Which mixes for trimix are better for 330 feet (100 meters)?

[JeffG]

Seems like alot of work for an awefully short dive.

Yea...Kinda falls into the section that I called "Why Bother."

Just to go that deep, for depths sake brings a lot of unnecessary dangers and (to me) not enough time to enjoy a wreck.

 

[jtivat]

I consume about 16 liters/minute (0.57 pi cu)

Yes, 5 min, but I calculated 6 min:

Desc à 70m (7) Trimix 18/33 10m/min Descente.
Niveau 70m 6:00 (13) Trimix 18/33 1.42 ppO2, 39m ead, 43m end
Rem. à 50m (15) Trimix 18/33 -10m/min Remontée.
Rem. à 36m (16) Trimix 18/33 -10m/min Remontée.
Palier à 36m 0:36 (17) Trimix 18/33 0.81 ppO2, 18m ead, 20m end
Palier à 33m 1:00 (18) Trimix 18/33 0.76 ppO2, 16m ead, 18m end
Palier à 30m 1:00 (19) Trimix 18/33 0.71 ppO2, 14m ead, 16m end
Palier à 27m 1:00 (20) Trimix 18/33 0.65 ppO2, 13m ead, 14m end
Palier à 24m 2:00 (22) Trimix 18/33 0.60 ppO2, 11m ead, 12m end
Palier à 21m 2:00 (24) Nitrox 50 1.52 ppO2, 9m ead
Palier à 18m 1:00 (25) Nitrox 50 1.37 ppO2, 7m ead
Palier à 15m 1:00 (26) Nitrox 50 1.22 ppO2, 5m ead
Palier à 12m 2:00 (28) Nitrox 50 1.07 ppO2, 4m ead
Palier à 9m 4:00 (32) Nitrox 50 0.92 ppO2, 2m ead
Palier à 6m 5:00 (37) Nitrox 50 0.77 ppO2, 0m ead
Palier à 3m 10:00 (47) Nitrox 50 0.62 ppO2, 0m ead
Surface (47) Nitrox 50 -10m/min Remontée.

Le dégazage commence à 45.1m

OTU pour cette plongée: 41
CNS Total: 16.0%

1947.8 ltr Trimix 18/33
684.7 ltr Nitrox 50
2632.5 ltr TOTAL

You really want to spend 50 min in the water to spend 5 on the real dive???

You are spending over 6 times on deco to your BT.

The dives I do in that range are for 30 BT with 90 min RT that is a 3 to 1 and much more enjoyable. Try getting that ratio with one gas not to mention if something goes wrong.

 

[rjack321]

You really want to spend 50 min in the water to spend 5 on the real dive???

You are spending over 6 times on deco to your BT.

The dives I do in that range are for 30 BT with 90 min RT that is a 3 to 1 and much more enjoyable. Try getting that ratio with one gas not to mention if something goes wrong.

1 min BT to roughly 2 mins deco is enough for me. I think the least amount of BT I'd consider is 15mins. Less than that isn't worth the logistics for a dive.

I'm in cold water and a hypothermic wuss, so I limit my runtime to ~70mins. More than that and its also not worth it to me.

Touching 100m for giggles is completely foreign to me.

 

[Phrenzy]

I consume about 16 liters/minute (0.57 pi cu)

Yes, 5 min, but I calculated 6 min:

There must be something pretty cool down there....

 

[Tomeck]

You really want to spend 50 min in the water to spend 5 on the real dive???

You are spending over 6 times on deco to your BT.

The dives I do in that range are for 30 BT with 90 min RT that is a 3 to 1 and much more enjoyable. Try getting that ratio with one gas not to mention if something goes wrong.

You are right, BT is short. But in the Swiss lakes, there are many spectacular cliffs, they are vertical and it is not interesting to stay a long time in the same depth.

 

[Tomeck]

1 min BT to roughly 2 mins deco is enough for me. I think the least amount of BT I'd consider is 15mins. Less than that isn't worth the logistics for a dive.

I'm in cold water and a hypothermic wuss, so I limit my runtime to ~70mins. More than that and its also not worth it to me.

Touching 100m for giggles is completely foreign to me.

The temperature in Swiss lakes is 40°F even in summer (from 60 feet), but the surface in summer is 70°F.

 

[jtivat]

1 min BT to roughly 2 mins deco is enough for me. I think the least amount of BT I'd consider is 15mins. Less than that isn't worth the logistics for a dive.

I'm in cold water and a hypothermic wuss, so I limit my runtime to ~70mins. More than that and its also not worth it to me.

Touching 100m for giggles is completely foreign to me.

Early in the year the temps in the Great Lakes are 36 to 38 top to bottom. The bottom is 38 year round but we might get a toasty 68F for deco latter in the year.

 

[amascuba]

You are right, BT is short. But in the Swiss lakes, there are many spectacular cliffs, they are vertical and it is not interesting to stay a long time in the same depth.

A better gas selection at 70m will get you out of the water in about 20 minutes with your bottom time of 5 minutes. Although, logistically it would be easier to just take a snorkel.

 

[nereas]

...

I don't know about "the majority of agencies," but there are different ways to plan dives safely. You are welcome to bring two bottles to 150 feet if you want to. I'd rather bring one and reserve enough backgas that I could get out on it (doubling deco from 70 on up) should my bottle fail.

Blackwood, if your back-gas on your 150 ft dive is nitrox, then fine, only one bottle of EAN 50, as long as there is enough nitrox (EAN 25) in your twins to deco completely on, should the EAN 50 bottle fail. It would sure be a long deco period.

Backgas deco normally either takes a really long time, and is miserable, or else is not feasible at all, when the backgas is trimix.

Those who teach backgas deco as a backup have often not even considered how much deco time that would take. For anyone seriously considering doing that, I would suggest hanging a spare deco bottle from the boat, as well.

Generally, 2 of everything should apply to deco bottles also. And that is where the beauty of EAN 50 combined with 100% O2 works out nicely.

And I don't see how you got confused on my previous post, regarding EAN 50. If someone is bound and determined to bring only one deco mix, then I suggest that should be EAN 50. Even though I do not agree with the notion of only 1 deco bottle.

[Sorry, Tomek, this is all off-topic. That's why UCF and TEX are muted, because they ramble off topic too much, and too many ad hominems and trolling.]

 

[nereas]

Tomeck why are you asking this question?

I don't see any way to cover your butt on a 100m dive with only 2 deco gases. No way. What you've proposed leaves some massive gaps and has all sorts of other issues, but more importantly you seem to be missing the magnitude of the planning and balancing of volumes, CNS toxicity, and deco necessary for this dive.

Exactly!