Gas planning for diving in mixed company?

[lermontov]

I'm only trained to carry 1 deco cylinder and plan to adhere to my training.

What extra training do you need that you already haven't had- you have a long list of certs and i would have thought you have enough bases covered to carry and extra bottle? or do you mean extra deco as opposed to extra travel gas?

With your bud being on CCR, I would plan the dive as solo. Plan for YOUR gas as the CCR diver should be doing the same from his CCR training.

This is my base line - I stage my deco gas and take travel gas - once i reach the overhead i drop off travel gas and I use my back gas for 1/3 (with 2x12litre) which gives me plenty to get back and pick up my staged gas to return . The problem if CCR diver only take a 6litre BO so if he has a break down he cant make it back without me but i can make it back without him due to my sidemount independent system

So in short at dive plan stage we go through the gas pan and I ask them how much BO are they going to carry and make sure they realise the issues of becoming separated and they have a breakdown. At TP of 140 BAR (on a 210 fill) with 2x 12 litres they simply dont have enough gas to get back on their own with their 6 litre BO

Even with my 140 BAR (x2 tanks) remaining get back to the staged Travel gas ( which I always allow enough for 2 pax to get back to deco ) This leaves his 6 litre BO as reserve for both of us and when you consider elevated SAC rates its pretty marginal

One solution is for him to take min of 140 BAR reserve in a 12litre (or whatever Gas allowance you have calculated fro a thirds penetration) that way he has enough gas to get back to the travel gas .That makes him empty as he reaches the travel GAS and I still have 140 BAr (x1 tank ) left

 

[packrat12]

I do plan to have OC gas to take a buddy pair up to the surface. My bailout reg has 2 second stages on it for this purpose.

You must really shorten your dives or carry a lot of gas.

A typical 180' dive for me is 30 min. BOs ~20/35 and 80 with GF 50/85. For BO I need 38 cf of 20/35 and 35 cf of 80. The OC (using 19/20 or so) will need 47 cf of my 20/35 and 34 cf of my 80. Total needs of 85 cf of 20/35 and 70 cf of 80. Even 2 80's would not be enough for this dive, never mind extra time at bottom time to determine what is up, elevated breathing from the issues, penetration distance, what depth the OC needed my gas and maybe even a CO2 hit for the CCR diver.

I am a firm believer that my gas is mine, your gas is yours. As there is no excuse for a technical diver to run out of gas for any reason, any need to share should not be planned or expected. If I have it to share I will but I will seriously question your ability as a diver for a long time. The guys I shared with have shown that they learned from the mistake and I consider them good divers... now... Even a recent dive I went on, 5 of us jumped, I saw 1 diver for a short while and then saw 1 other diver's strobe for just a second. Other then that, none of us saw each other and all of us hit 250' before we gave up. If we had any dependence on each other, it went out the wayside with the current and visibility. We were needing to be totally self sufficient. And before any comments on it, even the husband and wife team got separated....

 

[Kevrumbo]

...This is my base line - I stage my deco gas and take travel gas - once i reach the overhead i drop off travel gas and I use my back gas for 1/3 (with 2x12litre) which gives me plenty to get back and pick up my staged gas to return . The problem if CCR diver only take a 6litre BO so if he has a break down he cant make it back without me but i can make it back without him due to my sidemount independent system

So in short at dive plan stage we go through the gas pan and I ask them how much BO are they going to carry and make sure they realise the issues of becoming separated and they have a breakdown. At TP of 140 BAR (on a 210 fill) with 2x 12 litres they simply dont have enough gas to get back on their own with their 6 litre BO

Even with my 140 BAR (x2 tanks) remaining get back to the staged Travel gas ( which I always allow enough for 2 pax to get back to deco ) This leaves his 6 litre BO as reserve for both of us and when you consider elevated SAC rates its pretty marginal

One solution is for him to take min of 140 BAR reserve in a 12litre (or whatever Gas allowance you have calculated fro a thirds penetration) that way he has enough gas to get back to the travel gas .That makes him empty as he reaches the travel GAS and I still have 140 BAr (x1 tank ) left

Here's a better way to refine this, and make it more simple using stage bottles and backmount or sidemount doubles Third's Turn Volume/Turn Pressure: http://www.funteqdiving.nl/website/Downloads/duikplanning/Trewavas - Rethinking Thirds.pdf

 

[RainPilot]

@packrat12

We have a different buddy philosophy but that's no issue. Each to their own, literally in your case...

I'm not doing any overhead dives, also my particular diving preferences don't run to profiles as you described. My post was intended more as an expression of a philosophy. In a profile like you have provided, using a SAC of 1cf a minute for maths purposes, that means that the deep BO of 85cf could be reduced to 80cf by reducing your time at 7 ATA by ... 2,3 minutes? It's 1 am here so if I'm missing something correct me please.

In a case like that I'd probably reduce the BT by the few minutes. Or take an extra 19cf of back gas or similar small tank.

