Bigger tank or continue diving more?

[Mel.B]

I'd say in the short-term getting a larger tank is obviously going to help you get longer bottom times, but in the long term it's going to be your cardio fitness that will make a big difference. I have been diving for 4 years and dive on a regular basis (pretty much every weekend) and after the initial newbie going through my air quickly it settled and I was probably average with my air consumption. When I started running 12months ago I noticed a huge improvement in my air consumption (that and running helped me loose 20kg which also helps!)

Good luck,
mel.b

 

[FastAttack]

Well I am one of those step guys in sac lol

6"0 180lb ( was packing a few pounds post a knee surgery) , started diving my SAC was around 0.95

25 dives into it my SAC went down to around 0.5.
I started loosing some weight ( loosing the love handles) and started swimming once more , came down to 164 lb and now my SAC at an avg of 60 feet dives is around 0.34

in other words.. time contributes , and your excercise routines and diets can fine tune your SAC even more..

If you go with a bigger tank you won't go wrong with it , but just be aware if your sac drops to a range were you can pull off over an hour using an AL80 then your big tank will last you longer ( in many cases you will never use it up as your buddies tend to use a smaller tank)

anyhow..

all the pointers here are great, just from experience time/exercise an a proper diet will impact your SAC greatly

 

[dsteding]

Here is my two cents, I'm 6'1" and about 215 right now.

Trim and technique took me a long way, I started diving in cold water here with a SAC around 1.0-1.2, with wavey arms and poor trim. The advice I got was to consider that water is much denser than air, so any movement of your arms will get your breathing rate up. In addition, poor trim--swimming in an upright position--and poor buoyancy and weighting added to my problems at first.

Since then, I've focussed on the above, and have layered in some cardio work (running and rowing). I think that just getting quiet in the water helped me drop my SAC down to 0.75 or so, it then came up when I went to doubles and back down as I got used to them. On my most recent dive(in doubles) I was very relaxed and got it down to 0.6. That's probably the floor of what I can do from technique alone, and I'll now start to increase my cardio workouts to get more improvements. Given my size, I'd be happy to get it down to 0.5 or so (I dive with some people that bust 0.4 on a bad day . . . )

There is lots of great advice here, I'll just add this point about working on technique to get really quiet and efficient in the water. Trim, a good frog-kick, and a willingness to not move your hands and go slow will help a lot in terms of air consumption. As you get quiet in the water, you will get more relaxed, and as you get more relaxed your air consumption will come down. In fact, I've found my SAC to be at its worst when I am obsessing over how fast I am breathing.

I'd say that is step 1. Step 2 may be to get in better shape, but these skills issues can help a lot in the interim.

As you can see, this is a natural progression, everyone who has posted in this thread has gone through it. My biggest improvements have come in the last ten dives or so (I'm nearing 60) and I understand most people see things happen between 50 and 100 dives (which to me jives with the value of working on the above skills).

 

[CARHILL]

Try yoga it helped me

Still on a little rock in the Pacific

 

[Midnight Star]

Hey Mike! (tell Frank I said hi also , and that me and my son are heading back down to Panama City Thanksgiving week!)

It could be a couple of things. I'm on the lower end of the diving count also, like you - and working on improving my diving time. Getting a larger tank might help, but according to tank size vs. time, your looking at 80 x 2 (160cu) to get around 40-50 minutes diving time - i've seen 130 hp, but nothing that large (160cu). Plus, if you do go doubles and not a single HP (high pressure - 3500psi), you have a much larger trim to deal with, which takes alot more effort to move through the water and will use up more air with the effort. Here's some things that might help out:

1) Try not to be overweighted when you dive. Alot of divers, new and experienced alike, are usually overweighted. BC adjustements for neutral are harder in shallow water, when overweighted, due to the fact that it takes slightly longer to see any difference in boyancy with a few small puffs of air. By the time theres any noticable difference, almost always theres too much boyancy. Another way to tell if your overweighted, is by looking at your trim underwater. If you feet sink lower than the rest of your body, pivoting down, there's too much weight. The more weight you have, the more work you have to do to keep your trim level. Here's what I do when adjusting for neutral boyancy. I know that my lungs also effect my boyancy, depending on how much air i'm holding in them. So as I go down, and near the bottom (within a foot or so) I take a deep breath and hold if for a second (usually about 5 or 6 - it takes me about his long to adjust my BC), then start pressing the power inflator on my BC - one quick puff at a time until I start to become neutral. Now, if i'm pretty close to neutral, and I exhale, I should sink slightly ... inhale and I should rise back to where I was. The allows my lungs to control the finer part of boyancy, by using my BC to roughly set neutral, saving air. Remember not to hold your breath to long, or while you descend or ascend (especially!).

2) Go at a steady, even pace. Believe it or not, different people, even though they're wearing the same types of gear, move a different speeds. Drag and trim play some here, along with body type and fitness level.

3) Outside of diving, practice finning and breath holding in a pool as often as you can. I go to the pool almost everyday and do the following: tread water for about 15 minutes to warm up, swim laps using just my legs and scuba fins for 15-30 minutes - on my back, on my side, face up (not using my arms just my legs), then I use my arms and fins both. This helps to build up my "endurance" level. Not so much that I can run miles without stopping (Ii'm a terrible runner), but to help my body work and use oxygen better when under a load. Another thing to try is breath holding. I start at one end of the pool, hold my breath and sink down, then trim out and begin to slowly swim across the pool to the other side. Don't try and swim it fast, go slow. The idea is to get your body working more efficiently when using oxygen. It also helps to get your mind used to the fact that you can hold your breath, and be completely in control of it (much like marine mammals do). It helps to exercise your diaphram and lungs. As i'm doing this, i'm slowing down my heartrate and learning to control anxiety and focus. It really does help.

