I won't ask you if you can get you plus a buddy up on the gas that you have left as this would require two simultaneous major failures)

If you have been prompt and accurate in your switching, you have 70 bar in a single 12. If your breathing rate does not alter at all (which is unlikely if you have just lost two thirds of the gas that you thought would be available to you) you have roughly 10 minutes of gas left to play with. Depends what gas mix you are diving as to whether you would have to miss any deco to ascend safely.

I have to say that I have considered gas management abroad with two independant cylinders - but configured as a stage and one back tank. In this scenario I'd breath the stage down completely leaving back gas (with the two regs it provides) available for ascent plus sharing. I find the management issues interesting and worthy of consideration.

You have two choices in gas planning. Enough in one tank to get me to the surface. Enough in one tank to get me + 1 to the surface.

30m to the surface @ 15 SAC = 3mins 135ltrs of gas + safety stop 5min at 6say another 120ltrs so in total 255ltrs of gas or 21 bar

So to get me and my buddy to the surface lets say 50bar in one tank on a no deco dive.

On a deco dive id plan for minimum gas in a singel tank using 100/100GF.

Once the figure got over 100bar id start using deco stages.

ATB

Mark Chase
 

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You make the most important point in your former post Mark -
Reserve is enough gas in either tank to get you to the surface or the next available gas source safely?? Thats it.
If we can retain that at all times then we have good gas management. Thirds is a rule which I sought to point out does not suit all diving scenarios. If our 30 metre dive was indeed non deco then a third of one tank may be enough. If we have used the additional gas capacity of our twinset and incurred deco it may not be enough.
 

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aka Chimp 1 or Mavis...
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Discussion Starter · #14 ·
Mmmm, just like my Post #2
 

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The smell of freshly turned delrin is more powerfu
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As soon as you get in the water.


ATB

Mark Chase
This is a real answer. If you don't accept the truth of it then thats up to you.

Mark Chase

ok so to cut through all the waffle then and get to a real answer.

"when does diving a single become dangerous."

I guess Marks answer is its dangerous below 18 meters. yep I would agree with that. :)

life is to short somtimes...

DAvid
 

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Jesus don't want me for a sunbeam
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Diving with independants is exactly the same as diving manifolded doubles when it comes to gas management. Work out how much gas you need to get home and turn the dive at or before that point. Work out how much gas you could lose at the worst point and either go diving because you have enough or recalculate your turn point until you get a figure that works. No different from diving a manifold.

I really only use independants on cave dives when I'm diving sidemount. On a typical dive 1/3's works fairly well as the bottom line. For example, my favourite set is 2x7/300's. Each bottle contains 2100l, turn point is when you've used 700l from each bottle i.e. 1400l total. You have 2800l of air divided between two bottles, if one packs in then you have enough to exit in one bottle. In reality, I turn before I reach 1/3's, it's an absolute bottom line not the aim of the dive -- if there was somewhere I was trying to get to then I'd always over-estimate my gas needs. For deco dives I tend to drop another bottle for stops.

With stages, I look at what would be the minimum amount of gas I'd have for the exit if one of the bottles died. For example if I use a pair of 7's and a 10/232bar stage (because it's a nice figure to work with, I hate 10's) then I'd have 2800l to exit with if the stage died at the furthest penetration. I'd have used 1400l off the 7's plus 1000l off the 10 on the way in (assuming I was diving 1/2's minus 30bar from the stage and 1/3's from the 7's) so would need 2400l to exit. I'm happy with that. If one of the 7's died at the furthest penetration then I'd have 1000l in the 10 and 1400l in the remaining 7. I'd make it (there's still the 30bar buffer in the 10) on paper but realistically there's a good chance I'd be dead because I would have dropped the 10 on the way in and I'd just be reaching it on the way out as the 7 spluttered and farted to an end. Not good. In that situation I'd probably consider a more conservative turn point on the 7's.

Pretty much all my OC diving is on independant cylinders (sidemount caving, otherwise I dive CCR). I switch every 30bar or so to keep the set as balanced as possible, both for buoyancy and gas management should something fail. The benefit of sidemount is that you have full access to cylinder valves, you can shut down the cylinders very quick and work the valves manually to get at the air the bottle contains.

I have a 2nd stage, gauge and suit hose on each bottle (though only one bottle connected to my suit, the other is a backup). Gas sharing is a non-issue so no long hoses.

Cheers,

Stuart
 

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aka Chimp 1 or Mavis...
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Discussion Starter · #18 ·
Thanks all for the comments. It has explained some things which I hadnt thought of as I thought that all Indies used 4 regs...
 

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PADI Internet Specialty Diver
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Thanks all for the comments. It has explained some things which I hadnt thought of as I thought that all Indies used 4 regs...
I've found it interesting too as I am working on this route for cave diving (for porterage reasons). The only debate I have seen is whether to long hose the right hand can or not (pass off the spare can to the casualty and take his/hers to balance out the weight or jetison being the alternative(s)).

I cannot imagine why anyone would think, or worse still use, two regs per tin.

Where did you get than notion mate?

Chris
 

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aka Chimp 1 or Mavis...
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Discussion Starter · #20 ·
I've found it interesting too as I am working on this route for cave diving (for porterage reasons). The only debate I have seen is whether to long hose the right hand can or not (pass off the spare can to the casualty and take his/hers to balance out the weight or jetison being the alternative(s)).

I cannot imagine why anyone would think, or worse still use, two regs per tin.

Where did you get than notion mate?

Chris
Preconceived ideas which lead to a false truths!
 
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