Drysuit and squeeze question

[happy-diver]

Did anyone ever try getting into one of these

 

[davehicks]

As the ambient pressure increases (and hence the pressure inside the suit - they are equal because the suit is not a pressure vessel but made of flexible cloth) the air inside the suit gets compressed. This allows the suit fabric to come closer to your skin. You may wear some undergarments, winter overalls and such, and as the clothing gets compressed and stiffer (or, in the worst case scenario, the drysuit hugs the naked skin), you movements become more and more difficult. If this causes panic in you, you're gone.

Note, that your skin is flexible. It allows for movement. The suit is not flexible. Add friction. See the problem?

In a wetsuit you have pressurized water on both sides of the wetsuit. Water does not (practically) compress, but the wetsuit will compress and get thinner. It won't get pushed against your skin though. And in any case, neoprene wetsuits are also more flexible than trilaminate drysuits. I am not an expert on wetsuits, though.

I once had a little mishap with my drysuit, and the only thing I could move, somewhere between 60 and 90 ft, was my wrists to send a distress signal with my light. Not fun, I must say. Pressure in the lungs is the same as outside, so one will not get crushed, and the diaphragm can do its work inside the rib cage. Fully inhaling might become difficult because of the cloth of the suit. This would only allow for partial breathing and would make CO2 control a challenge. This is something cavers are intimately familiar with. Some of us actually enjoy some amount of squeeze, with the breathing techniques necessitated:

Not friction. Pressure. Your skin and body is almost entirely water and thus non-compressable. Your air spaces in the lungs and sinus become equalized with ambient pressure from the regulator. An unpressurized drysuit gets squeezed down with the full pressure of the water at depth.

 

[crofrog]

Watch this. Different suit, same physics.

Not the same physics because there is no hard hat. Everything in the drysuit is flexible.


You shouldn’t dive without equalizing your drysuit obviously. It’ll be uncomfortable and it’ll start getting hard to breath and move but as stated above. It’s from the friction more than anything else.

 

[Pumpkin King]

Did anyone ever try getting into one of these

It’s a thing. Don’t yuck somebody else’s yum.

 

[quick_dry]

Not friction. Pressure. Your skin and body is almost entirely water and thus non-compressable. Your air spaces in the lungs and sinus become equalized with ambient pressure from the regulator. An unpressurized drysuit gets squeezed down with the full pressure of the water at depth.

I'm struggling with this as a lot of the explanations seem more dogmatic than making any sense of what is actually happening.

So we have the "a wetsuit lets water in and water can't be compressed but air can" explanation, which isn't a good explanation IMO. Dive inside a stretchy waterproof morphsuit and you'd be fine regardless of equalisation air injected or not.

Am I off base to say that a drysuit squeeze is not due to the water being able to press more directly on the body, i.e. water -> suit -> skin, versus westsuit which is water->suit->trapped water->skin, it is because you drysuits are fairly unstretchable fabric and the folds will press together, effectively 'pulling' the suit closer against the body, as the folds are pressed more and more tightly together by the external water pressure they stick together more and are even harder to move/pry apart when the suit must stretch as your breath. When the air is added, it expands those folds a little, which effectively 'lengthens' that part of the suit.

think of a sweater someone is wearing, grab the middle of the back of it, and scrunch it together, keep pulling it more and more scrunched together. It'll feel 'tight'. Adding air, or any fluid into that space would lessen the 'scrunch' and make the suit/sweater 'longer' (effectively) in that direction.

Consider a drysuit with an internal teflon/coating, or was generously rubbed down internally with lube so the suit might be squished together - but can now slide and not stick? what effect does an expanding chest/lung have when the fabric can slide? does that act like a stretchable fabric, 'expanding' and contracting with pressure, but not changing the internal volume between skin and fabric?

