.41 seems right Lynne. I'm generally in the .35 to .4 range in warm water.
Air integrated vs. SPG, a small study
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Aren't the only two choices here either the Suunto average depth figure is incorrect or you are incorrect in the air used figures?
It appears that your true SAC rate is lower than the numbers you've come up with.
On your next dive maybe you could do a timed swim thus eliminating the initial cooling off of the tank and the initial air used in your wing and drysuit. Stay at one depth and you don't even need to rely on the Suunto average depth number.
Through several dives and the process of elimination you can figure out the problem.
It appears that your true SAC rate is lower than the numbers you've come up with.
On your next dive maybe you could do a timed swim thus eliminating the initial cooling off of the tank and the initial air used in your wing and drysuit. Stay at one depth and you don't even need to rely on the Suunto average depth number.
Through several dives and the process of elimination you can figure out the problem.
bperrybap
Contributor
The hour time in the second calculation for
the 72s, Is that how long the dive with the 95 was?
If not, I think you aren't comparing apples to apples.
Ignoring all effects due to temperatures, and assuming
the average depth is correct.
If I look at your first example, either your SAC is much lower
or you are not under water for an hour.
Assuming your .45 SAC is accurate, then
If I used your
AVG depth = 46 = 2.3939 ATA
SAC = .45 cuFT/Min
1500 PSi = 53 cuFt
Time = 53 / .45 / 2.39 = around 49 minutes
There seems to enough gas for two 49 minute dives using
the double 72s and your SAC of .45
The other alternative is that the hour time is correct.
If so the SAC rate is wrong.
Same assumptions:
SAC = 53/60 / 2.39 = .37 cuFT/min
I am unable to use the same assumed parameters used for
the calculation with the 72s and get the measured results
you have for the dive with the 95.
------------
There seem to several "about"s, and "typical"s used in the 72
calculation projections. Perhaps, the combination of all
the accuracy deviations and rounding along with an unaccounted
factor (temperature) is creating a final result that doesn't
seem to make sense.
In other words the result is a very precise yet inaccurate answer.
--- bill
the 72s, Is that how long the dive with the 95 was?
If not, I think you aren't comparing apples to apples.
Ignoring all effects due to temperatures, and assuming
the average depth is correct.
If I look at your first example, either your SAC is much lower
or you are not under water for an hour.
Assuming your .45 SAC is accurate, then
If I used your
AVG depth = 46 = 2.3939 ATA
SAC = .45 cuFT/Min
1500 PSi = 53 cuFt
Time = 53 / .45 / 2.39 = around 49 minutes
There seems to enough gas for two 49 minute dives using
the double 72s and your SAC of .45
The other alternative is that the hour time is correct.
If so the SAC rate is wrong.
Same assumptions:
SAC = 53/60 / 2.39 = .37 cuFT/min
I am unable to use the same assumed parameters used for
the calculation with the 72s and get the measured results
you have for the dive with the 95.
------------
There seem to several "about"s, and "typical"s used in the 72
calculation projections. Perhaps, the combination of all
the accuracy deviations and rounding along with an unaccounted
factor (temperature) is creating a final result that doesn't
seem to make sense.
In other words the result is a very precise yet inaccurate answer.
--- bill
OP
Very carefully measured dive in the 95 last night gave a SAC of .35. It was a simple dive, and I'm pretty good on air consumption, but I simply can't believe it's that low. Starting pressure was measured at the surface, air temp approximately 75 degrees; ending pressure was noted after the dive, and confirmed this morning, air temp approx. 55 (so should have made delta P as great as possible). Time and average depth were taken off the Vytek I was wearing. Something's just screwy!
I don't understand why you cannot believe it is that low? You're a small woman.
lamont
Contributor
I can get .45 on a good day and I weigh about 200#.
OP
I guess because when I read the ranges people quote, numbers below .4 seem to occur almost exclusively in warm water diving.
lamont
Contributor
TSandM:
Well, you either need to be female or Uncle Pug to get below .4 up here...
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Because of the limited space and power available, and the amount of testing and reveiw that happens before a device goes into production, small device-embedded systems tend to be much more stable than general purpose PCs.runamonk:
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Terry
We haven't actually met Lynn but I saw you in the parking lot last night. Marc is a buddy of mine and I believe you two were in the same group. You are a very small woman. I can believe .35 for a normal, calm dive. You're the doctor but I have to believe that your body's need for oxygen must be dramatically less than mine at 6'1".
In calm conditions on a timed dive I've measured .45.
In calm conditions on a timed dive I've measured .45.
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