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Newbie questions regarding how wetsuits work

Discussion in 'Exposure Suits' started by Cosmographer, Apr 12, 2012.

  1. TSandM

    TSandM Missed and loved by many. Rest in Peace ScubaBoard Supporter

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    It isn't even the rubber in the neoprene that keeps you warm -- it's the gas bubbles trapped in it. The useful nature of neoprene is that it traps bubbles in an insoluble and impermeable substrate, so that you can immerse the stuff without the gas being displaced by water. The thicker the neoprene, the more insulating capacity it has.

    The ideal wetsuit admits as little water as possible, just enough to fill the air spaces, as described. It then minimizes the exchange of that water with the water in which you are diving, so that you expend only the heat you have to to warm that first bit, and don't continue to lose heat to water that then is lost to the ocean.

    A perfect neoprene wetsuit is a neoprene dry suit ( :) ), but then you do need to add a little air to avoid squeeze. Neoprene dry suits are very warm in shallow water.
     
    300bar and nimoh like this.
  2. nimoh

    nimoh Public Safety Diver

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    great description
     
  3. rhwestfall

    rhwestfall Woof! ScubaBoard Sponsor

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    Interesting side story - I am actually working with a vendor for a custom WS right now. They are actually suggesting I go to a thinner (5mm vs. 7mm) suite due to the material (stuff mentioned above), because of the insulating capability.....
     
  4. Lorenzoid

    Lorenzoid idling in neutral buoyancy ScubaBoard Supporter

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    Good explanation. I get it now. So the only reason that water permeability is important is for the pressure equalization aspect, not for any insulating effect. My attempt to sum up my understanding: Neoprene is probably the best material available short of a drysuit because it is semi-permeable or semi-porous but not TOO porous, as a very porous material would not insulate well, and a completely impermeable or non-porous material would need to have the characteristics of a drysuit--that is, the ability to add and vent air. I also suppose neoprene foam might have some sort of cell structure that makes it more suitable than a completely open-cell insulating foam material or completely closed-cell insulating foam material--that is, some mix of closed cells that provide insulation (yet compress with depth) and open cells that let water through.
     
  5. Crush

    Crush Solo Diver

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    A good description, except that wetsuits are made of neoprene which is impermeable, or effectively impermeable on the timescale relevant for a dive. The water will enter your wetsuit at the wrists, ankles, and neck.
     
  6. go-scuba-dive

    go-scuba-dive Angel Fish

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    Yup. It's the water that warms you, which is why it's called a wetsuit. The more layers you add on, the more insulation there is, and as a result the warmer you are. Dry suits are sealed at the neck, arms, and legs not allowing any water to get in.
     
  7. dfx

    dfx Regular of the Pub

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    :facepalm:

    The water isn't warming you, you are warming up the water!
     
    Last edited: Apr 13, 2012
  8. acrofrag

    acrofrag Angel Fish

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    Curious to know the difference between air compressing to the pressure of the water around it vs. water at the same pressure. Why would air cause bruising, but replacing it with a "incompressible fluid" (it is, just not for our purposes here) wouldn't?
     
  9. dfx

    dfx Regular of the Pub

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    Boyle's law dictates that a gas under double the pressure shrinks to half its volume. An air bubble trapped in your wetsuit thus has half its volume at 10 meters depth than it had at the surface. Since none of the surrounding materials (wetsuit, your body, water) shrink in the same manner (they're all incompressible), that shrinking air bubble can produce a suction cup effect under the right circumstances, for example at a fold in your suit.
     
  10. Lorenzoid

    Lorenzoid idling in neutral buoyancy ScubaBoard Supporter

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    Ugh--I thought I understood, but now I'm not so sure again. If neoprene is impermeable to water, then I go back to my original question: Is there not another impermeable material that's a better insulator than neoprene? You could line an impermeable exterior with just about anything.

    Also, what about so-called "semi-dry" suits? I thought the whole point of those was that they had seals at the wrists, ankles and neck that inhibited entry of water? That would only make sense if the suit allowed water to enter through some other means--like saturating through the walls of the suit. If a semi-dry suit is effectively sealed, and there is (inevitably?) air trapped inside, then you'd have the same issue as with a dry suit. This is another reason why I was under the (mistaken?) impression that neoprene is semi-porous.
     

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