Ascending/Decending/Buoyancy

[kaylee_ann]

Most (if not all) agencies modern direction is to NOT use the BC to initiate depth changes (except initially leaving the surface).

Instead think of the buttons as brakes:

• The add button is the down brake (or fine tune if drifting down)
• The dump button is the up brake (or fine tune if drifting up)

Lol- this takes me back to my OW dives where I was trying so hard to control buoyancy on descent totally through my breath, but just could not inhale and hold enough air to slow the descent. Well….the pressure is greater the lower ya go, too much to correct with just your lungs, ding dong. (referring to myself). so that’s when I add a little air. Beyond that, they say don’t hold your breath when diving, but if I want to ascend a little bit I’ll take a small breath and hold it for a second. Then just exhale and breathe normal when I rise to whatever depth I wanted. Which probably wouldnt be more than 3-5 feet at a time I’d think

 

[John C. Ratliff]

Most (if not all) agencies modern direction is to NOT use the BC to initiate depth changes (except initially leaving the surface).

Instead think of the buttons as brakes:

• The add button is the down brake (or fine tune if drifting down)
• The dump button is the up brake (or fine tune if drifting up)

Thanks for the correction; I was taking what I read here as the new directions from agencies.

SeaRat

 

[BlueTrin]

You can use breath control for adjusting quickly and initiating ascent descent. But usually, you’d want to adjust with your inflator so you are neutral when breathing neutrally during most of the dive.

One thing I didn’t realise at the beginning is that it’s much easier if you do your adjustments by tapping on the inflator or dumping by tiny bits for smaller adjustments.

I remember that when I started I did long inflates/deflates too late: it’s much easier if you adjust your buoyancy more often but with small adjustments.

 

[John C. Ratliff]

Think back to the time when there were no LP inflator hoses. We used to use our breath to breath out into our vest-style BCD, orally inflating the BCD, then replace the regulator, hit the purge button to purge out water (you didn’t have much breath after breathing into the BCD), and resuming breathing. There would be no change in buoyancy until you got that first breath from the purged second stage.

SeaRat

 

[wetb4igetinthewater]

I thought the inflator buttons were elevator controls. Hold the inflator button to go up. Hold the deflator to go down. What could go wrong?

Seriously though, if you dial in your weight, you can go to the bottom of the pool back to the surface using only your lungs. But that takes a bit of work.

 

[schuylerclark]

Like a lot of folks just learning, I started out overweighted and reduced that weight as I've gone along. What's made the most difference for me is getting familiar with the concept of breathing off the top of my lungs vs the middle or the bottom. I think of it as 4 levels of breath - top, middle, relaxed, and bottom. (Maybe with more experience it will become 5 or 6 levels?) Starting out, I always kept my lungs topped off (as a runner and mountaineer this is second nature when doing something exciting). I could also breathe out hard, and this is how I could control my buoyancy early on. So I used a good bit of the inflator at this stage. As I got more comfortable underwater, I started to breathe normally - like I would walking leisurely. I shed a couple lbs of lead and could control my buoyancy even better than before. I still wondered at instructors and DMs that wore no weights at all, but thought it was just their 5% body fat build that let them be so lucky. After more dives, I found I could relax my breathing even further like I was sitting on the couch or meditating. I shed a couple more pounds and my buoyancy control got even better. I kept shedding weight since every drop in weight had so far improved my buoyancy control. On my last few dives, I found myself underweighted ever so slightly and had to struggle to maintain my safety stop (15 fsw, all air out of BCD, exhaling as much as possible and breathing from the very bottom of my lungs, with 900 psi still in my tank). I also had to really, really empty my lungs to descend at the start of those dives. I took this as a sign that I'm pretty close to the correct weighting for me at my current level (and I've added 2 lbs back in the dives since then and so far I'm happy).

All told, I've dropped 8 lbs of lead from where I started, and I can now generally start descending by breathing out and might add one to three tiny taps on the inflator as I reach depth and control my depth by lungs while at depth. I might adjust my BCD once or twice in a typical dive, almost always letting out air rather than adding as we get shallower. I almost always dump any remaining air before ascending to the safety stop and can control my depth there by breath. As a bonus, I'm pretty confident now that I can complete a dive either a couple lbs heavy or a couple lbs light if I have to.

From the past couple years of diving and breathing practice, I find I'm now more conscious of my breathing in all aspects of my day. And surprisingly (for me at least) I can run or exert myself at that middle breathing level just as effectively as the top level. Who knew I was overworking at breathing all these years?

 

[divingdayz]

It is a best practice to learn to dump just enough air that you settle out at the depth you want. This is hard in a pool, but excellent practice. Most do this by letting out enough gas to sink, then adding a bit more in while descending to stop sinking.

Good advice. It's a common mistake to release all the air. Just release enough air to start sinking and then exhale. You should be virtually neutrally buoyant then. You should never touch the bottom, either in the pool or while diving. Sign up for lessons with a good scuba diving center, and learn correctly.

 

[MacDuyver]

Most (if not all) agencies modern direction is to NOT use the BC to initiate depth changes (except initially leaving the surface).

Instead think of the buttons as brakes:

• The add button is the down brake (or fine tune if drifting down)
• The dump button is the up brake (or fine tune if drifting up)

100% this

Give it some practice and eventually you’ll be doing this with little bumps of air instead of a big continuous dump or fill

 

[Eric Sedletzky]

Hi,

In my pool sessions I have almost exclusively been using my LPI hose to adjust my buoyancy in the pool (i think im slightly overweighted too). Is this typical or is descending/ascending meant to be based on breath control?

My typical situation is to dump all air in BCD til i hit the pool bottom, then do 5-7 ish presses on my inflator hose to bring me to neutral buoyancy. I've been doing some research the past few days and this seems to be entirely incorrect. Any input is greatly appreciated!

If you’re dropping like a rock as soon as you dump the air out of your BC then you’re overweighted.
You should be able to float at about eye level with a full tank and then have to do a full exhale to begin to sink or in some cases actually flip forward and kick down until water pressure begins to do it’s thing. At the bottom of a pool you should have very little or almost no air in your BC. Pools aren’t deep enough to have to start filling BC’s to be neutral. Stay flat and don’t touch the bottom.
However, in a real world dive, perfect weighting is determined how your weighting is at the end of the dive. You should be able to hold a 15’ stop with a near empty tank with no air in your BCD and control your buoyancy with breathing alone.

 

[DeepSeaExplorer]

When diving with heavy steel tanks, I have to dump a lot of air to break contact with the surface. Then, immediately start adding back to control the descent. Once those heavy tanks start down, they accelerate faster than AL tanks.

With AL tanks, I can just go head down. That’s harder to do with steel doubles because the mass of the tanks wants to fight big changes in direction. It also can create a big weight shift, especially with deco bottles.

I have to add air to both the dry suit and wing. Suit to fight off the squeeze, and wing to control the descent.

I stay horizontal and close to neutral all the way to the surface. It’s better to control the ascent and easier to level off for any potential deco stops.