When do you Consider Surface Assistant.

[tbone1004]

It is just my perspective how I will do a dive like that, for the reasons I mention.

the risk is that you are making the dive more complex with no significant increase in safety by adding the third bottle. What @PfcAJ said is right. That dive for me would be a pair of LP104's, an al80 of 32% or 30/30, and an al80 of 100%

 

[Remy B.]

Understood

 

[LiteHedded]

the risk is that you are making the dive more complex with no significant increase in safety by adding the third bottle. What @PfcAJ said is right. That dive for me would be a pair of LP104's, an al80 of 32% or 30/30, and an al80 of 100%

the problem with swapping the 70 bottle for something deeper (i assume you're going to use that nitrox32 bottle at 100 or 120?) is that you're putting all of your eggs in one basket and if you lose that bottle you have a long way up to 20 feet sharing that one remaining bottle (if you are surfacing with a buddy)

if you're bringing it for minimum gas concerns (you shouldn't have any problems with 104s) just bring a stage IMO. you could add the 120 bottle as a third deco gas but it's not really giving you any deco benefits on this small exposure.

the dive in the op is a pretty typical dive you would do in your tech 2 class with gue. i've done it with 85s and a stage and i've seen others do it with your 104s just fine (with a rough go up the boat ladder)

 

[tbone1004]

@LiteHedded you lost me. Are you saying you would do that dive with 85's, a stage, and 3 different deco mixes? That's a bit excessive...

I would use either 32%, 30/30, 35/25 pick your poison in lieu of the 50% bottle. The 50/50 bottle isn't going to give you that much of an advantage on deco vs the other mixes, and also reduces the risk of ICD due to the sudden shock of losing the helium. The time if you lose that bottle is annoying, but the risk of that vs. the pain of carrying the extra bottles is not something I would weigh in favor of carrying an extra bottle.

dive plan as described by the OP, would be LP104's or similar with 16/45 ish, AL80 of nominal 30/30 *could be 35/25, doesn't really matter*, AL80 of O2, and I would either hang an AL80 of 50/50 or 100% on the downline as contingent deco bottle depending on what the dive profile looks like. If it was 50/50, I would switch to it at 70ft, but would plan to make sure I didn't need it.

 

[LiteHedded]

no i'm not saying that. i'd do it (and have) with a 70 and a 20 bottle. swapping the 70 for a 120 like you suggest isn't a great idea. the 120 isn't needed at all and has some pretty big drawbacks.
taking a 120 instead of a 70 is getting cute.

 

[Diver0001]

Well.... my BS-o-meter is going off. I'm hearing a lot of theory spinning about deco schedules and seriously wondering if people are actually making those dives.

 

[LiteHedded]

Well.... my BS-o-meter is going off. I'm hearing a lot of theory spinning about deco schedules and seriously wondering if people are actually making those dives.

i'm wondering the same thing

 

[PfcAJ]

Downline?

Absolutely not. Carry your gas with you.

Backgas (15/55 in 104s) 50% and oxygen.

You're in for a very ****** time if your 120 bottle fails compared to losing a 50% bottle (100ft of stops vs 50ft).

 

[oldschoolto]

The oldschool way was to hang your deco gas on the down line, plus any extra gas that maybe needed.. We never slung 6 plus back gas like you see some of these guys doing today.. But, We never did the dives that they do...

Jim..