dstrout
Registered
OK, please bear with me - I'm trying to learn how gas budgeting works. For the most part, what I've gotten in training so far was "keep an eye on your computer, but you'll run out of gas on an AL80 before NDL anyway", and I'd like to do a bit better than that.
My two dream dives are the USS Blenny (70') and the John Morgan (110'). Assuming a 120 cu ft tank and a .6 SAC:
Blenny:
70' = 3.1 ATM = 1.86 cu ft / min
40 cu ft ( rule of thirds) / 1.86 cu ft per min = 21.5 mins out & 21.5 mins back = 43 mins total bottom time (including decent & ascent)
NDL for 70' = 45 mins
So for that dive, I'm very close to my NDL if I'm not careful
John Morgan:
110' = 4.3 ATM = 2.6 cu ft / min
40/ 2.6 = 15 out, 15 back = 30 bottom time
NDL at 110' is 15 mins total, so it would be really easy to blow past NDL
And, to run it backwards:
2.6 cu ft / min * 7.5 mins per "third of a tank" = 19.5 cu ft per "third" = 58.5 cu ft total, so an AL80 would be a fine tank for that dive.
Am I understanding the basic idea correctly?
thanks,
dave.
My two dream dives are the USS Blenny (70') and the John Morgan (110'). Assuming a 120 cu ft tank and a .6 SAC:
Blenny:
70' = 3.1 ATM = 1.86 cu ft / min
40 cu ft ( rule of thirds) / 1.86 cu ft per min = 21.5 mins out & 21.5 mins back = 43 mins total bottom time (including decent & ascent)
NDL for 70' = 45 mins
So for that dive, I'm very close to my NDL if I'm not careful
John Morgan:
110' = 4.3 ATM = 2.6 cu ft / min
40/ 2.6 = 15 out, 15 back = 30 bottom time
NDL at 110' is 15 mins total, so it would be really easy to blow past NDL
And, to run it backwards:
2.6 cu ft / min * 7.5 mins per "third of a tank" = 19.5 cu ft per "third" = 58.5 cu ft total, so an AL80 would be a fine tank for that dive.
Am I understanding the basic idea correctly?
thanks,
dave.