VERY basic BC technique questions

[web.boards]

I am brand new to diving and am going through the process of getting certified. I will not meet with my instructor again for another week, and in the meantime, have a couple of basic questions I'm hoping someone can help me with:

1. At various times while practicing in the pool, I found myself ascending without even realizing it. Does this mean I am not properly weighted? If so, is letting air out of my BC the main thing that I can do to not ascend without being able to get more weights?

2. When descending, at what point do you let air into your BC?

3. While ascending at the end of a dive, at what point do you let air into your BC? While at the surface only?

Thank you for your patience.

 

[g1138]

I am brand new to diving and am going through the process of getting certified. I will not meet with my instructor again for another week, and in the meantime, have a couple of basic questions I'm hoping someone can help me with:

1. At various times while practicing in the pool, I found myself ascending without even realizing it. Does this mean I am not properly weighted? If so, is letting air out of my BC the main thing that I can do to not ascend without being able to get more weights?
Do not add weight to sink yourself. You should have to pike dive down to about 3ft before you start to sink. The ideal weight is enough to hold you neutral @ 15ft with a low tank of air. That's ideal. It be better to be slightly negative than positive at a safety stop, but don't overdo it. Alot of new divers do.
In a pool, because it's so shallow, you should have a bit more weight, BY RATIO (salt water and wetsuits make you more buoyant than freshwater).
Your instructor should be able to help you sort this out.

Also to descend you should deflate your BC fully

Forgot to mention, your breathing has a big impact. A full breath can make you rise, while exhaling can sink you. Having control of your breathing comes with time in the water, so don't stress it. Get you BC filled under the water to maintain a decent neutral state and try your best to calm down and breath calmly, and relaxed.
And never hold your breath ;D


2. When descending, at what point do you let air into your BC?
You should let all the air out of your BC before descending. With a full breath you should be a little above eye level with the water. Exhale and you should sink to a little under eye level. Do a dive and swim down.

When you approach your bottom or the depth you want to hold at, put a little input into your inflator. Tap the inflate button in short bursts and wait for the air to take effect. Achieving neutral buoyancy isn't instant, there's always a delay as your momentum slows.
This comes with practice. I'd say in a 12ft pool, give your inflator a tap about 3 ft from the bottom. Begin by practicing a descent where your feet hit the bottom lightly, and gradually work up to where you can stop and hover on your belly above the bottom.

In a pool, 3-4 bursts are usually the max anyone needs. Provided they're aren't overweighted.

3. While ascending at the end of a dive, at what point do you let air into your BC? While at the surface only?
Never use your BC as n elevator. Swim up at 30ft/min. Or slower than your tiniest bubbles.
Inflate only at the surface.

Thank you for your patience.

To further add on, your BC is to float you only on the surface, and on the bottom it is used to keep you neutral so you're off the bottom.

Definitely don't be hesitant to ask your instructor any sort of questions.
Or the people here for that matter.
Welcome to the board btw. =]

 

[Garrobo]

1-Not enough weight or air in your BC. 2-When you want to stop descending. 3-Yes.

 

[aquaregia]

1. At various times while practicing in the pool, I found myself ascending without even realizing it. Does this mean I am not properly weighted? If so, is letting air out of my BC the main thing that I can do to not ascend without being able to get more weights?

If you have air in your BC and are unwillingly ascending, remove air from the BC. If you can no longer maintain a depth that you wish to maintain and your BC is empty, you are likely underweighted.

I do not agree with surface diving to depth in the general case. In my opinion, it is important to maintain effective buddy contact at all times, which might necessitate you hovering with your buddy at 3' while he or she clears his or her ears. The non-general cases are, IMHO, out of scope of "Basic Scuba Discussions"

2. When descending, at what point do you let air into your BC?

When descending, you want to be negative. You should add air to your BC to make sure that you are only negative enough to be descending at the rate you wish. You shouldn't need to kick up against your weight in order to clear your ears or watch your buddy. I would never descend fast enough that I couldn't arrest my descent within my limit of visibility. You should not hit the bottom.

More directly, with largish tanks and a thick wetsuit, I start hitting my inflator button perhaps at 4'.

3. While ascending at the end of a dive, at what point do you let air into your BC? While at the surface only?

While ascending, you want to maintain control of your buoyancy. That is, you will need to remove air from your BC to prevent a buoyant ascent. Reinflate your BC at the surface for comfort and to prevent yourself from drowning if you're overweighted.

I know this is a lot of non-answers. Basically, you need to maintain control of your buoyancy at all times. The BC is used to compensate for the compression of the wetsuit at depth and the gas you will consume. For warm water diving with a small tank, I hardly touch my inflator at all.

