SAC Rates - Comparing

[HowardE]

For gas planning; I use 20 for bottom segment and 17 for deco, even though my actual average is 14.5 on the bottom and 10 on deco.

I calculate my SAC (in CFM not L usually) from one of my dive computers. I have a wireless air integrated computer with transmitters on my back and one on my deco bottle.

(I keep a hardwired standard SPG on my back gas as well)

 

[Slamfire]

We did the exercises as part of our TDI courses. They are very informative but I felt that using SAC rates based on only one dive is not representative enough of your true real-world SAC.

So, sometime before taking the TDI courses, I started measuring SAC rates for all my dives and have never stopped doing so. I do not have an air integrated computer nor does my computer calculate average depth for me. I have resorted to downloading all the depth readings of the computer to excel and then calculating an average depth. I use that in conjunction with the total gas consumption (initial psi minus final psi) and then calculate a real world SAC rate. Based on this I use .7 cu ft / min for bottom and .6 cu ft / min for deco for planning. I feel it's an accurate and slightly conservative real world breathing rate for me.

I am attaching a file with 2 spreadsheets that includes samples of my calculations. Hope it helps.

 

[Zeke XA3]

Thanks bud. I have some old SAC rates from when i was BSAC but that was drysuit in 7C waters so a bit different to what im planning for.

I agree SAC rates on one dive are very generic. But at the moment it is hard for me to work with any other figures. Of my 500 dives, the overall average depth for all of them is only 8m. And a 40-50 min dive at that average i only use around 1000psi but because i can be up and down with students sometimes making many ascents and its all drift diving so not using much air its hard to use those dives as a comparison.

Thanks for the spreadsheet, i can just modify my own dive log to show this though i work in BAR and liters which i find a lot easy to think in!!! But i know have some more number to compare with ;-)

 

[Kevrumbo]

Here's Slamfire's spreadsheet with some metric equivalent values appended to his data: