Trimix dive 65m 30min

[Dominic]

Originally Posted by [b

Quote[/b] ]counts O2 as narcotic (which it is).  

Ahh, that old chestnut

Does anyone know of any research which has been done into the narcortic effects of Oxygen? I know people have reported subjectively both ways, but what about objective tests such as have been done for Nitrogen?

AIUI, Oxygen is at least as narcotic as Nitrogen going by its lipid solubility properties, but has less effects as it gets metabolised, therefore it's pp in the tissues is much lower than an inert gas would be. So in theory, after the tissues are saturated with O2, the excess becomes narcotic in a linear fashion..? ie you can ignore Oxygen for low pp O2s but it's very relevant on higher ones.

[malcolm smith]

Andy, sorry to but in, why do you have such a deep END?
Having more helium gives the benefit of an ultra clear head.
Isn't that the whole point of trimix, apart from the possible lower ppO2.
What are the costs of more He in the mix to give a lower END, not financial, is it just a bit more deco?
I am dashing back to work so can't run any figures through my palm just now.
Cheers, Malcolm.

[Mark Chase]

WL: I was questioning the use of 50% for the 6m stop. If your a stroke fro using 80% are you a super stroke for using 50%

Also your 6m stop and 6 -3m stop times were 21 and 23 mins respectivly. theirs were 11 and 13. thats 20mins of shallow stops missed isnt it?

What ever way I look at those profiles they were ultra agresive at best and wrong at worst.

Lanny

END is a personal thing isnt it? Some people I know go for 30m some for 35 and some for 40. on deep dives. Not only is Helium expensive but it racks up the deco too. I would expect a table plan like these ones to be bassed on max depth rather than dive depth so I would normaly plan for a max 40END on the deepest part of the dive and enjoy 35m END on the bulk of the dive. This works for me but my depth limit for narcosis to be a noticible problem is 40m.

If the dive is one I hevent done before I will rack it up to 18/40 just in case.


ATB

Mark Chase

[peter k]

Sorry to jump in lads. What's GF stand for and what does it do/not do?

Peter

[daz]

Originally Posted by [b

Quote[/b] (peter k @ Aug. 28 2003,16:51)]Sorry to jump in lads. What's GF stand for and what does it do/not do?

Peter

Gradient Factor I think...  Now someone explained this to me before but can someone explain it again for me and Peter in a manner that can be understood by complete simpletons  

Daz

[Andy Phillips]

Mark,

Thanks that saved me the bother of replying

Daz,

It is explained earlier in the thread

Andrew

[Bob Cooper]

Very interesting thread this....

Haven't had time to read it through in detail but I would chip in that 65m for 30 min is not really viable.  You don't have enough back gas (unless you both have a set of twin 18's perhaps).  With twin 15's it's too marginal. And with twin 12's it's a no-no.

Also, the run time is a bit more than I'd be comfortable with in UK conditions.  Without regurgitating all the details, I'd probably cut the bottom time to 25 mins, do the deep stops and end up with 3 at 12, 7 at 9 and about 15 at 6 (a RT of about 100 mins).  Gasses would be 15/55, 50% and 100%

Cutting the BT to 25 mins would keep everybody happy according to the deco progs.

I would add that this sort of dive planning shouldn't be copied or mimicked from anybody else.  You need to find your own comfort level and do the deco YOU are happy with.

Jez and Michael would freely admit that their problem last year was caused by not following this advice.

It's not a race or a competition, despite what some people might tell you.

Bob

[Mark Chase]

Originally Posted by [b

Quote[/b] (Bob Cooper @ Aug. 28 2003,20:28)]

Originally Posted by [b

Quote[/b] ]Haven't had time to read it through in detail but I would chip in that 65m for 30 min is not really viable.  You don't have enough back gas (unless you both have a set of twin 18's perhaps).  With twin 15's it's too marginal. And with twin 12's it's a no-no.

Why?

I did two 65m dives on twin 12s with 40min bottom times. Top of the wreck on the Illonys was admitidly 59m but my print out showed an average depth of about 61. My second dive had an average depth of 63m.

On the first dive I came up out of the water with about 90 bar and on the second about 80bar on twin 12s blown to 260 admitidly but probably at about 250 by the time we were in the water.

