Question on drysuit and buoyancy

[eelnoraa]

Instead of going head forward, it is easier if you roll a bit to you left. What your want is to have the dump valve at the highest location, rolling to the left also archieve that.

But, let's get Andrew, you and me, and go diving sometime. My drysuit is at DUI for repair, should have it back soon.

 

[Ouvea]

Hi Ben:

I've only been diving with a drysuit for about two years, so I consider myself a beginner with this type of exposure suit. I have tried method #1 but achieving trim was quite difficult in my experience. I had better luck with method #2, which is what I practice today. Your mileage will vary of course. In the pool where you'll first practice, try both methods and see what works for you best. Of course, as you be come proficient with the use of your suit, you may decide that what initially worked may not be the best. We use the same dive shop. You'll be in good hands.

As for the cost of the drysuit, please do yourself a favor and just put up the cash up front. Don't fall for the hype of semi-drysuits. Drysuits don't allow water inside, yet without the proper insulation, we will FREEZE in them. The compression, that neoprene undergoes at depth, simply cannot keep you warm, regardless of its seals. You'll be able to dive comfortably and more often on the same day with a drysuit. For the gloves, I would recommend Si-Tech Glove Lock QCP (but its size can make it cumbersome). I can take mine off faster than any wet or dry gloves out there on the market.

 

[Diver0001]

That's why they teach to leave the BC empty . . .

That's part of it.

When drysuits first came out a lot of people either didn't use BCD's or they used the horse collar ones that tend to ride up around your neck and become quite uncomfortable if you put much air in them. Hence the advice to use the suit for buoyancy.

Instructors these days teach it because they collectively got to thinking that it must be simpler. The fact is, there's a lot of monkey-see-monkey do going on, which is what made it a common practice these days. Agencies don't prescribe either way but PADI does state in its materials that a trilam suit is easily managed with just the suit because it doesn't compress and they say (correctly) that it's infeasible to manage buoyancy entirely with the suit if the suit is made of neoprene.

The truth of the matter is no matter how you slice it, you do both. A given diver may develop a preference for doing it more with the suit or more with the BCD but in my experience few divers do it entirely with the suit. Part of this may stem from the fact that most divers carry more weight with them than they need and find the suit unmanageable with a lot of air in it, but I'm sure there are other reasons too.

What should be made absolutely clear is that there is no *right* or *wrong* way to do it. What works and feels comfortable (and under control, of course) is what the diver should do. I'm often surprised how complicated people try to make this. It's really not complicated at all if you don't over-think it and just do what feels right.

R..

 

[Ben Prusinski]

Folks,
I ordered a new DUI CLX450 custom drysuit with CF bottom in Special Production format since my upper body if bigger than the rest and regular sizes did not fit me well. It should come in few weeks. PADI teaches buoyancy control one way compared to other folks methods. I would use the drysuit inflation just to eliminate suit squeeze and BCD for rest. I will experiment. When I did the DUI demos, I did not have to use my BCD except on the surface and was fine inflating the suit. Had ok dives except when I test dove the TLS350 which I did not like as much as the CF200 drysuit. Rugged is good for me and since I want to dive wrecks more durable.

 

[Them]

... PADI teaches buoyancy control one way compared to other folks methods. ...

PADI seems to be absolutely mainstream regarding buoyancy control. I have looked at material from three agencies, five suit manufacturers, and a few other groups promoting dry suit usage. The vast majority say use your dry suit for buoyancy. They range from, "you should use the dry suit for buoyancy because air in the dry suit will keep you warm and air in the BCD doesn't," to, "use the dry suit for buoyancy because if you don't you'll die!!!" OK, not so many exclamation points but they put big exclamations in yellow triangles in front of the paragraph so cut me some slack.

Your DUI suit's manual is interesting in that they don't much care, saying, "Use your dry suit and/or BCD to adjust buoyancy." -unlike mine, which is adamant that only the dry suit be used except at the surface.

