Sources Barsky, S., D. Long, B. Stinton. 1992. Drysuit Diving – A Guide To Diving Dry. Watersport Publishing, Inc., San Diego, California. T. Joiner (ed.). 2001. NOAA Diving Manual - Diving for Science and Technology, Fourth Edition. Best Publishing Company, Flagstaff, Arizona.
Thermal Protection Some measure of thermal protection is necessary for diving - even in warm waters – Average body temperature is 98.6°F To one degree or another, the body will lose heat in water cooler than body temperature. Hypothermia can occur in water as warm as 91 °F – Hypothermia occurs when the core body temperature is lower than 95 °F. However, A diver can become incapacitated by chilling - without ever becoming hypothermic.
Chilling Chilling: Increases fatigue Reduces dexterity Affects short-term memory and the ability to think clearly Increases air consumption (a divers metabolism increases as the body burns more calories in an effort to maintain temperature) May increase the risk of decompression sickness
Wetsuits Wetsuits are made from foam neoprene. The neoprene has thousands of closed cells containing nitrogen. These cells provide insulation. – Wetsuits work by trapping a thin layer of water next to the divers skin. This water is warmed by the diver. Wetsuits come in a variety of thicknesses – one mm up to 7mm. The thickness of the wetsuit determines its insulating capacity.
Wetsuits VS Dry Suits Wetsuits are most effective at 60°F and above - diving in water temperatures 50°F and colder usually requires a dry suit. Table 1 (next slide) indicates that the efficiency of wet suits declines at a much faster rate than that of dry suits during multiple dive days. Dry suits are the most efficient form of passive thermal protection for the diver – they can greatly increase the amount of time a diver can stay underwater. Dry suits afford greater protection against contaminants in polluted water
Table 1. Thermal Efficiency of Wetsuits vs. Dry Suits WETSUITS DRY SUITS Water Temperature 1st dive 2nd dive 3rd dive 1st dive 2nd dive 3rd dive 70°F 100% 100% 100% 100% 100% 100% 60°F 100% 90% 80% 100% 100% 100% 50°F 80% 70% 50% 100% 100% 100% 40°F 50% 25% * 100% 85% 75% 32°F * * * 100% 75% 55% Table is based upon 30-minute dives at 50 fsw, with one hour surface intervals between dives. The * indicates an exposure not recommended unless involved in a contingency situation.
Wetsuits VS Dry Suits The initial cost of a dry suit is greater than that of a wetsuit Dry suits require more maintenance Dry suits are more bulky and more buoyant, requiring more weight than wetsuits More care is required to manage buoyancy in a dry suit
Dry Suits – What Are They? One piece suits with a waterproof zipper for entering the suit, attached boots, and seals at the divers wrists and neck. Water does not enter the suit. Undergarments are worn under the suit for insulation. The type and amount of undergarments worn determine the level of insulation. Suits have inflator valves – generally located on the chest - for putting air into the suit. They also have exhaust valves – generally located on the upper left arm – for venting air from the suit.
Dry Suits – 2 Entry Styles Shoulder entry suit – Zipper for entry located on back. You must have assistance to get in suit.
Dry Suits – 2 Entry Styles Self-donning suit – Zipper for entry is located across front of suit, So assistance entering suit is not necessary. However, these suits are generally more expensive than shoulder entry suits
Dry Suit Types Foam neoprene (compressed neoprene) – The same material wetsuits are made of – Advantages The material stretches well, and can be tailored to fit the body closely. Has good insulating properties –may require less or even no undergarments –beneficial in the event of a leak The only type of dry suit that is inherently buoyant. Most inexpensive type of suit.
