Who is riding trimix dil all the way to the surface and who is flushing to a nitrox dil?

[fullytek]

In less you can actually measure 2 of the 3 gasses in the look its kindof a moot point.

If you flush to nitrox and actually off gas you are going to be breathing some flavor of trimix anyway

 

[RedSeaDiver2]

I for one don’t bother, I’d just ride it out, as others have said it’s flushing out anyway, I used to have mates that would change dil (with a flush) on the way up on deep deep stuff, my personal issue was that in reality the gases on ascent are coming out of our system so telling the computer that your now on mix X isn’t strictly true, put basically I’ve known a few folks get bendy when they exit the water and sometimes there has been this school of thought, another thing that I had drummed in to me by one of my (legendary) instructors was to work out the Po2 setting requirement prior to dive and apart from changing set point to high when nearly at target depth he disproved of altering it on ascent , ie “tweak it to 1.5 at 6m” to hurry up the deco, he alluded that there was a consensus among the elite that the Po2 being raised may have been responsible for some people being lost, as this was their habit (you may of heard of some of them but I’m not wanting to divulge as it’s not scientifically proven and just a theory) sorry to digress

As said earlier I won't be telling the computer about the dil switch - will be leaving it to run the deco as per trimix dil schedule

 

[rjack321]

The plan isn't to save time on deco - it is to run the same time, but use the N50 switch to build in an extra safety factor.

Risk assessment and mitigation is looked at differently when you have a dozen divers doing scientific diving doing the same profile day after day after day.

You dont really have any evidence that your dil switch is making you safer. Some of these folks probably haven't ever done one, nor are they setup to actually do it efficiently. By requiring or expecting folks to do this dil switch you might actually make their overall dives riskier. Splashing with the 50% still plugged in from the last dive and dropping to 60m would be pretty bad.

Don't really have much option about the 2.5 hour run time in the ocean - unfortunately the wreck sank where it sank and we just have to work with the location.

Bunkus. Nothing about a wreck in the 50-60m range is forcing you to do 50min bottom times. Cut back to 35min and you're getting out nearly an hour sooner - and could way more easily even do 2x 30min BT dives a day instead of 1x 50min

 

[Alex Ouroboros]

Well, if I’m honest here it sounds like you pretty much want to do the dil switch, and on a dive of that depth, the gasses your intending to use and the fact your not doing this to get out of the water quicker I really can’t see a negative of implementing it, I certainly wouldn’t be arguing against it, the only pitfall comes from someone fluffing the change, but even that would have to be quite catastrophic to be dangerous,
For my money though I’d just stay on the original dil and pad out the shallower stops,
If I’m doing any form of tec diving laying off the booze for a week or two before and during the week, keeping myself well hydrated (rehydration powders in 2ltr water in the hour before I go in ,,,,,, as a result always using a pee valve)
And I just pad the stops, one other thing that has always made me feel better is an extra 10% stop at 6m (last stop in the sea) then coming up so slowly it’s comical, then I celebrate by being incredibly lazy for the next 90min,,, oh I forgot, once on the boat I sit there for a few minutes with the machine set back to 100% and then breathe it down to 21% whilst monitoring how I feel, so I tend to read what’s written about me on deck, (this cautiousness comes from the dreaded bendy-wendies which I don’t want to repeat, and it’s usually my vision that becomes a bit pissed as an early sign) I’ve never had any issues since sticking to my routine,,, and this is something that’s kept me safe on super-deep and longs…

(Not telling you to do this but,,, your not going to be taking the Mickey out of your O2 clock so if anyone felt a bit funny and there’s a full face mask I’d have no qualms in jumping in on the end of a 6m rope ,, ahem)

 

[LFMarm]

I would not switch and rather do an O2 flush at 6m which will get rid of the little He left by then.

 

[bubblemonkey2]

flush/switch to say 50% at 18 metres while staying on the deco plan for He dil in order to increase deco efficiency and therefore building in extra safety margin. In a way it follows on from this thread from three years ago - Dil switch off helium during deco

How much time spent between 18 and 6 metres? Up to 0.75 atm of He (50/27 loop) will be free to re-enter during that time, since gas atoms don't "see" each other.

Might not matter so much until you're doing @GF99/99 's 5-hour dives

 

[formernuke]

I'm not sure I understand.

On ascent I'm not adding dil to my loop just O2. So switching to a different dil bottle won't do a thing. The He in the loop isn't leaving unless I do a flush or exhale from my nose to control loop volume.

 

[rjack321]

How much time spent between 18 and 6 metres? Up to 0.75 atm of He (50/27 loop) will be free to re-enter during that time, since gas atoms don't "see" each other.

Might not matter so much until you're doing @GF99/99 's 5-hour dives

If you're doing 50min bottom times and 2.5 hr runtimes its roughly an hour. Dil switching saves you ~20mins overall

I'm not sure I understand.

On ascent I'm not adding dil to my loop just O2. So switching to a different dil bottle won't do a thing. The He in the loop isn't leaving unless I do a flush or exhale from my nose to control loop volume.

It's a dil flush, actually many dil flushes, to maximize the helium gradient since you're offgassing He into the loop. But those 50% flushes of course actually make the N2 gradient less attractive.

 

[formernuke]

If you're doing 50min bottom times and 2.5 hr runtimes its roughly an hour. Dil switching saves you ~20mins overall

It's a dil flush, actually many dil flushes, to maximize the helium gradient since you're offgassing He into the loop. But those 50% flushes of course actually make the N2 gradient less attractive.

Ok, I keep mine at about 1hr per dive.

 

[Cthippo]

Random question, but what is the minimum O2 percentage at the surface to not worry about passing out from hypoxia?