Neutral Buoyancy for a safety stop

[Mike1967]

7mm wetsuit I need ~32lb

That is a shlt load! I'm carrying 26lb in a 7mm and I'm pretty sure I'm still over weighted.

 

[stevensamler]

Hi, I am having trouble maintaining Neutral Buoyancy for a safety stop. I am diving a waterproof drysuit with winter thermals and a ranger BCD. I have no problem maintaining neutral at depth,but coming up for a safety stop and the last 20 ft I can't seem to bleed off the right amount of air.Does anyone have any tricks or advice?
thanks

Number one , stay ahead of the gas expansion in the wing and dry suit especially when ascending through the last 40' of seawater. Your lung volume is all you need to initiate the ascent and at the end of your next dive do a weight check. While on the surface with a teammate dump your gas down to 500 psi remaining in your tank reg in mouth dump all gas out of dry suit and then dump gas from wing. At this point if you sink like a rock you're over weighted and are going to have to add gas to wing to arrest descent. If you descend slowly or have to expel lung volume to start descent and only have to add a small amount of gas to wing to stop at 10' you're close to perfect weighting.

 

[stretchthepenn]

Basically being a pilot as well I was told to think of the BC as trim on the plane. Its not there to control the plane, its there to balance the controls to make it easier. So you should be swimming first and using the BC to take the effort out of it.

I'll both agree and disagree with your statement, @Aanderson81. If you're doing basic rec dives, this technique of using forward motion to control your ascent/descent works. If you're getting into anything more advanced, though, it becomes a liability; you'll need to hover and/or ascend without creating forward motion.

 

[BlueTrin]

So I have been doing yesterday a dry suit training and I have been told that during the final part of the ascent I should probably leave the valve opened to automatically release: the idea is that when you are properly weighted you should be able to float at eye level with an empty bcd and drysuit.

In my case as it was a rental drysuit i had to use the BCD because it had flooded

Also my drysuit seemed to not release air fully unless I squeezed it by crossing my arms over my chest while holding vertical.

Please anyone with more experience, feel free to correct me.

 

[KenGordon]

This is my approach. I still consider myself a newer divers, but I have never had any real issues with safety stops and this is what I do. I tend to let the air out and slowly swim up rather than ride my BC up.
<snip>
So you should be swimming first and using the BC to take the effort out of it.

I am not sure of the extent of swimming you are suggesting, so don’t take this as criticism but as addressing a point.

The point of proper buoyancy is to be able to stay at one place in the water as the diver wishes. It is about being in control without having to think about it too much.

If a diver swims up to ascend and reaches a stop in an upright position they can usually maintain a depth easily enough but might be semi consciously finning. Give them an extra think to think about, they stop finning and they sink. There are other disadvantages too, smashing up the bottom and wasting gas being two.

Horizontal divers cannot support themselves by finning, so they avoid those problems. It all comes down to the gas in the BCD, suit and lungs. Once those are in equilibrium for the depth all should be good and relaxed.

 

[KenGordon]

So I have been doing yesterday a dry suit training and I have been told that during the final part of the ascent I should probably leave the valve opened to automatically release: the idea is that when you are properly weighted you should be able to float at eye level with an empty bcd and drysuit.

In my case as it was a rental drysuit i had to use the BCD because it had flooded

Also my drysuit seemed to not release air fully unless I squeezed it by crossing my arms over my chest while holding vertical.

Please anyone with more experience, feel free to correct me.

Sounds like you had no fun.

Personally I use the bcd for bouyancy control and only put enough gas in the suit for comfort. People will also teach just using the suit.

A flooded suit will still work for bouyancy unless the reason for the flood is pretty dramatic. The usual loose neck or wrists is letting water in more than air out. Earlier this year I took a student to Wraysbury and it took an hour of trying on suits to find a good fit, but she was dry through the lesson. This was very important as the water was 10C colder than it is at the moment. Drysuits must fit.

Once the dump valve is open gas will usually find its way out if you lift your arm/shoulder a bit. Very thick undersuits can get in the way of that though. If you are vertical it can be a bit difficult, especially if using the suit for buoyancy and being at all overweighted. There will be a fair old bit of gas in the suit and if it gets out faster than necessary you will sink.

I dislike this eyelevel floating thing. An empty drysuit (unless and extremely soft neoprene one) and an empty BCD offer the same buoyancy at the surface as at your last stop. So if you float at the surface with half your head (3kg?) out of the water then you must be light at your last stop. A proper buoyancy check is to go to 3 to 6m with a nearly empty cylinder and adjust weights until you can only just stay down.

If you are in London and learning with a rented suit I guess you are learning with a shop. Join a club Find a club or centre

Drysuit Training

 

[Edward3c]

Hi, I am having trouble maintaining Neutral Buoyancy for a safety stop. I am diving a waterproof drysuit with winter thermals and a ranger BCD. I have no problem maintaining neutral at depth,but coming up for a safety stop and the last 20 ft I can't seem to bleed off the right amount of air.Does anyone have any tricks or advice?
thanks

Hi,

Before changing anything you need to establish whether you still have air in you suit at these shallow depths. Changing to use your BC is a not the answer. I’ve seen too many divers lose control of their buoyancy trying to control both the bubble in the suit and BC. Using the suit prevents task overload; I’ve had instructors hit the surface when doing rescue skills training for Advanced Diver because of diving on their BC.

I’ve attached a graphic from our Buoyancy and Trim Workshop.

 

[chrisch]

... I’ve seen too many divers lose control of their buoyancy trying to control both the bubble in the suit and BC. ...

Something is wrong if anyone has excess gas in both the suit and the BC. The suit should have enough gas to stop a squeeze and no more. As you ascend this gas expands and exits the open dump valve. There is no need to "control" it whatsoever.

I've seen the same mistakes and they can mostly be traced back to the misunderstanding that buoyancy should be controlled by a suit that is there for thermal protection.

If, however, a person elects to use the suit (as taught by some agencies) then under no circumstances should they need to put gas in the BC. You fully empty the BC at the surface and use the suit the rest of the dive. Only once back at the surface do you add gas to the BC.

I'm not surprised if you have seen people lose control as you describe. Clearly they do not remotely understand the basics. Who is teaching these people for goodness sake?

 

[taimen]

Doing a proper weight check with (almost) empty tanks was important for me when learning drysuit buoyancy.
After a dive, go to confined shallow water with a buddy and bleed your tanks to reserve pressure. Something like 30 bar or even less with doubles.
Then drop or add weight until you barely get underwater but are able to hold a stop at 3 m.

 

[Neal Yang]

Since nobody has pointed it out yet, I would like to add that if you find yourself ascending too much during a safety stop, you can try swimming away from other divers. Sometimes, the bubbles from other divers are what's lifting you.