I find it fascinating, personally. Every agency I have found says do X. Most other material says do X (but some acknowledges that you can also do Y), some people say "X and Y are both good," and here on scuba board the vocal seem to favor Y.

Congrats on your suit.

 

[Ben Prusinski]

This is confusing. I plan to take the drysuit class when my new drysuit arrives and experiment with what works best for me. In the DUI event, I did fine just using my drysuit for buoyancy control with a steel 100 tank.

 

[Diver0001]

This is confusing. I plan to take the drysuit class when my new drysuit arrives and experiment with what works best for me. In the DUI event, I did fine just using my drysuit for buoyancy control with a steel 100 tank.

This thread illustrates one thing, which is that there is no consensus. Just keep the brain engaged and do what feels right and you'll be fine. It's not nearly as difficult to dive in a dry suit in reality than the internet makes it seem.

Good luck.

R..

 

[turnerjd]

It surprises me that nobody has so far mentioned correct weighting.

If you are correctly weighted then the bubble in the drysuit at the start of the dive should not be that big. My steel 15L tank changes its buoyancy by less than 3kgs over a dive. This should equate to a bubble with an "at depth" volume of less than 3L at the start of the dive, and it gradually gets smaller over the dive. But, correctly weighted, this should be the same volume as you would put in a BCD. (actually at 200bar my 15L should lose 3.6 kgs full to empty, but it is rarely either completely full or completely empty)

Each diver for his equipment *should* over time start to know how changing undergarments / tank / other equipment changes the size of the bubble, and how they weight themselves.

Now, how you do your buoyancy it depends on the bubble size. Single tank diving (upto and including an 18L tank) can be easily controlled on just the suit, as can small twin tank setups (twin 8Ls). However, when you start having larger twin tanks such as twin 10s or 12s, then the bubble volume gets larger and harder to deal with, simply because you have a greater buoyancy change as you use up the air.

Personally, as I descend when I know I need a large bubble (with a twinset for example) I will take off the squeeze with the suit, and add air to the BCD. As the dive progresses I will do the majority of the boyancy on the suit, but gradually reducing the air in the stab.

OTOH with a single tank then I just do everything on the suit.

Another minor point is that all divers are different, and I for one find that getting air into the legs of my suit quite difficult. Perfectly horizontal I have the bubble around my back, and it is actually quite hard to get the bubble to go past my weightbelt. This leaves me quite nicely trimmed. Also, with a thinsulate undersuit on, the bubble is less mobile as the air appears to be "stuck" in the undersuit, although it does not affect purging or inflating the suit. (hard to explain, but the undersuit compresses to quite thin, but when you put air in it springs back to its normal thinkness, and the bubble doesn't move around as much)

As said many times above, stop, think, optimise, and do what works for you.

HTH

Jon

 

[NAM001]

put me in the #2 camp. a run away bubble is so much easier when it is in the confines of a wing. no more than min air in a dry suit and youhave no bubble to chase. as long as i can be shoulder up the suit will auto vent so i dont have two things to keep up with. let a bubble go to your feet and it is over till you right your self with a tuck and roll. the dir folks harp on no bungies on wings because of trapped air in wing. the dry suit is a giant wing all bound up with harness ect. no, for me just enough air to relieve the grip and the wing does the rest.

 

[manni-yunk]

You serious?? trying diving double hp100 with the dry suit only, or maybe even single hp130. YOu will quickly find it doesn't work, or it is a highly sub optimal way to do it. Again, OW students are taught that only becase 1)they use smaller tank, 2)one less thing to manage becaue they are already "very" task loaded.

I dive double HP 120s, double LP95s, and double HP100s. I use my drysuit for everything (buoyancy)at depth. I only start to add air to my BC if I have my 7 lb hammer and bag of tools with me. I do this to about 145 feet.

I have no problem manageing the air in my suit.

I know, through trial and error - and a lot of quarry and ocean practice - EXACTLY how much weight to bring(if any) based on every undergarment combination I have and what gear I am strapping on.