Balanced rig limits, no bcd?

[Trace Malinowski]

My lung volume is approximately 8 liters (tested for freediving) at 5'11" and 211 lbs. High muscle to fat ratio. Only wear 6lb. backplate with drysuit in salt water. The last time I tried an all lungs no BCD buoyancy test, 40 feet was pretty much my maximum neutral depth in double AL80's with SS plate - both dry wearing just Xerotherm wicking layer and in a 3mm wetsuit. Around 40 feet, I feel like I'm breathing off the top of my lungs. Good job on the 65!

 

[RayfromTX]

My lung volume is approximately 8 liters (tested for freediving) at 5'11" and 211 lbs. High muscle to fat ratio. Only wear 6lb. backplate with drysuit in salt water. The last time I tried an all lungs no BCD buoyancy test, 40 feet was pretty much my maximum neutral depth in double AL80's with SS plate - both dry wearing just Xerotherm wicking layer and in a 3mm wetsuit. Around 40 feet, I feel like I'm breathing off the top of my lungs. Good job on the 65!

160'

 

[Trace Malinowski]

The 6 lbs. on my backplate is obviously too heavy.

 

[CT-Rich]

Thinking about this, it occurred to me that you are planning your dive so that you are neutral on your safety stop. There is absolutely nothing to say you can’t dive like this, it was done like that for decades in the 50s, 60s and 70s. If you are diving in a t-shirt, you can also do it.

But there is a reason so few people dive with just a balanced rig. If you are trimmed out to be neutral during your safety stop, you are going into the water significantly negative at the start of the and will be negative on the bottom after your suit compresses.

Great when everything is perfect, not so good when it isn’t. If you need to abort the dive early, wearing twin 80s, you are going to be trying two stay at the surface when you are 12 lbs negative. That a lot of work when the fecal material hits the oscillating blade. You are going to need to dump weight, possibly for something really small or really stupid. Seem like a lot of compromise for some pretty minor benefits, IMHO.

 

[REVAN]

...If you need to abort the dive early, wearing twin 80s, you are going to be trying two stay at the surface when you are 12 lbs negative. That a lot of work when the fecal material hits the oscillating blade. You are going to need to dump weight, possibly for something really small or really stupid. Seem like a lot of compromise for some pretty minor benefits, IMHO.

Or, just don't overweight and swim around on the surface 12 pounds negative.

Diving without a BC requires some discipline in weight management. You cannot use the same sloppy and over-predictive rules of thumb BC divers use to calculate how much weight to put on the belt. That just won't work when diving without the BC. Realistic weight measurements for air consumed must be used, as well as accounting for the variability of structured breathing techniques and suit compression (i.e. - you want to be neutral with the suit compressed to the safety stop depth, not expanded to its surface buoyancy).

 

[northernone]

I've been enjoying these replies!

I'll fill in a little more about my contingencies on that test.

1.The hard bottom was my go to in case of trouble. (@RayfromTX your joke is my dive mantra. Majority of my diving is shore or cave. Both your can remove fins and walk home)
2. I was carrying my camera about 2lbs negative which can be easily dropped (easily in theory, I'd hate to lose it).
3. 5lbs lead weigh could have been dropped.
4. My dsmb and 250ft reel would be an option. Regarding narcosis, it's significantly easier to deploy than manual dual strobe macro photography holding position in a solid current.

I've experienced significantly worse narcosis under heavy workload in deep cold blackwater diving back home in Canada (Where I originally learned to dive as a youngster, no bcd) doing valueless salvage for pleasure. The experience this was built on was learning to dive from mentors who considered around 320-340ft the limit for air and who dove near there extensively. I've put in a few hundred dives below 240 on air myself. Narcosis management I've never been taught formally, would like to. Reading everything I can online, particularly the gas density studies. My background involving deep air might derail the thread so I hesitated to mention it. Anyone have a stick? I'll bring the dead horse.

In way of update: I enjoyed the dive so much I left my camera behind, switched to lighter fins and did it again today!

With the 3lbs further ballast removed I was comfortable to 75ft and could still hold neutral quite a bit deeper, seems the extra ballast reduction make for significant comfort increases deeper as the wetsuit seems to reach crush depth and doesn't get much less buoyant. Not having the drag of camera and needing to hold against the current for pictures made a huge difference as well.

Held deco comfortably at 15ft @ 500psi (X2). Turns out I didn't miss the 3lbs.

I've not measured lung volume since a serious health issue 5-4 years ago. Use to freedive extensively and am rebuilding slowly. Lung capacity, particularly the "comfortable" range, is the decided factor in how much buoyancy we can compensate for internally. I'll test it out soon to run some hypothetical math.

Regarding getting positive on the surface if needing to call a dive: Dropping the 5lbs and (worse case) emptying the tanks would give me nice lift when combined with a safety sausage hobby horse to ride. I really like the idea of the snorkeling vest, because dropping lead for a stupid reason would be annoying. For a while I use to carry an aircraft emergency life vest with a co2 cartridge as a security blanket.

