Wetsuit compression

[dv]

Hey all,

I am currently in week 3 of my OW course and had a question related to wetsuit compression/depth and it's effect on buoyancy.

I will be diving in primarily colder waters, and so my exposure suit will likely be a 7mm full suit, and another 7mm on my torso.

Will the wetsuit compress the most during the first 33 ft and if so, does that mean my positive buoyancy (from the wetsuit) is halved by the time I reach 33 ft?

Just wanted to understand the physics of it so I know when to be adding to my BCD on the way down.

Thanks!

 

[Thalassamania]

Different rubbers have different compression coefficients. The stretchier the rubber the more it will compress for a given depth. In any case it will not compress as though it were air (e.g., 1/2 at 33 feet).

 

[Ste Wart]

Without wanting sound to much like Mister Miyagi, you will feel it when you need to put air in your BCD.
If you're properly weighted once you empty your BCD you should need to exhale to leave the surface. At first your descent should be slow and controlled, once you start to feel any acceleration then it is time to start adding air to the BCD.
If you unsure as to whether you are neutral, pause, stop finning and see if you are rising and falling on your breath. If you are then you are neutral. This the case for all wetsuits and neoprene drysuits. You don't need to think about what depth you should be adding just feel the descent speed increasing.

Hope this helps.

 

[fire_diver]

Your wetsuit will see the highest percentage of change in compression in the top 33 feet. But the deeper you go, the more it will compress. If you are adding #20 to offset bouyancy at the surface (just a random number there), your suit could lose up to 75% of bouyancy by 100 feet, which means you are now 15 pounds heavy (plus extra air you havent breathed from the tank). Plus, you just lost that much insulation properties.

Of course everything is dependant on brand and age of suit since different material compresses at different rates and older suits can become permantly compressed to some degree.

 

[Garrobo]

Wow, 14mm of neoprene. You'll feel like the Michilen man.

 

[--tom--]

& with the compression of your wetsuit at depth, if you wear a weight belt, you may want to cinch it a bit tighter when you are at depth.

 

[j yaeger]

Wow, 14mm of neoprene. You'll feel like the Michilen man.

nah...you get used to it!!!!!
you feel actually a lot more streamlined than in a shell trilam
the water temp is at 33* f right now
14 mm on chest and torso is a warm fuzzy!
have fun!
yaeg

 

[Thalassamania]

Wow, 14mm of neoprene. You'll feel like the Michilen man.

Our suits used to be 3/8" jacket and farmer john, that's about 19mm on the torso ... no big deal.

& with the compression of your wetsuit at depth, if you wear a weight belt, you may want to cinch it a bit tighter when you are at depth.

Rubber weight-belts solve the problem nicely.

nah...you get used to it!!!!!
you feel actually a lot more streamlined than in a shell trilam
the water temp is at 33* f right now
14 mm on chest and torso is a warm fuzzy!
have fun!
yaeg

19mm is even more comfortable, even under the arctic ice.

 

[--tom--]

Rubber weight-belts solve the problem nicely.

I knew you would say that Thal. As usual, you are correct.

However, I just don't see them offered in shops very often, & I have never seen rubber belts for students, so I was hoping the OP could dodge an additional issue during the sensory over-loaded initial dives (assuming [foolish I know] that the OP isn't wearing a weight integrated system).

 

[Thalassamania]

Ask your shop to order one from Trident.