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Dry Suit Training


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#1 TCdamsel

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Posted 10 September 2011 - 09:14 PM

I've been contemplating diving with a drysuit for colder temps for over a year, but have hesitated after reading of the dangers if you aren't well-trained. When looking for a class I came across this article about how PADI teaches maintaining primary buoyancy control with the drysuit itself rather than the BCD and that this can cause uncontrolled ascents feet up! The article also stated that ironically in PADI tech classes, they teach drysuit buoyancy control by means of the BCD. I find all this really interesting and wonder if NAUI teaches differently. Knowing nothing about drysuit diving, I don't want to learn the "wrong" way. I am freezing once the water gets below 80 degrees, so I'd like to expand :-D my options .

http://precisiondiving.net/blog/padi-dry-suit-classes-more-dangerous-than-technical-diving/


BTW, to everyone who responded to my post about fundies, thanks so much!

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#2 Greg@ihpil

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Posted 11 September 2011 - 07:09 AM

Ellen,
Being a "landlocked diver" in Chi twn area,I appreciate your issue on water temp:-D & the B/C vs Drysuite bounancy control.I just got cert on dry last yr thru a PADI course.And yes I had to experience the upsidedown accent.It was a, "if you don't succeed try again" manouver,by the 3rd time I had it. I think once you get to depth thats where you find the real control. You will add some weight so,you want to be close to your entry point,as a ++.
I will say this,"Its like starting all over,learning your control.As for the difference in Naui/PADI.I can't comment .I do know it was nice & "warmer" in the DRY. The other thing you will want to get FAMILIAR with is the different Materials used in Drysuites. Front entry's & Rear,trilaminates ,crushed neoprene & vulcanized rubber.I'm sure you know it's a higher price tag suite. It does take a little more time doning & doffing your suit.I can relate info on the GCM trip if your care to .I'm sure there are others here that will add to my .02.Good Luck.

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#3 Greg@ihpil

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Posted 11 September 2011 - 07:10 AM

Ellen,I can bring the PADI book if you want..


Edited by Greg@ihpil, 11 September 2011 - 07:11 AM.

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#4 georoc01

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Posted 11 September 2011 - 07:46 AM

Ellen,I can bring the PADI book if you want..


I did the PADI class, and yes they teach to use the suit exclusively, which is a good skill to have. Once you finish the class, you can choose which way to go, where I choose to just put enough air in the suit to prevent squeeze and use my BC.

You do need to learn how to deal with the circumstance of getting air in your feet, getting flipped over etc, so you will know how to handle it if it occurs outside of class. Plus now you have the complexity of managing two inflation sources, so focusing on one for training purposes is why they do it. Confusion between the two inflation sources can create an uncontrolled ascent as well. So I wouldn't treat this form of training as a bad thing. In fact, one of the reasons that tech divers use dry suits is for redundancy, and if your BC fails, you need to know how to work with just the dry suit. I wouldn't want to wait until I had a BC failure to learn the skills on the fly.

#5 peterbj7

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Posted 11 September 2011 - 10:06 AM

When I was originally taught to use a dry suit, AFTER I had already had an uncontrolled ascent "incident", I was taught to use both devices for buoyancy. The suit was to be used (in its capacity as a buoyancy control device, which of course is not its primary function) for macro control, and the BC for micro control. I was shown how to get out of and avoid an incipient involuntary ascent, and how to slow an ascent that was becoming uncontrollably rapid (as they do quite rapidly in dry suit diving. I did not do a formal course under the auspices of PADI, NAUI or any other agency, but was taught by an experienced diver (who was incidentally an instructor with both PADI and NAUI, and a National Instructor with BSAC) what he had found to work. The way he taught me made sense, and since I have been teaching it myself I have followed his lead.

