Drysuit and squeeze question

[MidOH]

On your skin, off your skin, lotion in the basket or it gets the hose again?

If there's differential pressure, then I'm betting that there's going to be force and squeeze.

At some point in that Mythbusters vid, there was no air gap under the suit, and it still just kept squeezing harder.

 

[OMyMyOHellYes]

On your skin, off your skin, lotion in the basket or it gets the hose again?

If there's differential pressure, then I'm betting that there's going to be force and squeeze.

At some point in that Mythbusters vid, there was no air gap under the suit, and it still just kept squeezing harder.

I found the Mythbusters video a red herring.

They had a suit at depth and then vented the topside hose (with no in-line check valve) to ambient atmospheric pressure to see if it would liquify the occupant and squeeze it into the helmet and up the hose. That part was a no-brainer (not an intentional pun). It was not a closed, contained pressure vessel of any type when they opened the valve. It was more like an open tube of toothpaste getting stomped which doesn't really address the inability to breathe or causal factors that would make breathing difficult.

But, back to the point of the thread: thanks much to all that did respond. I can get my head around the part where friction inside a compressed suit at great enough pressure could cause immobilization. I was operating under the assumption that the suit would be more flexible, not just becoming a rigid whole body splint. It is not the inability to draw from the reg because of any differential pressure between the water and the pressure inside of the lungs, which if given enough room to flex the diaphragm, would not seem to pose a problem.

 

[Alex Ouroboros]

Speaking from experience I can tell you that clearance divers in the uk used to dream up (as all armed forces personnel do) daft “games” and one such story involves the lads seeing how deep they could cope with before heading up due to the agony of a drysuit with no inflator valve, the “winner” (or person with most pain threashold) managed something in the region of 40m+ (131+’)
This story aside I was once on my way down the shot line and encountered a mate of mine waiting and gesticulating at his suit inflation,, which after a few moments of hysteria on my part I turned on for him (hearing some very strange sounds from his delight) and that was at about 30m (100’) both cases displayed wonderful purple welts post dive so

35m (120’) is possible

 

[Jim Lapenta]

I am very familiar with the incident that occurred. I have spoken to and been in regular contact with Linnea's mom and her attorney. I've written letters to the Assistant US Attorney and the Attorney General on behalf of the family and the incompetence of the investigation.
I'm also the author of the revised SDI drysuit course.
In addition, I had my own minor incident with a drysuit I was not able to inflate due to cold hands not making the inflator connection and ensuring it was done. Fortunately, I was only down to about 15 feet under the ice when I discovered my error.
This incident was thoroughly discussed on this forum and on the Facebook Accidents page.

Suit filed in case of "Girl dead, boy injured at Glacier National Park

I'd have a lot more sympathy for this degree of poor performance if they knew that they were just the first line and actual experts were going to come along and redo everything anyway. (Like if they were the first on scene and needed to take some kind of report just to write down initial...

scubaboard.com

In short, an instructor allowed and even encouraged the deceased to dive in a drysuit without an inflator hose attached.
The suit required a hose with a non-standard BC inflator connection, which was not provided with the suit. In addition, the deceased was loaded down with rocks in her drysuit pockets that could not be ditched.
She had never taken a drysuit course and had no pool training prior.
As she entered the water she was taken by the instructor to depth and then abandoned by the instructor.
The squeeze on the suit to someone who had never been in a drysuit at depth would have felt like being pressed in a vice over her entire body.
In a shell suit, the squeeze actually feels like the material is getting stiffer and stiffer.
When I was at 15 ft and realized what was happening, I grabbed the descent line and stopped myself. I hooked up the inflator and that first burst of air in felt like the weight of the world had been lifted off of me.
The compression of the suit and the feeling of stiffness made it difficult to move my arms and being vertical to try and get what air there was in the suit up around my chest so I could breathe, left welts on my legs.
That was at 15 ft and I had around 300 dives in a drysuit at the time and was a drysuit instructor. I knew what I was doing.
She did not and was in great distress. The photos show her trying to get someone's attention. The instructor was oblivious swimming away from her looking at her compass. Linnea was on a ledge and her trying to get someone's attention resulted in her falling backwards.
As she fell, the compression got more intense, and I can pretty safely assume her distress and panic levels probably shot through the roof.
Unable to add air to the suit, and by now probably not even able to move her arms to use the BC inflator, she had to have been terrified.
The diver who tried to assist her was not rescue trained, could not dump her weights, did not know about the weights in her pockets, and did not have enough lift in his BC to get her up.
She was at roughly 85 ft when her descent stopped. Around 3.5 atm, 51.5 lbs per sq inch. The avg human body is around 255 sq inches. That's a total pressure of just over 13,000 lbs.
Lets take the legs and arms out of the equation and just consider the torso which is going to be over half of that surface area. That's still 6,000lbs of pressure? So tell me how you are going to breathe with 1 1/2 tons of pressure on your chest and back.
Yes, it's distributed, but did your instructor ever explain why you could not use a 4ft long snorkel or even 3 ft? Your diaphragm cannot overcome the pressure at that depth to breathe.
Some instructors give a rudimentary idea of what squeeze feels like by telling someone to submerge their hand in a bucket of water wearing a latex glove. A supple material that feels soft out of the water. But put your hand down into the water and it starts to feel like it's made out of much stiffer material.
A wetsuit allows water in and so does not need to be equalized. But as you go deeper and the material compresses, it starts to feel a little stiff if you are paying attention.
Drysuits can kill you. They need to be respected.

