Big gasser

[billt4sf]

I have an issue that I am struggling with - having enough gas. Before you say "Overweighted", I am 6'6" (197cm), 240 lbs (110kg) and I use 3kgs including my backplate with a 5 mil wetsuit so that's not an issue.

My dives are usually 45 mins with a max depth of 25 - 30m (100ft) and my buddies are usually around 60min or more - this is with a 15L (100c.f.) tank. Here in Indonesia I was almost always doing my safety stops on my own, and starting my ascent before anyone else, and breathing the tank down to 400 - 500psi (around 30Bar). Often I was 10 - 20m above them for a large segment of my dives. Fun, maybe, but not the best and if there was current on top of the reef I was drifting along on my own. Doesn't seem the best idea.

I've tried to work on my breathing, maybe I will continue to improve, but with 300+ dives I don't think that a dramatic improvement is in the offing.

The way I see it, I could get a 3L (19c.f.) pony bottle, which I have seen people in my groups use for safety, that's a 20% improvement which would help BUT: (1) they are supposed to be for emergencies only; and (2) a 20% improvement would on average get me around 6 - 8 - 10 mins more diving -- still not the same dive time as most groups. But still safer I would think, at least for those solo safety stops.

A friend mentioned that I could go the "extended range" option and get a second tank that is "slingged" to my waist and chest D-rings. I have a hard time seeing that used in the resort / recreational contexts in which I dive. As soon as they see that second bottle, operators / DMs are going to think "Decompression diving" which is ABSOLUTELY NOT what I am after! Also it seems to me it will be a much larger effort to get on, I already am the last guy because I use a BP/W and long hose with minimal webbing and a crotch strap. No one likes the guy that everyone has to wait for, and I hate being that guy all the time.

Arrrrgh! The choices for great diving!

Any comments?

Thanks,

Bill

 

[Diving Dubai]

This is always a hard one. It's easier to help someone if you've actually seen them dive

First off I recommend reading this blog article - Written by a UK GUE instructor. Even if you think you have your'e buoyancy down pat, little things help.

I'm a few inches shorter than you, a couple of kilos lighter (and a smoker) - I would need to be in screaming currents to get to 30 bar on a 15l in 45 mins. I think here that there maybe a psychological effect going on here. i.e worrying about your air consumption, which causes bad air consumption.

It used to happen to me. put my in an AL 80 and I'd scream through - maxing out at 40mins (while my wife you end the dive with loads of gas left.

My solution this year, was to take another reg set and travel sling. I asked each op if I could have a second 80 as a slung pony because most had no larger cylinders) Each one (all 4) said yes happily - (I cited bad consumption)

I used to enter the water using my back gas, then descend on my pony taking maybe 30bar from it, before switching back to my back gas.

At the end of the dive I would finish with 60-80 bar on my back having not touched my pony any further. I could stay down deep as long as teh dive/my computer allowed without worry. The fact that I had so much gas meant it was not a worry (sub consciously), I knew I was never going to be the limiting person on the dive.



After the vacation I worked out all my gas consumption's and it transpired that my rate was down so that (at home) rather than use a 15l I could dive a 12l.

Worrying about air consumption leads to bad air consumption.

I'm not saying its a cure all, but it can help as well as making your divign more enjoyable and relaxing

 

[bamafan]

I am 6'4 250 pounds so I understand this issue. I have heard that you only use 25% of the gas you take in with each breath. The other 75% is wasted. So the bigger you are the bigger your lungs are going to be so no matter what you do you will never keep up with a similarly skilled 5'0 tall 100 lb woman. Taking an 80 as a pony is a viable option. I asked an old time cave diver how he got so good at his air consumption and he said just don't breathe. I have done a little free diving and when I am working on that my air consumption improves drastically. There are some apnea apps you can get on your phone to work on your breath hold. Cardio such as running helps too. If you are relaxed and not working heavy you should be able to only take about 3 breathes per minute. If you get to where you can do that you probably won't need the 80 stage bottle.

 

[rongoodman]

Also it seems to me it will be a much larger effort to get on, I already am the last guy because I use a BP/W and long hose with minimal webbing and a crotch strap. No one likes the guy that everyone has to wait for, and I hate being that guy all the time.

I'm not sure why people are having to wait for you, but I don't think you can attribute it to your use of a BP/W. I use the same type of rig and am usually sitting there waiting for everyone else to get ready. As for your gas use, aside from your size, the first thing that comes to mind is being in trim and still in the water.

 

[Drone076]

+1 for rongoodman

Right trim could improve your air consumption drastically.

 

[Diving Dubai]

I concur with the post above. A BP/W should make you slower to kit up, infact the other way around. I personally don't believe in the long hose for rec diving, I think it's overkill. I use 40" hoses (both primary and secondary) which I believe from experience are the ideal length for an air share when not diving overheads (thus includes stops etc). But that's a whole different discussion.

