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A bounce to 190 would not bother me in the least.
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How deep are you willing to go on a specific size tank?
For example, on an Al 80 would you dive to 115 ft?
Well, let's see, assuming:
-Normal SAC of 0.75, stressed SAC of 1.0
-Two minutes to sort out a catastrophic gas failure
-30 second stops every 10 feet starting at 50% max depth, with 30 seconds glide time to the next stop
-30ft/min ascent rate; 60ft/min descent
Gas burned sorting out the problem before starting ascent:
2 min * (1.0 cu. ft. / min) * 4.5 atm = 9 cu. ft.
Gas burned ascending to first stop:
60ft ascent / (30 ft/min) = 2 min
2 min * (1.0 cu. ft. / min) * 3.65atm = 7.3 cu. ft.
Gas burned doing stops at 60,50,40,30,20,10ft:
6 min * (1.0 ct. ft. / min) * 2atm = 12 cu. ft.
-------------------
28 cu. ft. per person * 2 people = 56 cu. ft. gas required
To do such a thing safely (and I agree with the earlier comment about wanting redundancy at that depth), you should turn the dive at 2100psi on an Al80. When was the last time you turned a dive at 2100psi? Seems hardly worth the bother for about 5 minutes of bottom time.
A bounce to 190 would not bother me in the least.
Interesting question. I'm heading to Coz Saturday and one of the signiture dives is at Punta Sur - The Devils Throat. From what I've read it comes out around 130 ft. I've had a few 100+ ft dives on al80s. My average sac rate is .52 so I'm certainly not the most efficient breather down there. The dive op I'm going with does have some al 100's which I will ask for if we do that dive. I see no problem either way. The only downside (unintended pun) is lack of bottom time. I assume it will be a fairly short dive.
How deep are you willing to go on a specific size tank?
For example, on an Al 80 would you dive to 115 ft?