wetsuit vs cold air

[GrumpyOldGuy]

Awhile back, my gf asked me, if wetsuits work so well in the water

Wet suits don't really work all that well in the water. A dry wetsuit is a great insulator until you get wet (dive in or sweat). If you moving and generating heat, they are tolerable for a period of time. Once you get out on the SI, you are no longer expending as much energy the the cold catches up to you.

I believe you will find 3 methods of heat transfer going on.

Evaporation: This doesn't do anything under water but surface side it may cool you. Since the suit is a sponge with a constant supply of water (and or pee) to evaporate it is significant and becomes dominate.

Convection: It does a great job here just as any semi-air tight garment would, its a toss up here.

Conduction: The wetsuit neoprene provides a much better barrier than water for heat conduction. But in turn air (or the loft in a garment) is a much better barrier to heat loss than wet neoprene.

 

[Damselfish]

As far as the as the old wive's tale about the "thin layer of water" thing - it's true you will warm up any water in the suit, and any water that continues to get into the suit. But warming any part of the ocean isn't productive when you're trying to stay warm - that's why they make "semi dry suits" that are warmer, where the idea is to prevent water getting in as much as possible.

 

[DCBC]

Wet Suits do provide good insulation outside of the water. They are excellent in stopping wind, however a problem can occur with overheating (which is difficult to regulate).

As a matter of interest, I designed the Rescue Swimmer training program for Canada Coast Guard in 1992. One scenario that we had to address, was how to deliver a Rescue Swimmer to the shoreline of the NE coast of Canada (through high winds/waves) and for him (and those being rescued) to survive until they could be evacuated by air (assuming evacuation to sea was impossible or too risky). The RS wore a dry-suit during prolonged exposure on land and 'sleeping bags' were provided for the victims that were made of neoprene. Testing showed that these bags would provide insulation from snow and moisture, provide cushioning and capture body warmth. The bag could be unzipped to prevent overheating. Obviously it's not the idea solution for all situations, but considering it's durability and waterproofness, it can be a good choice in a survival situation.

Awhile back, my gf asked me, if wetsuits work so well in the water, then why don't people using them when dealing with the cold outside the water? Needless to say, I didn't have a good answer for her. Yesterday, I got some first hand experience of being perfectly comfortable in the water with my wetsuit, but 10 minutes out of the water, and I was cold. I pulled my wetsuit down to my waist, dried off, and put my jacket on, and in a few short minutes, I was comfortable again.

I think I understand the concept of a wetsuit i.e. to create a thin layer of water between the body and suit, and once that thin layer is heats up, heat loss from the body will be minimized.

So my question is, why won't this same concept work in a dry environment
i.e. once you get out of the water? I suspect evaporation is at play here but I have a well constructed suit with a good seal, in other words, i don't feel like my suit is allowing for evaporation to be a factor. Does anybody want to take a stab at the physics going on here?

As always, TIA

 

[Hatul]

A dry wetsuit does work topside, it's just not comfortable like regular clothes. Clothes don't squeeze you like a wetsuit and they're easy to doff or don.

 

[DA Aquamaster]

As far as the as the old wive's tale about the "thin layer of water" thing - it's true you will warm up any water in the suit, and any water that continues to get into the suit. But warming any part of the ocean isn't productive when you're trying to stay warm - that's why they make "semi dry suits" that are warmer, where the idea is to prevent water getting in as much as possible.

Sort of but not exactly.

A good fitting wet suit can be quite warm indeed as with a good fit, the suit does not "pump" water in and out the openings when you move. However, if the suit fits badly, especially if it is loose in the joints (the shoulder/armpit area is the biggest problem), then the voids between you and the suit become powerful pumps that will cause water to flow in and out of the suit, and as you point out, that's all ocean you now have to warm.

The semi-dry was developed to improve the seal at the wrists, ankles and neck better to reduce the water flow from a slightly less than great fitting suit, and that change meant that stores could stock fewer sizes as a great fit was no longer needed. It also meant that buying a suit online or through the mail was also now a slightly more viable option.

However, the same problem still exists - if you have a semi-dry that fits too badly, it will still pump water past the seals and/or through the zipper and it won't be as warm as a good fitting wet suit.

On the other hand, I've had a great fitting semi-dry in the past - one that also had fold over skin in neoprene wrist and neck seals and a dry suit zipper across the back - and it was common to end hour or two long dives and still have parts of the inside of the suit still be dry. It had almost no water flow. But the reality is most semi-dry suits are not that dry.

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With that said, even with a neoprene or crushed neoprene drysuit, or for that matter a Fusion drysuit with a neoprene tech skin or bullet skin, you will still have the evaporative cooling swamp cooler effect between dives and you'll either want to cover the suit or take it off if the air temps and or wind chill index is low enough.