Newbie questions regarding how wetsuits work

[Cosmographer]

So back in the OW course, they taught that wetsuits work by creating a layer of warmed water between the body and the wetsuit. If this is correct, how does wearing an extra vest over a wetsuit help?

Related to that question, if a full 3mm or 5mm wetsuit is appropriate for a given location, can a 7mm shortie with rashguards do the trick just as well? (One's limbs might get a bit cold, but it seems like that would be a minor inconvenience at most as long as your core is warm).

 

[tstormdiver]

After the water is warmed by the body, the Neoprene foam holds the heated water in & insulates it, kind of like a Coozie holds the cold in, in a cold drink. By adding layers, you add more foam insulation to hold the heat in more efficiently.

For your second question, if the limbs are exposed, it will allow for loss of body heat. That may or may not make you cold, but then, full coverage may make you hot. As for how well it would work, for some, it would work well, for some, not so well,.... it is very individual. I will personally even wear at least a beanie style hood to keep my head warm & myself more comfortable. I try to hold as much heat in as I can. Even though I dive cold waters, I'm more of a warm water wus.

 

[rhwestfall]

despite that teaching, the less intrusion of water, the better.... If water can get in, it can get out. That takes heat from the body. Keep in mind, the body is 98.6. Any water temperature below that is taking heat away from your body. Your systems have mechanisms to address this, but well fitting insulation is best (aside from going dry).

 

[johnboywalton]

You might be able to find a system that works where you have that 7mm shortie, a hood, gloves, boots and rashies for the limbs, but unless you absolutely need to find a set-up that maximizes flexibility and agility, why would you bother? I'd liken it to wearing a parka-thick vest over just base-layer clothing for something like a high altitude ski trip or a trip out on a glacier.

There are two things to keep in mind about wetsuits. One is that the ability of the suit to restrict water is just as important as how thick the neoprene fabric is. A thick, loose suit with no seals around the wrists, ankles and neck is about the same thing as wearing a lighter, tighter suit with better seals. If the water doesn't stay in your suit, it can't warm up and you lose heat.

Also, neoprene is much less buoyant at depth than it is on the surface. If you pile on thick neoprene when you don't really need to, then the weights that make you neutral on the surface are a real drag on the bottom, making buoyancy control more of a pain.

Or at least that's my experience comparing thick, loose suits to somewhat thinner, tighter suits...

 

[dfx]

It's a common misconception that the layer of water between your body and your wetsuit helps keeping you warm. It's the neoprene that really does it. Neoprene provides thermal insulation, so more neoprene = better insulation. Water hardly provides any insulation. The warm water story is merely explanation for why you're not getting cold despite being wet.

 

[Lorenzoid]

It's a common misconception that the layer of water between your body and your wetsuit helps keeping you warm. It's the neoprene that really does it. Neoprene provides thermal insulation, so more neoprene = better insulation. Water hardly provides any insulation. The warm water story is merely explanation for why you're not getting cold despite being wet.

I've been persuaded by the "water story," too. That's certainly how it was explained to me in OW class.

If the "water story" is false and it's only the insulating ability that matters, then why neoprene as a suit material in the first place? If the permeability characteristics of neoprene--that it's semi-permeable to water and tends to hold the water in once it's warmed by the body--are NOT what in fact keeps the wearer warm, but rather it's only the insulating characteristic of neoprene that keeps the wearer warm, then surely there must be a better insulating material than neoprene?

 

[rhwestfall]

aside from fully waterproof materials (aka - the dry suit with separate insulation), there really isn't... also there are various types of neoprene, and some really aren't so fantastic... keep in mind there are neoprene dry suites ... Bottom line - fit is the most important factor

 

[dfx]

I've been persuaded by the "water story," too. That's certainly how it was explained to me in OW class.

If the "water story" is false and it's only the insulating ability that matters, then why neoprene as a suit material in the first place? If the permeability characteristics of neoprene--that it's semi-permeable to water and tends to hold the water in once it's warmed by the body--are NOT what in fact keeps the wearer warm, but rather it's only the insulating characteristic of neoprene that keeps the wearer warm, then surely there must be a better insulating material than neoprene?

The ability to keep the water in place and keep it from circulating is a very important factor. But that's not because a layer of warm water keeps you warm, it's because colder water getting in would make you colder and would defeat the purpose of an insulating suit. If you had a suit with only the ability to keep water from circulating but without any insulating properties, you would be freezing to death. On the other hand, if you had a suit with the same insulating properties as a wetsuit, but one that doesn't provide a layer of water (but instead, let's say, keeps you dry), you would be able to keep even warmer. Guess why they make neoprene drysuits?

 

[Crush]

All the responses so far have been correct - it is the neoprene that keeps you warm, not the water. It is also true that you want to minimize the exchange of body-warmed water with colder, ambient water. A few things so far have not been mentioned:

1. Not all neoprene is created equal. I believe that Thal regularly extols the virtues of Rubatex G-231 neoprene as a suit material. Try searching this string: site:scubaboard.com rubatex neoprene ;
2. Water entering your wetsuit is, in fact, desired. It is a design compromise - you either need to be able to add air to your suit as you descend to offset the growing external pressure of the water (this is called a drysuit) or you need to fill the air-pockets in your suit with an incompressible fluid. A perfectly air-tight wetsuit would continue to compress as you descend, possibly leading to bruising from suit "squeeze." Pouring warm water into a wetsuit before a dive is a good way to get rid of air pockets.

 

[johnboywalton]

Yes, it's true - the water itself isn't a great insulant. The point is to restrict the flow of water in and out, since if it flows relatively freely, the water carries heat away from you. That's why I always think of tighter fit and better seals before I think of getting thicker.

@ dfx - I've heard that some guys who are literally in freezing water use special tanks with exotic gases (argon?), which have better insulating properties than ordinary air.

@ Crush - YES. You are absolutely right, and not all neoprene is created equal. Of course, every company calls their neoprene this and that, which is why it's important to see if there is anything truly special about it. Do your homework, in other words.

Another often overlooked issue is how the seams in the wetsuit are put together - are they just stitched, or stitched and glued? How are they stitched? Etc.

The colder things get, the more these things matter. If you are in 75 F water, not so much. In 55 F? You can't get by without every last thing being top notch.