Larger Nitrox tanks in Bonaire

[billt4sf]

I am an air hog and we do Nitrox. Does anyone have a suggestion where I could go to rent larger Nitrox tanks? Tropical Diving Bonaire suggested I could use their steel tanks with 8 (= 63 cft), 10 (= 78 cft) and 12 liters (= 93 cft) with free Nitrox but even the 93 cf doesn't sound alot larger than 80cf to me. Am I wrong? Suggestions?

Thanks!!

- Bill

 

[RJP]

Suggestions?

- Slow down
- Get your weighting right
- Slow down
- Get into horizontal trim
- Slow down some more
- Stop paddling with your hands
- Slow down even more
- Adopt more efficient kicking style
- Did I mention slowing down?
- You're still moving too fast. Slow down just a bit more.

Assuming you get free unlimited Nitrox... do six short dives a day. Who cares how much gas you suck down on each dive. Plus, you can stay fairly shallow since there's not much too see at 60ft that you can't see at 40ft... but with more light!

 

[billt4sf]

I agree, and we're working on all that (not just talking here), but there's only so much you can do when you're 6'6" and 240 lbs. I think I will always be an air hog as compared to my wife 5'2" 125 lbs. Hence the request for a place that offers large tanks.

- Bill

 

[drrich2]

Bill:

Been there. In a nutshell, I've dropped about 8 lbs of lead over the years, go slow, tend to average fairly shallow and work to control my breathing (e.g.: Use my tongue to interrupt exhalation, so I exhale over about 3 bursts instead of just 1 long one, and I inhale maybe 1/3 - 1/2 lungful of air instead of a big breath). Optimizing breathing is one of those topics discussed in other threads & not universally agreed upon, but there it is.

Richard.

 

[Tunaman68]

My limited understanding is that a High Pressure steel tank will hold the same amount of air as an aluminum but in a smaller size. My 100cf HP steels are a bit smaller than a standard AL80. Also, the buoyancy characteristics of the steel cylinder may allow you to loose some lead off the belt and streamline you as they tank is smaller. It will still be negative at the end of a dive, where an empty AL80 will be buoyant. Less lead, less drag, less fatigue carrying it around less air use. So to go from an AL80 to a HP steel 93 IMHO will give you more advantage than just 13 extra cf of gas.....

Scuba Tank Capacity and Pressure

From Dive Gear Express website......

"Start with the benchmark of the "Standard Aluminum 80" (AL80) that actually holds about 77 cubic feet of gas at 3000 psi. This is plenty of gas for the experienced air diver, and usually the air no-stop-required time is what limits the dive. The most consistent complaint about the AL80 is its poor buoyancy characteristics. It is very positively buoyant near the end of the dive, which means that you have to start your dive with too much weight, yet sometimes you are still struggling to stay neutral at your safety stop.
If you usually return to the boat with 1000 psi or more of gas in an AL80, then you might consider a smaller tank such as the Aluminum 63 (AL63) or high-pressure steel 65 (HP65). Obviously, one advantage of the smaller tank is less weight to carry and haul up the boat ladder, but more important are significantly improved buoyancy characteristics over the AL80. Many women prefer these compact and lightweight tanks for sport diving.
On the other hand, if your gas consumption is sometimes the limiting factor on your bottom time, you might choose a larger tank like the high-pressure steel 100 (HP100). The aluminum 100 is the largest aluminum tank available, but at a weight of 40 pounds, is considered quite heavy. The HP100 is the same weight as aluminum AL80, but has a service pressure of 3442 psi. The HP100 is the most popular steel tank choosen by sport divers.
An excellent compromise solution, if 80 cubic feet of gas is enough but you don't want to deal with the buoyancy hassles of the standard aluminum 80, is the low-pressure steel 80 (LP80) and the high-pressure steel 80 (HP80). These tanks have a little more capacity (remember the AL80 capacity is only 77 cubic feet) and the much better buoyancy characteristics of steel, yet are the same weight or even slightly less weight than the AL80. The LP80 service pressure of 2640 is easy on equipment, and the HP80 is exceptionally compact. The low-pressure steel 85 (LP85) represents a option for those divers who need a bit more gas but balk at strapping on a really big tank."

 

[DiveMaven]

I would ask if they always have the 12L tanks filled and available for you, or will you constantly have to wait for fills? One of the best parts of Bonaire is having a ready supply of tanks available at all times and not having to wait for fills.

 

[RJP]

(e.g.: Use my tongue to interrupt exhalation, so I exhale over about 3 bursts instead of just 1 long one, and I inhale maybe 1/3 - 1/2 lungful of air instead of a big breath). Optimizing breathing is one of those topics discussed in other threads & not universally agreed upon, but there it is.

Manipulating your breathing, is what you mean. You're not "optimizing" anything.

Since respiration is a function of "demand" rather than "supply" what you're doing really has no meaningful effect on how much oxygen your cells need or use. You can screw around with your inspiration rate (inspiration being different than respiration) but what you're doing is not "optimizing" anything. It may make a tank last a few moments longer, but you're screwing with your blood chemistry and other things. The known equations for how your body's cells utilize oxygen don't change based on what you do with your tongue or how many bursts of exhalation you take. This is as universally true as the Earth being round - disagreeing with it is really just sort of silly. What you're essentially saying is that, in an attempt to get better gas mileage, you only fill your gas tank half way rather than filling it up. That way you use less gas, right?

I would suggest that you'd see better improvement in SAC rate if you stopped thinking about how to "optimize" your breathing.

 

[redacted]

If you must get more dive time, you could make up a stage bottle rig and add a slung 63 to extend your dive. But I agree that you should be able to get a good dive in Bonaire on an AL80. I weigh in in the 225 range and worked to get my SAC well below .5. Practice slow easy breathing. Then look at those things you do while diving that raise your level of effort and seek ways to stop them.

 

[uncfnp]

If it is the difference of dive time between you and your wife, another option is for her to use 60's usually readily available in Bonaire, much more so than 100's.. That's what Eric and I do and it helps equalize our dive times. He's on the 80's and I'm on 60's. I also like diving with the smaller tanks. Lighter, and even better, shorter making dive entry and exits much easier for me. Steel 93 would give you more time but may not be worth it in lost convenience.

 

[RJP]

It (steel tank) will still be negative at the end of a dive, where an empty AL80 will be buoyant. Less lead...

Interesting, but ultimately meaningless piece of information. And corresponding faulty conclusion. The net buoyancy CHANGE is the important thing, not whether the tank ends negative or buoyant. Which tank has the greater buoyancy SHIFT?

An AL 80 goes from -1.4lbs when full to +4.4lbs when empty; a 5lb buoyancy shift
An HP100 goes from -8.5lbs when full to -1lb when empty; a 7.5lb shift

So all other things being equal, to offset the larger CHANGE in buoyancy from full to empty you will actually need 2.5 MORE pounds of ballast if you're diving the steel tank that ends the dive negatively buoyant than if you're diving the AL tank that ends the dive positively buoyant.

You may end up with "less lead" by diving the steel tank, but you've simply replaced it with an even greater amount of steel.

That said, I dive double 119's that I overfill...