Data on Neoprene compression at depths?

[FFMDiver]

Does anyone know of any data illustrating how 7mm compresses at depth? For example:

20'=5mm
30'=4mm
etc.

Thank you.

 

[redacted]

No data but a little mathmatical analysis may provide an answer. Compression should effect the thickness of the bubbles in the neoprene such that a bubble of radius 1 at the surface will have radius .8 at 2 atm (half the volume), .69 at 3atm (1/3 the volume), .63 at 4 atm and .58 at 5 atm. Assuming the thickness of your 7mm wetsuit is about 1mm of rubber (uneffected by compression) and 6mm of N bubbles, the thickness at 99 ft (4 atm) should be 1mm of rubber plus .63 times 6mm of gas bubbles for a total of about 4.8 mm.

 

[DA Aquamaster]

Awap's calculation is pretty cool and is the best model for predicting neoprene compression that I have seen yet. The variable here would be how much gas and how much rubber is present in a particular batch of neoprene and that is a factor to consider as neoprene varies a lot in both quality and physical characteristics.

I did see a study of both stretch and compression in neoprene several years ago and it identified several different grades of neoprene used by wet suit manufacturers and they all varied in compression, stretch and general durability. In general the stretchiest ones tended to compress more and not hold up as well over time, showing more permanent compression over a given number of dives. But, there were some noteable exceptions of softer and stretchier neoprene that also held up well in terms of compression resistance.

 

[kidspot]

http://www.wetwear.com/chambertest.htm has some info on neoprene compression, comparing theirs to "the competition" - interesting reading.

Aloha, Tim

 

[FFMDiver]

No data but a little mathmatical analysis may provide an answer. Compression should effect the thickness of the bubbles in the neoprene such that a bubble of radius 1 at the surface will have radius .8 at 2 atm (half the volume), .69 at 3atm (1/3 the volume), .63 at 4 atm and .58 at 5 atm. Assuming the thickness of your 7mm wetsuit is about 1mm of rubber (uneffected by compression) and 6mm of N bubbles, the thickness at 99 ft (4 atm) should be 1mm of rubber plus .63 times 6mm of gas bubbles for a total of about 4.8 mm.

This makes sense. I'm thinking for recreational diving limits, a neoprene drysuit might not compress to tri-lam levels and might not loose an extreme amount of thermal capacity as I have heard on occasion. Thank you.

 

[Don Burke]

I took some measurements with a bag of neoprene gear and some dive weights in a pool.

The buoyancy change tracked a bit off the reciprocal of total pressure. It was about one pound more positive than it should have been.

I would expect the thickness to track thicker than the reciprocal of total pressure by a considerable margin since the neoprene itself is not significantly compressible.

 

[DA Aquamaster]

This makes sense. I'm thinking for recreational diving limits, a neoprene drysuit might not compress to tri-lam levels and might not loose an extreme amount of thermal capacity as I have heard on occasion. Thank you.

Your thinking is accurate.

I used to believe the DUI inspired indoctrination that neoprene drysuits got very cold with depth due to compression. After about 15 years of trilam drysuit diving I switched to a 5/7mm neoprene drysuit and changed my opinion. I use it on deco dives to depths of 150-160 ft with bottom temps in the 30's and low 40's and run times of 45-60 minutes. I use a polypropolene sweat shirt and sweat pants for insulation and stay warmer than I did on the same dives in my trilam with 400g thinsulate underwear. Even with dry gloves on my trilam, my hands would get cold due to my core temp falling. With a neoprene drysuit I am using 5mm wet gloves and my hands stay warmer.

I am not real concerned why the neoprene drysuit is warmer, I am just happy it is. It also swims better in the water and is much more comfortable in termsof squeeze than a trilam and can be dove with less air in it than with a trilam. Neoprene suits have been much aligned by the trilam crowd and are badly under rated both in terms of effectiveness and value.

 

[PerroneFord]

DA,

What tradeoffs do you see going with the Neoprene drysuit? I am very interested in diving dry in the near future and this would be helpful to me. I hear they can be quite heavy when wet. Do you see more or less issues with leaks? Are they as hard to don as neoprene wetsuits? I have very little familiarity with them.

Thanks for any info.

 

[matt_unique]

Your thinking is accurate.

I used to believe the DUI inspired indoctrination that neoprene drysuits got very cold with depth due to compression. After about 15 years of trilam drysuit diving I switched to a 5/7mm neoprene drysuit and changed my opinion. I use it on deco dives to depths of 150-160 ft with bottom temps in the 30's and low 40's and run times of 45-60 minutes. I use a polypropolene sweat shirt and sweat pants for insulation and stay warmer than I did on the same dives in my trilam with 400g thinsulate underwear. Even with dry gloves on my trilam, my hands would get cold due to my core temp falling. With a neoprene drysuit I am using 5mm wet gloves and my hands stay warmer.

I am not real concerned why the neoprene drysuit is warmer, I am just happy it is. It also swims better in the water and is much more comfortable in termsof squeeze than a trilam and can be dove with less air in it than with a trilam. Neoprene suits have been much aligned by the trilam crowd and are badly under rated both in terms of effectiveness and value.

100% ditto for my experience. I dive similar deco profiles (160' max) and I am not colder than my buddies in $2000 trilam suits. I get $2000 worth of warmth for 1/4 the cost

 

[moneysavr]

Hi on the Neoprene Dry suit,I own a Bare Neo 7MM and dive depths out of rec at 165' in 3oish water and stay nice and warm in just some cheap under wear Wallmart Lycra/Poly,the suit swim's nice and I like the idea that I use the same lead in my 7mm wet suit,
The bad thing on neo is the lead you need,other wise for cold water use,deep dives cost they are the way to go! Hard to ruin one,and the feel is not like diving a palstic bag.

Perrone: In Florida all you need is a shell suit,and cheap Lycra/Poly Underware for fluff