buoyancy ??

[jesstotheocean]

When I did my Open Water Test I was having major problems staying Neutrally Bouyant. I would either just not go down (I know I had enough weights, it was my breathing and exhaling). I know how to fix that now, but when I did get down I couldn't stay neutral, I would either hit the bottom or I would inflate my bc a bit and fly up. I gues my question is how long should I wait after I inflate my bc a bit to realize if I should do it more? I'm going on a cruise in March and plan on diving every place we stop and I don't want to harm any coral or anything in the water.

 

[MikeFerrara]

The idea is to anticipate needed adjustments and stay ahead of things. If you wait until you're sinking or rising...it's too late and you're playing catchup and only marginally in control...if at all.

It's really too bad. You should have a pretty good handle on this before ever going to open water checkout dives. It can be dangerous (not to mention not fun) otherwise.

I think you should ask your instructor for your money back.

 

[Don Burke]

When I did my Open Water Test I was having major problems staying Neutrally Bouyant. I would either just not go down (I know I had enough weights, it was my breathing and exhaling). I know how to fix that now, but when I did get down I couldn't stay neutral, I would either hit the bottom or I would inflate my bc a bit and fly up. I gues my question is how long should I wait after I inflate my bc a bit to realize if I should do it more? I'm going on a cruise in March and plan on diving every place we stop and I don't want to harm any coral or anything in the water.

I have come to use my lungs as my primary short-term buoyancy control. I only use my BC to keep the buoyancy within the limits that my lungs can handle.

It sounds like you are overweighted and are using the BC as an elevator.

 

[NauticalbutNice]

I know this is a horrible, and possibly patronising question, but how quickly do you put air in your BC? Do you add it in tiny bursts, or just shove some in?

Just add the air in little bursts, with a pause between each, and you should be ok. Otherwise it may suggest weighting problems or something else.

Fab attitude by the way!

Nauticalbutnice :fruit:

 

[mossym]

I have come to use my lungs as my primary short-term buoyancy control. I only use my BC to keep the buoyancy within the limits that my lungs can handle.

It sounds like you are overweighted and are using the BC as an elevator.

same here, but that wasn't something i had mastered by my ow checkout dives!!

 

[donacheson]

When I did my Open Water Test I was having major problems staying Neutrally Bouyant. I would either just not go down (I know I had enough weights, it was my breathing and exhaling). I know how to fix that now, but when I did get down I couldn't stay neutral, I would either hit the bottom or I would inflate my bc a bit and fly up. I gues my question is how long should I wait after I inflate my bc a bit to realize if I should do it more? I'm going on a cruise in March and plan on diving every place we stop and I don't want to harm any coral or anything in the water.

You should realize that being neutral is usually an unstable equilibrium: if you're light and ascend, you get lighter; if you're heavy and descend, you get heavier. It's something like being on top dead center. The only circumstance in which you can remain neutral while ascending or descending is if your carrying nothing that's comressible - no foam wet or dry suit, no air in your BC or dry suit. But that condition obtains only at the end of a dive when you're not wearing a compressible wet or dry suit and you've depleted almost all the air in your tank so that, if you're properly weighted, your BC is empty.

The more air you have in your BC, the more pronounced will be in instability. The way to minimize the amount of air in your BC is to be properly weighted: neutral just below the surface with an empty BC and near-empty tank and breathing normally.

With experience, you'll learn to anticipate chnages in buoyancy and compensate for them smoothly. Breathing normally but off fuller or emptier lungs is used by divers to control buoyancy. A little finning also helps maintain depth.

That raises a question for the experienced divers out their. A single Al80 contains about 6 pounds of air. Can any of you compensate for the loss of that much weight using their lungs alone? In other words, can you get neutral at the beginning of a dive and then remain neutral for the entire dive, including a safety hang at 10 or 15 feet, without adding/subtracting air from your BC? I can't.

 

[simbrooks]

That raises a question for the experienced divers out their. A single Al80 contains about 6 pounds of air. Can any of you compensate for the loss of that much weight using their lungs alone? In other words, can you get neutral at the beginning of a dive and then remain neutral for the entire dive, including a safety hang at 10 or 15 feet, without adding/subtracting air from your BC? I can't.