Using the suit as primary or exclusive buoyancy is in my view crazy and likely to lead to an accident, and regardless of what PADI may say I won't teach it that way.. IMO you should have enough air/argon in the suit to reduce squeeze and provide insulation, but any additional air should be in the BC. On the way up I always reduce the air in the suit first, so that the whole way up I still have air in the BC. Then in the event of an incipient ascent I can dump air from the BC, which is quick and predictable. Dumping air from the suit is usually slow and unpredictable, and if I need to lose air quickly is hazardous.

Sorry this may not be very clear - I'm suffering from a bad cold and not thinking clearly!

Edited by peterbj7, 12 September 2011 - 04:36 AM.


#6 Jerrymxz

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Posted 11 September 2011 - 05:51 PM

I took my dry suit training with a PADI shop. So I learned the empty BC and control with the suit method. In my HP100 steel doubles and a steel BP my Whites dry suit with my standard underwear is about neutral so this works for me. I empty my wing and just use my dry suit to control buoyancy. I use the Wing on the surface for added flotation. It simplifies the management of ascents not having to juggle two systems. If my gear configuration is different I may need to add gas to my wing to avoid doing the Michelin man imitation. But most of the time not. Thatís the way I was taught and it has, for the most part, worked for me. My 2 PSI.

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#7 TCdamsel

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Posted 12 September 2011 - 06:52 AM

Using the suit as primary or exclusive buoyancy is in my view crazy and likely to lead to an accident, and regardless of what PADI may say I won't teach it that way.. IMO you should have enough air/argon in the suit to reduce squeeze and provide insulation, but any additional air should be in the BC. On the way up I always reduce the air in the suit first, so that the whole way up I still have air in the BC. Then in the event of an incipient ascent I can dump air from the BC, which is quick and predictable. Dumping air from the suit is usually slow and unpredictable, and if I need to lose air quickly is hazardous.

Sorry this may not be very clear - I'm suffering from a bad cold and not thinking clearly!


Thanks everyone for your feedback! Actually, Peter, this makes a lot of sense to me. (Hope you feel better!) It just seems counterintuitive to me to use the suit for primary buoyancy. However, the other posters make valid points. I just need to stop thinking about it and go take a class :diver: .

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#8 MNJoe

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Posted 13 September 2011 - 05:50 AM

My drysuit course was taught by a PADI instructor, but she still taught me to use the suit inflator just to keep the squeeze off and my BC for bouyancy. I will say that I felt slightly task loaded inflating and deflating both for my first few dives. Shortly after I took my drysuit course I did happen to be talking to a diver that turned out to be an instructor, I do not know what agency, he told me that if I needed air in my BC I was overweighted. Well any less weight and I would be floaty especially on shallow dives. I posted as you did asking questions, and the responses I got really seemed to be that there were two schools of thought. After thinking about it and analyzing my situation, I came up with, of course I am over weighted when I start my dive, I have to have weight to compensate for the air I am going to consume. So I do use my BC and my suit. A large air bubble in the suit isn't anything I like. After a few dives, using BC and suit inflators wasn't a big deal. I also will say that I highly recommend the drysuit course as it will give you a chance to experience stuck inflators, dumping air from your neck seal, that infamous feet first ascent, all under controlled conditions. You will also get a little insight as to what you want in a suit, as they are a big investment and there are a variety of them to choose from. If you have a DUI Dog Days event near you, go, in a day you can dive every type of suit DUI makes. Even if you don't want a DUI suit, it will help you figure out what you want or don't want in a drysuit.

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#9 shadragon

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Posted 13 September 2011 - 06:25 AM

Hi Ellen,

I have ~150 dives in dry suits in 35 - 55F waters. Given the amount of fish farm weirs where I trained in eastern Canada a dry suit is necessary to protect you from more than the cold. :P When you are correctly weighted and use a dry suit for buoyancy you will find that adding enough air to offset suit squeeze is typically enough to generate neutral buoyancy so there is no need for a BC. The BC is there in case of a major suit flood and considered the backup device.

