PDA

View Full Version : Good SAC rate???



DRhodes
02-20-2008, 10:56
I now have my first computer (Pro Plus 2) that tracks the SAC rate. What is a good rate to shoot for. I realize this is an extremely open ended question, and it all depends upon what kind of physical shape I am in and comfort in the water.........

Just looking for a ballpark to shoot for.

No Misses
02-20-2008, 11:02
I usually have a SAC of around .6 cf/min. It goes up and down depending on dive activity. I can burn through some gas when swimming hard.

cummings66
02-20-2008, 13:31
I have ranged from .34 to .6, now in doubles it's starting to look like .8 is more the normal for me. We'll see how it goes as I get more comfortable with it. I'm not ill at ease, but I'm sure I'll get smoother and that will help the air consumption.

CompuDude
02-20-2008, 14:21
It varies highly from diver to diver, since everyone is a different size and everyone's individual body chemistries require slightly differing amounts of air.

In general, however, from what I've seen, for an average size diver with average lung capacity with average gear in average temps, newer divers tend to consume around 1.0 cf/m per ATA, even when relatively relaxed, and easily double that when excited, and significantly more experienced divers tend to use around 0.4 cf/m per ATA. Some people getting it lower than that, but it's somewhat rare to see that on a regular basis.

SkuaSeptember
02-20-2008, 17:44
While getting in better shape and improving your comfort in the water are great objectives, the numbers that you track for your various types of dives and conditions are used for planning purposes as opposed to being a benchmark to shoot for. Don't worry about what anyone elses sac rate is. Use yours to have enough gas to finish your dive.

DRhodes
02-21-2008, 08:15
Well, I have only used the comp one time so far. I can't even call it a dive anyway. When we (wife and I) got our gear from ST did a check out dive in the pool. Got back home installed the downloader on the PC, and the dive profile is giving me an SAC rate of 17cfm. It didn't seem like I was burning through that much air in the 10-15 minutes we were in the pool. If I convert the units I've got 0.28 cfs. Are you guys measuring cfm or cfs?

Thanks for your help

Kingpatzer
02-21-2008, 08:21
I personally think the way to look at SAC rates is not to "shoot for" anything (as that can encourage very bad habit that can be dangerous at depth, such as skip breathing).

Instead, use it as a measure of your own skill progression and gear configuration. Whatever your rate is today is what it is. As you improve as a diver, the SAC rate will decrease. As your gear configuration improves, your SAC rate will decrease. As your ability to manage your dive increases, your SAC rate will decrease.

You can see the impact of gear changes (such as moving to doubles) on your SAC rate, and you can use that measurement as a gauge as to how comfortable you really are with new gear choices.

The journey is the thing.

No Misses
02-21-2008, 09:37
Well, I have only used the comp one time so far. I can't even call it a dive anyway. When we (wife and I) got our gear from ST did a check out dive in the pool. Got back home installed the downloader on the PC, and the dive profile is giving me an SAC rate of 17cfm. It didn't seem like I was burning through that much air in the 10-15 minutes we were in the pool. If I convert the units I've got 0.28 cfs. Are you guys measuring cfm or cfs?

Thanks for your help

DRhodes, you can calculate your SAC manually. What are the dive parameters?

Example:
Dive time ___36___min
Average Depth___52.89____ft
PSI Used____2300___(Start PSI - End PSI)
Tank Volume Rating ____80_____cf
Tank Working Pressure rating____3000____PSI

CF used = PSI used*(Cap/wp) = 2300*(80/3000) = 61.33333 cf
SAC = (time/cf used)/((AvD/33)+1) = .654 cf

If you do a web search for SAC calculator there are a bunch of sites out there.
Good Luck.

ianr33
02-21-2008, 10:01
Well, I have only used the comp one time so far. I can't even call it a dive anyway. When we (wife and I) got our gear from ST did a check out dive in the pool. Got back home installed the downloader on the PC, and the dive profile is giving me an SAC rate of 17cfm. It didn't seem like I was burning through that much air in the 10-15 minutes we were in the pool. If I convert the units I've got 0.28 cfs. Are you guys measuring cfm or cfs?