 

[LiteHedded]

You must really shorten your dives or carry a lot of gas.

A typical 180' dive for me is 30 min. BOs ~20/35 and 80 with GF 50/85. For BO I need 38 cf of 20/35 and 35 cf of 80. The OC (using 19/20 or so) will need 47 cf of my 20/35 and 34 cf of my 80. Total needs of 85 cf of 20/35 and 70 cf of 80. Even 2 80's would not be enough for this dive, never mind extra time at bottom time to determine what is up, elevated breathing from the issues, penetration distance, what depth the OC needed my gas and maybe even a CO2 hit for the CCR diver.

I am a firm believer that my gas is mine, your gas is yours. As there is no excuse for a technical diver to run out of gas for any reason, any need to share should not be planned or expected. If I have it to share I will but I will seriously question your ability as a diver for a long time. The guys I shared with have shown that they learned from the mistake and I consider them good divers... now... Even a recent dive I went on, 5 of us jumped, I saw 1 diver for a short while and then saw 1 other diver's strobe for just a second. Other then that, none of us saw each other and all of us hit 250' before we gave up. If we had any dependence on each other, it went out the wayside with the current and visibility. We were needing to be totally self sufficient. And before any comments on it, even the husband and wife team got separated....

That kind of thinking doesn't make any sense. What about bad gas? There is more than one reason to have to donate gas to a dive buddy. It's not just 'gremlins took all my gas'

 

[lermontov]

Here's a better way to refine this, and make it more simple using stage bottles and backmount or sidemount doubles Third's Turn Volume/Turn Pressure: http://www.funteqdiving.nl/website/Downloads/duikplanning/Trewavas - Rethinking Thirds.pdf

thanks yes iv read that just recently and am considering trying it

 

[packrat12]

What about bad gas?

Bad gas does not happen at the end of a tank (typically) so if it was my back gas, dive terminated early and minimal deco. My planning has always allowed for removal of 1 or 2 of my deco tanks depending on what I was doing. So if both were contaminated, deco on back gas (part of my planning). Swap regs if needed or able. So unless all of my gas was contaminated and I even understood that is was (as my buddy's would also probably be), I would still have gas to get up.

The philosophy was taught to me by a very well known and respected wreck diver. Proper planning on the surface will negate most potential issues such as gas. It is always possible that you are not meant to finish (survive) a dive due to gas but then things have gone very south. I am thinking of the experienced divers in EN in this case. Notice I said that I would never plan on using someone gas. I also have allowed for failure of 1 to 2 pieces of equipment in planning. So yes, there is no reason for any technical diver to run out of gas. If you do, what did you do wrong.... and I would seriously reconsider my level of diving. I doubt many people can tell me of an incident where planning and execution was not the main issue, or something very odd like getting lost, stuck or taking your gear off....

I am not talking about expedition level diving here. This is technical level 'fun' diving. I am also not talking long distance penetration in caves although I am sure the same philosophy applies there. If you often need to borrow gas, you will have no buddies eventually.

 

[PfcAJ]

You must really shorten your dives or carry a lot of gas.



I am a firm believer that my gas is mine, your gas is yours. As there is no excuse for a technical diver to run out of gas for any reason, any need to share should not be planned or expected.

A diver with bad gas could easily need to share depending on what all is compromised.

Only a sith deals in absolutes.

 

[Centrals]

As the only CCR diver in my diving group this comes up often.

Because There is nothing down there worth having to deal with a dead friend, I do plan to have OC gas to take a buddy pair up to the surface. My bailout reg has 2 second stages on it for this purpose.

Murphy is the invisible dive buddy, if my partner has a gas failure and ends up taking my bailout tank, that WILL be the time I lose the loop.

If I can't carry the gas for the two of us, I don't do the dive.

I have done a "mixed team" dive couple of times and NEVER again.
1. The deco profile is different and buddy separation is common on OW drift deco.
2. I have yet to meet any CCR diver who is willing to carry my bail out(back gas).

 

[packrat12]

A diver with bad gas could easily need to share depending on what all is compromised.

Only a sith deals in absolutes.

And the entire team did not fill at the same place???? On OC, I had 3 different tanks often with 2-3 different fills. I am not sure the team is any safer on bad gas here. It is possible everyone is in trouble. So how often have you dumped all of your CCR/BOs or Backgas/Decos because of bad gas? But now we are talking way outside standard deviation of risk....

Now lets get back to reality - So how many failures do you plan for. On OC, I did 2 critical failures on my breathing system and still surface. If a diver has more than 1 critical failure, I suspect they are the problem. Maintenance, Planning, Execution - etc.

The reality of the statement I made is - I do not plan on or expect to give gas to any technical diver. If they need it, they have made an inexcusable error in their dive philosophy. I have given gas to divers in deco to get them up, when they were not even my team. Go figure - have you.... Would you dive with them again, considering your life may be put at serious risk?