What happens if you take your BCD off at depth.?

[pasley]

If you are below say 60 feet, then even a full 7mm wet suit should not present much, if any of a problem as the suit compresses and loses its buoyancy.

Ask yourself this question - "Why do we wear a Buoyancy Compensating (BC) in the first place?" Seriously think about it. The principle purpose of the BC is to ADD buoyancy at depth. You put lead on because if you don't you won't get under water. So why do you need a device to ADD buoyancy at depth? Because the wetsuit looses its buoyancy and you need air to offset the weights. In theory you could almost (note almost because of the buoyancy of the body and air tank) take you weights off at 100 feet and leave them until you were ready to go up. Please note I said ALMOST, don't try it.

Now if you are at say 15-20 feet, then you have more of a challenge.

 

[IslandHopper]

Odd that I stumbled across this thread ... I just spent the last two days practicing this stuff.

I have dove with a weight integrated BC since day 1 ... as long as you realize the bouyancy issues, you can compensate. Keep the removed BC close to your body... I bring a knee up and try to keep that thigh under the BC ... keeps me from floating up in my 3mm suit As someone else mentioned though, in an entanglement scenario, you might not have much choice in how you position things !

For the second day, I used a weight belt (doing a DM class next month, so I thought I'd try some configurations out before hand). This is a MUCH EASIER way to handle the removal of your rig underwater ! Keeping your weights on your body allows you to position yourself however you want and simply hold onto the BC to maintain positive bouyancy. ... I'll definitely use the weight belt for class. I'll probably just use it full-time now.

 

[jagfish]

The principle purpose of the BC is to ADD buoyancy at depth.

Actually, the most concise explanatoin I have heard on this topic is that the principle purpose of the BC is to compensate for the changes in bouyancy created by the changes in the gas supply in our tanks. Initially, when the tank is full, we should be heavy by approximately the weight of the air in the tank. By the end of the dive, with 500 psi or so in the tank, our BC should be ideally empty, or just about so. Divers may or may not be wearing significant or compressable exposure protection.

If there were no changes in boyancy due to the tank, then I agree that the only factor you would need to compensate for would be a thick wetsuit. You might have seen pictures of hookah divers in warm waters with no wetsuit or BC at all, because as pasley points out, there is no change in bouyancy for them at all (except for lung volume changes as they breath)

So why do you need a device to ADD buoyancy at depth? Because the wetsuit looses its buoyancy and you need air to offset the weights.

Unless you are wearing a trilam or crushed neoprene drysuit...

 

[Woofa]

If for any reason you need to take your BCD off at depth 15-30 mters, How do you deal with Bouancy? I have been trying to visulise what would happen if , say for examlpe, You become entangled in Line or netting and you cannot reach behind to cut free. (I wear a two piece 5mm wetsuit , gloves boots and hood with a weight intergrated BCD.)

If i was to remove my BCD i imagine that my body would tend to immediatley want to float to the surface due to all the neoprene. The picture conjurered up in my mind is, me upside down hanging on to my BCD for dear life while trying to cut the entaglemnet free.

Has anyone actually experienced this? if so what actually happens and how did you handle it...

Thanks for the anticipated responses.

Dive with a lawyer they are full of hot air and will keep you afloat

 

[fmw625]

Our instructor in OW demonstrated this skill in a 7 mm wetsuit and integrated BC in about 8 ft of water. He had less trouble than we did.

 

[pasley]

Actually, the most concise explanatoin I have heard on this topic is that the principle purpose of the BC is to compensate for the changes in bouyancy created by the changes in the gas supply in our tanks. Initially, when the tank is full, we should be heavy by approximately the weight of the air in the tank....

we agree in general, we just have a different pont of emphasis. I see your point. For a tropical diver wearing no wetsuit or only a skin, I agree that would be the case.

I was thinking about my own type of diving in Southern California’s 54-58 degree water with a 7mm suit. So from my perspective, for the way I dive, a BC’s primary purpose is to compensate for the changes in buoyancy caused by compression of the wetsuit becasue it represnets the biggest change. Here is my logic as it applies in my case (your case may differ depending upon your diving environment and equipment).

