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Stupid question: Why?
If your pony or stage is an Al80, what's the functional difference to independent twins or a sidemount rig? From a gas reserves POV, that is.
Planned deco on a recreational dive?
- Thread starter irsubmarine
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If your pony or stage is an Al80, what's the functional difference to independent twins or a sidemount rig? From a gas reserves POV, that is.
I have noticed this bias by some tech divers (especially SB divers) as well. No concrete rationale was ever given, just a sort of "just because" type of answer.
I disagree.
If you are talking about PADI or SSI then yes.
As mentioned above, BSAC doesn't consider Deco a "technical" dive. it's part of the rec course
GUE (I believe) recomend (or insist?) on Tri Mix below 100' - now that certainly is technical. However everyone else says it's fine on Air.
I'm sure Nitrox was considered technical once.
Making a single tank dive to 100' or 33m on Air and incurring some deco should be within the scope of an AOW diver. after all it's just basic gas planning and buoyancy skills which should have been taught.
You can of course do the same dive on EAN 32 without deco.
The fact is, the training has been dumbed down by some with deco being this huge scary thing to be avoided at all costs, rather than being easily taught as part of the standard course.
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lermontov
Contributor
DevonDiver
N/A
I disagree. It's a minimum of 9 total training dives..... insufficient to have developed the consistency and reliability of skills application, over any given dive.
An AOW.... or most recreational divers, have the capacity to complete such dives under the best possible circumstances and assuming nothing goes wrong.
However, the fundamental factor in committing to mandatory decompression is proving a capacity to complete that obligation under the worst possible circumstances... assuming things will go wrong.
This is where over-confident recreational divers fall foul... and can get hurt.
Advanced OPEN WATER has never been dumbed down from the point where divers were authorised to complete deco.
Neither does AOW... in respect to the number of training dives/time, or required diver performance, reflect a fair comparison to those other agency that have decompression diving at 'recreational' levels.
Criticising the PADI recreational programme for not providing deco training is akin to criticising McDonald's for not asking how you want your burger cooked (medium rare sir?)
PADI, et al, have never made such claims. They provide cheap convenient diving based on LIMITED DIVE PARAMETERS to manage associated risk.
For those who wish to extend their dive parameters, they offer higher level training that effectively fulfills those relative training needs.
@DevonDiver
1. I was not criticising PADI or any other agency. If it came across that way then I apologise.
2. I'm in agreement with everything you wrote, I was being deliberately provocative. I fully understand ( a point you have made numerious times) how the current commercial model has been driven by market forces i.e. the customers wanting to pay less and train for less time
That said, I believe my point is still valid, that Single tank Deco is (or should be) within the realms of the rec diver. People should be introduced to it in theory at least, rather than teh current model of No Deco, where people get into a tizz if their computer shows 2 or 3 mins of deco
Certainly within the current model it would require an extra course and training with some established limits.
Personally I think that putting a label on Deco as being a Technical activity - devalues technical diving.
Single tank deco, at depths above 30m and cavern certs etc are not a tech qualification (in my mind) But some will suggest they are because they involve overheads. However they are certainly Advance Rec
For the record, I don't consider myself a technical diver, I still use the definition of technical as Below 40m, Cave, Adv Wreck, He, CCr etc.
Encouraging people to consider themselves a technical diver because of the course name, rather than just an advance rec diver to my mind at least is more troubling.
1. I was not criticising PADI or any other agency. If it came across that way then I apologise.
2. I'm in agreement with everything you wrote, I was being deliberately provocative. I fully understand ( a point you have made numerious times) how the current commercial model has been driven by market forces i.e. the customers wanting to pay less and train for less time
That said, I believe my point is still valid, that Single tank Deco is (or should be) within the realms of the rec diver. People should be introduced to it in theory at least, rather than teh current model of No Deco, where people get into a tizz if their computer shows 2 or 3 mins of deco
Certainly within the current model it would require an extra course and training with some established limits.
Personally I think that putting a label on Deco as being a Technical activity - devalues technical diving.
Single tank deco, at depths above 30m and cavern certs etc are not a tech qualification (in my mind) But some will suggest they are because they involve overheads. However they are certainly Advance Rec
For the record, I don't consider myself a technical diver, I still use the definition of technical as Below 40m, Cave, Adv Wreck, He, CCr etc.
Encouraging people to consider themselves a technical diver because of the course name, rather than just an advance rec diver to my mind at least is more troubling.
2airishuman
Contributor
<<Manifolded doubles: ok -- Sidemount: ok -- large stage: insufficient redundancy>>
I'm not a technical diver and can't speak with authority on this, but here is my understanding.
