Buoyant ascents

[tbone1004]

that pressure drop is on the hose not the tank

Here is pressure flow
Tank at whatever pressure is in the tank
First stage reduces to some pressure over ambient, typically 135psi or so
The hoses have pressure on them from the water which is compressing the air inside of them. As the pressure is relieved, the gas volume in the hoses increases which increases the pressure inside of them, this someties allows you to take a breathe.

Now, you say again that you surface, take a deep breath, ditch weights and orally inflate the bc. Why would you ditch weights? There are only 2 reasons that I can think of that would result in ditching weights. Being an idiot and diving an unbalanced rig, i.e. thick wetsuit and deep, overweight in the first place, diving big steel tanks and a wetsuit, etc. or a total wing failure when you had to stay at the surface for a long time and didn't have a safety sausage to help keep you at the surface. There are no other reasons that would justify ditching weight that I am aware of

 

[RJP]

Ok, so this statement from the above linked Undercurrent article is wrong then? Or am I interpreting it wrong?

They've written it poorly: as you ascend the ambient pressure drops to lower than the pressure in the tank... which does not change.

 

[CuzzA]

Got it. Thanks for clarifying.

edit: Tbone, I'm not suggesting ditching weights. In fact in my first post I stated I felt the first thing to do is get air into the BCD.

 

[TMHeimer]

Given your scenario:

1. Sart CESA.
2. Right hand on weight belt poised to release.
3. Left hand on inflator raised ready to dump air to control ascent.
4. When surface is reached, dump weights and orally inflate BCD.

5. If surface is still a long way off, ascent is slow, and no more breath, try breathing from reg.
6. If still no air from reg, no more breath, ascent is slow, and surface is still ways off, dump weights.
7. Continue emit ahhh or eeee sound. Any remaining air in your lungs will continue to expand as you ascend.

No matter what, never remove reg throughout the UW ordeal and dump weights upon reaching surface (this is why PADI has now included emergency weight release in the new OW curriculum).

The decreasing ambient pressure will likely permit the higher pressure from your tank/reg to deliver a breath or two as you ascend.

This list seems logical to me. Start with CESA and prepare to drop wts. Two things to consider with CESA are how deep you are of course (I can do it from 30'--haven't even tried from deeper), and the fact that if you are completely OOA you will be starting out with less than full or empty lungs. If you weren't completely OOA then you could start up with a normal ascent, then when you feel the last of your air coming (from the pool simulation....) get the biggest breath you can and begin CESA, ready to drop wts.

 

[Iralub]

Now, you say again that you surface, take a deep breath, ditch weights and orally inflate the bc. Why would you ditch weights? There are only 2 reasons that I can think of that would result in ditching weights. Being an idiot and diving an unbalanced rig, i.e. thick wetsuit and deep, overweight in the first place, diving big steel tanks and a wetsuit, etc. or a total wing failure when you had to stay at the surface for a long time and didn't have a safety sausage to help keep you at the surface. There are no other reasons that would justify ditching weight that I am aware of

Is there a downside to ditching weights on the surface? Apart from losing the weights, but if I'd just had an emergency ascent due to ooa, I really would not care about losing some weights I'm wondering if that is the safest thing to do if you've reached the surface, whether you strictly need to do it or not. Would it not be better to be more buoyant than necessary than insufficiently buoyant (especially if exhausted, panicked, unable to orally inflate due to being out of breath, etc)?

I didn't know there was some guidance about below 18 meters versus above 18 meters. I think the answer is supposed to be:

When you run out of options, then you gotta shoot for the surface.
If you had just run "out" or are very low on air and it is hard to inhale... AND you are neutrally buoyant.. then you can probably kick up gently and sip the air.

For me, if I had some air in the tank, I would pop some air in the BC, begin a buoyant ascent and try very hard NOT to kick and to conserve my energy. I would plan on riding the BC up and vent air and try to come up as slow as I think I can.

What if you are diving without much of a wetsuit, you are weighted to be heavy and to be able to work on the bottom and you slam yourself under a ledge and it rips off the second stage hose from the regulator? Now you have nothing the breathe, nothing to inflate the BC and are negatively buoyant. Unless you are very shallow and/or a very strong diver, you should probably be thinking about ditching lead. In a situation like this, you HOPE you have some ditchable lead, but if you have little or no wetsuit on, you probably have less than 10-12 lbs of ballast to ditch. Dumping 10-12 lbs is NOT going to send you rocketing to the surface.
...
I think the best answer is.. ditch the lead if you think you must.