Lead worn to compensate for the buoyancy in the tank = 4 pounds (AL 80)
Lead worn to compensate for the buoyancy of my wetsuit = 14 pounds (7mm, plus vest and hood)
Lead worn to compensate for the natural buoyancy of my body and uh, um, fat = 2 pounds (6 ft. 145-148 pounds, age 51 male)
Total lead weights worn = 20 pounds.

At say 100 feet of sea water my neoprene wetsuit no longer has significant buoyancy, hence I need the BC to compensate.

Since my wetsuit has the potential to lose up to 12 pounds of buoyancy with the changes of depth, and my air tank will change buoyancy by only 4 pounds with the consumption of air, I will argue that the BC is principally worn to compensate for the changes in buoyancy caused by depth and the resulting wetsuit compression or expansion.

 

[matt_unique]

If for any reason you need to take your BCD off at depth 15-30 mters, How do you deal with Bouancy? I have been trying to visulise what would happen if , say for examlpe, You become entangled in Line or netting and you cannot reach behind to cut free. (I wear a two piece 5mm wetsuit , gloves boots and hood with a weight intergrated BCD.)

If i was to remove my BCD i imagine that my body would tend to immediatley want to float to the surface due to all the neoprene. The picture conjurered up in my mind is, me upside down hanging on to my BCD for dear life while trying to cut the entaglemnet free.

Has anyone actually experienced this? if so what actually happens and how did you handle it...

Thanks for the anticipated responses.

First it depends what kind of weight system you have. If you wear your weight on a belt - you need to worry about sinking (unless you are on the bottom). If weight integrated you will float so you need to keep an arm in your BC. I wear weight integrated and I have removed a BC at depth. I kept my right arm in so when I rotated out I would be closer to my reg side and of course still held down. Something to practice with a buddy though.

--Matt

 

[mdsd]

Interesting thread.
Went thru this situation in my mind in 4 typical scenarios for me:
(1) temperate, shallow (7 mil) (eg, california)
(2) warm, shallow (3 mil to trunks) (eg, carib or hawaii)
(3) temperate, deep
(4) warm, deep

In all scenarios I assumed current and/or surge. So I would be moving, at least not stationary. I assume I'm alone and entangled where I cannot reach the entanglement and don't want to chance an errant knife slash (hoses, etc). As I am working towards a basic configuration for my diving, my best solution is weight distribution. I wear 1/2 the lead on weight belt. I split the other 1/2 in my two integrated weight pockets in the BC. (This gives me options for ditching too.) This seems to be the best solution that limits floating up in shallow water. In practice, you gotta hold on to the BC. I stick my arm thru one of the arm holes for safety. Or you can sit on/straddle the tank (slim plickens style) after defalting the BC. In shallow water, the lack of rubber compression for 7 mil and 3 mil is an issue. But below 80 feet the 7 mil suit compresses big time, not as big an issue.

I'm sure there's more to consider but it pays to have a plan.

 

[Rick Inman]

In my SS BP/Wing with STA, steel tank and 8#'s in pockets on the waist webbing, wearing my dry suit, when I take this off I am going to be positive - regardless of depth. I would vent every bit of air out of my DS that I could before I unwrapped the long hose, took the bungeed 2nd off, disconnected the DS hose and slipped out.
If I ever do have to attempt this ridiculous maneuver on a real dive, I'm going to be mad as heck at my buddy.

 

[Buoyant1]

I had the opportunity to try out my new gear in a pool this morning, and decided that it was a good time to see if I COULD do it with my WI BC. Wasn't as tough as I expected. (at 14' with a full 3mm) Glad I tried it, now I KNOW I can do it. (also ironic that I had less trouble today, than when I had to do it for my OW class)

Tried doffing and donning at the surface also, and that's MUCH easier without a weight belt on!

(as a side note...my LDS is awesome for giving the opportunity to get used to my gear before I use it on a trip next month!)