S.A.C. and How to not suck so bad :/

[bdshort]

Seems like an excellent SAC rate for a new diver. Looking at my log and plugging the numbers in, I had an early SAC rate of .8 or even over 1 sometimes (though this is also in cold water). I'm about the same size as you and my current sac runs around .5 to .56, though I've had it under .5 a few times. Looking forward to seeing how it changes when I dive in Cozumel this winter.

 

[jpcpat]

T,

.65 for a guy your size is pretty good. A 180 lb man will usually use more air than 100lb diver. Go with a bigger tank, and enjoy the dives.

In terms of using less air; go with the Yoga breathing. Long, slow breath till your lungs are ALL the way full, then a looong, slow exhale is the most efficient way to go. This makes bouyancy control trickier, but you do get used to it quickly.

Bouyancy control is more important than you would think: If you're always either adding or venting air from your BCD, you'll use a lot of air that way, especially in a heavy wetsuit.

I've also noticed that many, many divers like to swim up against slight negative bouyancy (occasionally you see one swimming down against positive bouyancy). This is a real air waster both because of the extra swimming effort and the extra drag. During your next dive, stop kicking for a bit; you should go into a horizontal hover. If not, your bouyancy off. Adjust it to neutral, then off you go. Repeat now and again.

Last advice; Slow down. Using less air is very Zen.

 

[tschmitt]

Search->... you'll find over 70 discussions from other folks that didn't use the search function either.

I figured I'd get one of these responses. In my defense, I did search on "SAC" which yielded nothing and then "Surface Air Consumption" which resulted in a bunch of crap. I suppose "Consumption" would have been better.

Thank you to everyone else for some good info and going easy on someone new to diving and Scubaboard.

 

[scubamickey]

I'm 5'4 and 125lbs. My hubby is about 5'9 and 200 or so pounds. We both have the same SAC rate of .4 to .45 or .5 in strong current or cold water. Sometimes I score a .35 and have a field day rubbing it in that he sucked more gas than me

 

[TSandM]

tschmitt, there are many topics where it's difficult to compose an effective search string, using the search engine on Scubaboard. And there are a lot of us who don't mind answering questions which have been asked before -- after all, those old threads disappear into the archives, and each time the question is asked anew, a bunch of lurking dives will see and read it. Don't stop asking questions -- you WILL get answers, even if you have to read past a few grumpy posts to get there.

 

[vicdiver656]

First of all, I try to go in PSI, as it's easier to see how much of your tank your emptying. Your varying rates at SS and 95 make sense, as you're concentrating much more at the safety stop than when swimming around. A reasonable goal?? Where you're not getting hypoxia headaches, and breathing as little and as comfortably as possible. Or at least that's what my instructor told me!!

 

[Deefstes]

First of all, I try to go in PSI, as it's easier to see how much of your tank your emptying.

I'm not sure I understand that approach. While under water, sure, you'd want to keep an eye on your PSI as that tells you how much air you have left. But for calculating your air consumption after a dive, measuring it in PSI would only make sense if ALL of your dives were to the exact same depth.

Otherwise, if you make one dive to an average of 33 feet and a second dive to an average of 66 feet and all other things being equal, your air consumption would be exactly double on your deeper dive. Not only does it not make sense but it also makes it impossible for you to measure your improvement. Also, it makes it impossible for you to calculate in advance how long a dive should last given the average depth.

That is exactly the point of SAC (as opposed to AC). Surface Air Consumption gives your air consumption in a standardised unit which applies to any dive.

 

[Sas]

I figured I'd get one of these responses. In my defense, I did search on "SAC" which yielded nothing and then "Surface Air Consumption" which resulted in a bunch of crap. I suppose "Consumption" would have been better.

Thank you to everyone else for some good info and going easy on someone new to diving and Scubaboard.

I understand completely about how doing searches can be difficult! And because certain words are said on threads that aren't really related to what you are searching for it the results get quite diluted. So don't be put off by people with bad attitudes, there is no rule here against posting a thread that has been asked before (that would probably remove aout 90% of the content here )

Anyway, I find it better to search for my key word by selecting 'Show Posts' rather than 'Show Threads'. That way if it appears in lots of posts in one thread you know that thread is a lot more relevant than in a thread that only has one post with your keywords. Also I often use google to search for stuff and then add 'Scubaboard' on to the end, Google has better search than this forum software

Back on topic though
I have an air integrated computer so always review my air consumption to see what triggers an increase in gas consumption. They usually are
-getting cold - my first dive usually has the best air consumption, and after a 60min second dive in 10C water, my air consumption is quite high towards the end
-being stressed, even not significantly so. If I find a cool creature my SAC goes up for example as I get excited. When I have trouble equalising it goes up too even though I am not overly stressed.
-when I am having buoyancy issues
-when I am moving at more than an inch a minute ;p Me + my buddy often dive with a camera and move *very* slowly, even sitting around for a bit watching creatures. My air consumption is at its lowest here (well unless it is at the end of a second or third dive and I am shivering badly). Most new divers fin constantly, you only need to fin to move forward, you shouldn't be doing it when you are hovering (i.e. at a safety stop).

It is interesting you had a lower air consumption at depth. I have had this happen too, like the few times I have been below 30m and been a bit narced, I get incredibly relaxed and my SAC drops heaps. Also when my buoyancy control was a lot worse, at depth I didn't have to touch my BC but when I was in shallow water I was constantly fiddling with it so that would have increased my gas usage too.

But yea, if your SAC never improves, don't stress too much about it, just get a bigger tank than what your girlfriend has

 

[Inalara]

I've never actually calculated my SAC rate, however, I know I can happily do a 30 meter dive profile and a 15-20 meter dive profile and end up with the same air left in the tank (assuming same max dive time and same water temp/conditions).

I've always put this down to a silent effect of narcosis, because I am more relaxed, which is good for dive time (within limits), but it's something to remember in terms of being more aware of my surroundings etc.

Without getting into a discussion on narcosis, I personally dive with the assumption I will be narced on every dive, the difference being some dives I will notice it, which is why I put my breathing rate reducing down to narcosis even though I don't *think* I feel any different.

It may not be your reason, but its the reason I came up with for my changes.

Ultimately, its better to have an enjoyable dive with a larger tank, than to worry about reducing your air consumption; it will improve with time and experience as others said, but some people just breath more than others (lung capacity etc) and better to accept it than end every dive with a headache.

 

[on_two_wheels]

I'm a relatively new diver, too. I also use the Cobra. Let me assure you, .65 is a fine SAC rate!! If I could have that same number all the time, I'd be thrilled. I'm sometimes up in the 8s....still!!


On the search issue, here's my take: He might get his answer and never post it. Then another new diver that didn't even think of asking or looking it up (didn't think of the topic at all) until he/she reads the NEW post suddenly learns something unexpected. If it's in the subject line, I don't have to open it!!!