Thanks for your help

cfm is the normal method.

17 cfm is impossibly high. Any chance you have some parameter set wrong? e.g tank size.
Another possibility is that the tanks had just been filled and were hot,then cooled down quickly in the pool which would give a high apparant SAC rate.

To answer the original question: 0.4 is about as low as it can reasonably get for an experienced diver on an easy,relaxed dive.Anything much over 1 is way high and probably indicates some sort of problem.(Really bad bouyancy control,panic,leaking O ring etc. )

Single tank,tropical dives I probably average 0.45. Doubles,drysuit and a bit of flow pushes it up to 0.6something.

cummings66
02-21-2008, 16:34
I know several divers who are new and have 1 cfm rates based on my measurements of them. I'd say for an experienced diver that rate means they're doing hard work.

UCFKnightDiver
02-21-2008, 17:09
SAC Calculator (http://www.spearfishing.org/bruces_tips/java/sac.html)

you can use this to help you calculate ur sac rate if you are not integrated

scubajane
02-21-2008, 17:52
SAC Calculator (http://www.spearfishing.org/bruces_tips/java/sac.html)

you can use this to help you calculate ur sac rate if you are not integrated


Great site!!!! My sac is between 0.4 and 0.7 depending on conditions. I figured I was doing OK because I can stay down for 90 min at 30 ft at Mt Storm.

DRhodes
02-21-2008, 21:33
17 cfm is impossibly high. Any chance you have some parameter set wrong? e.g tank size.



Yep, went back through the settings on the software and the tank size was incorrect. Came out with a .65 SAC rate....imagine that doing the math correctly give you the right answer :smiley9:

DRhodes
02-21-2008, 21:38
I really appreciate all of the help I have received here....man I love this forum, nobody bashing or flaming you for a simple oversight .....

Thanks again guys....and Scubajane

berick
02-21-2008, 22:00
SAC rates really depend on conditions. Drift diving in Cozumel I'm .35-.40. Finning in warm water I'm .50-.60. I don't do that cold water/dry suit stuff yet which I'm sure will raise it.

Rockhound76
02-22-2008, 09:24
My teenager got certified last summer. I checked his SAC ("sounds creepy", he would say.) Anyway, he started out on his checkouts around 1.1cf/min., but after just a couple of dives, settled around .6.

On our last dives, he was right at .5. My "standard" warm water SAC is .4-.44, if I'm not too task-loaded. As I get older and fatter, "task loading" is sometimes just a moderate current or a long swim "in a hurry".

SAC varies with a lot of factors, some beyond your control, so I agree that it ought not to be a focus beyond making sure your breathing rate is "controlled".

One of my best buddies is very experienced and a good diver, but he sucks air like a jet engine. He finally gave up on trying to get it lower, and now dives with a 120 steel. That way, he matches up with me pretty good.

mm_dm
02-22-2008, 10:39
I personally think the way to look at SAC rates is not to "shoot for" anything (as that can encourage very bad habit that can be dangerous at depth, such as skip breathing).

Instead, use it as a measure of your own skill progression and gear configuration. Whatever your rate is today is what it is. As you improve as a diver, the SAC rate will decrease. As your gear configuration improves, your SAC rate will decrease. As your ability to manage your dive increases, your SAC rate will decrease.

You can see the impact of gear changes (such as moving to doubles) on your SAC rate, and you can use that measurement as a gauge as to how comfortable you really are with new gear choices.

The journey is the thing.

