Target SAC Rates....

[FishFood]

Im still a fairly new diver. Im finally starting to have about the same amount of air left in my tank as my dive buddies. Id like to keep going though, and keep working on my breathing and improve my consumption. Ive been calculating my SAC rates but need somethign to compare them to. Can someone break the numbers down into a good better best for me? THanks!

[Dive-aholic]

Average SAC for a new diver will be in the .7 to 1.0 range depending on conditions, your body size/type, etc. .5 is about average for divers with some experience. The best SAC you can probably hope for is .35-.4 with a lot of experience.

Again, keep in mind this depends on conditions, body size/type, etc.

[ianr33]

If your SAC is above zero you are having a good dive

[cummings66]

I have different rates. I'll vary a lot depending on the dive type, if I work I know the rate for it, if I'm solo I know the rate for it, if I'm with a buddy I know it's rate, if I take pictures I know the rate for it.

So I know what my rate's going to be like based on the dive plan. It will vary from .3 to 1.0 with the 1 being work like cleaning the platforms or chasing an errant buddy down. .6 would be with a good buddy, .3 would be taking pictures. You can see the pattern.

[namabiru]

I know I've seen it somewhere, but what is the equation for SAC calculation? Now *I'm* curious.

I expect, too, that SAC rate will depend on diving frequency. If you have a 3 month surface interval and get back in the water, then you may be a bit rusty. It probably also depends on exercise. If you've been keeping up with your other activities at the same rate, and remained in shape, then you won't "bounce" as bad.

[tc_rain]

Originally Posted by namabiru

I know I've seen it somewhere, but what is the equation for SAC calculation? Now *I'm* curious.

I expect, too, that SAC rate will depend on diving frequency. If you have a 3 month surface interval and get back in the water, then you may be a bit rusty. It probably also depends on exercise. If you've been keeping up with your other activities at the same rate, and remained in shape, then you won't "bounce" as bad.

Here is a website you can use to figure SAC


http://www.spearfishing.org/bruces_tips/java/sac.html

[cummings66]

The way it's figured is fairly simple, but does involve a bit of math. Look for postings from me and compudude on it.

To get in the ballpark you could breathe for a timed period on the surface. That tells you how many psi per minute. From there you'd take tank volume / tank working pressure * the above figure.

I hope I got it all in, my 4 year old daughter is trying to wrestle with me and it's hard to think, got to go now. My other posting is much more detailed.

[plot]

Originally Posted by namabiru

I know I've seen it somewhere, but what is the equation for SAC calculation? Now *I'm* curious.

I expect, too, that SAC rate will depend on diving frequency. If you have a 3 month surface interval and get back in the water, then you may be a bit rusty. It probably also depends on exercise. If you've been keeping up with your other activities at the same rate, and remained in shape, then you won't "bounce" as bad.

comfort in the water, proper weighting, bouyancy, trim, how physically fit you are from other activities (sports, treadmill, running, walking, whatever cardio it may be) all improve/effect your SAC rate.

comfort in the water and bouyancy come with practice, as does weighting to a degree. If you're carrying around 4 extra pounds of lead, it makes a difference. If you're constantly finning upwords or downwords instead of straight forward to keep at a certain depth, you're obviously going to be using more energy and breathing harder thus effecting your SAC.

type of dive makes a big difference too... at depth you have more pressure pushing on you so you tend to breath harder (I do anyways). drift dives you just sit there and float along (assuming you have bouyancy down), so you use almost no air and have an excellent SAC. Strong currents make a difference, or if it's a night dive or some other type of dive that makes you a bit uneasy so you breath harder.. water temperature can effect it (jumping into really cold water makes me breath harder)... there are hundreds of variables you can factor in!

The one's I'd recommend working on though is bouyancy, weighting, and trim.

[cummings66]

I did a dive yesterday that had the highest SAC of any dive I've done in my life. It was over 1 cf per minute. The reason? I had to walk a bit over 1/10 of a mile to the dive site in 100F temps, carrying my drysuit, tanks (steel HP120 and al 40 stage) plus the lead. I'm still hurting today from all the work. You should have smelled my dive gear when I was done, you'd have thought something died in there.

By the time I got there I was tired, hot, sweating like you can't imagine and not very happy. It was an OK dive however and I still did better than my buddies did air wise.

Did I mention I had to walk back to my car fully zipped up in the drysuit with undergarments and all because my buddies beat me out of the water. That was miserable. I was sopping wet inside the drysuit. I'll say one thing, never again.