Ascent with little or no air in BCD??

[MauiScubaSteve]

I am going to hazard a guess that he was probably wearing a thicker wet suit, experiencing more suit compression and subsequent decompression, and carrying a lot more weight than you have experienced in your lifetime of diving Key largo and Hawai'i. You probably do not realize what a difference that makes. Having some experience with cold water diving and the buoyancy problems inexperienced divers have with it, nothing in what he wrote surprises me at all.

My first ~150 dives were in Idaho, Washington and Montana, including ~80-100 feet deep dives in Priest Lake, Lake Pend Oreille and Flathead Lake. Granted a home made neoprene vest was my only exposure protection, but my dad was wearing old school beaver tail jack / john and he never seemed tired after swimming up his no BC rig.



Why hazard a guess when one can just ask for more details?

When reading typing, is the "tone" only in the reader's head? I've been told over and over that in person, my dead pan delivery needs more tone, to sort out the dry sarcasm. As I remember the typing of my first post in this thread, there was no sarcasm (all wet) and the answers to my questions could really only remotely lead to a hostile "tone" towards the instructor(s).

:shocked2:

 

[RonFrank]

There are three parts to a dive, The decent, The dive, The ascent. I like to try and combine parts two and three.

When its time to go up, you stay horizontal, ascend up maybe 5', and dump a little air to maintain buoyancy. You should always be neutral. Hover at that depth for maybe 10 seconds and repeat.

When you get to 20' stay at that depth for 3 minutes. That is your safety stop, and it never hurts to practice a good SS. When you are ready to ascent from 20 feet, again do it slowly 5 feet at a time.

Going slow, maintaining a Horizontal position in the water, and maintaining control are all signs of a competent diver. It's easy to be an UW spaz, work instead on control. Your movements should be efficient, controlled, and precise.

A good diver is still UW. When you see one, you will know it, and you will likely say to yourself that's how I want to dive. A good diver can stop motionless and just hang.

The next time you end a dive a weight check is a good idea.
Have fun

 

[farsidefan1]

As a warm water wuss I am of course totally puzzled by this thread. The only time air goes into my bc is on the surface. I'm a fat bald 60 yr old. Going up? take breath, don't hold it and start finning slowly keeping eye on bubbles and computer (just the computer if it is a blue water ascent). No problem.

 

[Tigerman]

One of several warmwater luxuries

 

[miketsp]

From what I personally remember various agencies prior to 2000 taught students to dump their BCs and fin up negative. I myself was taught to do this.
Then the navy published a study showing that the risk of breath holding while finning hard vertically was significant so all the agencies adopted neutral ascents.
But of course, there will always be instructors and divers from the old-school passing on the old standard.

I ran a quick search - it's commented here:
Learn To Scuba Dive | Scuba Diving Magazine

New Rule
Become neutrally buoyant before beginning your ascent and maintain neutral buoyancy throughout.

Old Rule
Dump all air so you are negative before beginning your ascent and fin upward against negative buoyancy.

Reason for the Change
The old rule was designed to prevent runaway ascents. But Navy studies revealed that the strain of finning hard while ascending sometimes causes divers to hold their breath. Also, it can lead to air trapping in the lungs. Both present embolism risks. The change also reflects greater confidence in modern BCs, particularly their dump valves.

Exceptions to the Rule
In an ascent from very shallow depths, say 30 feet or less, it's OK to fin up against slight negative buoyancy. The risk of losing control because of rapid buoyancy changes in your BC and exposure suit, and the low stress in finning such a short distance, makes this the better bet.

 

[raoulsttexas]

To Mndiv:
I am not an instructor, so I will refrain from giving my opinion on the actual question.

However, I am a diver who was fortunate enough to have an EXCELLENT mentor who taught me all the details of diving in my (former) local area up in Pac NW. It was cold, dark, drysuit diving. I'm now a rescue diver and, aside from CPR, I learned more from him than I did in OW, AOW, and Rescue.

Now, I'm not diminishing these classes (rescue is great!), but I am advocating the benefits of finding a very experienced diver who truly knows how to safely dive where you are diving.

So, my advice....find a mentor...and dive as much as possible with that mentor. They will catch errors that you are making and correct them.

Good Luck!

 

[Flguy76]

Ha ha I dove with ONE Navy diver one time. He was absolutely terrible in the water and had near zero bouyancy control. That was over 30 years ago.

