BackMounted Doubles and mixed gas - is that technical?

[TrimixToo]

I've read this thread with some interest, and though others have said much of this, here is a somewhat different slant on it.

The whole technical vs. recreational diving thing is sort of a red herring.

The most important thing, in my view, is to have the right tools in your personal toolbox to manage the risks of the dives you choose to plan and execute. Rock climbers have written of "climbing contracts," those you sign with yourself before undertaking a climb.

We should apply that to diving.

When you splash with a dive plan, you have signed a contract with yourself to execute it with whatever you bring with you, and *no more*, no matter what happens. This means a responsible diver is prepared to assess the risks, and has decided which to manage, which to ignore, and how to manage those one chose to manage, all in advance, with the full knowledge that one can get hurt (or dead) if one fails to identify the risks, manage the ones that should be managed, and respond calmly and appropriately when one of them materializes. Because sooner or later, many of them *will* materialize. Make no mistake about that.

So: Looking at what you're contemplating, can you identify the risks? Can you make reasoned choices about those to manage (and how) and those to ignore? Nobody needs to answer here in public, but if the answer to either question is "I don't know," or "I'm not sure," then either more training of some sort is indicated to make up the shortfall or the dives need to be less complex.

I find it surprising how many seemingly simple things kill divers, risks that could be easily managed if they'd been considered without much trouble, but they cannot be managed unless they are recognized. It's far easier to recognize them when taught about them, and easier and safer to manage them when the solutions are well-known and taught to you rather than derived.

Just my four cents. (It started out as two, but....)

(Edit: Fix t7pos)

 

[wetb4igetinthewater]

I have - really I want to take AN/DP - but I had 4 kids in under 5 years - My oldest is entering college - 2 more right behind her... Money will be tight... So I made my wife a promise I will start diving deeper to see if I really need the AN/DP course... Competing resources are forcing my hand - but I told her I would dive within my means and if I can no longer get the longer dives I would come back and discuss alternatives... Hence I am exploring within my means... Air and Nitrox dives.

Please read what you wrote again. You have a family to look after. That is such a valuable thing. How will they be provided for if you are dead? Please hold off on the technical diving until you can spend the money on training and equipment.

 

[Scared Silly]

I have - really I want to take AN/DP - but I had 4 kids in under 5 years - My oldest is entering college - 2 more right behind her... Money will be tight... So I made my wife a promise I will start diving deeper to see if I really need the AN/DP course... Competing resources are forcing my hand - but I told her I would dive within my means and if I can no longer get the longer dives I would come back and discuss alternatives... Hence I am exploring within my means... Air and Nitrox dives.

After I reading this all I can say is WTF???

 

[Davide Marchetti]

Technical diving is USE OF SPECIAL EQUIPMENT AND SPECIAL PROCEDURES TO ACCOMPLISH A MISSION, whenever we use SPECIAL EQUIPMENT without SPECIAL PROCEDURES or vice versa.... we are doing a very dirty dive that shouldn't exist. There is ONE thing that defines a TECHNICAL DIVER, it's ATTITUDE. If you are a recreational diver doing strange things, as we all did, your attitude is not appropriate, maybe you are not ready yet. I feel I became a real tec diver after my first tec certifications, because my attitude was still changing and it's still improving.... I have been very superficial and egocentric... not good attitude for sure!

Tek Diving can be more more philosophical than technical sometimes...

 

[beester]

I have - really I want to take AN/DP - but I had 4 kids in under 5 years - My oldest is entering college - 2 more right behind her... Money will be tight... So I made my wife a promise I will start diving deeper to see if I really need the AN/DP course... Competing resources are forcing my hand - but I told her I would dive within my means and if I can no longer get the longer dives I would come back and discuss alternatives... Hence I am exploring within my means... Air and Nitrox dives.

Well your decision should be very clear:

- OR you take a entry level tech course that will give you the training to do the dives you do. (130ft, limited deco, 1 gas switch to deco gas, maybe solo)
- OR you just don't do these kind of dives and revert back to strict recreational NDL diving without deco gas.

It is NOT a question of money... it NEVER is. It is a question of responsibility and risk management.

 

[Dave Bevan]

Honestly independents with different gases? One of which isn't breathable at the depth planned.

To me you sound like you are stumbling into tech which little to no idea of what you are doing?

To be honest staying within your NDL isn't what you need to be doing. IMO You are better off at this point in accepting the fact the mission requires you to go into your NDL and picking a more conservative dive profile.

Saying you can't afford the course is no excuse for you to take unacceptable rocks with your life. Especially when you have people who rely on you.

You won't be much help if you get bent and end up in a wheel chair. Or worse if you switch to the wrong gas.

Hook yourself up with an experienced instructor and either do the course or at least get him to give you guidance on what you are doing. To me you sound like an accident waiting to happen.

I don't mean to sound harsh but reading your post I'm genuinely concerned for your safety.

 

[Neilwood]

And for the record - I agree with your assessment.
I remember a thread that Akimbo did on penetrations - something like - If you would not let your brother who has a pregnant wife do that dive - what the hell are you doing?
In that spirit - I was missing the safety of myself or others that may come knocking for OOG scenarios. I was and do think selfishly at times - so the take away is redundancy and process. Cover yourself with enough back gas to do your incurred deco should your mix gas become completely unusable. In my scenario I had a sling for the gas but chose to put it on my back. Sling the gas and don't put the regulator on my person until I have checked the depth, marked my switch and have everything squared away - then breath away.
Everyone has opinions and everyone has a risk threshold - I chose a risk that I did not see and it was pointed out. I have taken note and will think about this for a while and determine my best course of action.
I lived to tell about it and got further in my understanding of knowing what you don't know or think about...

