Improving my SAC rate

[NothingClever]

This looks like a dazzling RMV of about.....7.4-7.6 ltr/min

Well, call me insolent but I’m having to stifle a laugh here.

Crusader, are you sure your inputs are right?

I trust scubadada’s ability to run dive calculations but if the inputs are aspirational versus actual, well, then....they’re just aspirations.

 

[scubadada]

Well, call me insolent but I’m having to stifle a laugh here.

Crusader, are you sure your inputs are right?

I trust scubadada’s ability to run dive calculations but if the inputs are aspirational versus actual, well, then....they’re just aspirations.

It's certainly possible, just not very common. I have a reasonably low average RMV of 0.36 cu ft/min or 10.2 ltr/min over the last 1,450 dives. This is my 2nd lowest RMV ever, an absolutely effortless boat dive off of Klein Bonaire. This would be 7.6 ltr/min

There have been 2 polls on SB asking for average RMV, SB caveats apply

The easiest, and arguably, most accurate way to follow your RMV is to have it auto calculated by your download software while using an AI computer. My Teric computer calculates my SAC, and can easily be converted to RMV using the cylinder characteristics. It matches my Oceanic computer nearly perfectly.

 

[Blackcrusader]

I assumed a 93 min dive, an avg depth of 14.2 m or 47 ft, gas consumed 210-50 bar or 3046-725 psi, and a standard AL80 (77.4).

If your SAC was 8.5 psi/ min, that would be a RMV OF O.22 cu ft/min or 6.2 ltr/min. Now, that would be really low. This also assumes an AL80

Maybe I made some incorrect assumptions

Correct standard AL80 or this calculates as 11l. I did the calculations on a 12l oops
On some of my dives my sac rate is 9.5 so that nice 93 min dive was at a really relaxed pace.
So mainly I can calculate dives at 10l/min if gas planning and have a nice safety margin.

 

[Blackcrusader]

Well, call me insolent but I’m having to stifle a laugh here.

Crusader, are you sure your inputs are right?

I trust scubadada’s ability to run dive calculations but if the inputs are aspirational versus actual, well, then....they’re just aspirations.

I'm sure my inputs are correct I just assume a sac rate of around 8.5l per dive. Could be more or less and doesn't really matter as it's rare I finish a recreational dive with less than 100 bar. So I get a bit lazy and let others calculate. Was just going thru my sports diving books to practice calculations again. also rarely done and not necessary for recreational diving.

I now also run a Cressi Digital Console along with my Perdix although I do not use the Perdix AI
Another read on the forums is this thread where SAC rates are also discussed. The console on the top right says range, that means from any point on the dive how much dive time you would have left to get to 50 bar. So obviously it changes throughout the dive.

Overshooting NDL and mandatory deco stops

 

[Blackcrusader]

del

 

[Blackcrusader]

Buoyancy, trim, kicking and breathing are all connected together. If one of these 4 factors gets out of control, it will adversely affect all the others.... Compare this with the photo above and you learn how static trim has little to do with proper dynamic trim:
View attachment 573129

Here I am in perfect trim on one of my dives. It's really easy to see under coral shelves this way. I often find cleaner shrimp and octopus hermit crabs and other critters this way.

 

[Blackcrusader]

Strange, some seem to think that fitness doesn't mean much for SAC.
.

Fitness is one small component. I did a fun dive with a US Army Captain, West Point Graduate based in Korea. Fit as a fiddle. He went thru air like there was no tomorrow. He had a great time but hid dives were done in less than 30 minutes. He chased the marine life, was doing all sorts of crazy stuff and having a hell of a time. He would run from 200 bar to 60 bar in 30 minutes.

On the other hand here is a DM with over 12000 dives I dive with. Better on air than I am. He is the DM I did my 93 minute dive with. It was his birthday that day so asked the dive center if we could just dive to 50 bar the two of us with no time limit. Most of our dives are with the currents in warm slow waters. Always good fun, not stressful, relaxed, and we find lots of critters to take photos or video of.

 

[Blackcrusader]

It's certainly possible, just not very common. I have a reasonably low average RMV of 0.36 cu ft/min or 10.2 ltr/min over the last 1,450 dives. This is my 2nd lowest RMV ever, an absolutely effortless boat dive off of Klein Bonaire. This would be 7.6 ltr/min.

This was my best ever SAC rate. I think I was in a trance the whole dive. A low drift carrying us along. I shot a couple of videos, was really the laziest dive I have done. This is just nuts.

 

[leadduck]

@BLACKCRUSADER : definitely agree that the main factor is: what you do, how much energy do you spend. Experience with scuba diving, good trim, ... matters a lot. A relaxed unfit diver doing nothing will have a lower SAC than a marathon runner swimming hard because of too much lead and bad trim.

Comparing a marathon runner to an unfit diver doing the same, If both are relaxed and do nothing in the water, then the marathon runner will still have a higher SAC than an unfit diver. Whereas if both have to swim, then the unfit diver will hyperventilate much earlier than the marathon runner.

Having a very low SAC and feeling like in trance is not always a good sign however; there may be CO2 retention going on with all the negative effects of hypercapnia. One of my buddies (former trained apnoe diver) is close to your SAC rate and knows he has to consciously breathe more to avoid dizzyness at depth.

 

[Blackcrusader]

@BLACKCRUSADER Having a very low SAC and feeling like in trance is not always a good sign however; there may be CO2 retention going on with all the negative effects of hypercapnia. One of my buddies (former trained apnoe diver) is close to your SAC rate and knows he has to consciously breathe more to avoid dizzyness at depth.

I meant being in a trance as was just so relaxed on the whole dive. I'm well aware of keeping away from hypercarpnia and have never had a headache after a dive nor been dizzy on a dive. I do know I need to breath

If you are super relaxed you are not creating as much CO2 as if you were hard charging into a strong head on current. I breath as I need and if I need to breath more then I do. This dive was just that perfect combination of nice sunny weather, good visibility, a very slow current we drifted with, shallow depth and I think the only time I had to actively fin was to get back to the dive boat and back up the ladder at the end of the dive. My dive buddies have given me the nickname The Corpse as I move so little on dives.