Because water is neutrally buoyant 
wetsuits and wool
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"The sodden sheep's wool has lanolin on it, which provides the water-proofing. My Army blanket sure weighs more when it is wet than when it is dry."
Well, it weighs more in the air when it's wet than it does dry because you're weighing the water. Jonnythan is right that the water is neutrally buoyant. But the weight of a wet woolen blanket out of the water doesn't tell you anything about its buoyancy, which depends - as with everything else - on the weight of the thing itself (without the water) and the weight of the water it displaces.
Well, it weighs more in the air when it's wet than it does dry because you're weighing the water. Jonnythan is right that the water is neutrally buoyant. But the weight of a wet woolen blanket out of the water doesn't tell you anything about its buoyancy, which depends - as with everything else - on the weight of the thing itself (without the water) and the weight of the water it displaces.
jonnythan:The fibers are semi-hollow, but not watertight. When the wool is saturated, there are no trapped air spaces. If there were we wouldn't need closed-cell neoprene
There's no volume loss. The wool soaks up the surrounding water, and you have a totally waterlogged space of a wool and water mixture (with no air) between yourself and the actual insualation (the air spaces in the neoprene). The wool fibers do absolutely nothing to insulate when they're soaking wet. It would provide the same amount of underwater insulation as a cotton layer... zero. Out of the water, the wool will dry significantly faster, and should add slightly to surface insulation, but underwater it's highly counterproductive.
Been having a think about this, and I think wool probably can make a suit warmer.
The thermal conductivity of wool is considerably lower than that of neoprene (approximately a factor of 10), so if we were talking of a dry suit then wool would clearly help.
In the case of a wet suit, it depends. If the suit is a semi dry type siut, then very little water will actually get in, so most of the air that was trapped in/around the wool will surely still be there. So the above thermal conductivity argument is still partly true.
With a thin leaky wetsuit, I guess the air will all escape. But why would you put wool inside a warm water suit anyway?
"With a thin leaky wetsuit, I guess the air will all escape. But why would you put wool inside a warm water suit anyway?"
I can only think of a few real advantages, and don't know how much weight I would attach to them, not having tried wool inside neoprene except in my boots - it goes on very easily compared to neoprene when it's dry, it feels more comfortable against the skin than neoprene (I think), and some people react badly to neoprene on the skin (allergies), and if there's enough wool in there to matter, I think a layer of wool probably would slow the movement of water inside the suit better than smooth neoprene.
I can only think of a few real advantages, and don't know how much weight I would attach to them, not having tried wool inside neoprene except in my boots - it goes on very easily compared to neoprene when it's dry, it feels more comfortable against the skin than neoprene (I think), and some people react badly to neoprene on the skin (allergies), and if there's enough wool in there to matter, I think a layer of wool probably would slow the movement of water inside the suit better than smooth neoprene.
What's the thermal conductivity of neoprene compared to, say....... water?MacHeath:
jviehe:
I have been diving for about 23 years, let me give you my view on this subject, the purpose of a wet suit as we all know is to trap a thin layer of water between your skin and the suit it self. your body heat, heats the water and you keep warm for the duration of your dive.
What I find is that unless you have a custom made wet suit you rarely get an ideal fit.
so in as far as using a wool sweater, the puropse of this would be to keep the water trapped in your wet suit from moving around and holding the heated water in place and not being flused out as you swim along, if your wetsuit is slightly to big for you, as you swim along the water inside your wetsuit is flushed out leaving you with cold water inside your suit.
You can use anything to achieve the same thing as the wool sweater, i use any shirt or tee shirt i can find, as long as the wet suit isn't to big they work.
try using different types of shirts and see if one works any better than the other.
christopher520
This is not at all true.Christopher520:
http://www.scubadiving.com/gear/exposure_protection/wetsuit_hype:_10_big_lies/0/
jonnythan:What's the thermal conductivity of neoprene compared to, say....... water?
Similar actually:
Neoprene 0.15-0.45 W/m.K
Water (273k) 0.56 W/m.K
Wool 0.03-0.04 W/m.K
Air 0.025 W/m.K
Obviously with water/air there is convection to consider too.
So to sum up:
Dry wool, much better than Neoprene
Wet wool, depends how wet, maybe better than neoprene.
Mm hmm... and how about *foam* neoprene?MacHeath:
Plain neoprene is just plain rubber. The black rubber gloves at Home Depot are neoprene.
Air is the good insulator. The air trapped *in* the neoprene.
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