To offer a contrary argument to the use of a BC with a dry suit: If you use two buoyancy devices then you have two things to handle in an emergency. I have two wings on my technical rig. Only one is connected at any time for just that reason. There are techniques you will learn on your dry suit course to counter feet-first and rapid ascents. I do use the BC on the surface to float as it does not restrict motion like an inflated dry suit and also I do not look like the Michelin man. :D

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#10 peterbj7

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Posted 14 September 2011 - 07:38 AM

My drysuit course was taught by a PADI instructor, but she still taught me to use the suit inflator just to keep the squeeze off and my BC for bouyancy. I will say that I felt slightly task loaded inflating and deflating both for my first few dives

But I'm sure that after those first few dives you did feel in control.. Task-loading is not in itself a bad thing. Some types of diving have a vastly higher task load, but people manage OK.


Shortly after I took my drysuit course I did happen to be talking to a diver that turned out to be an instructor, I do not know what agency, he told me that if I needed air in my BC I was overweighted

I often hear this, usually from warm water-only divers. Dry suits are usually used in cold water when you need lots of insulation at depth. Insulation = air which = excess buoyancy., so in cold water you cannot avoid having excess weight at depth which requires the addition of artificial buoyancy. You NEED air in your BC. If this guy was an instructor I would be wary of anything he said.

#11 peterbj7

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Posted 14 September 2011 - 08:33 AM

When you are correctly weighted and use a dry suit for buoyancy you will find ... there is no need for a BC. The BC is there in case of a major suit flood and considered the backup device

"Correctly weighted" in cold water doesn't have the clear-cut definition that it has in warm water. The primary function of your drysuit is to provide insulation, and that depends on air being present. The colder it is the more air you will need, hence the more lead you'll need to allow you to descend. On a long deco dive in cold water I need enough air to provide adequate insulation at long deco stops (sometimes upwards of an hour) and that typically means I have to have several pounds more weight at the beginning of the dive.

With a lot of air in the suit, especially in rough water, it is very easy for an involuntary ascent to start, especially in the last 20ft or so, and from those depths there is little time to correct it. A drysuit simply doesn't have the sensitivity of adjustment to be able to dump air quickly and accurately. This is why in those final stages of a dive, which may nonetheless last 30 minutes or even much longer, I want to keep my body + suit negative at all times, with neutral buoyancy enabled by having air in the BC. Then in the event of inattention or currents causing an involuntary ascent I can quickly dump air from the BC to restore neutral buoyancy, or a measure of negative if I have already risen higher than desired. Dumping air the standard way from the suit is always slow and can be unpredictable, and as a control mechanism is unacceptable. Air can always be dumped from the suit in an emergency by pulling the neck seal, but that is especially unpredictable and liable to make you wet. Get much water in the suit and isn't merely uncomfortable but can be very dangerous, as it may rapidly make you negatively buoyant. I'm minded especially of a friend whose suit filled with water (something wrong with one of the dumps) at 80mtr and who then had to ascend and climb a boat ladder with a suit full of water and weighing a massive amount. He managed to get to the surface, with extreme exertion and stress, but couldn't have exited the water. He dumped all his gear and weights and took the suit off in the water, not easy with north Atlantic rollers, and was then able to get out of the water.

Remember also that in the event of a partial equipment failure you can always orally inflate a BC. That is not possible with a drysuit. I recall one person who had had a regulator failure on one post of a manifolded twinset and had to shut that valve down, forgetting that his drysuit was also attached to the regulator. Luckily he was then intending to ascend and didn't need top add more air to his suit, but back on the surface it was a sobering thought that he couldn't have done anyway.

Another consideration. Some agencies (not all) teach that it is essential to be horizontal in the water, especially near the surface. I have never agreed with this, but whatever. If you are horizontal in a drysuit your ability to control accurately the amount of air in the suit is very limited, and near the surface (where the rate of change of pressure with depth is high) you need very adroit action to prevent an involuntary ascent. More than is convenient, for sure.

