Once you start getting your buoyancy and trim dialed in, then think about replacing the flutter kick that everyone starts out with with a nice, relaxed frog kick. Kick, glide, kick, glide,...
Air Hog
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scubafanatic
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...well, the problem is, it's fine to get 'hooked' on 'big' tanks diving 'locally' where you can easily bring/access your own tanks....but what do you do when you travel to dive and you are limited to say, the 'standard' Aluminum 80 sized tanks ?
rstofer
Contributor
OP:
You know, you didn't provide a shred of data. How large is your typical tank? How deep is a typical dive, what are your beginning and ending pressures and how long is your dive time?
We just went through this the other day and the fellow that was complaining had a SAC rate of about 0.7 cfm. That's pretty respectable for a new diver. Sure, it's 40% more than a 0.5 cfm diver but it's not that bad.
Start logging more information about your dives: max depth, some guess of average depth (maybe a computer provides this), tank size, weights carried, tank size, beginning and ending pressure, water temperature, some qualitative estimate of current, etc. Every physical fact of the dive. Then start calculating your SAC rate and see how it comes out.
Slow, deep, breathing is the key to air consumtion. You need to concentrate on breathing properly. Do NOT try any kind of 'skip breathing' or any other scheme where you delay breathing. This just allows your CO2 level to build up and the CO2 still has to be flushed.
Richard
You know, you didn't provide a shred of data. How large is your typical tank? How deep is a typical dive, what are your beginning and ending pressures and how long is your dive time?
We just went through this the other day and the fellow that was complaining had a SAC rate of about 0.7 cfm. That's pretty respectable for a new diver. Sure, it's 40% more than a 0.5 cfm diver but it's not that bad.
Start logging more information about your dives: max depth, some guess of average depth (maybe a computer provides this), tank size, weights carried, tank size, beginning and ending pressure, water temperature, some qualitative estimate of current, etc. Every physical fact of the dive. Then start calculating your SAC rate and see how it comes out.
Slow, deep, breathing is the key to air consumtion. You need to concentrate on breathing properly. Do NOT try any kind of 'skip breathing' or any other scheme where you delay breathing. This just allows your CO2 level to build up and the CO2 still has to be flushed.
Richard
Last edited:
OP
bjexpat
Registered
Lots of excellent advice here. As many noticed, I don't have a lot of dives and without my own gear yet, I haven't developed a comfort level with any of the rental equipment. Someone mentioned that comfort is the first factor. The variance of buoyancy of different rental BCs, inconsistent weighting and leaky hoses were all factors which probably contributed to high SAC on my last trip. I'm certain that the combination of owning my own gear, more dives, and breathing techniques will definitely improve things.
To address my original question...
I'd love to own a big honkin' tank but I have to fly to dive and I've only seen 80s for rental at the dive shops. I just wasn't sure if it's possible to bring gear to convert rental tanks into doubles versus the rare chance that I can find a larger tank to rent.
I'm doing my first wreck dive in a couple weeks. I don't think it's possible to not be excited. But I'll try to come back with more precise numbers. But for example, I did my AOW staged deep dive on 32% O2 - 30M for about 5 minutes, 20M for 10 min., 10M for 8 min., 5min safety stop and left with about 45 bar in the tank that started with about 195 bar.
To address my original question...
I'd love to own a big honkin' tank but I have to fly to dive and I've only seen 80s for rental at the dive shops. I just wasn't sure if it's possible to bring gear to convert rental tanks into doubles versus the rare chance that I can find a larger tank to rent.
I'm doing my first wreck dive in a couple weeks. I don't think it's possible to not be excited. But I'll try to come back with more precise numbers. But for example, I did my AOW staged deep dive on 32% O2 - 30M for about 5 minutes, 20M for 10 min., 10M for 8 min., 5min safety stop and left with about 45 bar in the tank that started with about 195 bar.
Some places provide larger tanks. You may look into this before planning a dive trip. Keep in mind, however, that the other folks on the boat will also have access to them. So you will have more air available, but others on the boat may as well. So ask yourself if you want more time underwater, or if it is a matter of embarassment for calling the dive. If its the latter, don't sweat it. We've all been there, and it shouldn't be an issue. If I were diving with you, I would get more upset if you stretched out your turn pressure than if you turned the dive early.
Converting rental tanks to doubles is not feasible in most places. It will also increase your breathing rate and workload, so you might not get much savings out of it. I would recommend strongly against this. If you're going to do it anyway, a better option would be to rig up a stage to bring along, but I don't recommend that either.
That is about 18m for 28 min. It works out to around 1.9 bar/min/ata. I don't know what size tank that was, but assuming an AL80...2200psi AL80 ~ 0.72cfm SAC. This is fairly average. It's nothing to worry about. In time, it will simply go down. I am 6'6", and I started out around .65cfm. It has since gone down significantly due to just experience.
Tom
On a recent trip to Cozumel my girlfriend that's 1/2 my size was burning through air much faster than me - like I had 1750 and she was at 600! After we got back on the boat, she was quite upset, as you can imagine. It turned out that it wasn't her.
The issue, we found, was a slow leak in her HP hose! We had the shop swap it out and she was back to normal. Her stuff was less than a month old, and Scubapro was awesome - they sent us a new HP hose to keep w/o charging us. Now we have a backup that we've added to our save-a-dive kit.
Best,
The issue, we found, was a slow leak in her HP hose! We had the shop swap it out and she was back to normal. Her stuff was less than a month old, and Scubapro was awesome - they sent us a new HP hose to keep w/o charging us. Now we have a backup that we've added to our save-a-dive kit.
Best,
vfox
Contributor
As has been stated, more practice with buoyancy will help and more dives will help you become more comfortable. Along with those pieces, though, one other thing my husband started doing was staying about 5 feet higher in the water than me when not looking at small critters. That's allowed us to come up with about the same ending air now...
Good luck !
Good luck !
If your numbers are right, then she lost almost as much air from her HP hose as she breathed during the dive. You would definitely have noticed that much bubbling. I would imagine something else was also going on during that dive. The amount of air you lose through a leaking HP hose is very small. If you severed the hose completely, it would take over 20 minutes to empty the tank, and typical HP hose failures are not nearly as dramatic.
Why did you put a bad hose in your save a dive kit? If you have a dive where something has already gone wrong, would you really want to do a dive with HP hose that is known to be on it's way out; especially if it's spent several months/years in a dive kit getting worse?
Tom
Generally, she uses more air than I do - most every dive we do together. Between the dive where she ran out of air early and the next dive was when we noticed the issue. When she turned on the air for the next tank we heard the hissing and found the small hole in the HP hose. We really couldn't do much more troubleshooting than that. I wouldn't rule anything else out or in for that matter. To finish the days dives, she took my reg stuff and I took a spare they had b/c theirs wouldn't connect to her Scubapro BCD and I would rather have to manually inflate than force her to. She did like my computer, I better watch out!
We put the bad hose in the trash. In Cozumel, we bought a new hp hose. Scubapro sent a new hose to our local shop, that new replacement hose is in our save a dive kit.
I think you misread it. He got a replacement when it happened, and then ScubaPro later gave him a new one. He therefore has an extra new hose.
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