Hmm, I haven't considered the issue of the amount of weight. That is an excellent point. I only dive in warm water and am small, so my ditchable weight is usually only between 4 and 8 lb (depending on 3mm or 5mm suit), with the same amount in trim pockets that are not ditchable. It may be too small an amount to send me rocketing to the surface.

Given your scenario:

1. Sart CESA.
2. Right hand on weight belt poised to release.
3. Left hand on inflator raised ready to dump air to control ascent.
4. When surface is reached, dump weights and orally inflate BCD.

5. If surface is still a long way off, ascent is slow, and no more breath, try breathing from reg.
6. If still no air from reg, no more breath, ascent is slow, and surface is still ways off, dump weights.
7. Continue emit ahhh or eeee sound. Any remaining air in your lungs will continue to expand as you ascend.

No matter what, never remove reg throughout the UW ordeal and dump weights upon reaching surface (this is why PADI has now included emergency weight release in the new OW curriculum).

The decreasing ambient pressure will likely permit the higher pressure from your tank/reg to deliver a breath or two as you ascend.

This is a very helpful and methodical suggestion, thank you very much. Looking at this sequence, I'm glad for my one-handed integrated weights release - I could just see the fumbling to remove weight from both pockets while trying to use the inflator and ensuring adequate out-breath!

Thanks so much for everyone's suggestions and feedback.

OOA is obviously a very unlikely scenario, but I'm glad to have suggestions of how to deal with it. On a liveaboard earlier this year one diver had an ooa situation due to apparent equipment failure, his gauge was still showing plenty of air. Executed a perfect air-share with his buddy and ascended with no issues, but it brought home the point to me that these things can happen. It certainly won't be happening because I didn't pay attention to my air!

 

[Macan]

The scenario given by the OP is OOA at 18 meters. A CESA from that depth or deeper, upon reaching the surface will leave an inexperienced diver completely spent, gasping for air, threading madly, possibly still no air to inflate BCD, need to orally inflate BCD, etc. Task loading at that critical moment can be fatal.

Establishing positive Buoyancy is the most critical task upon surfacing. A well trained diver will instinctively act and Drop the weights upon reaching the surface in that situation.

The downside for dropping weights in a real CESA situation is lost weights and possibly bruised corals. The trade off is a higher chance of survival. Release the weights the moment you break the surface in an actual CESA situation.

 

[Patoux01]

Add possible homicide to your list if there are other divers underneath you. Which is not as unusual as people may think. One of the "big" training sites here around is a wall that drops to 45m or so (and not very wide, about 20m), so you get OW students on the top, AOW below, and beginning tec divers at the bottom.

 

[Doby45]

I do not live in a glass house. I only have over 40 years of instructing in the northeast with over 5,000 dives. As an instructor he is to stick to agency standards and teach as any other prudent instructor would. If a former student tried this trick that this instructor recommended and gets hurt, it would be instructors fault and no insurance or certification agency will assist him in a law suit.Dodgy with your very limited next to no experience with less than 25 dives , what expertise can you bring to the table to back up why you think this is a cool thing?

It is EXACTLY my lack of experience that tells me that this "procedure" you are all riled up about could possibly save my life. Your "resume'" of accomplishments mean nothing to me due to the horrible attitude you have. If it even remotely could keep me from drowning at 20', that last ditch effort of sipping from my BCD was worth it.

 

[uncfnp]

Add possible homicide to your list if there are other divers underneath you. Which is not as unusual as people may think. One of the "big" training sites here around is a wall that drops to 45m or so (and not very wide, about 20m), so you get OW students on the top, AOW below, and beginning tec divers at the bottom.

One hopes that if you are forced to CESA it is because there is no assistance nearby.

 

[Steve_C]

My pony solves the problem.

But I will note that with many integrated weights, like mine, there is an option of dropping half the weights.

There are a lot of examples of folks who surface for some reason, have a problem, and are found dead on the bottom with their weights intact.

Oral inflation assumes that you are in good enough shape that you can calmly inhale and inflate. May be tricky in 4-5 ft seas, exhausted, and possibly suffering other problems.

You drop weights in NC they are usually off in the sand.