30mins would be a doddle

If you are talking rule of thirds yes it cant be done but rule of thirds is cave diving stuff and shouldent be transposed to deep diving.

Originally Posted by [b

Quote[/b] ]Also, the run time is a bit more than I'd be comfortable with in UK conditions.  Without regurgitating all the details, I'd probably cut the bottom time to 25 mins, do the deep stops and end up with 3 at 12, 7 at 9 and about 15 at 6 (a RT of about 100 mins).  Gasses would be 15/55, 50% and 100%

Cutting the BT to 25 mins would keep everybody happy according to the deco progs.

We were doing 120 -140min profiles in 16c water in chopy conditions day one and calm on day two. I wouldent atempt this in the winter but I dont see a problem in the summer.

Originally Posted by [b

Quote[/b] ]Jez and Michael would freely admit that their problem last year was caused by not following this advice.

I would be realy interested to here what you think of their dive profile. I just couldent get it to work on Decoplanner. I apreciate from their comments about 'getting used to two stages' that they were novice divers and I will withhold any scathing comments about doing such depths at their level of experaince as I have done some silly things my self but I was amazed at their choice of 50% for deco.

I know I am bashing my head against a brick wall but is there a small inkling of a possabuility that you could admit that if they had a VR3 straped to their wrist screeming a warning at them they could have realised they screwed up the manual tables and avoided the bend?

I am honistly not singling this out as a DIR thing I am just noteing an event (as I have in the past with non DIR divers) where manual tables (it was a computer last time) failed miserably and where dispite missing a shead load of stops the divers still hold to the mistery bend theory convinved their profile was safe.

If you can make the profiles work on Decoplanner let me know the settings because I cant.


Mark Chase

[Bob Cooper]

Mark

I can't get this bloody "quote" thing to work so I'll reply with your test in "quotes":-)

"Why?

I did two 65m dives on twin 12s with 40min bottom times. Top of the wreck on the Illonys was admitidly 59m but my print out showed an average depth of about 61. My second dive had an average depth of 63m.

On the first dive I came up out of the water with about 90 bar and on the second about 80bar on twin 12s blown to 260 admitidly but probably at about 250 by the time we were in the water.

30mins would be a doddle

If you are talking rule of thirds yes it cant be done but rule of thirds is cave diving stuff and shouldent be transposed to deep diving."

Yes, I'm talking about thirds here.  YOU may have surfaced with 80 bar or 90 bar or whatever, but consider the effect of a total loss of gas at your point of maximum penetration.  Would you have sufficient gas to get you and your buddy to your first gas switch?  True, this is a cave diving rule, but I don't see why it's different for an ocean dive.  Sure, we cut things a bit fine but strictly speaking, cutting hr BT by 5 mins isn't that big a deal.

"I would be realy interested to here what you think of their dive profile. I just couldent get it to work on Decoplanner. I apreciate from their comments about 'getting used to two stages' that they were novice divers and I will withhold any scathing comments about doing such depths at their level of experaince as I have done some silly things my self but I was amazed at their choice of 50% for deco."

I wasn't there but speaking to them afterwards I think this was a "peer pressure" thing.  We've all done it, myself included.  The profile was a bit aggressive, but nothing I wouldn't do myself and they are much fitter than me!

"I know I am bashing my head against a brick wall but is there a small inkling of a possabuility that you could admit that if they had a VR3 straped to their wrist screeming a warning at them they could have realised they screwed up the manual tables and avoided the bend?"

Sorry, no chance!  The VR3 won't teach them anything about deco.  A bit like flying a plane.  I could sit in a cockpit, turn on the autopilot and fly from here to Miami....It won't teach me anything about flying though!

"If you can make the profiles work on Decoplanner let me know the settings because I cant."

It's not just a matter of making the profiles work using a dive planning prog.  It's got more to do with adjusting the deco. to suit the individual.  I am gradually getting to know what deco. I NEED to do.  The trouble is the DECO that diver A "needs" may be more or less that the deco. diver B "needs" to do.

This isn't a DIR thing.  This thread is really interesting and you have some valuable input here.  Don't take it as a "DIR vs Stroke" thing.

Bob

[Bob Cooper]

Can somebody help me with the "quote" thing!