Question regarding neutral buoyancy

[Raphus]

Now I understand how important proper weight is, I will request a weight check if and when I take another course

No, not when you take another course.
Do it when u go diving. You can do it on your own.

A weigth check is usually done with a "empty" tank, means 700 psi/50 bar.
If you do it with a full tank, you should be slightly overweighted, because you will loose about 1.5 kg of weigth, when the tank is empty(thats the weight of the gas, depending on tank size ofc..)

I will explain the check for an empty tank:
Ok stay on the surface. Inhale as much as you can. And release all the air from. Bcd/wing.
You sink? - > To much weigth.

You dont sink? Ok fine. Now exhale a bit so you have a "normal" full lung.
Your head should now be partialy underwater. Some people say the surface needs to be on eye level. Other say it needs to be on top of your head. Doesnt really matter that much. And is abit personal preference(i will come to that later).

Now fully exhale. Do you sink fast? Maybe still to much weigth. Sink slowly, or staying neutral with the head fully submerged? Then you are good weighted.

The goal is to hold a 3m (some say 5m) with a normal lung capacity, without any air inside the bcd.
If you are neutral at 3m with a bit air in your lungs(yes you need to breath on the saftestop), then you are about neutral without air in your lungs at the surface.
Of course there is more to think about.
Wetsuit thickness and all that stuff, but thats a good estimate.

Personally I like to be able to hold a 1m stop, with very shallow breathing.
So i dont have problems when ascending.

I dont do formal Weigth checks. If i have a new configuration i just see how fast a descent and how much air i got in my bcd at the sateystop. If i dive new gear i take a kilo more then i need, becasue underweighted is worse then overweighted. And then ditch as much as i neednafter the first dive.

Being properly weighted is very important. And makes diving so much easier.
I remember one guy, who dived with 8 kilo. And he had so much peoblems holding the stop, or even ascending in a controlled way. He said he was underweighted and wants to take 2. More kilos with him.

I convinced go to go into the next dive with only 2 kg instead if his 8 or 10 kg.
He disnt believe me, but he tried it out and it was enough weigth for him(5mm in fresh water). And he dived soooo much better.

So dont wait until your next course. Do it yourself

 

[scubaozy]

Fin tips are a practice that need to stop. When a diver's fin tips touch the bottom, they are foot heavy and not neutrally buoyant.

I watched a video in another thread about teaching OWD course NB, they were holding a bar and course was advertised as NB teaching and had the same thoughts as you; how can you be NB when holding a bar?..

PADI does NOT teach buoyancy as a seated Buddha position.

Buddha position pictures are in OWD manual also in a lot of videos. But, yes, its not part of the standards. I have never enforced such position but it has its benefits as well. It will inhibit uncontrolled hand flutter and fin kick forcing the student to focus on the breath control.

Many of you have pointed to overweight as the possible culprit here

This might not be the only problem. Usually once you establish NB you are neutrally buoyant within a range that you control with your breath. If you are overweight, that range is very narrow, so you may loose your control much easier if you:
1. Start finning anything less than perfectly horizontal; so any thrust you generate must be horizontal when transitioning from motionless neutral position to swimming
2. Once you start swimming (kicking that is), you are already breathing more erratically, which will also ruin your nicely maintained buoyancy, so you might want to pay attention to your breathing and anticipate and compensate any change in your buoyancy, when transitioning from idle neutral buoyancy to swimming.

 

[CAPTAIN SINBAD]

Lets break down the breathing cycle.

There is a positive part, where you inhale and you go up. Then there is mid point - where the air in your lungs is more or less enough to keep you neutral. Lastly, there is negative when you exhale and you sink.

As a new diver, we all have the need for mental assurance that we can breath!!! We create that mental assurance by taking exaggerated breaths. This exaggerated breathing is nothing but the new divers way of convincing him or herself that they are still alive! It has nothing to do with you actual need for air. What is does it create buoyancy swings. Keep in mind that if you rise up only slightly from a state of neutral buoyancy, the air in your bcd will expand a tad bit and make you positive. It will cause you to rise and the higher you go the more buoyant you get.

The solution is simple. When you are in the water, focus on relaxing your body. Ask yourself, "Am I as relaxed as I would be if I was lying down on my bed? If not, then try to let go of your body until you have achieved this state of super relaxation. You will notice that your breathing cycle will also start stabilizing into a state of calm and neutral breathing.

Then you can fine tune your bcd to give you a perfect hover in that state of breathing. Ascent breaths can then be used to make you go up but always remember to vent the bcd when you are at the desired depth.

Its a long journey but you are on the path so good luck!

 

[wetb4igetinthewater]

I watched a video in another thread about teaching OWD course NB, they were holding a bar and course was advertised as NB teaching and had the same thoughts as you; how can you be NB when holding a bar?..

I don't use a bar, but I think that they can be used for momentary stabilizing. If a student never let's go, that's an issue in my view. However, they are likely not applying as much weight on the bar as they would with fin tips for the simple reason that people are typically foot heavy.

IBuddha position pictures are in OWD manual also in a lot of videos. But, yes, its not part of the standards. I have never enforced such position but it has its benefits as well. It will inhibit uncontrolled hand flutter and fin kick forcing the student to focus on the breath control.

Still needs to go. Have students hold one wrist with the other hand. If you distribute weight properly, they are not sculling with their fins.

