Wet Suit Logic
- I dive a 3mm wetsuit in temperatures down to 39 degrees F (and lower) at Fortune Pond. I've been doing it for 5-6 years now and have not died of hypothermia. Usually they are 30-40 minute dives but I have done a few for nearly an hour when we did the last half of the dives at shallower and warmer depths. I've tried thicker suits and other combinations and have formed some opinions I'd like to share.
- Suit Thickness and Warmth - While it is true that thicker wetsuits are warmer at the surface, the advantage becomes less and less the deeper you go. For example, a 5mm suit is compressed to 2.5mm at 33 feet. A 3mm compresses to 1.5mm... So there's only 1mm difference. And the difference becomes less and less the deeper you go. There's been some discussion about how the original "Rubbatex" wetsuits were less compressible than modern suits. I believe compression isn't the only factor and modern suits have several advances that make them better than Rubbatex.
- Other Warmth Factors... Modern suits fit better, so there's less cold water flushing in and out. Modern suits have advanced thermal linings that insulate via the lining properties rather than the suit thickness. Modern suits can be "semi-dry"... I have BARE brand wetsuits that won't drain water out the ankles unless I pull the cuff open to let the water out. I remember one of these suits still had a dry spot inside after a dive.
- Targeted Warmth Strategy... I wear a 3mm hooded vest under my 3mm suit. This gives me 6mm of thickness over my core. But remember this compresses to only 3mm at 33 feet. I think the added thickness contributes, but I also think that the hooded vest seals the hood/suit joint better than just a hood and restricts water from flushing in and out. I've tried wearing the hooded vest on the outside and it didn't help my warmth at all... So, added thickness alone without restricting cold water flush isn't much help.
- After Dive Warm-Up Strategy... I used to unzip and pull off my wetsuit top but leave the pants on between dives. I noticed that I felt coldest AFTER a dive than during the dive. I read an article about the wet suit actually becoming a refrigerant due to the evaporation of water... The article said to get the wet suit off ASAP, dry off and put dry clothes on. Wow, what a difference that made in warming up between dives.
- Why Do I Prefer a Thin Suit? Mainly because there's less influence of suit compression on buoyancy. I can wear less weights. I rarely put any air into a BCD (when I dive one). And, a thin suit is less confining.