advice on Deep diving, please

[tom]

I think he meant that trying to plan for a 50 SAC using GUE rules was 'silly', or at least led you to silly conclusions re the feasibility of the dive discussed, not the rules themselves. And sure enough, you don't plan for 50.

Just thought I'd point that out to head off the flamewar...

[Mark Chase]

Originally Posted by Mal Bridgeman

Mark

As you know, GUE advice on gas planning is different and describing it as "silly" is at best discourteous.

The GUE approach is that you should always keep enough gas in reserve to get you and your buddy to the next available gas source. At the fundies level this means calculated on a rate of 30l/min on your way back to the surface whilst still performing your minimum deco stops.

If the next available gas is deco gas then the minimum gas reserves enough to get you and your buddy to that point observing all deep stops.

This sounded quite a sensible approach to me.

Mal

OK lets look at the facts again.

30lpm for you 30lpm for your buddy so 60lpm total

Assuming you and your buddy bailout after 25mins at 40m on a single 15 (ignoring the fact you wouldn't dive it or the gas) you would need over 2200 (a guess, I cant be assed to work it out again) ltrs of gas in reserve.

A 15ltr only holds 3525ltrs of gas so that leaves 1325 for the dive

So 88 bar for the dive 147 in reserve

OR a single 15ltr and a 10ltr pony again

Am I the only person who finds this silly. I have never seen any one diving a single 15 take a pony bigger than a 5ltr


ATB

Mark Chase

[Paul Oliver]

Originally Posted by gobfish1

he could well be talking out his arse as well , i would not plan to use or tell some no one else to use a ppo2 of 4.8 on a dive , would you ,

His point is that you are not going to go into an OxTox immediately at a high Po2, this view is based on his personal experience of one of his Fcuk ups, we can all learn from mistakes and his is a very well documented and open one.

Others on this thread are advocating a very low Po2 to some of us, if you are doing deco on your back gas working your Po2 close to the wire has advantages in longer bottom time to better off gassing during your stops, so say 35% at 30m gives a good long limited deco bottom time, certainly a good time for the amount of gas available in a single tank and is not bad for off gassing in the stops incurred. But the Po2 would be high in some peoples view, not in others, including mine

A pony of 36% would compliment this, but swapping to it at say just deeper at 32m is not going to Oxtox you straight away although some instructors/people would give this impression.

It all needs to be balanced out sensibly and there are many views on sensible

[Mark Chase]

Originally Posted by tom

I think he meant that trying to plan for a 50 SAC using GUE rules was 'silly', or at least led you to silly conclusions re the feasibility of the dive discussed, not the rules themselves. And sure enough, you don't plan for 50.

Just thought I'd point that out to head off the flamewar...

Thanks Paul and Tom, exactly right. However seeing as the actual GUE number are up I have adressed them as well.

ATB

Mark

[Mal Bridgeman]

Originally Posted by Mark Chase

(ignoring the fact you wouldn't dive it or the gas)

but, to me, that's why these discussion don't work. Picking one part of the GUE approach and then misapplying it doesn't help anyone understand why people choose to follow the GUE training route.

The dive would be done on 21/35 and one would have to reserve enough gas to get you and a buddy to 21m where you would both have a deco cylinder of 50% to switch to.

If my maths is correct that's about 50 bar in a twinset leaving plenty to do the dive.
HTH
Mal

[stevechesh]

Originally Posted by Mal Bridgeman

The GUE approach is that you should always keep enough gas in reserve to get you and your buddy to the next available gas source.

I've picked this part of the quote - not to have a dig, but a serious question to any GUE diver. . . . As i understand it, GUE divers dive as a team of 3. . . With that in mind, do you plan gas logistics on both buddies losing a deco gas or just one? The chances are remote to say the least, but it's still a probability. . . . .

If not, does your training give you any options?

I personally don't carry enough gas for me and a buddy to both bail out on backgas. It's simply impracticle to carry that amount of gas around. . . . If you do the maths honestly, i doubt many people have enough backgas to do their full deco commitments on backgas alone, let alone help someone else out. . . .It might be selfish but all my gas planning is for me only. . . . .