I heard somewhere that you can affect your buoyancy by as much as 9# (i think those were some decent sized lungs - about 1 gallon displacement) and at least by 6# with smaller lungs (2/3 gal), cant recall where i heard/read it, but it doesnt sound too far out. I think those numbers are from max to min usable volume. Throughout my dives i hardly have any air in my wing - or at least it always feels kind of empty until i ascend a good distance, when diving with an AL80. With my double 120's i have a good amount of air in my wing

As for the original question, is there any chance you can get out there and dive in your area, even if not with an instructor, sounds like a little extra time getting through this might help you a good deal before your trip next year. Its a tough balance to try to get right at the beginning. Have you done a good weight check to ensure you arent overweighted (method as suggested above), the tiny bursts (1/2-1 sec) of air in the BC is your best way to add more air, then go through a breathing cycle, if you are still sinking add more air. On my decents i always give a little burst every 10ft or so to try to avoid over-compensating at the bottom - playing catch up as Mike Ferrera mentioned. There are a few threads on proper buoyancy control as well as info in your OW text, it just sounds like you need to go somewhere fairly shallow and practice a while - which is never a bad thing for anyone of any experience level once in a while

 

[RICoder]

Bouyancy takes time to get good at, and even longer to master. My first recomendation is to take the PADI Peak Performance Bouyancy Specialty course. THAT will change your life.

Here's my 2 cents:

1) Most, if not all, divers overweight for the simple reason that they "can't get down". This is normal, because the first 10 feet are always the toughest. Indeed NAUI and PADI both have calculations to estimate dive weight. My experience shows them to be about 6-8 lbs heavier than necessary.
2) If you're overweighted, and you most likely are, you're not going to find nuetrality, ever, period, end of story. You'll pitch, you'll roll...it sucks.
3) As much as being able to control your depth precisely with your lungs goes...don't worry about it right now...that comes with time. Your biggest concern as a new OW is getting trim in the water, conserving air, and stability / nuetrality. These things are a natural affect of being properly weighted.

My suggestion is this: Get wet once, just to be comfy in the water again. Shave 4lbs from your weight belt on the next dive. At the surface, be sure your BC is totally empty and breath all the way out, only breath in shallowly and don't pause before you breath out again. You'll get down fine. Be careful doing all of this, maybe even ask one of the dive masters on the boat to hang with you and help you with your bouyancy. The second dive is always shallower, and is the right time to get squared away with this. If you do it on the first dive day, your trip will be more fun.

I'd also hit the LDS and grab a PADI Specialty Course book and read the Peak Perf. section...keeping in mind that their calculation for weight is kinda heavy.



-------------------
As to handling an empty tank with your lungs...it can be done by breathing shallower at the safety stop...or hold onto the line real tight


**if you're using your lungs to control bouyancy, just remember NEVER to hold your breath. You can suck in some air, and sustain that, but don't close off that airway.

DIVE SAFE
-RIC

 

[simbrooks]

One of the great "cant get down" reasons is that people dont realise that they are finning (ie pushing themselves up), try to hold your feet together and motionless as you drop the down - i would suggest going horizontal, but that is something else entirely, get it down this way first then move on to more helpful practices

 

[donacheson]

I heard somewhere that you can affect your buoyancy by as much as 9# (i think those were some decent sized lungs - about 1 gallon displacement) and at least by 6# with smaller lungs (2/3 gal), cant recall where i heard/read it, but it doesnt sound too far out. I think those numbers are from max to min usable volume. ...

I used to go to a doctor for my annual physical who measured my lung capacity regularly. It was about 6 liters, equivalent to about 13 pounds - totally empty to totally full. With age, that's undoubtedly diminished, but it's impossible to breathe normally (some above and some below) with a full lung nor an empty lung. Since I Know my air consumption rate and about how often I take a breath, I can estimate that each breath takes in and lets out two in 2 liters. That suggests that perhaps I should be able to adjust my breathing from 0 to 2 liters around an average lung volume of 1 liter up to 4 to 6 liters around an average lung volume of 5 liters. That's an average difference of 4 liters.

Since a liter of air displaces 2.2 pounds of water, that would imply I could compensate for almost 9 pounds of weight change with my lungs alone. I can't do nearly that much. Can anyone?