I assumed that given you took fundies the OP should dive in trim.

Being relaxed is important. My wife by her own admission isn't the fittest, and she has a larger than usual lung capacity, yet she zones out during a dive and her breathing really slows, indeed she can surface with more gas remaining than a 20 something Indonesian guide who weighs nothing

While you worry and faff, consumption will always be higher. Relax and slow down

 

[mattia_v]

I'm not sure why people are having to wait for you, but I don't think you can attribute it to your use of a BP/W. I use the same type of rig and am usually sitting there waiting for everyone else to get ready. As for your gas use, aside from your size, the first thing that comes to mind is being in trim and still in the water.

Indeed. I'm almost without fail the first one in a BC- slip the two straps over the tank, tighten up, attach reg, thread and connect inflater hose, clip off SPG, and simply don the BP/W (hog webbing). Take hold of crotch strap, and tighten the single buckle that's on there. Done. Faster than most jacket BCs with two straps, cummerbund, fiddling with the SPG between the cummberbund and the strap, and continuous tightening up of various bits and pieces and at least 3 buckles to check for most. I do dive weight integrated, so no weight belt issue.

As to air consumption - how's your physical fitness? I'm fairly fit (more now than before) and a slow breather anyway (at rest 5-6/min). Also remember you don't need huge lungfulls of breath. I've got fairly decent air consumption, about on par with my much lighter and smaller girlfriend, likely because I'm in decent shape. Cardio will help, but so will weight training (which also stretches aerobic capacity), so whatever sport works best for you.

 

[jfe]

.....................Worrying about air consumption leads to bad air consumption.
I'm not saying its a cure all, but it can help as well as making your divign more enjoyable and relaxing

I have to agree with this 100%. I'm 6'3 and 250 and I'm now at the stage where I can switch to 12l for regular rec diving and I'll make the 50 - 60 minute dives at shollower dives. I just stopped to worry about my air usage. The other thing was to practice breathing techniques I read on a free dive post some time ago, and I do this at my desk at work a day or two before a dive. Slow inhale and long exhale, I practice to exhale 3 times the inhale i.e. 3 seconds inhale and 9 seconds exhale. It's supposed to force you to "clear" the unused air from your lungs. It also helps to get you in a good breathing rythm and slows your heart rate.

 

[dumpsterDiver]

In other words, you should be getting dressed faster, all those buckles that allow instant adjustment and ease in slipping into a normal recreational BC don't really function and a crotch strap actually allows you to bend the time space continuum. so the crotch strap requires negative time. BP/W really are magical on Scubaboard. a better answer might be to start getting dressed earlier, so you don't make people wait for you.

Carrying a pony bottle, can allow you to extend your dive time to some extent, if you are willing to sacrifice some, or all of the redundant function of the bottle itself. This might require actual use of the pony bottle during a dive, which might present a problem for repetitive dives.

If it requires 800 lbs in the main tank for you and a buddy to ascend safely from a dive to depth X, then it might be possible to breathe you main tank down to 400 lbs, and if/when the emergency occurs requiring sharing of gas, you and the victim will be relying on both the main tank and the pony. So it IS possible to use the pony to extend your dive time and not actuall use the gas in the pony.

4-6 minutes of additional bottom time might be a 20% longer dive.. might make sense

 

[tbone1004]

I'm about your size, and by the quick rough numbers that I can get from what you posted which is omitting a lot of info, your SAC rate doesn't sound that bad. Not having an actual SAC rate number though is problematic so we have to make some assumptions about the actual size of the tank *didn't specify aluminum or steel, but assuming aluminum 100 since a 15l steel is a lp95 or hp120*, the actual pressures used, and the average depth of that dive. Assumption here is a fill to working pressure, consumed down to 400psi, with an average depth of 80ft, and a 45min dive time
If it's an lp95, then 0.5cfm, if an al100, your sac is roughly .6cfm, or if a HP117 ish then roughly 0.7cfm.

These are roughly normal sac rates for someone our size, especially if you are kicking. 0.7cfm is on the high side, 0.5cfm is on the low side, but a sac rate of 0.6cfm is pretty normal for a big guy that is kicking around. It should go down to the 0.5ish range if you're on a drift dive, but there is nothing abnormal about your SAC rate and you may not be able to bring it down in a meaningful enough way to get it to make a difference. The best thing you can do is to get into good cardio shape, i.e. running, biking, or swimming. You need to get your legs into shape and your heart into shape so your heart rate stays down when you're kicking.

The pony bottle idea is something you can look at though at that point it could be constituted as a bottom stage not a pony. I wouldn't recommend this idea personally