The principle at work with manifolded doubles is that all the gas is available in the event of any failure. In particular, you can recover from a first-stage freeflow without losing access to any gas, or a roll-off and broken valve handle, or a blown hose or o-ring. The safety record with modern manifolded doubles is long and very, very good.
With sidemount, the idea is that the lack of a manifold is made up for by the fact that the valves and regulators are readily accessible. In the event of a freeflow, it is practical to feather the valve because it's right there. Feathering the valve can work to salvage at least some cylinder contents in the event of a blown hose or o-ring. Sidemount advocates will tell you that, with proper training and planning, sidemount as a system provides a degree of safety for technical dives that is on par with backmounted doubles. While the sidemount track record isn't as extensive as that of manifolded doubles, so far, experience is showing this to be true. The use of sidemount allows some dives to be undertaken that can't be done in backmount doubles, either because of a restriction, or because of the physiological limitations of a particular diver.
Neither a backmounted single with a stage of the same size, nor independent backmounted doubles, enjoy the advantages of either system. In the event of a first-stage freeflow on a backmounted cylinder, access to roughly half the gas would be lost because it is not practical to feather the valve during critical phases of the dive. Because these configurations aren't widely used by technical divers, there's no track record to tell us whether these limitations pose a genuine safety risk or only the theoretical possibility of one.
One of the attitudes prevalent in technical diving is to take no unnecessary risk. A corollary is that the most suitable gear should be used for every dive. Gear and configurations that are "good enough" are not used if a safer alternative is available. Because independent doubles and a backmounted single plus stage are configurations that pose risks not present with manifolded doubles, they are not used.
I'm not a technical diver and can't speak with authority on this, but here is my understanding.
The principle at work with manifolded doubles is that all the gas is available in the event of any failure. In particular, you can recover from a first-stage freeflow without losing access to any gas, or a roll-off and broken valve handle, or a blown hose or o-ring. The safety record with modern manifolded doubles is long and very, very good.
With sidemount, the idea is that the lack of a manifold is made up for by the fact that the valves and regulators are readily accessible. In the event of a freeflow, it is practical to feather the valve because it's right there. Feathering the valve can work to salvage at least some cylinder contents in the event of a blown hose or o-ring. Sidemount advocates will tell you that, with proper training and planning, sidemount as a system provides a degree of safety for technical dives that is on par with backmounted doubles. While the sidemount track record isn't as extensive as that of manifolded doubles, so far, experience is showing this to be true. The use of sidemount allows some dives to be undertaken that can't be done in backmount doubles, either because of a restriction, or because of the physiological limitations of a particular diver.
Neither a backmounted single with a stage of the same size, nor independent backmounted doubles, enjoy the advantages of either system. In the event of a first-stage freeflow on a backmounted cylinder, access to roughly half the gas would be lost because it is not practical to feather the valve during critical phases of the dive. Because these configurations aren't widely used by technical divers, there's no track record to tell us whether these limitations pose a genuine safety risk or only the theoretical possibility of one.
One of the attitudes prevalent in technical diving is to take no unnecessary risk. A corollary is that the most suitable gear should be used for every dive. Gear and configurations that are "good enough" are not used if a safer alternative is available. Because independent doubles and a backmounted single plus stage are configurations that pose risks not present with manifolded doubles, they are not used.
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Well, I beg to differ. Sidemount allows for a loss of half the gas under some (mainly theoretical) events.
There's absolutely no problem with diving a slung s80 and a backmounted S80. Heck, even a S40 might get you out of most situations you could face in light deco. Does it have advantages on the others? Not really. Does it have disadvantages? Certainly. Is it a problem? Certainly not.
Never read anyone making that claim here tbh...
BEVANJ
Registered
Wow. As a relatively new member to this forum, and as a TDI Adv nitrox + deco, CCR diver, reading this makes me want to flee.
DIVE WITHIN YOUR QUALIFICATIONS. YES, THAT'S A FULL STOP. No if's, no but's.
There is so much that people don't think about that can go wrong.
-Computer failure? Do you have a backup?
-Different decompression algorithms. (VPM-B, Buhlmann etc)
-Loss of a deco gas?
-Loss of backgas? (in this case single back gas - a very real possibility).
-Narcosis (in this case, deep air dive?!)
-PPO2 - what is acceptable on the bottom? What is acceptable for deco?
-OTU exposure.
-Redundant breathing gasses.
-Selecting optimal deco gasses for the planned dive.
-Logically sorting deco gasses on your rig.
-MOD calculation.
-Gas planning (SAC rates, etc).
-Medical training for dealing with DCS etc.
-Spare kit which should be carried (scissors/knives/spare masks, etc).
-Discussing as a team various failure scenarios.
-Practicing feathering valves on free-flowing regulators.
-Smb usage.
-Fixed vs dumpable weight. (Which is really better for deco diving?)