Dry Suit Types Foam neoprene – Disadvantages Loses buoyancy and insulation value as depth increases Tends to develop leaks over time as cracks develop in the bubble layers and water migrates through the material May be difficult to patch and repair May not last as long as other types of dry suits
Foam neoprene dry suits (note inflator valve on chest and exhaust valve on upper left arm)
Dry Suit Types Crushed neoprene – Advantages Very tough and flexible –Can be tailored into a suit of outstanding fit Good for swimming High insulation value Long lasting
Dry Suit Types Crushed neoprene – Disadvantages May be difficult to repair May be heavier than suits made of other materials More expensive than foam neoprene
Dry Suit Types Urethane coated nylon – Composed of nylon to which urethane has been applied in order to create a waterproof barrier. – Advantages Lightweight Low cost – Disadvantages Little stretch, so fit is loose and baggy
Dry Suit Types Trilaminate (TLS) – Composed of two layers of tightly woven nylon with a layer of rubber in between Originally designed for chemical warfare – Advantages Lightweight, yet very strong Flexible material, Easily repaired – Disadvantages Little stretch
Dry Suit Types Vulcanized rubber – Advantages Easily repaired Dries quickly Excellent for diving in polluted waters –Easier to decontaminate than other dry suit types – Disadvantages Has some stretch, but not as form fitting as neoprene suits Heavy
Vulcanized rubber dry suits (good for diving in polluted environments)
Dry Suit Seals – 2 Types Latex – the most common type – Advantages Good stretch, so more comfortable – puts less pressure on neck and rests Quick to repair Not as likely to leak – Disadvantages More easily punctured or torn
Dry Suit Seals – 2 Types Neoprene – Advantages Rugged – harder to tear and longer lasting – Disadvantages Difficult to repair Individuals with skinny necks may have difficulty getting a proper seal Do not stretch as well and may feel uncomfortable May fit looser as neoprene becomes permanently stretched
Dry Suit Undergarments Undergarments increase insulation by trapping air against your body – different materials are better at insulating than others. Undergarments also affect buoyancy, mobility, and comfort
Dry Suit Undergarments Open cell foam – Similar to a sponge in cross section – Loose fitting, baggy and bulky – Fairly resistant to compression – Maintains some insulating properties when damp, but not when soaked – Will lose all of its buoyancy if suit floods – Less popular today than competing synthetics
Dry Suit Undergarments Thinsulate – Lightweight and quick drying – excellent insulating properties even when wet – Repels water – Is bulky, does not stretch or breathe, and is more uncomfortable than some other materials
Dry Suit Undergarments Synthetic pile garments – Generally made of polyester Has a tendency to form lint which may block exhaust valves Buoyant Loses insulating characteristics when wet
Dry Suit Undergarments Polartec® – Good insulating characteristics with little bulk – Lots of stretch – easy to don and swim in – Does not retain its insulation capabilities once wet
Dry Suit Valves Most dry suits today have separate inflator and exhaust valves – Inflator valves Push-button, connects to a low pressure inflator hose running from the 1 st stage Typically located on the center of the chest, but can be located elsewhere depending on the manufacturer Must be accessible while diving and easily disconnected with heavy gloves
Typical Inflator valve with push-button operation located on the chest.
Dry Suit Valves – Exhaust valves Generally located on the upper left arm, but may also be situated on the wrist or chest Most exhaust valves today are automatic exhaust valves – that is, they will vent automatically when positioned at the highest point on the dry suit May also be vented manually Generally, dry suit exhaust valves do not vent air as rapidly as a buoyancy compensator (BC)
Typical dry suit automatic exhaust valve positioned on upper left arm. Note the manual vent button in center of valve.
Dry Suit Weighting Dry Suit Weighting Where weighting is concerned, your goal is to dive with the minimum amount of weight possible and, associated with that, the minimum volume of air inside your suit. This will simplify buoyancy control – a diver with excess weight will have to put a great deal of air into a dry suit to become neutral. When this air shifts in the suit it can create buoyancy control issues for the inexperienced dry suit diver.
Dry Suit Weighting You should wear only enough weight to allow you to make a safety stop at the end of your dive (15 – 20 ft) when you have 500 psi left in your tank.
Estimating Weight Requirements Generally, you will need 4 to 10 lbs more weight than you wear with a 7mm wetsuit. How much weight you need depends on a variety of factors including: – The type of dry suit – The type of undergarment – Your personal buoyancy – The type of tank you use All tanks become more buoyant as the air inside the tank is used – Whether youre diving in freshwater or saltwater More weight is needed to dive in saltwater (Table 2 – next slide)
Estimating Weight Requirements Check the manufacturers specifications for your cylinder to see how the buoyancy changes from the time the tank is full until it is empty. This change in buoyancy must be considered for proper weighting – aluminum 80ft 3 Luxfer and Catalina tanks are approximately 2 lbs negative when full and 4 pounds positive when empty – Faber steel 98ft 3 tanks are approximately 8 lbs negative when full and neutrally buoyant when empty
Checking Buoyancy After removing air from dry suit (see slide 38) and entering water – perform the following: – Place regulator in mouth and breathe normally. Vent all the air out of your BC. You should still float. – Vent any remaining air from dry suit In a vertical position – you should float with your eyes at water level with a lungful of air, and you should begin to sink slowly after exhaling all the air from your lungs. –If you sink rapidly you are too negative. –Add or subtract weights as necessary. – Now add weight to account for the change in buoyancy of your tank as you breathe Add approximately 2/3 the weight of the buoyancy change of your scuba cylinder from full to empty (you may find you have to adjust this slightly). –You should be able to become neutral at a depth of 10 feet when you have 500psi of air in your tank.
