Big Heavy tanks!

[jordaof]

Howdy to all, I have been monitoring my SAC and for the time being, a 12 liter tank goes from 200 bar to 70 bar in about 43-45 minutes at a depth of 11 meters to 12 meters, it is not wonderful, and I do have a lot to improve on my breath rate now that I'm approaching 24 dives, have 22 at the moment.

The thing is, I need to improve my longevity under water to accompany most of my buddies at those sorties that I've been doing, and I'm tempted to do an investment on a bigger tank, I've been seeing some huge ones, from 15 liters to 18 liters to even a mammoth 20 liter tank, I'm an heavy guy and I admit, I need to do a lot more exercise to be in shape, so, when I dive, even without a wetsuit I still need 4 kg's of led to at least .. sink, so my idea, and forgive me if it sounds silly "that's why I'm asking in the first place" is that if I have an heavy tank on my back I can avoid bringing led on my bcd and have more air, I am aware that buoyancy changes as the tank becomes depleted of air, so my idea is to invest in steel tanks.

I never tried something bigger than a 203 mm 12 liter tank "the fat one" so I ask for your knowledge, is a 18 liter or 20 liter to overwhelming to the balance of a diver? I am about 6 feet, does a tank as large as that one become to cumbersome to be of a efficient use?

Thank you for your atention!

 

[rx7diver]

Howdy to all, I hav ...

One "problem" with diving a larger capacity cylinder is you now have to dive with more gas in your BC--in order to offset the weight of the larger amount of gas in that cylinder at the start of your dive.

Another is a larger capacity cylinder probably has a larger outer diameter--which means more drag.

ETA: I own an OMS (Faber) LP121/125 cylinder. The box reads "19 ltr". It has an 8" diameter and it is ~29" tall, and it is neutrally buoyant in salt water when "empty." (See SCUBA Cylinder Specifications – Huron Scuba, Snorkel & Adventure Travel Inc. PADI 5 star IDC in Ann Arbor, MI.) I cannot dive it comfortably as a single cylinder. I am 6'2" tall.

rx7diver

 

[BrackaFish]

Howdy to all, I have been monitoring my SAC and for the time being, a 12 liter tank goes from 200 bar to 70 bar in about 43-45 minutes at a depth of 11 meters to 12 meters, it is not wonderful, and I do have a lot to improve on my breath rate now that I'm approaching 24 dives, have 22 at the moment.

The thing is, I need to improve my longevity under water to accompany most of my buddies at those sorties that I've been doing, and I'm tempted to do an investment on a bigger tank, I've been seeing some huge ones, from 15 liters to 18 liters to even a mammoth 20 liter tank, I'm an heavy guy and I admit, I need to do a lot more exercise to be in shape, so, when I dive, even without a wetsuit I still need 4 kg's of led to at least .. sink, so my idea, and forgive me if it sounds silly "that's why I'm asking in the first place" is that if I have an heavy tank on my back I can avoid bringing led on my bcd and have more air, I am aware that buoyancy changes as the tank becomes depleted of air, so my idea is to invest in steel tanks.

I never tried something bigger than a 203 mm 12 liter tank "the fat one" so I ask for your knowledge, is a 18 liter or 20 liter to overwhelming to the balance of a diver? I am about 6 feet, does a tank as large as that one become to cumbersome to be of a efficient use?

Thank you for your atention!

Just a thought. If your dive count is correct and you are a new diver, then don’t stress about it too much. Your SAC rate will improve as your comfort level, buoyancy and overall activity improve. Now if you are 6 foot 6 inches tall with lungs like Michael Phelps, then you might need larger tanks. Meanwhile just enjoy the dive and improve your skills. Be safe

 

[formernuke]

Focus on getting comfortable in the water.

If your dive buddies aren't willing to understand that your new, get new buddies.

 

[undrwater]

Just a thought. If your dive count is correct and you are a new diver, then don’t stress about it too much. Your SAC rate will improve as your comfort level, buoyancy and overall activity improve. Now if you are 6 foot 6 inches tall with lungs like Michael Phelps, then you might need larger tanks. Meanwhile just enjoy the dive and improve your skills. Be safe

Agree with this. Larger tanks COULD be the answer, but with more experience, you'll know, rather than having to ask.

Are you shore diving? Diminishing returns if so.

 

[jordaof]

Agree with this. Larger tanks COULD be the answer, but with more experience, you'll know, rather than having to ask.

Are you shore diving? Diminishing returns if so.

Boat diving, we generally group up with 4 to 6 people, some experienced guys do have a wonderful endurance, but myself and another guy are the ones that need to ascend like 12 to 15 minutes before the group, when we reach the "dreaded" 70 bar. It has been improving but slowly.

 

[jordaof]

I notice that might be a problem of anxiety, explaining, I run through the first 50 bars, from 200 to 150 very fast, then I start to breath more calmly and air tends to last a bit more.

 

[Barryattle]

My SAC was terrible when I started and I bought HP 119 steel tanks (short, fat). I have improved with time/experience and finally finding a mask that did not leak on my apparently peculiar face (clearing all the time was a huge waste of air, even though I tried to just do it on normal exhalations; I'd happily do commercial for the Hollis M1 and I have about 4-5 other masks available cheap...). Diving with buddies using HP100s (hey, Puget Sound/cold water), I am no longer reliably the diver who runs out of air first. Do I have a bit more water resistance? Probably - but I am fine with that tradeoff. So, yes, focus on getting comfortable and not overbreathing, but personally I'd say a bigger tank is a quick way to get more down time with the biggest cost being the tank cost. If I wanted to minimize my water resistance, would I drag a camera rig around???

 

[OTF]

Take your time to truly relax and catch your breath on the surface just before descending. Even if that means floating still at the down line for 3-5 minutes before putting the reg in your mouth. When I do this it saves a remarkable amount of gas. The exertion of gearing up, getting in, and acclimating to cold water gets your breathing rate up more than you realize. Taking some time to visualize and think through all the steps of a successful dive helps mentally as well.

That said, I'm also a big fan of steel high pressure 120cf tanks. They dive well and "nobody ever died from bringing too much air". If you need big tanks, and you are tall and strong enough to carry big tanks, they're a perfectly reasonable solution.

 

[Bob DBF]

Rent a bigger tank and see how it works for you, it will give you more air, and you can see if there is a down side for you.