SAC Rate, What is Normal?

[GoBlue!]

I agree with Reefraff, RE: the biggest factor

Besides, I don't think the above formula (That I saw) takes into account the descent and ascent plus S/S @ 15ft. As we all know, if you take your TRT as "Bottom Time" and use the Max Depth as the constant, you're not very accurate with the math. (Unless the "Test Dive" is "part" of a dive, meaning the Depth IS constant, and the time accurate)> But then, you're concentrating on the numbers then, "to get a good score".

Seems that if you use your computer's average depth, you should be quite accurate. Isn't that right?

Another question: Is a standard AL80 80cuft @ 3300 psi, or 3000 psi? Makes a difference in the SAC calc obviously.

Jim

 

[String]

Anyone know a fast way of converting this into a SAC in litres/minute ?

 

[GoBlue!]

Anyone know a fast way of converting this into a SAC in litres/minute ?

I believe there are 0.0283 liters/cu ft, so just multiply the SAC in cu ft/min by 0.0283 and you're all set.

Jim

 

[pasley]

I personally have not manually computed my SAC. My SUUNTO Cobra Dive Manager does that for me.

I agree that the SAC will change with the type of dive. Of my 132 dives, fewer than 20 are boat. I find beach diving to be both fun and affordable. There is also the dive on my schedule factor.

I have been diving 3 years and have 132 dives as of this morning (diving tonight) All dives in California with water temp in the 54F to 65F range (54-60 being normal) mostly beach dives.
SAC is as follows:
Dive 15 SAC 0.89
Dive 50 SAC 0.42.
Dive 100 SAC 0.6 long swim with current. A really off day. Normally I consider 0.5 high for me.
Dive 130 my SAC was 0.42.

Since dive 120 I have been seeing about half my dives in the 0.37-0.39 range. On a particularly strenuous dive with a current and a long swim (548 yards against the current comming back) I will drift into the 0.43 range or so.

My LDS manager (and dive instructor) teases me about my lack of air consumption. I routinely bring in my tanks for a fill with between 1000 and 1800 PSI in them. Most dives I end due to my dive partners being low on air. With my AL80 tank, I find I usually run out of bottom time, or my partner runs low on air well before air is an issue for me.

Anyway, that got me to wondering what is the average or “normal” SAC rate? I recognize it will change with currents or long swims or sometimes just plain my attitude.

 

[GoBlue!]

I noticed when I started downloading dives from my Suunto Vyper that the air consumption the software calculates is different (not by much...about 0.05 usually) than the one I calculate. It appears that the Suunto software normalizes air consumption to 0 deg Celsius, which I personally don't find helpful. Do you know if the Cobra does the same?

Jim

 

[Diver0001]

Anyone know a fast way of converting this into a SAC in litres/minute ?

One cubic foot = 28,3162 litres.

R..

 

[pasley]

I noticed when I started downloading dives from my Suunto Vyper that the air consumption the software calculates is different (not by much...about 0.05 usually) than the one I calculate. It appears that the Suunto software normalizes air consumption to 0 deg Celsius, which I personally don't find helpful. Do you know if the Cobra does the same?

Jim

I don't know. But since the software is the same (SDM) for all the SUUNTO computers, I would wager it does. Frankly, when my SAC stated dipping below 0.40 on normal beach dives in SoCal, I started wondering if the computer was screwy.

 

[eponym]

Well, I added my rate to the poll, but blanket averages among dissimilar divers can't say much. As we know, in addition to activity/exertion level, there's water temp, exposure suit efficiency, exposure suit constriction (again, exertion level), and sheer body mass needing to be supplied with O2. I dove with a shark researcher in the Indian Ocean and she's a little twig of a gal who can't have half the cells of an average American diver. Does hour-long dives on half an eighty.

I recently heard that my OW instructor (who had over 5000 hours logged dive time when he taught me) took yoga lessons in order to reduce his consumption.

-Bryan

 

[The Kraken]

So it follows that an 80 CF tank @ 3000 psi = .027 cf per psi
Therefore if I use up 100 psi in 5 minutes then my SAC =

(100/5)x .027 psi or 20 psi/min x .027 which equals a SAC of .54?

 

[GoBlue!]

One cubic foot = 28,3162 litres.

R..

uhhh, your decimal point's a little off. think about what you wrote a sec, and you'll give yourself a big grin.

Jim