What if drysuits were stretchy fabric? like a waterproof elastane? I'm going to say that if you go diving in a waterproof morph-suit, you wouldn't feel squeeze whether you added air or water - because you could stretch it. (a little like a waterproof version of the old idea for stretchy, squeezy space suits, maintaining pressure mechanically rather than via a hard barrier to vacuum)

One the other thing, consider a suit that was sealed and filled with water to the max. if it was sealed so that no water could escape, you _wouldn't_ be able to breath, since the lungs couldn't expand as the water in the suit can't compress.

 

[davehicks]

I'm struggling with this as a lot of the explanations seem more dogmatic than making any sense of what is actually happening.

So we have the "a wetsuit lets water in and water can't be compressed but air can" explanation, which isn't a good explanation IMO. Dive inside a stretchy waterproof morphsuit and you'd be fine regardless of equalisation air injected or not.

Am I off base to say that a drysuit squeeze is not due to the water being able to press more directly on the body, i.e. water -> suit -> skin, versus westsuit which is water->suit->trapped water->skin, it is because you drysuits are fairly unstretchable fabric and the folds will press together, effectively 'pulling' the suit closer against the body, as the folds are pressed more and more tightly together by the external water pressure they stick together more and are even harder to move/pry apart when the suit must stretch as your breath. When the air is added, it expands those folds a little, which effectively 'lengthens' that part of the suit.

think of a sweater someone is wearing, grab the middle of the back of it, and scrunch it together, keep pulling it more and more scrunched together. It'll feel 'tight'. Adding air, or any fluid into that space would lessen the 'scrunch' and make the suit/sweater 'longer' (effectively) in that direction.

Consider a drysuit with an internal teflon/coating, or was generously rubbed down internally with lube so the suit might be squished together - but can now slide and not stick? what effect does an expanding chest/lung have when the fabric can slide? does that act like a stretchable fabric, 'expanding' and contracting with pressure, but not changing the internal volume between skin and fabric?

What if drysuits were stretchy fabric? like a waterproof elastane? I'm going to say that if you go diving in a waterproof morph-suit, you wouldn't feel squeeze whether you added air or water - because you could stretch it. (a little like a waterproof version of the old idea for stretchy, squeezy space suits, maintaining pressure mechanically rather than via a hard barrier to vacuum)

One the other thing, consider a suit that was sealed and filled with water to the max. if it was sealed so that no water could escape, you _wouldn't_ be able to breath, since the lungs couldn't expand as the water in the suit can't compress.

I don't know what a morph suit is.

Dry suits often are stretchy material such as neoprene. But they are not permeable and have seals to keep water out. They don't shrink wrap you because the airspace within is equalized with air, just like your lungs. Unless internal and external pressure is equal, in any type of suit, you are going to have a bad time.

 

[davehicks]

I don't know what a morph suit is.

Dry suits often are stretchy material such as neoprene. But they are not permeable and have seals to keep water out. They don't shrink wrap you because the airspace within is equalized with air, just like your lungs. Unless internal and external pressure is equal, in any type of suit, you are going to have a bad time.

Is a morph suit just spandex? It is permiable and not water tight. Just like a wetsuit. Pressure can equalize as ambient pressure water is on all sides of a permiable suit.

 

[NW Dive Dawg]

For some reason I am unable to view the OP's video so don't have the benefit the whole story.... Seems to me like ditching weight would / should / could have been a factor in preventing this tragedy.

On the issue of squeeze, If a drysuit was perfectly fit skin tight with no air space or undergarment between the suit and human....but still totally keeping the diver 100% dry....... would there be any squeeze at depth? I don't think so......but I also could totally be wrong.

 

[inquis]

Not friction. Pressure

Yes friction, caused by pressure. Grab your wrist hard and try to turn that arm/wrist -- it's difficult to spin. Now put lotion on the grasping hand -- it's easier to spin. Same pressure, but the friction dictates difficulty in movement.

 

[davehicks]

Yes friction, caused by pressure. Grab your wrist hard and try to turn that arm/wrist -- it's difficult to spin. Now put lotion on the grasping hand -- it's easier to spin. Same pressure, but the friction dictates difficulty in movement.

I yield to your expertise in manners involving lotion and grasping hands. Tell us all more about how to generate that friction!