This might not be the only problem. Usually once you establish NB you are neutrally buoyant within a range that you control with your breath. If you are overweight, that range is very narrow, so you may loose your control much easier if you:
1. Start finning anything less than perfectly horizontal; so any thrust you generate must be horizontal when transitioning from motionless neutral position to swimming
2. Once you start swimming (kicking that is), you are already breathing more erratically, which will also ruin your nicely maintained buoyancy, so you might want to pay attention to your breathing and anticipate and compensate any change in your buoyancy, when transitioning from idle neutral buoyancy to swimming.

[/QUOTE]
I disagree on both points. Yes, if a student isn't perfectly horizontal, they will continue to ascend slowly as they swim forward. Except they can make adjustments by correcting their trim, exhaling completely, etc.

I don't think that students comfortable in the water start breathing erratically. Keyword is comfortable. There are a number of things I do prior to having students in scuba, including a modificaiton of some mask/snorkel skills taught to me by @Peter Guy.

 

[napDiver]

I never really understood the on the surface weight check. I skip all that and go right to the actual check.

1) Wearing all the gear you want to do the check with (lights, specific tank, specific exposure). I would put a 2lb lead weight on your tank cam band and another 2 lb lead weight on your buddy's tank cam band.

2) At the end of the dive, stay and hover at the shallowest depth you expect to dive in at the end of a dive (usually 15 ft) for at least 1 minute while your tank is at the lowest pressure you expect it to stay at (750 psi or what have you).

3) If you can't hover for 1 minute at that depth

A) You are floating up and need to swim down, ask and remove the 2 lb weight from your buddys cam band. Hold it in your hand and hopefully you can hover for 1 minute without issues. If you still can't, then you must redo the weight check with more weight on the next dive.

B) You are sinking and need to swim up to stay at depth. Have your buddy remove the 2 lb weight from your cam band and have them keep it. If you still have the same issue, then you must redo the weight check with more weight on the next dive.

C) If you have no issues floating or sinking, you can try to remove the 2 lbs. But basically you are weight check correctly and don't really have to change any weighting +/- less than 2 lbs.

Note: I'd do a weight check anytime you have major changes. Different tank type, different exposure (buoyancy will change from new to well used thick wetsuits), different bcd, lost 20 lbs, gain 20 lbs.

Cheers

 

[wetb4igetinthewater]

@napDiver

Is a minute really necessary? A few breath cycles of falling and rising with the breadth in a "tight" window should be sufficient.

 

[napDiver]

@napDiver

Is a minute really necessary? A few breath cycles of falling and rising with the breadth in a "tight" window should be sufficient.

True a minute isn't necessary, I just choose an arbitrary but sufficient amount of time. Just enough to dump all your air, make sure you are breathing normally. I guess 5-10 seconds could be sufficient. But 20 seconds would be more then sufficient too.

 

[wetb4igetinthewater]

True a minute isn't necessary, I just choose an arbitrary but sufficient amount of time. Just enough to dump all your air, make sure you are breathing normally. I guess 5-10 seconds could be sufficient. But 20 seconds would be more then sufficient too.

I was just looking at it from the instructor point of view, checking students' weighting at the end of OW1/2/3 (better have it dialed in by this time).

 

[Blackcrusader]

Doesn’t help that PADI teaches buoyancy as a seated Buddha position. Ridiculous. When In real life diving is this appropriate? No where. Should be starting with fin pivot then next exercise is horizontal neutral buoyancy. And it doesn’t help that PADI teaches breath deep for efficiency. Put an new or relatively new diver in 15-20 feet of water and they are all over the place.

There are times when the buddha hover is appropriate. In this thread a diver asks why he cannot do so. I do it at times when in a nice drift dive and sometimes at the end of a dive as I get a better view of where other divers are. I was never taught this in any of my courses either padi or bsac. A diver who is correctly weighted and balanced can go from horizontal trim to vertical trim or hover or be in whatever position is required.

I get divers who ask me how can I maintain depth control when in the hover position with my legs crossed and not using fins. So they learn from other divers how to be correctly weighted and be able to use their lungs for controlling depth and to allow for themselves to move in the water and not flail their hands or legs. There are times when using hands for propulsion was taught which was also discussed.

Buoyancy question how do you maintain a sitting hover?

 

[wnissen]

Many of you have pointed to overweight as the possible culprit here, and upon more reflection of my experiences, I think you are probably right. I checked my divelog and it turned out I was given 3kg(6.6lbs) more weight in my aow course than in my ow course(my physique hasn’t changed much), and I remember this wasn’t much of a problem during ow. My aow instructor actually mentioned that he was giving me more than enough weight for reasons I don’t remember and probably didn’t understand. He said you will need less weight as you get better, to which I thought “ok?”. Indeed all the dives except one deep dive were also done with less than 10m(33ft) depth, that explains the more drastic change in buoyancy brought by air volume expansion.

Neither in ow nor in aow did the instructor do the float-at-eye-level weight check with me, probably due to time constraint or other logistic reasons. Now I understand how important proper weight is, I will request a weight check if and when I take another course.

Thank you for your wisdom!

This part makes me worry about your instructors. Some kind of weight check is essential, otherwise you have no idea how much you might be overweighted. Yes, if you're badly underweight you can't descend, but presumably everyone figures this out on their own and it does not cause a problem except having to exit the water and get more weight.

And the instructor should never give you what they think is proper weighting, unless you're in a new exposure suit or other big change in gear, and in that case they should be asking you what you had before and then modifying it. You tell them, not the other way around.