sudden uncontrolled ascent!

[Blackwood]

Oh yeah and for me, missed deco means im going back down to try to clear it and NOT staying sat on the boat just waiting for the bend to happen.

FWIW, there's a big difference between omitted decompression procedures and going back down for a short 'safety stop' (as I believe is described in this thread).

 

[SkimFisher]

Please make sure to post that, you now have me curious

ditto

 

[TheScubaBOB]

My physics sense is tingling. I don't buy it, regardless of what witnesses reported.

If I fill a wing or BCD at depth and let it go I bet it won't jump out of the water even without the weight of a diver attached to it. There is a fundamental difference between a missile and a buoy.

In fact, next time I'm on a boat I'm going to suggest we do just that, and film it for posterity.

Simple small scale test...

1. Take an empty water bottle down to 30ft.
2. Fill it to almost full of air with your regulator & recap it.
3. Release it.
4. Have a surface observer video taping the surface above you.

It will Polaris Missile out of the water...

Now repeat with a BC, heavier object but also a larger air bubble.

Maybe we should ask Mythbusters to do a Scuba Episode and include this.

 

[*dave*]

Simple small scale test...

1. Take an empty water bottle down to 30ft.
2. Fill it to almost full of air with your regulator & recap it.
3. Release it.
4. Have a surface observer video taping the surface above you.

It will Polaris Missile out of the water...

No, it won't.

Velocity is all there is to carry the object above the surface. As soon as the object clears the water, it becomes negative. Terminal velocity for a buoyant object is not all that high. The larger the displacement, the greater the buoyancy, but that is offset by drag and resistance.

I have held on to the bottom @60'+, filled my 60lb wing, then let go and kicked for the surface on several occasions. The result was less than dramatic. As I recall, I surfaced to the point that my belly button was out of the water.

***Disclaimer****
I'm well aware of the risks at this point, but didn't know what I didn't know at the time I engaged in this stupidity. It is a dangerous practice no one should attempt. At the time (late 70's), my instruction lead me to believe the only issue would be related to over expansion.

 

[String]

It will Polaris Missile out of the water...

No it doesn. IT ascends upside down, clears the water about as far as the neck, falls over and then floats on top.

 

[Ayisha]

...a diver was seen popping up to his waist area.

bold added

And yes its really really hard (likely impossible) to breach entirely. Best ive seen is up to the waist.

bold added

As I recall, I surfaced to the point that my belly button was out of the water.

bold added

As you can see from my post above, the eye witnesses observed the diver popping up to his waist area. It was never stated that the diver fully breached the water. It seems both of you are familiar with this phenomenon.

 

[*dave*]

The issue I took with your post was the conclusion that a person experiencing such an ascent would succumb to their injuries.:

If that happens, you will more than likely succumb to your injuries, so let's all be careful down there.

What injuries?

bold added

As you can see from my post above, the eye witnesses observed the diver popping up to his waist area. It was never stated that the diver fully breached the water. It seems both of you are familiar with this phenomenon.

 

[Ayisha]

The issue I took with your post was the conclusion that a person experiencing such an ascent would succumb to their injuries.:

Nope, I said "more than likely" - NOT "would". There is a difference. I'm certainly not willing to take the chance if I don't have to. I'm also not willing to pump up a wing or BC while holding the bottom and then let go and kick for the surface as you did to test a theory either. I would not want to give newer divers the impression that any ascent where your body pops up to the waist is ok. Again, the quote was:

If that happens, you will more than likely succumb to your injuries, so let's all be careful down there.

What injuries?

The diver died instantly.

 

[TheScubaBOB]

No it doesn. IT ascends upside down, clears the water about as far as the neck, falls over and then floats on top.

I speak from experience regarding the empty plastic water bottle. After taking an empty water bottle down to 30ft demonstrating the effects of pressure to my 17yr old daughter at the surface while discussing the "Wow it's crushed at depth" and how rigid it was at the surface (it actually hissed when I opened it on shore) I was playing with the bottle. I held it just 1ft below the surface and the entire bottle cleared the surface of the water when I released it.

 

[TheScubaBOB]

No, it won't.

Velocity is all there is to carry the object above the surface. As soon as the object clears the water, it becomes negative. Terminal velocity for a buoyant object is not all that high. The larger the displacement, the greater the buoyancy, but that is offset by drag and resistance.

The water bottle is accelerating through the water defeating the resistance of the dense environment (water). The velocity is fed by the buoyancy.

When the bottle hits the surface it loses the buoyancy and the acceleration but it also loses the increased resistance as air is less dense than water.

While the bottle doesn't continue to accelerate it has reached escape velocity and will clear the surface before the air resistance completely decelerates it.

Saturday while diving I'll repeat my experiment and video it, you do the same and we'll compare the videos, okay?