Solicit simple SAC solution

[scubadada]

What tank volume do you use for an Al 80 with a working pressure of 3000 psi, 80 cu ft, 77.4 cu ft, or something else?

Thanks in advance, Craig

 

[MXGratefulDiver]

The Luxfer and Catalina AL80's are both spec'ed at 77.4 CF.

... Bob (Grateful Diver)

 

[scubadada]

Thanks Bob. Simple SAC solution sought and simple SAC solution supplied

Good diving, Craig

 

[captndale]

Since SAC calculations are, at best, good to only one significant figure, 80 CF is good enough.

 

[PfcAJ]

Call it what is is (77.4) and not what it isn't (80).

 

[scubadada]

Call it what is is (77.4) and not what it isn't (80).

That's my bias, thanks

Craig

 

[Dyno Bill]

Forgive my ignorance but what is SAC and what is the value used for? I know an al 80 filled on a boat to say 2700 lbs drops 2-300 when you hit the water so knowing that I always just figured to be back on board before it was gone. I know it's not very scientific but neither am I.
Bill

 

[Cave Diver]

Forgive my ignorance but what is SAC and what is the value used for? I know an al 80 filled on a boat to say 2700 lbs drops 2-300 when you hit the water so knowing that I always just figured to be back on board before it was gone. I know it's not very scientific but neither am I.
Bill

SAC stands or surface air consumption. It's a way of calculating how long a tank will last at a given depth calculated from a baseline consumption rate. A lot of people use it as part of their dive planning and figuring gas reserves, or rock bottom turn pressures.

 

[scubadada]

captndale has a very good point.

I just did 18 dives off Little Cayman. Using a tank volume of 80 cu ft, my SAC had a range of 0.36-0.44 and a mean and sd of 0.39 +/- 0.02 cu ft/min. Using 77.4 cu ft, my SAC had a range of 0.35-0.42 and a mean and sd of 0.38 +/- 0.02 cu ft/min.

Conclusion, under the conditions off Little Cayman, my SAC is 0.4 cu ft/min with a relatively narrow variation. It's always good to prove it to yourself. This happens to be my normal SAC in relatively warm water with little to modest exertion over the last couple years.

Good diving, Craig

Cave Diver, where is the Defender badge???

 

[Dyno Bill]

SAC stands or surface air consumption. It's a way of calculating how long a tank will last at a given depth calculated from a baseline consumption rate. A lot of people use it as part of their dive planning and figuring gas reserves, or rock bottom turn pressures.

Thanks for the quick response, I can see how a technical diver could benefit from that type of calculation. Especially a cave diver or anyone who enters overhead situations. Another question if I may, doesn't the sac value vary with changing depths and if so wouldn't exploring a place or area that your not totally familiar with effect the accuracy of the calculation. And forgive me but where do you usually turn a dive around to start your return to the surface and or boat. Thanks again for the information.
Bill