wAdditional Information 2
Gaiters, etc have been mentioned in posts. So a little extra information.
Those using drysuits for the first time are often concerned with inversion. Which is a situation where air migrates to the feet and you end up upside down, going towards the surface.
Firstly let me say this is a very very rare occurrence even with new drysuit diver.
For newer divers it is often a concern because part of the drysuit training involves learning how to roll out of an inversion. So a bit of time is spent on this exercise. In addition, instructors rather cruelly enjoy teaching this exercise. Which includes tipping you upside and adding air to the drysuit to force an inversion, letting you go, and letting you roll out.
It is also taught in shallow water, so there is little room (depth/time) to achieve a roll out.
Also, in a drysuit you can actually feel the air moving around, especially if it pools in one place, ankles/feet or arms.
When you are new to drysuit diving you are hypersensitive. Rather like you where breathing with a regulator when you first started.
Experienced drysuit divers actually often force air to there feet to get a horizontal position in the water, especially on decompression stops where they want to be horizontal. Bending at the knee with air in the feet/ankle helps keep you horizontal with no effort.
Because of the concern over air in the feet, there are a number of solutions.
1. Gaiter
2. Ankle weights
3. Fit
4. Boots.
In reverse order.
The newer suits with 'rock boots' (see previous email), and neoprene socks. The rock boots should fit snuggly (like a normal pair of shoes (allowing for all the thermal socks) . By there nature, they stop air entering the FEET, air can still pool around the ankle and lower leg.
This does mean that even if the suit is a bit long in the leg, or the foot (sock) of the suit a little large. The boot will keep your foot in the sock, the sock in the boot, and the fin on your foot.
Poor fit - suits that are too large are hardwork. Especially if the foot is too big, and the leg too long. There does need to be sufficient room to have a full range of movement, crouch down bend at the waist, reach back behind your head etc. This need to be possible with ALL your thermal layers on.
Suit legs that are too long, and boots that are too big increase the risk of the boot being forced off the foot during an inversion. Although amusing for spectators, inconvenient and an annoyance for the diver.
If the boot is a little big WEAR EXTRA SOCKS! 1. it stops cold feet
. 2. It fills the empty air space in the boot/foot.
Gaiters. In the UK at least very seldom seen. They are strapped on to the lower leg, and compress the excess material, stopping air migrating into the lower leg and pooling here.
Ankle weights. Notably, a lot of women wear ankle weights. One of the female instructors who taught me many moons ago used to say women have floaty ankles, men don't. I do know that most men can remove ankle weights after a little time and experience with no adverse effect. It seems that for a lot of women this is far more of a problem. I leave that for the women to comment on.
THERMAL LAYERS
Dependent on the suit material, the water temperature, the wind chill, and the individual, the layering will differ.
There are many diving manufacturers making specific clothing to be worn under drysuits. Some people make do with a track suit!
The ideals are materials that wick sweat away from the body, that 'breath'. It is often advantageous to have layers. It is as dangerous to be too hot as too cold in a drysuit. With layering you can adjust what is worn to suit the time of year/environment.
Some materials are better at keeping you warm in the event of a suit flood. For many they would just get out of the water and get changed. For some, the option of leaving the water may not be viable (long decompression penalties, etc).
CVD
Constant Volume Dumps.
Most modern drysuits are fitted with CVD's. A sprung valve that is adjustable, and positioned on the left shoulder/arm.
The valve works by having a spring as you screw the valve down (closed) more pressure (force) is needed to open the valve. As air in the suit expands - on ascent - it forces open the valve and bleeds air out automatically.
Correctly adjusted, the diver never consciously vents air from the suit, the valve does this automatically as you ascend.
The position of the CVD should be high on the shoulder - air rises to the highest point, you want it to rise to the valve, not have a pocket of air in the top of your shoulder/arm and the valve below it!!!
A CVD can be over ridden. If you press on it, it will open, if you screw it down you force it closed - although by pressing on it you will still open it.
Tips and tricks.
Some materials may clog the valve, or at least restrict its effectiveness. Especially clothing that is not design for drysuits.
Fluffy bulky clothing as an example. Cut the foot off a sock, pull it up your arm so it sits below the valve. This keeps any padding or loose material out of the valve.
Roll right. On ascent, if you drop your right shoulder, and lift your left, you will force more air to the valve, and dump more air. This avoids having to manually push the valve and dump. Most drysuit divers do this subconsciously after a time. Especially if they are horizontal in the water.
Being cruel to your drysuit buddy. If you stay on high his/her left, and make him/her twist left to see you, they will go through gallons of air, keep crashing into the bottom and generally start swearing at you, if they figure out what is happening. If you look closely, every time they twist to look at you, you will see them venting air from their CVD.
ALWAYS - ALWAYS double check that the zip is fully closed, even if your nearest and dearest closed your zip. It will avoid a divorce or at worst a frosty drive home. A zip open half an inch lets a lot of water in!
Gareth