Bottom Time

[AquaGuy]

I am a newly certified diver (4 dives) and have noticed that I am always the first one to reach 1000 psi during all of my dives. I am a large guy (6'4 240 lbs) and use an AL 80 Tank. Most of my dives are about 60 -70 ft in coldwater (San Diego) 60 F. I average about 25 - 28 mins per dive. It appears that I can't last any longer than that. I know that over time as you get more experienced you tend to last longer underwater. It's getting to the point where some dive buddies don't want to dive with me because of the short dives. I was wondering if I got a larger tank - Steel 105 if that would make much of a difference? It appears I would have to buy one since the shops around here don't rent the larger tanks. Any suggestions on how to make my air last longer would be appreciated.

Thanks

 

[WreckWriter]

Dive more, get better consumption. Are you warm enough? Not swimming fast? A lot of it is mental, as you get more comfortable you'll get better.

Yes, a 104 would give you a good deal more air.

Tom

 

[JimC]

Things that will help your SAC, barring a sex change operation.

- Corect weight
- Corect trim
- Relax
- Don't use hands for propultion
- Streamline equipment
- Exercice

All said, you are a big lad (6'4" !!) and just have more mass to move and more body to keep full of o2. You may want to invest in bigger tanks in adition to the above. Based on your size, you probably wouldn't have any trouble handling the extra weight and bulk.

 

[Uncle Pug]

...get a larger tank. Buddies are valuable... don't lose them over this... (and you really can't blame them.) Yes you will get better consumption with time but probably never as low as a smaller person and you might be buddyless by then anyway.

Pressed Steel LP104 (or even LP120 since you are physically big enough to not only handle it but benefit from the increased tank length trim wise.)

 

[landlocked]

I plan on buying a LP95 for the simple reason that my buddy has a better SAC rate. (Actually, another reason is that I would like to get a little more weight off of the belt.) If she stays with an Al80, that should have us both using up our tanks at about the same time.

(Note: Welcome back UP. You have been missed.)

 

[Inspector#2]

I have been diving for a while and have the breathing down but a couple of my buddies are 5' nothing and can always outlast me. I'm 6'1" and the pressed steel 120 is no problem to cart around or dive with. Its a quick fix to a problem that will go away with more experience and allows you to enjoy your first 50 dives with you buds.

Dave

 

[Bigberg50]

Bigger tanks= more air= maybe more bottom time. But bigger tanks have more weight for you to pull through the water and have a bigger profile which means more work. more work=more air=less bottom time.

The best advice is to dive a lot, get very comfortable and breathe slowly and deeply. Also, topside a typical breath cycle is breathe in, breathe out, wait, breathe in, breath out, wait. Try and modify somewhat when diving so that the wait is after the breathe in. That will give your lungs more time for gas exchange. also, deeper breaths will help as when you breathe out there's still much CO2 in the airways. deep breaths will overcome the residual CO2.

Good luck!

 

[MNScuba]

Oops, my post re-showed up, read below... sorry!

 

[MikeS]

Bigberg50 once bubbled...
Bigger tanks= more air= maybe more bottom time. But bigger tanks have more weight for you to pull through the water and have a bigger profile which means more work. more work=more air=less bottom time.

I'm confused here.

With proper horizontal trim does't a HP120 present the same profile and hense drag as a AL80?

Also, while the tank weighs more a coresponding amount of weights can be removed, so isn't your total weight actually the same.

I recently switched to an HP120 and let me tell you, it's great to no longer be the first one out of air. Not to mention that with Nitrox the relationship between my air time and NDL times are much better.

Mike

As an after thought, I did not mean literally out of air, I meant the first to reach the agreed upon start to the surface pressure.

 

[MNScuba]

I apologize for not having the time to read previous posts, but in case it hasn't been covered:

Next time you dive, spend a couple minutes and do a buoyancy check. Not being neutrally buoyant can make a HUGE difference on air consumption... I recently did the Peak Performance Buoyancy course and here are my results:

Before the course:
Dive depth, 30 feet
Al80 3000 psi
Dive time to 500 psi = 45 minutes

After the course:
Same criteria, same dive
Dive time to 500 psi = 65 minutes

Note: I was also able to drop 8 pounds of weight off my BC! First dive was with 26 pounds, second dive was with 18 pounds.
(6.5 mil semi-dry suit, hood, gloves, freshwater)