Neutral buoyancy question.

[ajcyang]

Thank you guys for the pointer and explanations.

For people who doesn't like the fin pivot/buddha exercise. How then do you show students correct way to have neutral buoyancy?

I commented on the 10 second breathing is because there was another thread on SB and basically the conclusion I got was to exhale + inhale fully and slowly at ratio of 1:2 (exhale). Which got me wondering about how it affects my vertical axis while diving. Thank you Netdoc for pointing out that it will be harder to do so at 30-40fsw, which is where I do my diving.

 

[nimoh]

Thank you guys for the pointer and explanations.

For people who doesn't like the fin pivot/buddha exercise. How then do you show students correct way to have neutral buoyancy?

I commented on the 10 second breathing is because there was another thread on SB and basically the conclusion I got was to exhale + inhale fully and slowly at ratio of 1:2 (exhale). Which got me wondering about how it affects my vertical axis while diving. Thank you Netdoc for pointing out that it will be harder to do so at 30-40fsw, which is where I do my diving.

Basically it is similar to fin pivots, except that your fins aren't on the bottom.

 

[The Chairman]

Basically it is similar to fin pivots, except that your fins aren't on the bottom.

If you can do fin pivots, odds are your trim is off and your butt is down. My students would find it impossible to do fin pivots so I don't ask them. If they are too heavy, they simply add a touch of air. If they are about to hit the reef (not good) they use the one finger push away. There is always a dead spot on the reef and one finger is all you need to keep off the bottom. Fins should, never ever touch the bottom.

 

[TSandM]

ajcyang, Rick Murchison has an excellent ESSAY on why neutral buoyancy, isn't -- it addresses exactly your befuddlement about breathing and buoyancy. In short, people who can hover like Andrew does in the video you posted, have mastered the art of breathing in a certain rhythm, around a certain average volume, that results in very little excursion in the water column. In fact, in double tanks, the excursions may not even be visible, because the inertia of the diver/gear system is great enough that you end up not moving at all. This takes time to master! The idea behind the fin pivot is to show you that, if you inhale and begin to rise, that you can exhale and stop the rise. The exercise is supposed to give you the first sense of what that breathing rhythm is.

We don't do fin pivots with our students, or Buddha hovering, or kneeling. We start students out horizontal on the surface, and have them gradually let air out of their BCs until they are just underwater. They pick up the concept of neutral buoyancy pretty quickly that way. All skills are done either resting lightly on the fin tips, on the stomach on the bottom of the pool, or hovering. Most students can do the basic skills easily in midwater by the end of the last pool session.

And regarding your question about just picking your feet up -- Physics determines that. If you think about it, when you are floating in the water and not moving, you will rotate until the light things (lift) are directly above the heavy things. If your equipment is arranged so that the center of gravity of the diver/gear system is directly beneath the air in the BC bladder, then you can hang in a horizontal position. If your weights are too far down your body (tank too low, integrated weights too far down the bC) then your feet will sink. If you have a whole bunch of floaty neoprene on your legs and feet, you may tend to go head-down. Some of this can be compensated by posture (see THIS article on trim) but not all.

 

[nimoh]

If you can do fin pivots, odds are your trim is off and your butt is down. My students would find it impossible to do fin pivots so I don't ask them. If they are too heavy, they simply add a touch of air. If they are about to hit the reef (not good) they use the one finger push away. There is always a dead spot on the reef and one finger is all you need to keep off the bottom. Fins should, never ever touch the bottom.

re-reading my short answer, I seem to have implied that it is basically fin pivots, but a little higher up so that your fins aren't touching. I meant similar to fin pivots but without your fins being the lowest part of your body...you belly should be the lowest.

 

[Frosty]

Maybee my thinking is a bit twisted here folks but in my opinion the best place to practice boyancy control is diving is a shallow lagoon/pool etc.
With my kids Ive been getting them to try to stay at exactly 2.0m/7 feet underwater in a 4.0m lagoon.
Its the very fact its more difficult that apeals.
My thinking is "if you can get it right here then at 30 feet down its going to be easy"
The other advantage is that its a no harm situation to bob to the surface and discuss what they are doing right or wrong.