I don't care who is teaching that crap; it is wrong and stupid and dangerous (again for coldwater diving with a thick wetsuit).

Hey you could never fill your tank with more than 200 psi too, that way you can never get bent.

Take into account the average Navy diver is in far better physical condition that the average recreational diver and is trained much more extensively to handle emergencies underwater (navy dive school is about 6 months vs the average cert class which is about 3 to 5 days total) Also remember that most if not all of what we know about diving physiology was gleaned from tests done by the US Navy experimental diving unit. The 60 ( now 30) ft per minutes ascent rate came from US Navy tests, what we know about decompression and DCS ect. The average military diver is well able to handle an ascent under negative bouyancy. The average rec. diver may not be, so its a matter of whats good for the goose isn't always good for the gander. Theoretically and notice I said theoretically, a negative ascent would be a safer bet but in practical application given varying fitness levels, emergencies, ect it's not good practice. personally, and this is just me, I don't see anything wrong with doing it on very shallow (30 ft or less) dives as it simplifies things. I'm still learning the whole buoyancy control thing too....lots of good info in here. Thanks for every ones input.

 

[spectrum]

If you roll history back you find that the buoyancy compensator, meaning any sort of diver worn flotation bladder was considered advanced equipment. Initially it was not felt that divers could manage to avoid a runaway ascent during a dive or ascent while wearing a bladder containing air and subject to Boyle's law. Hence use it as needed at depth but don't even think about managing a neutral state while ascending.

Over time horse collars and Fenzys became jackets, wings and so forth. Along the way the knowledge base matured and the population of trainers became accepting and competent with this new fangled thing called a buoyancy compensator. In a similar time frame heavy wetsuits and more compressible, dry suits, larger cylinders and mixed gasses enabling deeper dives were also becoming more commonplace. All things considered in many circumstances swimming up a negative rig began to be a fools errand.

Also it became known that exertion is not conducive to optimal off gassing making the swim up less attractive.

Of course as the water gets warmer and the gear lighter this begins to be a moot point but training practices need to encompass the more severe situations.

Pete

 

[Rich Keller]

I would suggest that you weight yourself so you are neutral at the surface with your tank at 500 psi. At the beginning of your dive the BCD will only need to compensate for suit compression at depth and the weight difference between a full and empty tank. Scuba Cylinder Specification Chart from Huron Scuba, Ann Arbor Michigan At the end of your dive the tank weight will be where you want it to be so the only weight difference will be suit compression which will get better as you get closer to the surface. Another suggestion would be to do your initial dives at 30' rather then 60' if you are diving in murky water anyway it is all going to look the same. Take the initial time working shallow to get accustomed to your gear and just being there before you move onto something deeper or more advanced.

---------- Post added September 1st, 2013 at 08:49 AM ----------

I find it incredible that ANYONE would think that dumping all the air from a BC to initiate an ascent is good advice. Is this some new PADI Advice? I certainly don't remember ever hearing it when I was a PADI instructor?!!

Seriously, for cold water diving in wetsuits this is NOT a matter of opinion, it is F'n WRONG.

This is not something new, we did this all the time during cold water dives before BCDs were invented. For all the talk I hear about buoyancy it seems to me that people depend too much on a BCD. I still weight myself the same way I did over 40 years ago only wearing a BCD when it is required but I rarely ever put air into the thing.

 

[psychocabbage]

Holy post resurrection batman!!!
hahah

Ok, I will weigh in here as well. The OP, some 2 years ago posted this and stated that he put himself into an overweighted state to slow his ascent. His main question is regarding air in his BC to come up. I would not recommend this to any new diver. I don't think adding extra weight is the answer either. I would say practice and patience is the key. Take your time. I would rather know I am being safer and increasing my chances of diving another day than to shoot up and maybe not diving again ever.

I personally never use any air in my BC to come up and it is rare that I am adding air to it at all during the dive. It happens but not all too often. When its time to come up, what I personally do, is at about 40 ft, I deploy my safety sausage on a reel. I tend to be just a tad negatively buoyant and I reel myself in slowly. This ensures I come up slowly and I am occupied with a mundane task so I take this time to just look around. Typically my younger daughters would hang on me as I reel us up. At 20 ft, doing our safety stop is just a matter of turning the lock screw in and relaxing... Once our computers give us the all clear, back to reeling us in. I have found that the last 10 ft for some reason will always go way too fast for my computers liking.