Redundant buoyancy in warm weather

The impossibility, while doing technical dives, of always having a neutral rig or of having discardable weights makes it more complicated to plan for loss of BCD function than in recreational dives. This is often solved by using a drysuit. This solution, however, presents a problem in places with hot air temperatures. So, for hot air temperatures, warm water technical diving, I've seen four main approaches advocated:

1 - wear a drysuit anyway. This is probably the most straightforward solution. It has the advantage of offering a good deal of buoyancy control with little more effort required from the diver. The downside is a pretty miserable experience while out of the water, especially if no shades are available while doing the setup. It also offers the risk of loss of buoyancy at the surface by having air escape through the neck seal.

2 - use a wetsuit and lift bag. The upside is that a lift bag can offer plenty of buoyancy, surely more than a drysuit. However, it is harder to control precisely and requires constant use of hands to operate, making the use of other tools, such as jon lines, more difficult and adding to the task load. It can also interfere with communication with team members, being right in front of the diver. Moreover, it is argued that divers don't regularly practice making their ascents with lift bags, rendering its successful operation in an emergency less likely.

3 - use a wetsuit and a double bladder wing. It offers redundancy and does not require a change in method of buoyancy control in case of emergency - before the failure the diver adds air by pressing a button on a hose, which can also vent air. After the failure, the operation remains the same, although through a different hose. The downside is that a double bladder wing has more mechanical failure points and is more prone to operator error.

4 - no redundancy, just a wetsuit and a single bladder wing. The reasoning here is that a failure can be coped with. The most likely point of failure for a wing would be the inflator hose, especially where it attaches to the wing. As the wing shouldn't need to be completely inflated in the first place, sufficient buoyancy can be attained simply by adopting a butt up, left shoulder down posture. The downside of this approach is the increased risk of loss of buoyancy during the dive, reduced mobility and difficulty of maintaining buoyancy at the surface. A failure in the butt dump valve would be dealt with in a similar fashion.

That is just a small summary, covering, I hope, the main points of each method. Once again, I am talking about diving in a place that is very warm both above and bellow the water (you can think of Bonaire for reference).

What are your thoughts on the matter, and what is your preferred approach? Any comments are appreciated.

The first redundancy is your buddy, ask him for a lift.

1. Don't have a drysuit.

2. Without being in deep in my usual 7mm farmer john, I would probably just swim up. Diving Solo, actually on most dives, I carry a 30# SMB/ lift bag and a spool with line longer than the depth I'm diving. Shoot the bag and climb the line, if necessary.

3. Don't have a double bladder wing.

4. Have done an a** first ascent, was hilarious for others. I was close enough to the boat that there was no problem, if I wasn't I could have dropped weights or the whole rig if necessary as I was taught. I've had more interest in dump valves afterwards.

To avoid gear failure problems, check and maintain your gear constantly. At any sign of a problem check it out and repair it yourself, or get it to someone who can. In my years of diving I have noticed that I rarely have had any problem that did not give me fair warning. "It's good enough for this dive" is usually the expression that precedes an issue.



Bob
------------------------------------
I may be old, but I'm not dead yet.

I've heard very good things about DUI's 30/30 tropical drysuit. Those who have tried them say the fabric breathes and doesn't trap heat like a typical tri-lam suit. This could make Option #1 more tolerable.

I use a dry suit, even where the air temperatures are both hot and humid. If you are efficient about it, it can be managed. Get EVERYTHING ready before you finish getting into your suit; get the suit wet as soon as possible (including your hair). Gear up quickly and get in the water.

I cave dive in MX where the air temp can be 100F with high humidity, and sometimes no shade at all. You just have to be a bit clever.

Bob DBF:

The first redundancy is your buddy, ask him for a lift.

1. Don't have a drysuit.

2. Without being in deep in my usual 7mm farmer john, I would probably just swim up. Diving Solo, actually on most dives, I carry a 30# SMB/ lift bag and a spool with line longer than the depth I'm diving. Shoot the bag and climb the line, if necessary.

3. Don't have a double bladder wing.

4. Have done an a** first ascent, was hilarious for others. I was close enough to the boat that there was no problem, if I wasn't I could have dropped weights or the whole rig if necessary as I was taught. I've had more interest in dump valves afterwards.

To avoid gear failure problems, check and maintain your gear constantly. At any sign of a problem check it out and repair it yourself, or get it to someone who can. In my years of diving I have noticed that I rarely have had any problem that did not give me fair warning. "It's good enough for this dive" is usually the expression that precedes an issue.