Donning a Dry Suit Lubricate the seals with pure talcum powder (do not use scented talcs which contain oils that can damage seals). This will allow you to get through seals easier. Soapy water may be used as well. Remove all watches and jewelry including earrings, necklaces, bracelets and rings. Any of these may tear a dry suit seal. Once lower body is in suit, put on and adjust suspenders. They should be taut, supporting the lower part of the suit, but not tight. There should still be some stretch in them.
Donning a Dry Suit When putting hands through wrist seals, extend fingers (including thumb) and squeeze them together – this will give your hand the smallest diameter for getting through the seal. With your free hand, either grab the outside of the seal and pull it over the hand inside the suit, or alternatively, slip two or three fingers of the free hand inside the opening of the wrist seal and pull the seal over the hand inside the sleeve. In either case, do not dig your fingernails into the seal. Insure no undergarments extend through seal. Ideally, at least two inches of seal should be in direct contact with your skin.
Donning a Dry Suit Neoprene wrist seals – May be either cone-shaped or designed to fold under. If the seal is cone-shaped, insure that it is pushed far enough up the arm to insure a seal If the seal is meant to be folded under, then insure that at least 2 inches of material is folded under the top layer of neoprene
Donning a Dry Suit Latex neck seals – To spread the neck seal, reach through the seal with both hand and spread the neck seal by pulling against the palms of your hands. Avoid digging your fingers into the latex. Pull the neck seal over your head. – Insure that long hair and collars are not caught in the seal.
Donning a Dry Suit Neoprene neck seals – Position your head at the base of the seal, then, with your hands on the outside of the seal, pull the seal over your head. When the seal reaches your chin, fold the material inside itself.
Donning a Dry Suit Insure both inflator and exhaust valves work before entering water. Vent the suit. – After closing all zippers, it is necessary to remove the air from the suit. This will both make the suit more comfortable to wear on deck, and prevent air from escaping from the neck and creating a leak upon entering the water. Squat down, cross your arms over your chest and either manually open the exhaust valve, or let air out through the neck.
Diving a Dry Suit – Check for Leaks Do not dive if your suit is leaking. Upon entering the water, take a moment to check for leaks. If any leak is found, take the time to fix the problem – a small leak on the surface may get worse at depth, and will certainly continue throughout your dive.
Diving a Dry Suit – Venting air From the Suit To start the dive, vent all the air from your BC then vent the air out of your dry suit via the exhaust valve. – If you have an automatic exhaust valve, open it all the way and leave it open throughout the dive. If your automatic exhaust valve is located on your upper left arm, then lift your left elbow out of the water (thereby making the exhaust valve the highest part of the suit) while keeping your arm bent and your hand pointed towards the bottom. You will hear air hissing out of the valve.
Diving a Dry Suit – Descending and controlling buoyancy As you sink through the water column you will begin to feel squeeze on your body. Add just enough air to relieve the pressure and control your descent using short bursts. Control buoyancy at depth using only your dry suit. Do not add air to your BC to control buoyancy – it is very difficult to control buoyancy when you have air in 2 separate compartments – controlling both air compartments simultaneously is an advanced skill and is not recommended for the novice dry suit diver.
Diving a Dry Suit – Controlling buoyancy Maintain a minimum volume of air inside the suit – there should not be a large bubble of air inside your suit, nor should you notice massive air shifts as you change position
Diving a Dry Suit - Ascending If you have an automatic exhaust valve – insure that it is open before ascending. If valve is located on upper left arm (the standard location) – then raise it so valve is higher than rest of suit. Keep your lower arm pointed down -Do not extend the rest of your arm higher than the valve or air will rise to your wrist and bypass the valve. If you are not using an automatic exhaust valve, then, again, raise your arm so the valve is at the highest point and use your other hand to push in on the valve to vent air.
Diving a Dry Suit If you are using an automatic valve and find you are ascending faster than you should, raise the valve higher and air should vent faster. If air still isnt venting fast enough, vent the valve manually by pushing down on the valve. Inflate your BC at the surface – it is more comfortable to move on the surface this way rather than inflating your dry suit.
Dry Suit Leaks Small amounts of water may enter your dry suit through seals. Flexing your wrists and turning your head allow water to enter around pronounced tendons. This is normal, and can be avoided with knowledge and practice.
Diving a Dry Suit – A Warning Do not lift heavy weights by inflating your dry suit or BC – if the weight drops you will become dangerously buoyant
Diving a Dry Suit – Emergency Techniques Stuck inflator valve – An improperly maintained inflator valve can stick open – this will cause your suit to inflate continuously. You should attempt to disconnect your inflator hose immediately, and vent excess air through the exhaust valve at the same time (this can only be done if you have an automatic exhaust valve if you have a manually operated valve then disconnect the hose first, then vent the manual exhaust).
