easy on the air....

[Icarusflies]

Hello all;

Here is a question for you. I dive with my father that loves to breath too much.....of course that is good but the bottom time in on the short side. In the charters we rent the tanks that are 80 cf. I am thinking to buy 2 larger tanks for each of us so we can stay longer underwater. We are big fellows (6',3'') so we can handle the weight. What kind of tanks I should be considering..100, 130, I have even seen 149 cf....maybe some kind of doubles???? (must say that we only have 12 dives under our belts so no much experience)

 

[Halthron]

Before you go out and buy bigger tanks, you need to consider how the tanks will affect your buoyancy. A tank that is more buoyant at the end of the dive will require you to wear more weight to conteract the effect. Steel tanks are less buoyant that AL tanks are so you can remove some weight when using them.

The other key is not to take so much air that you get yourself into trouble. The NDLs are there for a reason but just because you haven't crossed them yet doesn't mean you can't get DCS if you ascend too quickly or forget to make stops.

Ultimately, you may want to get some more dives in. The single biggest component to most people improving their SAC rate is familiarity with diving. Do anothert 20-30 dives and see how you feel.

 

[SteveAD]

I second the more dives idea. every newbie is an air hog. your excitement level is running at a peak throughout the dive. when some of the newness wears off your breathing rate will come down.

 

[jonix]

Before you go out and buy bigger tanks, you need to consider how the tanks will affect your buoyancy. A tank that is more buoyant at the end of the dive will require you to wear more weight to conteract the effect. Steel tanks are less buoyant that AL tanks are so you can remove some weight when using them.

The other key is not to take so much air that you get yourself into trouble. The NDLs are there for a reason but just because you haven't crossed them yet doesn't mean you can't get DCS if you ascend too quickly or forget to make stops.

Ultimately, you may want to get some more dives in. The single biggest component to most people improving their SAC rate is familiarity with diving. Do anothert 20-30 dives and see how you feel.

agree. more dives makes you more relaxed at depth. also try adjusting the airflow of your reg as it might be giving much more air than is needed.

 

[cleung]

Many newbies use up a lot of air. Experience will certainly teach your father to slow down on the breathing and therefore use up less air resulting in more time. YOu can see from the trend that experienced divers of all shapes and sizes generally have sufficient air during any dives.

 

[Diveral]

Here is a thread on this same subject which had a lot of good advice.

http://74.52.40.164/showthread.php?t=153193

 

[TheRedHead]

100, 130, I have even seen 149 cf....

Of course, you'll get better, but there is no reason to think the AL 80 is the perfect tank for rec diving: it is really just the cheapest tank. The X7-100 HP tank is smaller than the AL 80 and about neutral at the end of the dive. Being big guys, you might find you trim out better in a 120. Leave the double tanks until you have a LOT more experience.

 

[Icarusflies]

Thank you guys for the info

 

[1_T_Submariner]

I agree with the dive more then see what you think theory.

Keep in mind with HP tanks if they only fill them to 3000 PSI they are not as big as you might think.

 

[TSandM]

I was too lazy to go read the thread that Diveral referenced, so I'll put my two cents in.

One is that an Al80 is probably not the ideal tank for guys as big as you are. But what tank you actually NEED will depend on what kind of diving you are doing, what exposure protection you are using, and even on what kind of buoyancy compensator you are using. So I wouldn't jump into buying tanks just yet. A friend of mine recently did that, because he was annoyed with running short of gas, and ended up with tanks so negative there was no way he could trim them out. He sold them, and is much happier with smaller tanks.

Second, a lot of the air usage of new divers is due to inefficient diving technique. If your buoyancy is iffy, and you are using your inflator a lot, you waste gas. If you are diving feet low, then every kick drives you upward, and you have to keep yourself negative in order not to rise. That wastes muscle energy, and thus gas.

Fixing your static balance means that, when you kick, all the energy you expend drives you forward. This is more efficient, and lowers your gas consumption. Working on your buoyancy, until you can relax and "hang" in the water, makes you more efficient as well.

Breathing techniques are also a part of being efficient. Rhythmic, slow breathing makes the most efficient use of the volume in your tank. Rhythmic breathing is easier to do when you are relaxed and horizontal, but paradoxically, concentrating on rhythmic breathing can CAUSE you to relax, as well.

HERE is a very nice article on static balance, to help you get started.

Stick with the short dives until you have spent some time working on all these issues -- then you'll have a much better idea of what you really need (which is probably something bigger than an Al80) and you won't end up spending a ton on tanks you eventually decide you don't like.