Dry Suit Question

[elan]

I understand that wet suits compress. But open cell insulators work by creating a dead air space which is loft. These materials compress as well under the shell. Even with an air pocket there is some compression and this results in a decrease in thermal protection.

I cannot see any physical reason supporting this statement. What will make them compress ?

I asked the question because a wet suit will resist the compression better than thinsulate.

I think you are missing the point that the undergarment is not in fact being compressed so there is no compression it has to resist.

 

[DCBC]

I understand that wet suits compress. But open cell insulators work by creating a dead air space which is loft. These materials compress as well under the shell. Even with an air pocket there is some compression and this results in a decrease in thermal protection. I asked the question because a wet suit will resist the compression better than thinsulate. So far, I have found that the air pocket is not uniform throughout and so my shoulders and upper chest area is warm but as you move down my lower body is cool. This was more of a brainstorming question than anything else.

Interestingly enough this line of thinking was partially attributable to Poseidon's development of the Unisuit and their use of 1/4" neoprene. The commercial diving industry wanted better protection from a flooded suit (which would result in a massive loss of buoyancy and insulation).

Diver overheating was not a concern due to it's loose fit, which allowed gas venting to regulate body temperature. This is not possible when wearing a wet suit under a dry suit.

In deep saturation diving, diver heating becomes more complicated as a result of the Helium breathing mixture. Hot-water Dry Suits were replaced by hot-water wet suits because any gas against the body increased heat loss when compared to a warm liquid. The hot-water wet suit is preferred for this reason.

They both have their benefits, but in combination they provide more problems than solutions.

 

[Garth]

don't think i would think of wearing a wetsuit under a drysuit but the thought is interesting. seems as though those with more experience have spoken here though.

 

[OneBoatNut]

Just do things correctly. I lived in Monterey Bay and dove in 50 degree water all the time. I tried other materials and then bought a DUI 400 gram undergarment. Never looked back, not the place to act all budget like...Dive with the right equipment.
You may want to read up on what happens if you lower your core body temp - you may have some serious issues...

 

[pdelannoy]

Thanks everyone. Appreciate your responses.
PD

 

[dave4868]

Has anyone wore a 7mm wet suit under their dry suit instead of using an undergarment? I am asking about this because in the multilevel diving I do at my local lake the depth changes significantly during the dive-the dive profile is not anywhere close to horizontal. I was thinking that my 7mm might work better because of its resistance to compression and its significant insulation qualities. Just wondering?

I understand that wet suits compress. But open cell insulators work by creating a dead air space which is loft. These materials compress as well under the shell. Even with an air pocket there is some compression and this results in a decrease in thermal protection. I asked the question because a wet suit will resist the compression better than thinsulate. So far, I have found that the air pocket is not uniform throughout and so my shoulders and upper chest area is warm but as you move down my lower body is cool. This was more of a brainstorming question than anything else.

It's a great question, thanks for clarifying!

Compression of drysuit insulation, primarily in areas lower in the water column, is an important consideration.

On very long dives in cold water, I'll begin to feel the cold on the front of my insteps, knees, thighs, shoulders and chest. I know those areas will be losing more heat than other areas.

Using a more compression-resistant undergarment is a good idea, but I agree with fppf about the drawbacks of using neoprene as an undergarment. Besides, I can't picture being happy with the inevitable clammy feeling or constricted feeling of neoprene. Even if one managed to wear it over a wicking undergarment, the moist air layer would still be very close to the skin.

There are better solutions. One could use compression-resistant and very efficient material like Thinsulate. Or one could simply increase the overall amount of insulation to retain adequate loft even after compression.

Alternatively, targeting the specific cold areas will help keep weight down. Presently, I add a 4-layer fleece chest pad. For me, that makes a big improvement in warmth.

This winter, for diving in 35-degree water in my Weezle Extreme Plus, I'm thinking of making some Thinsulate pads to wear over the cold spots I mentioned. I might even replace my fleece chest pad with one made of Thinsulate to save a little weight, since my winter insulation already requires over 50 lbs of lead! :shocked2:

Really good warmth has its price....

Dave C

 

[BabyDuck]

give it a try & report back. my thought is you'll pour a pint of sweat out of your suit after, and not be happy, but i've certainly been wrong before!

 

[fppf]

Hey, if you wear your wet suit under your dry suit is it still ok to pee in the wet suit???