SAC Rate

[The Kraken]

In order to establish a relationship between depth and SAC rate, all other variables must be either elimnated, which would be a faulty analysis, or brought to a common denominator.

Too many variables, temperature, thermal protection, amount of gear carried, visibility, current, stress level, etc . . .

the K

 

[mikerault]

The more dives you plot at similar depths the less these factors cause issues as they tend to cancel out due to averaging.

 

[The Kraken]

The more dives you plot at similar depths the less these factors cause issues as they tend to cancel out due to averaging.

From a purely statistical point, I concur.
However, doing this gives one the macro SAC rate average.
It's my opinion that a SAC rate, as a planning tool, would be much more effective if it were related to the specific characteristics of the dive, ie, the thermal protection, gear, yadda, yadda, yadda, so that one could plan one's gas consumptions based upon historical data.

Just my take on it . . .

the K

 

[ianw2]

mikerault...

You don't have any depth information in my data to plot! :no

The columns are: Dive Number, SAC, and RMV. The deviation you are seeing is rounding error in the calculations. Since all the dives have been on AL80, there really shouldn't be much scatter around a straight line when plotting SAC against RMV.

I'm at the office at the moment. I'll send you my XL table with my data later this evening when I get home.

BTW, the 1.67 was for my Rescue Class Open Water Session. On top of having lots of strenuous tasks to perform, it was pretty surgy that day, too. In short, we were luck to not have a real rescue or two. Sucking air? Damned straight I was! YOU try swimminga few "wind sprints" and see if YOUR SAC is less than 1 during your sprints!

 

[mikerault]

Well...that explains it! My bad...

Mike

 

[ianw2]

Mike:

Just sent the file to your yahoo email account.

Cheersx! It's all good!

Ian

 

[mikerault]

I believe you may have reveresed the SAC and RMV on the spreadsheet you sent me. Usually I see SAC at <1.0 and RMVs at 40 or so...

The equation that fits the trend line through a plot of depth verses SAC comes out to:

y = -0.0016x + 0.9122

Again showing a negative slope. (I only used the dives with average depth greater than 20 and tossed the .54 SAC in the first few as an outlayer.)

Mike