Bob
------------------------------------
I may be old, but I'm not dead yet.

Click to expand...

Thanks for your input, Bob. However, as to item 2 in your post, I don't think it would be practical in the context I was referencing. Perhaps I should have been clearer in my OP, but I was trying to discuss dives with deco obligation and maybe one or two deco bottles. In this case, I believe that maintaining constant depth by swimming or holding on a line would be very tiring and potentially contribute to DCS.

As to gear maintenance, no doubt it is paramount, but I think it is always good to plan for failures.

---------- Post added November 13th, 2013 at 03:41 PM ----------

TSandM:

I use a dry suit, even where the air temperatures are both hot and humid. If you are efficient about it, it can be managed. Get EVERYTHING ready before you finish getting into your suit; get the suit wet as soon as possible (including your hair). Gear up quickly and get in the water.

I cave dive in MX where the air temp can be 100F with high humidity, and sometimes no shade at all. You just have to be a bit clever.

Click to expand...

Do you use a drysuit there just for safety or also for comfort in the water? I've heard conflicting opinions in that regard. Some people I know (including a small, lean woman) feel absolutely comfortable doing >2h dives there, for several days, in a wetsuit (3 or 5mm, I can't remember which, in her case). However, I've read reports of people feeling very cold doing courses there in similar exposure protection.

In any case, thank you for contributing. I think I would need to be much more efficient during my setup to avoid baking in a condition like that.

As previously said, a few companies make a tropical drysuit. I don't go anywhere without my Whites tropical. I did have some hassles in Komodo with strong currents but the trade-off is exactly what you've described; redundacy of bouyancy control. In addition, my gear is setup exactly the same no matter where I dive (in cold or warm water) so its very comfortable to me & I can dial-in my exposure protection based on number of dives and temperature.

Single bladder wing, two reels and two 40lb CC SMBs for deco dives here in HI. I don't find managing a CC bag being used as a primary source of buoyancy all that difficult, and dispute that it requires constant use of hands to operate.

There are two ways you can use it: as a fully inflated bag on the surface while you climb the line and hang underneath it (does require hands), or, kept with you to acheive neutral buoyancy (no line, clipped off where you can easily reach the inlet and dump valve, not much more hand-y than a wing, though it's a PITA to have it in front of you). I dive double steel 100s or 130s plus the usual tech gear and 1-3 deco bottles out here in trunks and a lavacore, and having practiced both approaches I can say that you do not want to try to climb a line to a surface buoy during deco while very negative (i.e., simulated total failure of the wing). Because it's unsafe to clip the reel to yourself, you have to hold it the whole time (takes one hand at least) and it's tiring to dangle while negative. Much easier to have the bag with you, get neutral, and vent gas as needed during the ascent.

Very few, if any of the technical divers i know of here in Florida dive dry in the summer. When I did my full mix class for the rebreather we were required to dive dry. The class was in august and it was just about unbearable on the boat gearing up in a drysuit, rebreather and 3 bottles for the deep dives. Many time we do hot drops to the deeper wrecks which can mean you are geared up at least 5 minutes before the drop. 5 minutes may not seem like a lot…unless it's 87F 95% humidity and your drysuit boots are filling with sweat as you gear up.

As result all the divers i know, myself included use option number 2. SMB with 40-50# of lift.

As a side note. If you decide to go with a double bladder be sure you train with it. And i would recommend the second bladder not be hooked up until the first one fails. A tech diver recently died when she experienced an uncontrolled ascent to the surface from 100meters. Reportedly due to gas trapped in the second bladder and the diver not accessing the correct wing to expel the gas and control the situation.

I use my dry suit in MX for warmth. Our typical dive these days is 2 to 2 1/2 hours. I'm good in a wetsuit for about 90 minutes. After that, I'm not happy.

I also dove dry in the Red Sea, with similar air temperatures but much warmer water. My undergarments were light enough that I still found it quite possible to get geared up and into the water without having heatstroke. I liked getting out of the water after 90 minutes or more, unzipping the suit, stepping out and going for a Coke, while all the folks around me in the wetsuits were wrapping up in towels, shivering and looking for warm drinks.

Interesting thread. I'm nowhere near this level but I do like the idea of redundancy. What 40# smbs are you looking at? Are there one's made specifically for this emergency situation that are maybe a little stronger sewn together etc to reduce the risk of failure while you are "riding" it up? Is it preferred to have a smb or lift bag? It seems the lift bag might deflate when you get to the surface.