Diving a Dry Suit – Emergency Techniques Improperly functioning exhaust valve An improperly maintained valve, or a valve that has become clogged during a dive may fail to exhaust air – If your exhaust valve fails, you should immediately stop your ascent, if possible. Rotating or manually operating an automatic valve may get it to work. Little can be done to get a manual valve to work properly once clogged. – If your valve still does not function properly try to ascend an anchor line or some other fixed object while venting air by opening a neck or wrist seal – you will get wet doing this. If doing a free ascent, be prepared to vent air rapidly through the neck or wrist seals.
Diving a Dry Suit – Emergency Techniques Losing weight belt at depth – Will cause you to become very buoyant with an extremely fast ascent - It is doubtful you will be able to vent enough air through the exhaust valve to get control of the situation Work to stop your ascent and be prepared to vent air from your suit from the wrist seal or neck seal.
Diving a Dry Suit – Emergency Techniques Rapid ascent – You may slow your ascent dramatically by holding your ankles rigid with your fins parallel to the bottom (the fins act as water brakes), arching your back, and holding your arms out parallel to your body. – Another technique for slowing a rapid ascent is to swim horizontally, so your body presents a greater surface area.
Diving a Dry Suit – Emergency Techniques Righting yourself – It is possible for excess air to move to the feet of your dry suit, potentially making it difficult to return to an upright position. To right yourself in such a situation, tuck your body into a ball, give a slight kick, and roll to an upright position. Once you are upright immediately vent your suit through the exhaust valve to regain control.
Diving a Dry Suit – Emergency Techniques Complete dry-suit flooding – Occurs only rarely, possibly from the complete failure of a zipper, blow out of a neck seal, or the destruction of a valve. Total flooding of your dry suit may cause you to become negative depending on what kind of undergarments you are wearing. Usually you will be able to achieve neutral or positive buoyancy by inflating your BC. A flooded dry suit may make it extremely difficult to exit the water – someone may have to puncture the leg of the suit to drain water.
Removing a Dry Suit Remove a latex neck seal by sliding the fingers of each hand down between your neck and the seal, grasping firmly, spreading the neck seal with your hands, and lifting up. Remove a fold-under neoprene neck seal by first unrolling it, then firmly grasping the edge of the seal and pull the seal up and over the head.
Removing a Dry Suit To remove a latex wrist seal, insert 2 fingers under the wrist seal with the fingernails against the wrist, slide the fingers down past the seal, grasp the sleeve of the suit, and pull your arm out of the sleeve. To remove a neoprene wrist seal – simply unfold it and follow the instructions above for wrist seals.
Maintenance of Dry Suits Rinse dry suits thoroughly – especially the valves and zippers. Close the zipper and the seals with rubber bands to prevent water entry. Operate valves as you run water over them – rotate automatic valves and push the inflator button several times. Dry a suit out of the sun – you may need to turn the suit inside-out if it is wet inside.
Maintenance of Dry Suits Zipper lubrication – zippers should be lubricated either before or after you dive. Use bees wax or paraffin wax – never use silicone spray or grease on your dry suit zipper. (Also, be sure to remove any excess paraffin wax – otherwise it will cause deterioration of latex seals if let in contact with the seal for long periods of time) Close the zipper and only lubricate the outside – if you lubricate the inside dirt will collect and cause the zipper to fail. A thin film of wax is sufficient
Storage of Dry Suits Follow manufactures recommendations Store away from electric motors and other producers of ozone – ozone deteriorates latex Avoid storing in direct sunlight Never use metal hangers – they cause creases and rust Do not bend zipper in storage – roll suit with zipper open
Dry Suit Accessories Gloves – Wet gloves are most common – essentially wetsuit gloves pulled over the tops of wrist seals – Dry gloves Connected to suit with cuff rings Warmest gloves, but prone to flooding Work only with latex seals
Dry Suit Accessories Hoods – Wet hoods are most common Can be attached to suit or separate – Semi-dry hoods Neoprene – attached to suit and seal around face
Dry Suit Accessories – Dry hoods Warmest hoods Latex hood attached to suit that seals around face Requires separate insulating hood worn underneath latex hood Will not work with a beard Insulating hood
Dry Suit Accessories Ankle weights – ½ - 3 pound weights attached to each ankle – Help to keep feet down and retain trim underwater – May help for beginners, but NOT a necessary item for dry suits – Fatiguing during long swims
Dry Suit Accessories P – valves – Allows for underwater urination – Most convenient for males with condom catheter – Available for females, but not as convenient or easy to use – requires shaving and lots of adhesive – Adult diapers are the alternative
Dry Suit Accessories Pockets – Many styles and attachment points available – Creates drag underwater
Dry Suit Accessories Argon inflation systems – Requires separate inflation bottle and 1 st stage – Argon is more dense than helium or air, and provides better insulating qualities