 

[davehicks]

I found the Mythbusters video a red herring.

They had a suit at depth and then vented the topside hose (with no in-line check valve) to ambient atmospheric pressure to see if it would liquify the occupant and squeeze it into the helmet and up the hose. That part was a no-brainer (not an intentional pun). It was not a closed, contained pressure vessel of any type when they opened the valve. It was more like an open tube of toothpaste getting stomped which doesn't really address the inability to breathe or causal factors that would make breathing difficult.

But, back to the point of the thread: thanks much to all that did respond. I can get my head around the part where friction inside a compressed suit at great enough pressure could cause immobilization. I was operating under the assumption that the suit would be more flexible, not just becoming a rigid whole body splint. It is not the inability to draw from the reg because of any differential pressure between the water and the pressure inside of the lungs, which if given enough room to flex the diaphragm, would not seem to pose a problem.

This "get my head around it" logic is why people think the world is flat or the moon landings were faked. I hope nobody has this level of misunderstanding of physics when it comes to the topic of holding your breath on ascent.

 

[NW Dive Dawg]

She was at roughly 85 ft when her descent stopped. Around 3.5 atm, 51.5 lbs per sq inch. The avg human body is around 255 sq inches. That's a total pressure of just over 13,000 lbs.
Lets take the legs and arms out of the equation and just consider the torso which is going to be over half of that surface area. That's still 6,000lbs of pressure? So tell me how you are going to breathe with 1 1/2 tons of pressure on your chest and back.

Please correct me if I am wrong...... but isn't a diver in a wetsuit or even in no exposure suit at all still exposed to that exact same amount of pressure on their chest and back at that depth? And the only reason we are not crushed is simply because the body is primarily liquid and liquid does not compress?

 

[MidOH]

Correct

Body is liquid, and mostly uncompressable. And our air spaces were filled with equal pressure from the reg.

But if the inside of her drysuit was 14.7psi, and the depth was 30psi, that's a problem.

 

[davehicks]

Please correct me if I am wrong...... but isn't a diver in a wetsuit or even in no exposure suit at all still exposed to that exact same amount of pressure on their chest and back at that depth? And the only reason we are not crushed is simply because the body is primarily liquid and liquid does not compress?

I'll say it another way...

Your lungs and sinus most certainly do compress, and you will feel great pain and pressure because these are voids. We solve the problem with a scuba regulator to fill them with air that matches the pressure of the ambient water. You know, equalizing. The rest of your body is basically a bag of water, so no problem at scuba depths.

A drysuit is another void made of impermeable material with seals so water cannot enter. If you don't fill it with air at ambient pressure it gets crushed just like your sinus and lungs and you will feel great pain and maybe even become incapacitated if you go deep enough.

 

[Lorenzoid]

I'll say it another way...

Your lungs and sinus most certainly do compress, and you will feel great pain and pressure because these are voids. We solve the problem with a scuba regulator to fill them with air that matches the pressure of the ambient water. You know, equalizing. The rest of your body is basically a bag of water, so no problem at scuba depths.

A drysuit is another void made of impermeable material with seals so water cannot enter. If you don't fill it with air at ambient pressure it gets crushed just like your sinus and lungs and you will feel great pain and maybe even become incapacitated if you go deep enough.

That analogy seems easily understood. What I suspect is difficult for some people to grasp is that a drysuit does not behave like it's a diver's second skin. If a drysuit were literally like another layer of skin, it would not compress the rest of the body, which is, as you put it, "basically a bag of water." Rather, there is inevitably some amount of air in the drysuit, and it compresses with depth.

 

[John C. Ratliff]

Please correct me if I am wrong...... but isn't a diver in a wetsuit or even in no exposure suit at all still exposed to that exact same amount of pressure on their chest and back at that depth? And the only reason we are not crushed is simply because the body is primarily liquid and liquid does not compress?

No, you are not correct. The wetsuit compresses, and in fact a wetsuit at about 45 feet of freshwater looses its buoyancy completely (I know, as I took off my weight belt in Clear Lake, Oregon at 45 feet and swam around an neutral buoyancy). So the material compresses, but not against the diver as the pressure on the suit is in both directions (from inside as well as outside), and is therefore equalized. The diver’s lungs are also pressurized by the regulator providing air at the same ambient pressure as the surrounding water. But, you still need to clear your ears; if you don’t then there is extreme pain and a rupture of the ear drum.

Now, with the dry suit, because the pressure is from one side only, there is a compression force against the body. While the lungs get pressurized air, the pressure only on the outside of the suit will press the suit against the diver (as any dry suit user knows when standing up in the water prior to the dive, and “feels” this pressure against his/her legs).

SeaRat