-ETC, the list goes on...
There is so much thought which NEEDS to go into deco dive planning in order to do it safely. If you want to do it, get qualified, and find a good instructor at that.
Advocating for someone doing 10min of deco on a 45m dive, on a single tank is ridiculous. If anyone has a reg failure, and they wind up buddy breathing, the person gas sharing is probably going to run low, if not out of gas. Also, try holding stops, whilst sharing air on a standard recreational setup with a short hose, without any practice. I'm sure it wouldn't be fun - even after you have practiced it. That is one of the MANY MANY scenarios that could go wrong without the proper planning.
On a dive with 10min of deco, if someone doesn't realise that their computer is actually on the lenient side of the scale, as opposed to conservative things could easily go wrong. Something as simple as having a mask kicked off by an errant fin resulting in having to surface after no one else noticed (were they carrying a spare? Suspect not.) could result in a trip to the chamber.
Hell, I personally know people who have taken a bend within the realms of their NDL or staying within their computers decompression. And yes, the computers decompression model was relatively conservative.
This conversation is terrible, and the mods should shut it down. People are advocating for others diving outside of the limits of their training.
Flame me for being the new guy and saying this, I don't give a toss.
Bevan
DIVE WITHIN YOUR QUALIFICATIONS. YES, THAT'S A FULL STOP. No if's, no but's.
There is so much that people don't think about that can go wrong.
-Computer failure? Do you have a backup?
-Different decompression algorithms. (VPM-B, Buhlmann etc)
-Loss of a deco gas?
-Loss of backgas? (in this case single back gas - a very real possibility).
-Narcosis (in this case, deep air dive?!)
-PPO2 - what is acceptable on the bottom? What is acceptable for deco?
-OTU exposure.
-Redundant breathing gasses.
-Selecting optimal deco gasses for the planned dive.
-Logically sorting deco gasses on your rig.
-MOD calculation.
-Gas planning (SAC rates, etc).
-Medical training for dealing with DCS etc.
-Spare kit which should be carried (scissors/knives/spare masks, etc).
-Discussing as a team various failure scenarios.
-Practicing feathering valves on free-flowing regulators.
-Smb usage.
-Fixed vs dumpable weight. (Which is really better for deco diving?)
-ETC, the list goes on...
There is so much thought which NEEDS to go into deco dive planning in order to do it safely. If you want to do it, get qualified, and find a good instructor at that.
Advocating for someone doing 10min of deco on a 45m dive, on a single tank is ridiculous. If anyone has a reg failure, and they wind up buddy breathing, the person gas sharing is probably going to run low, if not out of gas. Also, try holding stops, whilst sharing air on a standard recreational setup with a short hose, without any practice. I'm sure it wouldn't be fun - even after you have practiced it. That is one of the MANY MANY scenarios that could go wrong without the proper planning.
On a dive with 10min of deco, if someone doesn't realise that their computer is actually on the lenient side of the scale, as opposed to conservative things could easily go wrong. Something as simple as having a mask kicked off by an errant fin resulting in having to surface after no one else noticed (were they carrying a spare? Suspect not.) could result in a trip to the chamber.
Hell, I personally know people who have taken a bend within the realms of their NDL or staying within their computers decompression. And yes, the computers decompression model was relatively conservative.
This conversation is terrible, and the mods should shut it down. People are advocating for others diving outside of the limits of their training.
Flame me for being the new guy and saying this, I don't give a toss.
Bevan
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Although this is oversimplifying things, the real difference between NDL diving and decompression diving is that fact that in NDL diving you should always be able to go to the surface in case something goes wrong, whereas when you go into decompression, there is an increasing likelihood that you will incur DCS if you do. As I tried to explain earlier, if you accidentally stray a minute or two into deco and have to surface before you have completed your required deco, the odds of getting DCS are not much more than for a NDL dive. The odds get worse and worse the farther you go into deco.
Consequently, the thrust of technical training is making sure you can solve any problem you encounter without going to the surface. The easiest problem to solve is loss of breathing gas--you just need to have a redundant gas source. That is the reason people oppose single tank diving for planned deco--you will have to go to the surface in the case of a sudden gas loss.
That is also why technical divers are not inclined to discuss decompression procedures in a forum like this. They are afraid of giving non-trained divers just enough information to get them into trouble.
Consequently, the thrust of technical training is making sure you can solve any problem you encounter without going to the surface. The easiest problem to solve is loss of breathing gas--you just need to have a redundant gas source. That is the reason people oppose single tank diving for planned deco--you will have to go to the surface in the case of a sudden gas loss.
That is also why technical divers are not inclined to discuss decompression procedures in a forum like this. They are afraid of giving non-trained divers just enough information to get them into trouble.
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