CESA Question

[Boarderguy]

Someone needs to teach that guy to frog kick to stop stirring up the silt!

That's how you know they're around. You see a silt cloud when solo at 100' lol

 

[wetb4igetinthewater]

That's how you know they're around. You see a silt cloud when solo at 100' lol

the way they contort their fat bodies gives me a real complex being such an inflexible fat a$$.

 

[dmaziuk]

In a CESA, the student should begin the ascent neutrally buoyant, as would happen on a real dive. During the ascent, the BCD will expand, and the student is taught to dump air a little at a time as that happens so that the ascent remains under control.

Unless of course they have little to no air in their BCD because it's the end of the dive and it's their empty Al80 that pulls them up.

 

[boulderjohn]

Unless of course they have little to no air in their BCD because it's the end of the dive and it's their empty Al80 that pulls them up.

A diver's buoyancy is based on the weight and volume of the entire package of the diver. If the weight of the diver, tank, and gear is equal to the weight of the same volume of water, then the diver is neutrally buoyant. If a diver is neutrally buoyant at the time he or she goes out of air, then at that moment, the diver, the gear, the weights, the now empty tank, and the amount of air in the BCD equals the weight of that volume of water.

If the neutrally diver begins to ascend at that point, the only change in buoyancy will be caused by the increasing volume of the air in the BCD and the increasing volume of bubbles in the wetsuit or drysuit. The empty scuba tank will not have any change in buoyancy during that ascent, and will have no effect on buoyancy.

 

[Bob DBF]

In addition to what I wrote above....

The navies of the world have used buoyant ascents for submarine escapes since the early 1950s. A Google search will find navy films showing it. The older ones are better because the escape is done with nothing but a very primitive BCD rather than the special suits used now. The students are taught to exhale fully before starting the ascent, and then continue to ascend the entire way up. This has been done from 300 feet.

600 feet now, although, as I remember when I served on submarines, my understanding @300' there was about 50% survival if there were not a chamber where you popped up.

I wrote to PADI about this, too. They told me that the dividing line between CESA and buoyant ascent was really your judgment.

It's just a matter of speed, now 30 fps is a normal ascent, not to exceed 60 fpm. My CSEA is the same 60 fpm I learned and practice at. So CESA can be fast, controlled is the operative word. 120 fpm was considered as an ascent rate by the US Navy at one time.


When I learned to dive, the S in CSEA was more important because I had no BC.

 

[RobPNW]

It's not just the total nitrogen in your body that causes illness. When at depth, the pressurized gas you breath remains stable and in solution in your blood. When you ascend too quickly, that gas can bubble out of solution from your blood. Imagine you have a bottle of pop and you shake it. With the cap still on, the carbonation is under pressure and it looks fine. But when you twist the cap off, and the ambient pressure drops quickly, not so stable anymore.

 

[BRT]

A diver's buoyancy is based on the weight and volume of the entire package of the diver. If the weight of the diver, tank, and gear is equal to the weight of the same volume of water, then the diver is neutrally buoyant. If a diver is neutrally buoyant at the time he or she goes out of air, then at that moment, the diver, the gear, the weights, the now empty tank, and the amount of air in the BCD equals the weight of that volume of water.

If the neutrally diver begins to ascend at that point, the only change in buoyancy will be caused by the increasing volume of the air in the BCD and the increasing volume of bubbles in the wetsuit or drysuit. The empty scuba tank will not have any change in buoyancy during that ascent, and will have no effect on buoyancy.

Really? The scuba tank displacing the same amount of water but having less weight doesn't affect buoyancy?

 

[johndiver999]

Really? The scuba tank displacing the same amount of water but having less weight doesn't affect buoyancy?

There is a fixed, linear decrease in the weight of the tank as the pressure is steadily declining during every dive. Initiating an ascent when the tank pressure is low, will not cause a buoyancy change in the tank.

 

[BRT]

There is a fixed, linear decrease in the weight of the tank as the pressure is steadily declining during every dive. Initiating an ascent when the tank pressure is low, will not cause a buoyancy change in the tank.

Ah yes, I missed the context of AFTER beginning ascent. Certainly it doesn't change with depth.

 

[Blackcrusader]

I also know that running out of air does not just happen by accident. It should never happen.

It sure can happen. O rings can blow, crud inside a tank can block the tubes, a freeflow 1st stage or second stage can occur. One forum member recently posted she was OOA even though her SPG showed she had air, her regulators got blocked from curd in her hoses being forced into her regulators.

In my training classes we were taught to use CBL controlled buoyancy lift using the BCD or SMB. Not easy to master for a new diver. In the old days we used to have a CO2 cartridge that you used to rapid inflate a BCD. No longer used

From deeper than 30ft there is another way but I won't bring that into the conversation right now as it is for a last resort cheating death adventure.