To offer a contrary argument to the use of a BC with a dry suit: If you use two buoyancy devices then you have two things to handle in an emergency. I have two wings on my technical rig. Only one is connected at any time for just that reason

I don't see the point of having dual wings if one is disconnected and therefore unusable. When I dive with dual wings both are connected, and to opposite posts. I don't routinely use both but I ensure both are available to me.

Your use of the term "emergency" intrigues me. If your emergency involves loss of use of your brain then I agree with you, but otherwise you should be aware of an incipient ascent before it has become established That can then be managed as I described above. If you are in an established involuntary ascent then you certainly do have a task-loading problem, but that should be managed by dumping all the air from your BC and breathing out full, whilst at the same time dumping air from your suit as rapidly as it permits. Once your established ascent has become an incipient descent then you can reestablish neutral buoyancy, and calm your nerves down so you won't be caught napping again. Still better, put yourself through effective tech training that tests your task-loading abilities to the maximum, and teaches you to deal with these and other predictable situations by reflex reactions. As IANTD mantra says, "in an emergency it is the poorest learned skills that are forgotten first".

All tech agencies that I recognise espouse the use of redundant buoyancy devices. Some teach that in cold water when using a drysuit that can act as one of those devices. In warm water a liftbag can serve. I have never tried ascending from depth to the surface just using a liftbag for control, and one of my reasons is that I have watched people attempting it as exercises. Every one would have ended up in a chamber or worse had they accumulated much deco obligation, and some would never have surfaced at all. Ascending just using a drysuit is easier but still highly problematical. For me the best redundant buoyancy is dual bladders, preferably both connected to tank air.

Edited by peterbj7, 14 September 2011 - 08:45 AM.


#12 shadragon

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Posted 14 September 2011 - 09:11 AM

"Correctly weighted" in cold water doesn't have the clear-cut definition that it has in warm water.

Correctly weighted is correctly weighted. Water temp does not affect how much weight you carry. Salinity does. Wetsuit thickness does. Drysuit thermals do. However, a diver in 80F water who is properly weighted for the gear they have can dive in the same water with the same gear at 32F without a change in weight carried.

The rest of your points I am not going to argue as I have no intent of hijacking the thread from the original topic. I think you are incorrect on several of them, but I am having an otherwise busy day and just cannot afford to take the time for the lengthy response that would be required.
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#13 peterbj7

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Posted 14 September 2011 - 05:25 PM

Water temp does not affect how much weight you carry. Salinity does. Wetsuit thickness does. Drysuit thermals do. However, a diver in 80F water who is properly weighted for the gear they have can dive in the same water with the same gear at 32F without a change in weight carried


Can't agree with this. Water temp by itself of course doesn't directly change your buoyancy, but it has a knock-on effect. I have made long dives in very cold water that necessitated a lot of air in my suit for warmth, which in turn necessitated more weight.

#14 techintime

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Posted 14 September 2011 - 10:00 PM

my two cents based on four years experience (i.e. not an expert, but still enough experience to hopefully give some decent advice)

I have seen both schools of thought in practice and here is my take...

The folks who use the drysuit for bouancy control seem to come from places where single depth square profiles.
The other camp seems to be favored by those who do more multi-depth level dives

What I have found works best is to take it step by step as follows:
On the decent
- as a starting point I want minimimum air in the drysuit to prevent squeeze and stay warm
- then use the BC as it was designed to maintain neutral bouancy

Once leveled out
- then also use a balance between the two to adjust trim
-- a little more into the drysuit tends to bring you more head up (vent a coresponding amount from the BC)
-- vice versa

On accent
- go back to minimum air in the dry suit consistent with warmth and trim (on accent you wont get squeezed)
- BC use as per normal

some extra equipment may prove usefull too...heavier fins and gators (and ankle weights as an absolute last resort) to help with trim issues from overly bouyant legs
Techintime




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