Extending bottom time by changing tank size

[Lloyd T.]

I've got a Uwatec Galileo Sol computer that is air integrated, but I do not have the Bluetooth USB cord that I need to download my dive profiles to my laptop. It is on my list though.

For everyone asking if I'm properly weighted, I usually dive during the summer in salt water. I live on the Mississippi Gulf Coast, so Pensacola, Destin, and Panama City is where I'm normally diving. During the summer, I wear just a rash guard and shorts, and I need 12 pounds to get slightly negatively buoyant. 10 pounds just isn't enough. In the early and late season when the water is colder, I have a full 3 mil wetsuit, and I'll need 14 pounds to get where I need to be. I don't normally dive fresh water, but I have been to Vortex Springs a few times, and I just stuck with what I knew because I'd rather be more negative than positive.

As as far as physically handling bigger tanks, I'm not the pinnacle of physical fitness, I could lose a few pounds, I'm 6'1 and around 260. I don't think bigger tanks would be too physically demanding, but I've never tried them, so I don't know.

Thanks again for all the input and thoughts. It's really helping me figure out what I need to do.

Lloyd

 

[Lorenzoid]

From the amount of weight you say you currently need, and if your profile is correct in that you have done fewer than 50 dives, then I say wait until you see whether your air consumption rate improves as you gain experience. For one thing, you will likely find that you need less weight as you gain experience. And less weight will help your air consumption.

If after 100 or so dives you still find you use air much faster than your wife, then by all means, do as others have suggested and look for a 100 cf tank.

My wife and I are apparently in the minority in that, with 160 dives under her belt, HER air consumption rate is still higher than mine. She likes the explanation that she is a professional singer with "big lungs." (Picture her with the viking horns.) She will usually rent a 100 cf tank while I stick with the common 80 cf. We usually end the dive with similar amounts of air in our tanks. Problem solved. No big deal.

 

[fjpatrum]

Get comfortable but also get a bigger tank. As you get comfortable so will your wife and her consumption is also going to go down (most likely). As such, you're always going to be her "limit". Personally I don't see that as a big deal but more down time is more down time and I wouldn't complain about that either.

I just bought 2 HP100s (3500 psi/240 bar service pressure) for purposes of having more bottom time and safety doing the Vandenburg on an upcoming trip but will enjoy the extra down time on shallower dives as well.

 

[Peter69_56]

I've got a Uwatec Galileo Sol computer that is air integrated, but I do not have the Bluetooth USB cord that I need to download my dive profiles to my laptop. It is on my list though.

For everyone asking if I'm properly weighted, I usually dive during the summer in salt water. I live on the Mississippi Gulf Coast, so Pensacola, Destin, and Panama City is where I'm normally diving. During the summer, I wear just a rash guard and shorts, and I need 12 pounds to get slightly negatively buoyant. 10 pounds just isn't enough. In the early and late season when the water is colder, I have a full 3 mil wetsuit, and I'll need 14 pounds to get where I need to be. I don't normally dive fresh water, but I have been to Vortex Springs a few times, and I just stuck with what I knew because I'd rather be more negative than positive.

As as far as physically handling bigger tanks, I'm not the pinnacle of physical fitness, I could lose a few pounds, I'm 6'1 and around 260. I don't think bigger tanks would be too physically demanding, but I've never tried them, so I don't know.

Thanks again for all the input and thoughts. It's really helping me figure out what I need to do.

Lloyd

Most times with new divers I have found they are overweighted. In particular when diving shallow <18m, it causes the following effect.

Due to overweighting you need more air than normal in your BCD, thus when you change depth by a meter or so its a large volume change of the air in BCD thus dump air or air in, then a depth change again, perhaps air out this time, so the diver yo-yo's about with their BCD air volume trying to maintain neutral buoyancy.

One significant reason why they think they need the extra weight is because as they are new divers, they are somewhat uptight when they first get in the water, and tend to unconsciously hold their breath and breath shallow with near full lungs. This means they have additional buoyancy when on the surface, thus take extra weight to compensate. Once below the surface they relax and now find they are heavy hence additional air required into the BCD.

The real test for this is to get on the surface (with a cylinder containing only 50 BAR) and relax totally and then with reg in your mouth breath totally out and count one to five. If you sink below the surface easily, take out some weight and keep doing it until you find you just sink a little below. Then you are correctly weighted. With a full cylinder you should sink more easily. If you then don't, remember, breath out FULLY and count 1-5 and you should sink, and RELAX and just let it happen. I have found a large number of new divers have this issue and its fixed so easily.

Then when you dive you hardly touch your inflator valve thus consume less air. And yes girls use less air, my wife has a SAC rate of 12 l/m, for me to achieve that rate I have to consciously work at it hard. Such is life.

 

[TSandM]

The smaller the person, the lower their energy expenditure, and the less gas they will need to use when everything is optimized. Although my husband has lovely trim and efficient propulsion, he still uses about 30% more gas than I do. Where we can, we have him in a bigger tank. Where we can't, we may actually share gas for a while at the beginning of the dive, which will negate the consumption difference. This is a controversial practice, and really isn't very feasible with the equipment configuration that is usually taught, with the 36" octo hose, but it does result in frequent practice of emergency procedures, and equalization of gas supplies.

All the things you've been told -- horizontal trim being probably the most important -- will improve your gas consumption. But in the end, the two of you may settle to different baselines. There's nothing shameful about that at all. One of the most beautiful divers I know has a gas consumption twice mine, but he's over 6' tall and solid muscle.

 

[mala]

there are only 2 types of people that are good on air.

1. small people

2. big people who know what they are doing and dive all the time.


if you have little experience and only dive the summer you will need a bigger tank.

 

[DivemasterDennis]

I concur with your wife sticking with the AL80. It won't hurt for you to go to a 100. However, you should be able to get close to ndl on most recreational dive profiles with an AL 80 if you are properly weighted, if you have proper fitting gear streamlined when on your person; you move smoothly and effortlessly in the water; you are properly weighted, and you maintain good buoyancy control. Even with all of that, some guys just have large lungs and use more air. However, paying attention to all those variables will improve you consumption rate. My wife is easy on air, and that is a great comfort to me. However, depending on activity and profiles, I can often match her. BTW I am 60 years old, 5'10: and 210 lbs. She is also 60, 5'5, and about 140 lbs.
DivemasterDennis