Trouble w/ inversion at Safety Stop

[Seaweed Doc]

The horizontal position generates drag as you slowly rise up or down, so it helps inhibit excessive speeds.

A good test to confirm that your are ascending in control
(But are still positive) is to exhale forcibly and more completely than normal. If a full exhale completely stops your ascent, then you are in control. If you are still floating up slightly, then inhale and dump a little from the bc.

If you inhale fully and your ascent stops, then you are a tiny bit heavy and you can drop your feet a little and give a kick and and move up a foot or two. I prefer this, than to add air to the bc.

I didn’t watch the video, maybe that is what they say. The real goal is to maintain your buoyancy imbalance to a magnitude that is less than the shift from normal breathing. If the imbalance is maintained within that envelope then you are never out of control, because manipulation of lung volume is sufficient to immediately arrest the change in depth.

For the last 10 feet of ascent, it may make sense to get vertical and stay negative and kick slightly so you can better see the surface and can be more aware of potential obstacles.

Interesting thought on controlling ascent that leads me to ta couple of questions.

1. Why not ascend face up and horizontal? It may be disconcerting at first, but allows you to see where you're going.

2. In thinking of failure modes, starting vertical allows you to flare to horizontal if the ascent loses control. Starting horizontal removes that option.

 

[chillyinCanada]

Ride your air? Slightly positive/neutral? Was that part of your training, or are you doing that on your own? All the training I know is to stay in control by being slightly negative/neutral, and to slowly swim up rather than ride up. Curious if something different is taught in some other context.

I always breathe myself up and can still hold my stops even at 10 feet. From my safety stop, I control my surfacing even more.

 

[rongoodman]

The main reason to stay horizontal is that you are set up to move quickly in any direction, especially to your buddy if he needs you.

(Off gassing is theoretically more efficient too.)

 

[ChuckP]

I'd think he has some control, coming off the bottom in a 5mm adds complexity too. I can just say that I use the same BC, the Hydros Pro, I only use my tail vent to release air cause it seems I can't get it all or it's hit or miss with the shoulder one - I only use my shoulder vent at the beginning of a decent.

If I'm vertical at safety stop, it's way harder to maintain depth compared to horizontal, maybe that's just me.

It sounds like more of a trim issue and just a slight issue at that. I personally hate ankle weights, I think you can get yourself figured out with them.

 

[elgoog]

Interesting thought on controlling ascent that leads me to ta couple of questions.

1. Why not ascend face up and horizontal? It may be disconcerting at first, but allows you to see where you're going.

2. In thinking of failure modes, starting vertical allows you to flare to horizontal if the ascent loses control. Starting horizontal removes that option.

1. Your reg will breathe much harder facing up. Also, I can imagine this will be quite disorienting as your head is basically upside down if you need to look horizontally. Sounds like a good recipe for a headache and vertigo.
In open water ascents, you should already know what's above you before you start an ascent - especially if you're shooting a DSMB - so, you shouldn't be looking up the entire time. Once you get shallower than 20ft, start looking up for boats and stuff but I can't think of any other reason to constantly do this.

2. When we do horizontal ascents, we're moving pretty slowly and there's a conscious effort to maintain a rate of ascent that we know we can control. Almost every loss of control event I've seen (and done myself) during an ascent was when the diver got vertical at the very beginning of the loss of control in order to try and vent their BC+drysuit - this just exacerbates the problem. A full forceful exhale stops you right quick if you're horizontal - this works for me consistently in a reasonably large rig (drysuit+doubles+deco bottle+DPV) and is almost effortless in single tanks.

 

[johndiver999]

Interesting thought on controlling ascent that leads me to ta couple of questions.

1. Why not ascend face up and horizontal? It may be disconcerting at first, but allows you to see where you're going.

2. In thinking of failure modes, starting vertical allows you to flare to horizontal if the ascent loses control. Starting horizontal removes that option.

I personally don’t ascend in a horizontal position. Being vertical allows better monitoring for sharks.

However, maintenance of horizontal position while in the water is a big goal for a lot of people and it has significant advantages, the primary one being the drag generated by any divergence from neutral buoyancy when changing depth.

In any regard, the ops goal was to stay flat during the ascent and there is certainly nothing wrong with that.

Laying on your back tends to put water up my nose, ruins your night vision and just wouldn’t seem natural to me

 

[Gareth J]

The rolling forward is generally an issue with the balance of the rig and you.
i.e. your centre of gravity is high (at the head). If the CofG was low then you would be tipping feet down.

In the days when I used to dive my twinset (12litre Steels), I actually had a trim tail weight. i.e. a weight at the bottom of the set to stop me tipping head down. I could dive without weight, but added the tail weight to correct trim.
These days, diving CCR, the trim weight is at the top of the unit, to stop my head coming up, due to the gas in the counterlung.

Re distributing your weight may well resolve the issue. You can fit trim weights to your cylinder, or use 'heavy fins' to shift the weight. I have in the past seen a weight on a cam band at the bottom of the cylinder to adjust trim, this is a good solution, especially if you are borrowing cylinders, or on holiday.

 

[Seaweed Doc]

Thanks for all the responses. Good food for thought. I'll stay vertical in this kind of safety stop, but I can see teaching both techniques to students. Whatever works to control position.

Edit:. Perhaps because I'm shortish, I can change position quickly. I don't get vertigo, so being oddly oriented doesn't bother me. But not everyone is me....

 

[MichaelMc]

A possible extra reason to spend much of your time horizontal is that it puts your 2nd stage and your lungs at roughly the same depth and thus reduces a need to fight any difference in pressure on inhale. Much like if you float in a pool on snorkel, you will find it much easier to breath if you float flat on the surface instead of vertical. Your lungs and the air they are trying to breath are closer to the same pressure when you are horizontal.

The BSAC annual incident reports have shown an increased concern for immersion pulmonary edema, which causes difficulty in breathing, as a likely contributor to several incidents. A pressure difference between the lungs and the air breathed is one possible contributor to it, which is eliminated if you are flat, a position that has other advantages already, as discussed above.

Annual Diving Incident Report. The 2016 video starting at 22:36 discusses it.

 

[BlueTrin]

Interesting thought on controlling ascent that leads me to ta couple of questions.

1. Why not ascend face up and horizontal? It may be disconcerting at first, but allows you to see where you're going.

2. In thinking of failure modes, starting vertical allows you to flare to horizontal if the ascent loses control. Starting horizontal removes that option.

Maybe I am wrong but if you need to fin back down and remove some air left in your wing because somehow you lost a bit control of your buoyancy it would be harder from being face up ?