Bouyancy control while ascending - What are the best practices?

[Bigd2722]

I'll double check, but I wear a 7mm FJ during the cold months in Florida, but I don't remember having a problem

 

[00wabbit]

The OP is learning to dive in a cold water quarry wearing lots of neoprene. This is something that takes practice, preplanning and proper weighting. Once it gets away from you, you are a cork. I dive the same quarry and initially had the same issues with many more dives than he has to date.

I recommend he practice his ascents alongside one of the platform lines. He will be able to check a runaway ascent, adjust his buoyancy and continue the ascent. Remember you want ideally to stay neutral and rise on slight fin actions. If you stop finning and continue to rise or sink, you are not neutral.

Keep practicing. BTW you will be amazed how easy it is in warm water with a thin suit.

This is true. I'm a big guy wearing a big 2 piece 7mil suit. I had 40 pounds of weight on in order to get down.

I am going on a trip to the carribbean. I'll probably just wear a rash guard type shirt or maybe one with 1.5mil neoprene. I just don't want to look like an idiot and shoot to the surface. I don't think this will be a real problem though because I am aware of it and will be watching for it.

After I get some dives down I am going to look into drysuits. I will probably continue diving cold water environments and I don't like the bouyancy change or constriction with neoprene.

 

[kdsmithjr]

What happened is normal and could be from many things.if you are an air hog and you were sucking your bottle near dry, you tank was exerting an upward force. It is unlikely, though, that was the cause. More likely is being under weighted, holding your breath (or at least not exhaling fully) or (surprisingly common) pressing the wrong button and actually inflating your bcd slightly when you thought you were deflating it.

 

[Paladin]

You would not likely have made it off of the bottom. Not at 80 feet.

Why? I never put any air in my BC underwater. I weight myself for depth and wetsuit thickness. I swim down, swim around and swim up. Old school. No problems with ascent.

 

[chrpai]

Why? I never put any air in my BC underwater. I weight myself for depth and wetsuit thickness. I swim down, swim around and swim up. Old school. No problems with ascent.

From your posting history you dive a 5mm Neosport and from your profile pic I can see how that is working out for you. Your trim is so vertical that it looks like you are practicaly walking along the bottom. BTW, don't you think your SPG hose is a bit long? Good news is it doesn't look like you need to worry about it dragging along the bottom.

 

[Paladin]

From your posting history you dive a 5mm Neosport and from your profile pic I can see how that is working out for you. Your trim is so vertical that it looks like you are practicaly walking along the bottom. BTW, don't you think your SPG hose is a bit long? Good news is it doesn't look like you need to worry about it dragging along the bottom.


View attachment 127378

I was posing for the photo as per the directions from the photographer. We were beside a vertical wall and I was floating, not swimming. There was thirty feet of water under me. I rested my hand on the tree root at his direction. If you'll look at my weight belt, I was only using ten pounds. And that TommyDSports suit is a 3mm, not a five. When I'm in motion, my trim is nice and horizontal, thank you.

That isn't my SPG hose you're looking at. It's an extension for my horse collar BC inflator hose. The original hose was too short when connected to my double hose regulator, so I temporarily added an extension (just a borrowed LP regulator hose) for that weekend. I have since purchased a longer inflator hose. My SPG was clipped to my left side, as the photo shows.

I bought that horse collar in 2009. It was the first BC I'd ever used or owned. It's convenient for surface flotation, but I don't need it underwater.
You really should get all the info before making a post.

 

[00wabbit]

I think this thread has reached its end. I got the info I need.

 

[cuyler]

Why? I never put any air in my BC underwater. I weight myself for depth and wetsuit thickness. I swim down, swim around and swim up. Old school. No problems with ascent.

Hmmm, great control over your lungs. A 7mm suit starts at the surface as about 13lbs positive, add a full jacket, good and gloves and you're at 22lbs, now add an empty 80 that's 25 lbs of buoyancy you need to offset with lead (not including diver fluffiness). Now, let's take that down to 100 ft at the start of the dive. We now have neoprene compressed by 4 atmospheres of pressure taking that from 22 lbs to 5-8 lbs, the air in the tank also is about 6 lbs itself.

We've just gone from perfectly offsetting 25 lbs with lead to being about 20-ish pounds heavy at depth. A normal person puts 20lbs of air in their bc. Basic math again, 20 lbs of lift needs about 5L of water offset - at 100 ft you actually put 40L of air to offset 5L of water (4x the pressure). When coming up you've got to release that air from your bcd since at the surface that air you out in becomes 80lbs positive plus the expanding neoprene - it'll vent through the over pressure valve but still, you would shoot to the surface. What paladin here is suggesting is jumping in 20 lbs light, being good at depth and then trying to not get pulled to the surface,

In cold water diving you're offsetting a lot of compression and if you work the math there is no way to do it with your lungs, regardless of what anyone says. The average male has a maximum lung capacity of 6L, 4 of which really they can only control. That means no matter what, you can only sway your buoyancy 8-9 lbs. A 3mm suit and an AL80 is really the most you should be able to compensate for (when diving warm I rarely add any air to the bc because of this)

One option is to poorly weight yourself so you have to swim down to get to the right balance - great news with that - on your assent try to slow it down, hover at 6 ft, try to hold a safety stop being 20lbs light.

The better option I find is ascend slowly, every 3-5 feet you should be able to exhale and stop the ascent. If you don't stop vent and pause. If you need air in your bc to hover at 5-10 ft at the end of the dive then you're overweighted.

Anyways, my 2 cents. I found understanding how much my buoyancy changed at different depths allowed me to visual how much air I had in my bc and how much had to come out,

 

[Paladin]

I dive old school. I learned to dive back in 1965. We didn't have BCs then. With a wetsuit, I weight to be neutral or just a tad negative at the surface at the beginning of the dive and a bit light at the end of the dive. I mostly use steel 72s above 60 feet or a set of double AL53s (that have similar buoyancy characteristics) when going below 60 ft. A steel 72 weighs 5 pounds full and about one pound at 500 PSI. I have never developed the safety stop habit. If, at depth, I have any concerns about ascending too fast, I just do what we did back then: I find a nice rock to carry to the surface. Some of the guys I used to dive with would carry an extra weight or two to help them get down, then leave it next to the anchor or dive float line. They would retrieve it for the ascent.

You must remember that divers were plumbing the depths for decades before BCs were invented. We had a bag of tricks we used that aren't being taught anymore. But that's OK. Some of us just like to do things the old way. There are more than a few divers who still don't use BCs, prefer double hose regulators and (gasp) service their own regulators and gear. That's why SB has the Vintage Equipment Divers forum.

 

[chrpai]

I guess I'm supposed to be impressed with all of that but personally I just consider you an old dino who's too smart to bother learning new tricks.

Sorry if this comes across strong but we have a person here trying to understand good technique and you are coming off making bragging statements about how you can do this or that without doing this or that all the while leaving out details such as changing the amount of weight you carry during a dive and blowing off safety stops or grabbing onto the mooring line ( or whatever else you can grab ) to control your ascent.

Your contribution here doesn't help the OP learn how to better dive at all.