I agree and I'd like to add one more thing. Work on your aerobic conditioning, too. Once you get used to everything else there's not much else you can do outside of using breath counts (skip breathing) which isn't safe. Get out and dive, get your conditioning level up and don't worry about your SAC rate unless you need it for some specific purpose, like you would in technical diving.

plot
02-22-2008, 18:37
17 cfm is impossibly high. Any chance you have some parameter set wrong? e.g tank size.



Yep, went back through the settings on the software and the tank size was incorrect. Came out with a .65 SAC rate....imagine that doing the math correctly give you the right answer :smiley9:

At 17 cfm you have time for a 3 minute safety stop then you gotta surface. No diving for you. :smiley2:

plot
02-22-2008, 18:40
Everyone talks about gear configs, getting in shape, and comfort levels in the water for reducing SAC... which are all good things...

But some often overlooked things that will also help your SAC:
1. Proper weighting (lugging around 5-10 extra lbs makes a difference)
2. Proper trim (it takes considerably less water to fin horizontally through the water, versus pushing yourself at a 45 degree angle or something on through the water)
3. Bouyancy. If you're constantly finning to stay at a certain depth or constantly readjusting your the air in your BC, you're burning up energy and air.

Working out and getting some diving in are all good things but also things that will come with time and patients. The 3 things I mentioned are things you gotta be proactive and work on, so get to it.

DRhodes
02-22-2008, 19:33
I agree and I'd like to add one more thing. Work on your aerobic conditioning, too. Once you get used to everything else there's not much else you can do outside of using breath counts (skip breathing) which isn't safe. Get out and dive, get your conditioning level up and don't worry about your SAC rate unless you need it for some specific purpose, like you would in technical diving.[/quote]


Well as far as the aerobic conditioning, we are about to get an elliptical trainer. So that will help the breathing and trimming down the extra ummmm uhhh....baggage...yea:smiley36:

DRhodes
02-22-2008, 19:38
Everyone talks about gear configs, getting in shape, and comfort levels in the water for reducing SAC... which are all good things...

But some often overlooked things that will also help your SAC:
1. Proper weighting (lugging around 5-10 extra lbs makes a difference)
2. Proper trim (it takes considerably less water to fin horizontally through the water, versus pushing yourself at a 45 degree angle or something on through the water)
3. Bouyancy. If you're constantly finning to stay at a certain depth or constantly readjusting your the air in your BC, you're burning up energy and air.

Working out and getting some diving in are all good things but also things that will come with time and patients. The 3 things I mentioned are things you gotta be proactive and work on, so get to it.





I am itching to get in the water and dive, but it's probably going to be about a month before I can. We are going to Coz in April. That will be my first time to Coz and am looking forward to it.

BouzoukiJoe A.K.A. wrecker130 AKA Chuck Norris AKA joeforbroke (banned)
02-25-2008, 15:30
Everyone talks about gear configs, getting in shape, and comfort levels in the water for reducing SAC... which are all good things...

But some often overlooked things that will also help your SAC:
1. Proper weighting (lugging around 5-10 extra lbs makes a difference)
2. Proper trim (it takes considerably less water to fin horizontally through the water, versus pushing yourself at a 45 degree angle or something on through the water)
3. Bouyancy. If you're constantly finning to stay at a certain depth or constantly readjusting your the air in your BC, you're burning up energy and air.

Working out and getting some diving in are all good things but also things that will come with time and patients. The 3 things I mentioned are things you gotta be proactive and work on, so get to it.

Absolutely.

My SAC went through the roof for several dives after I started diving dry. I believe its because I had to relearn proper buoyancy and re-establish my trim. Yet another reason to get used to new gear on easy dives.

doczerothree
02-25-2008, 16:25
MY sac rate has been as low as .45 and as high as .7 probably higher. with experience and diving yours will come down. as for "what to shoot for" be comfortable in the water and the rest will take care of itself. sac is one of the variables we use in determining how much gas we might use at depth and therefore how much we should carry to get back home. sca increases with work and decreases with relaxation. :blob11: (this just looked cool)