Top marks for admitting your "mistake". It takes guts to know and admit it.

I have to say I am not Tec and have no interests in that direction at this time.

I think that defining Tec vs Rec is important:
Rec - single gas, no deco with direct ascent to the surface possible
Tec - anything that is beyond the definition above. Whether that is 2 or more gases, deco, overhead etc.

The important thing about Tec and understanding the mindset required is that other divers have come before you and learned hard lessons either by taking a chamber ride or the last ride they will ever take. AFAIK with almost all tec diving the skills/equipment/procedures are a process to mitigate risk (as learned the hard way by the group of divers I mentioned above).

You can only know how to mitigate a risk if you know the risk is there in the first place - that was where you fell down. You didn't have the knowledge or experience to know it was a risk or how big a risk it was (I would probably be in the same boat tbh) so you can't mitigate it.

 

[2airishuman]

In many ways this thread seems to have run its course but I think there are a couple of important points that have been missed.

First, let's talk about the problem (other than helping another OOA diver) posed by having two different mixes in each of the cylinders in a pair of backmount, independent doubles. The problem is that there is no safe, established way to identify which gas you're breathing. While gas identification and gas switch protocols differ in their details across agencies, they are all based on identifying the correct gas based on cylinder markings, and confirming that the reg being switched to is attached to the desired cylinder. Back gas is by convention the gas for the deepest portion of the dive and (hypoxic trimix aside) is breathable at all depths. While other supplementary means of identification are used by some divers and taught by some agencies (reg, hose, or cylinder color; bag over the reg; different reg; different mouthpiece; location, etc), the gold standard remains visual identification of cylinder contents and visual or tactile confirmation that the regulator to be breathed is connected to the cylinder so identified. With independent doubles, you would have to remember which reg had which mix, or tag the regulators, or write it on your slate, or something -- and you would leave yourself open to making a mistake somewhere in the process, at some point, maybe not on your first dive like this, but eventually.

Second, one of the things I've come to realize is that no one is smart enough to come up with a new gear configuration and determine, based on a thought experiment alone, everything that could possibly go wrong with it. I believe that one of the lasting benefits of the DIR movement is that tech diving configurations are now far more standardized based (mostly) on actual dive experience including accidents and near misses. I have a copy of the TDI manuals from early in the tech diving era and there is great emphasis on alternative gear configurations and finding a system that will work for you. The configurations now considered standard have been field tested on thousands of actual dives and the trade-offs and shortcomings are well understood. When you try something that isn't widely used, you lose the benefit of field testing, and leave yourself open to finding problems on a dive that no one was smart enough to figure out beforehand.

 

[doctormike]

Second, one of the things I've come to realize is that no one is smart enough to come up with a new gear configuration and determine, based on a thought experiment alone, everything that could possibly go wrong with it. I believe that one of the lasting benefits of the DIR movement is that tech diving configurations are now far more standardized based (mostly) on actual dive experience including accidents and near misses. I have a copy of the TDI manuals from early in the tech diving era and there is great emphasis on alternative gear configurations and finding a system that will work for you. The configurations now considered standard have been field tested on thousands of actual dives and the trade-offs and shortcomings are well understood. When you try something that isn't widely used, you lose the benefit of field testing, and leave yourself open to finding problems on a dive that no one was smart enough to figure out beforehand.

This is a great point.

SO many SB threads come down to people angrily claiming "It's personal preference! Do what works well for you". Yeah, sure, there are some things that actually don't have a clear best practice, and people have different preferences. And a warm water recreational diver probably resents some techie saying that if they don't have a long hose they are going to die. But it's usually not as simple as that.

The gear configurations and procedures that have been worked out by the technical diving community come from hard earned experience and tragedies. And many of those are applicable to all levels of diving.

I get that it's social media, and everyone wants the last word. I would just admonish anyone, especially a new diver, to listen very carefully when someone with experience is speaking. To not give in to the urge to argue for the sake of winning, for the sake of making your point.

Does that mean that the techies are always right and that no one should challenge them? Of course not. But as 2airishuman pointed out above, it's pretty unlikely that a random diver doing limited basic diving is going to MacGyver something that's better than what has worked so well for so many big dives over the years...

 

[Dave Bevan]

I think personal preference can sometimes lead to doing things the easiest way which isn't always the best.

I was always thought to be a 'thinking diver'which means weigh up the pros and cons and most importantly UNDERSTAND the cons they make the best choices for you. A lot of people focus on the positives of a long hose (for example) but very few preach about the negatives meaning that someone reading it can get a skewed view.

There is no do it all system which works for every situation and being able to weigh up the pros and cons and decide what's safe is part of building up knowledge and experience.

Always keep an open mind and be willing to try different things and accept knowledge even from people you think shouldn't know better.

I really hope the OP takes on board what people are saying and does a course or at least finds a group which have the knowledge and experience to guide him before something bad happens.

You don't know what you don't know and 30m underwater is not the time to find out.