4) Make sure that your equipment and wetsuit arent too tight. If you overadjust something like a BC, it can become uncomfortable during a dive and increase respiration.

I hope that helps some - I highly recommend doing laps in the pool with the same fins you scuba in to build up your leg muscles (not just strength but endurance), and then doing some breath hold swimming (underwater, with both your scuba fins using your legs only and without fins using your arms - you can get a small swim paddle to put on your one hand to help give you more pull). I do breathhold swimming for about 40minutes to an hour. When breathholding, dont try to stay under 2-3 minutes - 60-90 seconds is long enough.

Let me know how everything turns out.

-----

Mike.

 

[Dive-aholic]

Mike, you're a big guy. You state you're out of shape. What's your ideal weight? If you're still looking at about 250, then a bigger tank will help trim you out. It will also let you drop some weight from your weight belt. It will probably increase your SAC though...at first. It sounds like you need to work on your breathing, not increase your air. You say you can last 20-25 minutes on an AL80, but you don't mention the depth. This information would help quite a bit.

Without seeing you dive, I'm going to guess it's more your newness than big lungs. Slow down. Don't kick or move as much when you're in the water. Kick and let yourself glide along. The less you move, the less oxygen your body will require and you'll see your respiratory rate start to drop. This will in turn drop you SAC. Keep diving as much and as often as you can. You should see a marked improvement around 50 dives or so.

As for your buddy, you're saving him money. He can dive the same tank twice while you're switching out tanks during your SI.

 

[Packhorse]

Just curious--were most people not taught how to calculate their SAC in their basic class? It's in cf/min/ata...that's all ya need to know.

When I did my nitrox class, I asked about others SAC rates. 50% of the class were instructors and not one person knew their SAC!
It was hardly touched on in the "deep" specialty either. What a waste of money that one was, so was the night and "wreck".

 

[Dive-aholic]

When I did my nitrox class, I asked about others SAC rates. 50% of the class were instructors and not one person knew their SAC!
It was hardly touched on in the "deep" specialty either. What a waste of money that one was, so was the night and "wreck".

You obviously did the class with the wrong instructors. SAC should definitely be discussed in deep and wreck. And instructors should at least know their SAC range.

 

[Luc Dupas]

I'm 6' 6" and 320lbs (Yes, I've gone up a few pounds.) and I'm a major air hog.

I'm 6.1' and 255lbs, so it's more or less in the same "order of magnitude" I guess... my SAC ranges from about 14liters/min (which is about 0.5cf/min/ata) in summer time and/or in warm waters to about 22liters/min (which is about 0.8cf/min/ata) in wintertime (1-5C range, 30-40F) in my 7mm wetsuit. It drops again to about 17liters/min (which is about 0.6cf/min) in winter time when I switch over to my drysuit... and this is after 900+ hours of openwater dives...
So... DON'T worry right now about your air consumption!!! It's perfectly normal that a novice diver consumes much more air since no matter how you look at it, you're still "new" in this environment and you still have to learn to "be like a fish in the water".
In any case, DON'T try to save air by changing your breathing, don't go for "skip breathing", don't hold your air while scuba diving... just FORGET about your air consumption underwater and fully enjoy being underwater... and over time things definitely will improve automatically. Initially, in order not to "disappoint" your buddies you might consider to initially rent a bigger tank... I'm standardly using a 15 liter water volume tank at 200bar which holds about 107cf of air and most of my buddies carry the same size of tank. In our region the 12 liter water volume tanks (85cf of air) are mainly used by women and youngsters who typically consume less air.
So if in your case your buddies typically use the 80cf tank you might consider for the time being to use a 110cf one.

Things which have a huge impact however on your air consumption are: proper weighting underwater (of course not too less but definitely also not too much) and proper trimming underwater such that at any depth you're perfectly neutral in the water and if you keep your hands and fins still you still stay at this depth.. also extremely important is take your time underwater, don't try to set a new olympic record in long range underwater swimming but enjoy your dive, look for a buddy who also prefers to swim very slow underwater and look around and enjoy the underwater world! And in terms of breathing: just breath whatever your body tells you it needs, don't try to 'save air', and make sure you breath normally and especially make sure you exhale deeply such that you manage to get an adequate ventilation of your lungs and by exhaling deeply and slowly (! try to stretch your exhalation to 10-15sec) and subsequently inhaling slowly (also in the 10-15sec range) you automatically will become very relax underwater and as such also start to consume less. But again, do NOT focus too much on your air consumption, this will only result in keeping it high, just enjoy and breathe normally.

 

[Stu S.]

The aluminum 80 was a marvel 30 years ago. Now that we have nitrox and computers, we have removed the constraints the "air tables" had on bottom times. The 80 now becomes the constraint. Many divers want to take advantage of the new gas and computers, and use cylinders in the 100+ cubic foot range. With 100 cu. ft., the computer tells me when to go up instead of the tank pressure gauge.