 

[knowone]

I have never considered doing a pike dive to the depth of half a body length.

Nor would I consider of much value anything in post 2, and certainly suggest that
most may be considered health detrimental when you progress, post course and the pool.

 

[g1138]

I have never considered doing a pike dive to the depth of half a body length.

Nor would I consider of much value anything in post 2, and certainly suggest that
most may be considered health detrimental when you progress, post course and the pool.

The pike dive was in reference mainly for ocean dives.
Guess I jumped the gun.
But you can still practice in a pool. You don't necessarily have to dive straight down, shallow angle dives work too.

Care to share your opinion in the matter?

In reference to what aquaregia said about surface diving. He's right, you should descend with your buddy, and stick with your buddy at all times. But if a surface dive is the only way to get you under, and you have the visibility to do so and see your buddy, you can do a surface dive and immediately revert yourself to be face to face w/ your buddy.
It's all personal preference how you get down. You could perform a kelp dive so you descend feet first and it would work the same way.

Just don't go in overweighted.

 

[MauiScubaSteve]

I am brand new to diving and am going through the process of getting certified. I will not meet with my instructor again for another week, and in the meantime, have a couple of basic questions I'm hoping someone can help me with:

How many times have you met with your instructor so far? What agency is your certification through? If it were PADI I would ask how much of the Manual have you read and how much of the DVD have you watched? How many pool sessions have you had with your instructor? How many chapters of your Manual have you gone over with your instructor? If you had done a couple sessions in the pool and gone over half the Manual with your instructor, and watched the DVD, then it seems you have been given most of your answers already.

1. At various times while practicing in the pool, I found myself ascending without even realizing it. Does this mean I am not properly weighted? If so, is letting air out of my BC the main thing that I can do to not ascend without being able to get more weights?

Situational Awareness! If you are near/on the bottom and suddenly you are unable to keep from corking to the surface you need to be more aware of what is going on with your body. Shallow water, like most pools, is where the greatest change in volume/lift happens as we change depth. If you have added air to your BC to be neutral at 10' depth with a half full lung, when you have more than a half full lung you will not be neutral. If you allow yourself to then rise a foot the air in your lungs and the air in the BC now expands giving significantly more than neutral lift. If you were on your knees you can exhale immediately, flap your arms with palms facing up to try to keep yourself down &/or let air out of you BC. If you are in a more prone position, you could orient more head down and add finning down to the above exhale, reverse arm flap and BC venting.

2. When descending, at what point do you let air into your BC?

That depends; you could wait until you are as deep as you intend to go and then add a lot of air to your BC to stop your decent, but you then also need to be ready to immediately let some air out of the BC if you added too much. Or you could add a little every few feet or so to keep your descent slower and more in control. With practice, some can fin down with free dive fins as fast as they can fin, all the way to 90 feet deep and then hit the button for a solid 3-4 seconds, leveling out for a photo like this;

​

3. While ascending at the end of a dive, at what point do you let air into your BC? While at the surface only?

In warm water, with less lead, many are content to just let all the air out of the BC and then just swim up (negative ascent), in colder water, with lot's of lead, many like to let air out as needed, using the deflating BC as the still positive lift for the ascent, but a slow controlled ascent not an out of control ascent (neutral ascent?). In both cases you are correct on ascent the only time we add air is to float at the surface, unless you were trying to make the ?neutral ascent but let too much out at some point. I think you should just swim up a little then and not add air on ascent.

 

[EevelMonkee]

I am brand new to diving and am going through the process of getting certified. I will not meet with my instructor again for another week, and in the meantime, have a couple of basic questions I'm hoping someone can help me with:

1. At various times while practicing in the pool, I found myself ascending without even realizing it. Does this mean I am not properly weighted? If so, is letting air out of my BC the main thing that I can do to not ascend without being able to get more weights?

Your instructor has probably given you weight that is pretty close to what you need based on your body weight/composition and exposure suit and he also should have shown you how to test for proper weighting. New divers generally have poor breath control (breathing too rapidly and not exhaling completely) which causes involuntary ascents, even if they are over-weighted. Additionally, once the involuntary ascent begins, they began flailing and breathing more rapidly and that leads to further lack of control. Breathing technique is very important in buoyancy control. With an empty BCD, you should be able to descend slowly in a heads up, vertical posture by exhaling. At depth, you should be able to make minor depth adjustments by exhaling and inhaling. A PPB course could help with this but it mostly comes with practice.

2. When descending, at what point do you let air into your BC?

Once you reach your max depth, if you cannot achieve neutral buoyancy with breath control, tap your inflator button to add very small amounts of air. After each tap, wait a few seconds and see how it feels. You should not be floating up and at the same time not feel like you have to take unusually deep breaths to keep from dropping.