 

[chrpai]

Yup. The Florida Keys and Bahamas are great for that. The Sapona wreck in Bimini is 15' last I checked. I was doing that dive with a buddy on BlackBeard's once and we just spent an hour working on getting his weighting and trim right. An hour later he said he felt like I showed him more then his OW and AOW class combined.

 

[Craig Werger]

Hello,

There are lots of good points here already but here are a few of my thoughts aimed to those who wish to build their skill level to those like the demonstration video.

In order to achieve your goal of perfecting your buoyancy control there are several areas to look at.

Equipment

Breathing control

Propulsion techniques

Not all diving equipment is ideal for diving... . Sounds strange doesn't it? At any of the advanced back mounted configuration levels pro's opt towards the backplate and wing configuration. This gives the diver the advantage of providing buoyancy where it is needed, in behind. This along with proper weighting helps keep the diver in the horizontal position. An ideal configuration wouldn't require a weight belt but either a stainless or aluminum back plate depending on the amount of weight required. For tropical diving, this is normally enough for most people. For those needing additional weights trim weight pockets or an active control ballast system can take care of this.

I prefer to use the halcyon infinity system for single cylinder diving or the evolve system for diving doubles.

There are already some really good explanations of breathing control on this forum so I won't repeat. Most importantly, slow controlled breathing avoiding co2 retention is best. Breathe what you need, not less.

You will notice any diver capable of maintaining this trim position is likely a master of the basic propulsion techniques such as:

Frog kick/mod frog kick
Helicopter turn
Mod flutter kick
Back kick.... This is usually the most difficult but most helpful skill to learn

There are a lot of divers who consider these skills 'tech skills' however at the end of the day we are the same divers in the same water. For myself, any skill set or equipment configuration that allows optimum performance is ideal. Enjoy your time underwater and avoid contact with the environment.

For best results seek advise and or training from a professional with a high skill set, look for pictures or videos and compare the model video you are referring to. You don't need to wait until you have a certain number of dives to improve your skill level, the sooner you start perfecting these techniques the better for you and the environment you choose to enjoy!

Safe diving,

Craig Werger

 

[spectrum]

Thank you guys for the pointer and explanations.

For people who doesn't like the fin pivot/buddha exercise. How then do you show students correct way to have neutral buoyancy?

I commented on the 10 second breathing is because there was another thread on SB and basically the conclusion I got was to exhale + inhale fully and slowly at ratio of 1:2 (exhale). Which got me wondering about how it affects my vertical axis while diving. Thank you Netdoc for pointing out that it will be harder to do so at 30-40fsw, which is where I do my diving.

The fin pivot and and buddah exercise are parlor tricks to illustrate the effects of breathing on your immediate buoynacy. They also force you to find that tipping point hopefully leading you that breakthrough realization that at some point you will rise from the bottom. Once the concepts are experieinced they are useless. Of course there is the guy I dove with once that dropped to the bottom and hit like a dirt dart. He then carefully inflated his BC, did a fin pivot fifted from the bottom and commenced the dive.

Forget about timing your breaths, just be calm and deliberately breathe deeply. You will settle into someting that is comfortable for you. This will change over the course of the dive and as you mature as a diver.

Some amount of porpoiseing is possible with a long and deliberate breating cycle but most of it never happens. Water is quite viscous and an immediate change in your displacement will not equate to immediate vertical movement. What usually happens is that you are ready to exhale just as you body is ready no move vertically and then after exhaling when you are going to sink it is time to inhale. Any remaining movement is of no consequence most of the time. To some extent it can be furter managed with a little posture and finning technique. Lastly there will be times when you will modify your breathing for pinpoint depth control. There are times when I am moving air not for respiration but to tune buoyancy.

Finally remember that correct weighting is step one. Placement of that weight and other adjustments to attain natural trim is a next step activity. More here.

Pete

 

[chrpai]

At any of the advanced back mounted configuration levels pro's opt towards the backplate and wing configuration.



For best results seek advise and or training from a professional with a high skill set...

Completely agree with everything you said if you change "professional" to "experienced diver".