How are you computing your SAC?

Please register or login

Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.

Benefits of registering include

  • Ability to post and comment on topics and discussions.
  • A Free photo gallery to share your dive photos with the world.
  • You can make this box go away

Joining is quick and easy. Log in or Register now!

The Kraken:
I use SAC to determine the capacity of the tank required for a dive based upon a general SAC rate developed for that particular type of dive. I use the SAC for planning.

The PSI/min rate is a great tool to use to determine one's activity at depth or to determine an inordinate usage of breathing gas. I use the PSI/min for monitoring.

the K


Bing, bing, bing, bing, bing ... give that man a cheroot !!!

:D

... Bob (Grateful Diver)
 
RIDIVER501:
so that begs the question: " are we looking for the best SAC rate or are we looking for a more accurate SAC rate?"

If I spent the bulk of my dive at 40 feet and dipped to 60 to pick up a dropped item for a couple of minutes, do I use the 40 to get a more representative idea of my sac rate for the dive or do I use the 60 to BS myself into thinking I have a much better consumption rate then I really do?

This is just food for thought

I just use the 'average' depth reported by my computer (Suunto Gekko) to calculate SAC. Don't know what algorithm it uses - sample every 30 seconds maybe?
 
If you don't have a computer and dive the tables (square profile), how do you figure your average depth?
 
If it is a "square profile" then your max depth IS your average depth.

Joe
 
Sideband:
If it is a "square profile" then your max depth IS your average depth.

Joe

Well, not quite.
Suppose you did a 100' dive for 3 minutes . . .

Say 2 minute descent, 3 minutes on the bottom and then another 1 minute to ascend to 30', then another 1/2 minute to ascend to 15' and then 3 minutes at a 15' safety stop.

That comes out to about a 46' average dive depth.

Hummmmmm . . . .
 
Right, but I wouldn't use such a dive to figure my SAC. I don't think 9.5 minutes actually constitutes a dive does it?
Joe
 
Sideband:
Right, but I wouldn't use such a dive to figure my SAC. I don't think 9.5 minutes actually constitutes a dive does it?
Joe

the 2 rules of thumb I was taught and always use are:

1. meeting any two of the following constitutes a dive.
depth of 15 feet or deeper.
burned 1500 or more psi.
down for 15 or more minutes.

2. any dive where a safety stop is recommended.
 
It's not "what" constitutes a dive, it's just an example that illustrates that the max depth of a square profile dive can't be used as the average depth of a dive with which to compute an SAC.

the K
 
This is a great discussion, but I need guidance in how to figure average depth for SAC calc. Max depth won't work, You will wind up short on air. I know because I was using max depth. When I figured the time I could be down using my Average SAC over the last 10 dives I had to surface sooner than expected. Monitoring my air regularly I never got into any trouble. I was disapointed that I had to cut the dive short.
 
fmw625:
This is a great discussion, but I need guidance in how to figure average depth for SAC calc.
If you have a computer or electronic depth gauge/timer that you can download a profile from, then just average that.

Otherwise, do as an earlier poster suggested and swim at a constant depth for a while and note how many psi you use over some period such as 10 minutes. Then just calulate SAC using that 10 minutes, the depth, and the PSI used.
 
https://www.shearwater.com/products/teric/

Back
Top Bottom