3. While ascending at the end of a dive, at what point do you let air into your BC? While at the surface only?

You will likely be releasing air from, not adding air to, your BCD during ascent. The air you add to stay neutral at depth will expand during ascent and cause you to ascend too rapidly once you reach <10m / 30fsw. You usually have to release some of this air (again, tap, don't hold the deflator) to stay neutral on the safety stop. Only inflate fully, or as much needed to float, at the surface right before you remove your regulator.

These air just tips. Discuss all this with your instructor!

Thank you for your patience.

Enjoy the rest of your course and Happy Holidays!

 

[MauiScubaSteve]

Do not add weight to sink yourself. You should have to pike dive down to about 3ft before you start to sink. The ideal weight is enough to hold you neutral @ 15ft with a low tank of air. That's ideal. It be better to be slightly negative than positive at a safety stop, but don't overdo it. Alot of new divers do.
In a pool, because it's so shallow, you should have a bit more weight, BY RATIO (salt water and wetsuits make you more buoyant than freshwater).
Your instructor should be able to help you sort this out.

At the beginning of a dive with a full 3000 psi 80 cft, you have 4-ish pounds of air that you will not have when you are making your safety stop with ~500 psi. If I plan to be a couple pounds negative for my safety stop, I will be ~ 6 lbs negative at the beginning of the dive. Why would I need to pike dive if I am ~6 lbs negative with a fully deflated BC?

Also to descend you should deflate your BC fully.

Perhaps the reason you need to pike dive is because you have not fully deflated your BC. Since we are 4-6 lbs negative, with a normal breath, at the beginning of the dive, if you fully exhale you should sink before you fully deflate. Then descending compresses both the air in the BC and the wet suit so you would get more and more negative as you get deeper. I often do not deflate at the surface and just haul myself down the mooring line. When I reach depth I still need to add air to my BC even starting with a fully inflated BC at the surface.

Another thing beginners do is remain vertical, squirm and twitch, which flexes the fins and pushes you up. I prefer to get the fins higher than my head and then squirming and twitching pushes down instead of up.

Forgot to mention, your breathing has a big impact. A full breath can make you rise, while exhaling can sink you. Having control of your breathing comes with time in the water, so don't stress it. Get you BC filled under the water to maintain a decent neutral state and try your best to calm down and breath calmly, and relaxed.
And never hold your breath ;D

Just wondering; how do you equalize your ears? The truth is that you should not hold your breath while ascending. Obviously since the majority of divers hold their breath to equalize their ears on descent the don't hold your breath rule is just a line we use because we don't think beginners have enough situational awareness to know if they are going up or down.

You should let all the air out of your BC before descending. With a full breath you should be a little above eye level with the water. Exhale and you should sink to a little under eye level. Do a dive and swim down.

With a 500 psi tank, many weighting guidelines suggest one be eye level with a fully deflated BC and holding a normal breath. At the beginning of an 80 cft dive, when you float eye level with a normal breath held and a fully deflated BC you will need to add 5-ish pounds to be right at your safety stop.

Swim up at 30ft/min. Or slower than your tiniest bubbles.

The tiniest bubbles may be going 60 feet per minute. That is how divers were trained back when the recommended ascent speed was 60 feet per minute.

 

[ajduplessis]

I am brand new to diving and am going through the process of getting certified. I will not meet with my instructor again for another week, and in the meantime, have a couple of basic questions I'm hoping someone can help me with:

1. At various times while practicing in the pool, I found myself ascending without even realizing it. Does this mean I am not properly weighted? If so, is letting air out of my BC the main thing that I can do to not ascend without being able to get more weights?

2. When descending, at what point do you let air into your BC?

3. While ascending at the end of a dive, at what point do you let air into your BC? While at the surface only?

Thank you for your patience.

1. Firstly, even if you are correctly weighted, it is difficult maintaining good buoyancy in shallow 5m (15ft) water, especially being new to scuba and using ALI tanks. Focus on your breathing, keeping it steady and relaxed. Normally workload and the added “stress” of the waterman skills will have an effect on buoyancy too. Also remember that inputs to your BCD will take a coupleof second to take effect. Generally students expect instantaneous results, give it time and watch your breathing.
2. While descending you gently every now and then add air to the wing. You want to maintain a descend rate of 10m (30ft) per minute. I inhale and keep it in just before arriving at my depth, adding air to the wing until you are neutral in the water works well for me.
3. Yes, only at the surface. You keep dumping small amounts of air out of the wing every 6ft or so until you reach your safety stop. Remember that the last 20ft the air in your wing will keep expanding more quickly. This is also the most crucial part of the dive. Keep it as slow as you can.