Max Depth vs. Cylinder Capacity

[ianr33]

If I do a dive on the yukon and turn the dive with 1300 psi in my tank, that's over 50% remaining on a no deco dive. .

How do you figure its over 50% ?

 

[elmer fudd]

How do you figure its over 50% ?

Low pressure tanks.

 

[Marek K]

Since the OP framed his questions around Advanced Open Water, the rule of thirds is kind of over his head perhaps?

I did my AOW in 1986... there was apparently no "deep dive" per se required then; because my deepest dive is AOW was a drift dive to 65 ft., according to my logbook from then.

Yes, I dive in non-overhead environments, almost always above 60 ft.

I do plan turnaround pressure for every dive, but you're right -- I don't use the rule of thirds.

I've never done depth x 10 + 300 -- never heard of it in fact. but I do like it.

 

[ianr33]

Low pressure tanks.

I thought this conversation related to Al 80s?

In which case the 10 X depth +300 guideline seems pretty reasonable to me. A little conservative maybe, but that's no bad thing for new divers.

 

[dumpsterDiver]

It seems a little conservative to me also, but if you can't do the math yourself and determine exactly why it should not apply to you, then follow a rule of thumb.

 

[elmer fudd]

I thought this conversation related to Al 80s?

In which case the 10 X depth +300 guideline seems pretty reasonable to me. A little conservative maybe, but that's no bad thing for new divers.

I was thinking that at first too, but 1300 is just about half the pressure of an LP tank with a 10% overfill and a bit more than that without and I guess if On Two Wheels has LP tanks, then for him, he's getting back on the boat with more than 50% of his gas.

 

[D_B]

I was thinking that at first too, but 1300 is just about half the pressure of an LP tank with a 10% overfill and a bit more than that without and I guess if On Two Wheels has LP tanks, then for him, he's getting back on the boat with more than 50% of his gas.

for any of the common larger LP tanks, then 1300psi is not the correct figure, 1000psi is
and the Yukon is only 100feet deep at the sand, I use 85 feet as an average depth to plan a dive there (outside only)
... I wonder he read the paper and what size tank he's referring to?

As to not being able to do the math in their head, yep, that would be me .... as long as I use good judgment and reasonable depths, that rule of thumb works and I can do the math in my head

 

[sea2summit]

The only safe competition to have during a dive is to see who can return with the most air in their tanks.

Doesn't matter what size, a whole list of other things matter most notably SAC. Plan your dive according to your gas use and if you need to adjust your tank do it. Maybe you need a tank bigger than twice you're planned depth and maybe an 80 would last you two dives (I've dove with both types).

My $0.02.

 

[elmer fudd]

Plan your dive according to your gas use and if you need to adjust your tank do it. Maybe you need a tank bigger than twice you're planned depth and maybe an 80 would last you two dives (I've dove with both types).

My $0.02.

I was thinking of just adjusting the valve a little to cut down on my gas usage. It really does work. Sometimes they even haul people back up with full tanks.

 

[DCBC]

Many instructors teach the fine points of gas consumption and projection on a basic/OW program. If the student doesn't apply this into their dive plan, they can running out of air.

I suppose if you can't workout your gas consumption and work it into your plan, it's easier to use a rule like this than learn the math. I'll continue assuming that my students have a brain and will use it, instead of repeating ridiculous rules like this for them to remember.