Streamlined diving, trim with equipment at the bare minimum is really enjoyable. Less drag has tangible results when dancing with the currents and contours.

The study in weight management as @REVAN describes is satisfying.

Great discussion!
Cameron

P.s. It's nice to hear some others are out there enjoying streamlined diving. Giving me good ideas too.

 

[CT-Rich]

Ok, how negative will you be when you drop into the water with full twins with no BCD if you want to be neutral at 15' with 500 psi? the idea of the BCD is your buoyancy is ADJUSTABLE. Watch any pre BCD dive movie. The only way to stay off the bottom was to keep swimming. Totally doable, but if you don't want divers kicking over coral or rototilling the bottom... How long would it take you to drain twin 80s? You might try knit a boat out the surrounding kelp while you wait.
I am not saying it can’t be done, but I question the wisdom saying I can be narc’d out of my gourd diving air below 240, but could manage deploying a DSMB because it is easier than to operate my camera... or that while totally narc’d I would even consider dropping the camera.
Generally, the whole deep air diving because I am loving the freedom of it seems careless. That you aren’t dead isn’t a guarantee that you won’t be dead in the future. Tons of experienced divers ended up dead diving deep air and thinking they could def#ckerize a problem if they needed to.
Dive any way you wish, but I hope you die at home of old age, because I wouldn’t want anyone to risk their lives on your body recovery.

 

[REVAN]

Ok, how negative will you be when you drop into the water with full twins with no BCD if you want to be neutral at 15' with 500 psi?

It depends on the diver and situation. From what I know about the conditions of the dives described here, and if I were doing something similar (wearing my 3mm suit), I'd be about 2 pounds positive on inhale at the surface, and about 6 pounds negative on normal exhale. That is a manageable situation, and weight can always be dropped if it starts to become less manageable for some reason.

For the record, my 3mm suit provides about 2 pounds of additional surface buoyancy beyond what it provides at 15 feet. I'd plan on using no more than 8.8 pounds of air from the tanks, because if I'm below 500 pounds I should be on the surface. If I want to stay down with less air than that, I'll kick down to stay down. That situation is highly unlikely, but an easy concession. As this would likely be a deco dive, I'd actually intend to use closer to 7 pounds, but then again I don't go out and do deco dives anymore or drop down to 160 feet either. That kind of diving is behind me. These days, I enjoy shallow fun dives on a single tank, with streamlining and no BC, or freediving with no tank at all.

 

[The Chairman]

Balanced rig: Neutral buoyancy limits with no bcd and related safety considerations. Curious what comfot limits others have who regularly dive without a bcd have and what gear configurations work well.

The wing/bladder use is two fold. One is to enable us to maintain being neutral at depth without having to get within a pound or two of the desired weight and conserve air. The second, and the most important is to float the diver AFTER the dive. I started diving without a BC and I did fine. Yes, the selling point of my fins was that I could beat the crap out of the reef and not hurt the fins, but too many urchins, fire corals, and other stingy things to want to do that. But if you had to surface (remember j-valves?) any distance from shore, survival was your immediate concern. I often resorted to a porpoising technique to get to shore. Take a breath, and kick like mad towards shore (boat, etc), and make sure you angled up when you needed a breath. Blow out your breath, breach the surface and take another breath before your weight pulled you down again. Today, with a BCD, I leisurely inflate it, flip to my back, and relax as I power into shore. No stress. No fight. All the air I care to breathe with nary a thought. On many drift dives I've waited a half hour for the boat to get to me as they picked up everyone else. Why? I always look pretty damn comfortable lying on my back on the surface of the world's largest water bed.

 

[northernone]

Ok, how negative will you be when you drop into the water with full twins with no BCD if you want to be neutral at 15' with 500 psi? the idea of the BCD is your buoyancy is ADJUSTABLE. Watch any pre BCD dive movie. The only way to stay off the bottom was to keep swimming. Totally doable, but if you don't want divers kicking over coral or rototilling the bottom... How long would it take you to drain twin 80s? You might try knit a boat out the surrounding kelp while you wait.
I am not saying it can’t be done, but I question the wisdom saying I can be narc’d out of my gourd diving air below 240, but could manage deploying a DSMB because it is easier than to operate my camera... or that while totally narc’d I would even consider dropping the camera.
Generally, the whole deep air diving because I am loving the freedom of it seems careless. That you aren’t dead isn’t a guarantee that you won’t be dead in the future. Tons of experienced divers ended up dead diving deep air and thinking they could def#ckerize a problem if they needed to.
Dive any way you wish, but I hope you die at home of old age, because I wouldn’t want anyone to risk their lives on your body recovery.

Me too. Much below 75 isn't comfortable enough for me to do often no bcd. A well fit bcd can be streamlined too. BP/W or my favorite a Mexican style SM rig with a bladder. Certainly enjoy my no bcd dives still and nice to see they can be done neutral. That wasn't a big consideration when I learned to dive.