[Mal Bridgeman]

Originally Posted by stevechesh

I've picked this part of the quote - not to have a dig, but a serious question to any GUE diver. . . . As i understand it, GUE divers dive as a team of 3. . . With that in mind, do you plan gas logistics on both buddies losing a deco gas or just one? The chances are remote to say the least, but it's still a probability. . . . .

If not, does your training give you any options?

I personally don't carry enough gas for me and a buddy to both bail out on backgas. It's simply impracticle to carry that amount of gas around. . . . If you do the maths honestly, i doubt many people have enough backgas to do their full deco commitments on backgas alone, let alone help someone else out. . . .It might be selfish but all my gas planning is for me only. . . . .

OK a bit of a misconception perhaps ..... diving as a three is not compulsory ... and often GUE trained divers will dive as a buddy pair. Diving as a three creates more opportunities for Instructors on courses though

If one is diving as a three though, then the gas planning would ensure there would be enough gas to share amongst the team.....same thing if there was two. One of the happy coincidences of minimum gas is that it also provides enough gas to deco out on back gas .... but there would have to be several coincident, and probably beyond the realm of possibility, failures to get to that point.

HTH
Mal

[stevechesh]

Cheers Mal. . . .

[Mark Chase]

Originally Posted by Mal Bridgeman

but, to me, that's why these discussion don't work. Picking one part of the GUE approach and then misapplying it doesn't help anyone understand why people choose to follow the GUE training route.

The dive would be done on 21/35 and one would have to reserve enough gas to get you and a buddy to 21m where you would both have a deco cylinder of 50% to switch to.

If my maths is correct that's about 50 bar in a twinset leaving plenty to do the dive.
HTH
Mal

I didnt put forward the GUE mind set on this thread. A GUE diver did.

I just pointed out why its not apropriate.


Having pointed that out, can I ask, are you not suposed to be able to deco out on back gas should your 50% fail?

As a result wouldent you need at least enough gas to pull off 37mins of deco (using 30/90GF which i beleive is the base line for GUE deco)


Genuine question and i really dont know the answer

ATB

Mark

[Finless]

Originally Posted by gobfish1

some right bollox getting put about on his thread , im gald i ant the one looking for answers of this threat , bollox bollox and more bollox ,

close it please , b4 some poor sod reads it ,

I breathed a 3 ltr of 80% dry at 28 mtrs. In fact, It may even have been 100%, I can't remember (it is what I used for deco mixes originally).

It is a fact that you dont suffer hyperoxia immediately you start breathing over a PPO2 of 1.4 or 1.6 or whatever you use as your target maximum. I know of a friend on a CCR course .............. well, suffice to say, I know personally of one other person who has breathed a verh high PPO2 and not oxtoxed.

If you are about to start trying to breath water then an 80% O2 mix is preferable.

I stand by my original post and I fail to see how anyone can dispute the facts. It is far from an ideal plan, in fact it is not meant to be a plan, it is just there along with other possible options like ........ breathing off the cylinder valve, which is an example that, to the best of my knowledge, one YDer has done?

I see nothing contentious in my reply? Furthermore, everyone has the chance to dispute what is said whether supported by evidence or not. Gobfish1 you are, of course, entitled to your own opinions and I really couldn't give a toss about how you express them. You are however incorrect, it is not bollocks (it is not recommended certainly) and not part of any plan but the option exists if needed.

I reiterate my point that people do not suffer hyperoxia the moment they exceed a PPO2 of 1.6 bar. Of course reactions will be different from diver to diver and indeed from the same diver day to day but, unless you have been there with empty lungs repeating to yourself "I'm going to die, I'm going to die" you have little understanding. I can assure you you will consider breathing off anything (probably even argon it you can get it out of your suit inflation bottle into your lungs).

I'm afraid I have to reciprocate the compliment and tell you that you are talking complete and utter orange squash (Mal said to keep ir cordial! ).

I can assure you that comments such as "OOA diver would rip your jaw off to get at something to breath" are very true. 100% at 50 mtrs under the right (or perhaps wrong) circumstances would seem like a godsend. Furthermore, I can assure you that even the much maligned Spare Air would be very gratefully received even if only meant another minute or so of life.