"Riding your Computer Up" vs. "Lite Deco"

[DevonDiver]

There is no penalty for skipping a deep stop.

The issue of penalties / drawbacks stems primarily, I believe from 2 factors:

1. How Deep Stops are implemented in some computers.

2. Incorrect application of 'manual' (unilateral or diver-driven) Deep Stops without prerequisite understanding.

I've seen many recreational computers that apply an either/or choice of Deep Stops and Safety Stops. I feel there IS potential drawback with applying Deep Stops at the expense of safety stops.

Doing Deep Stops as an additional measure is one thing. However, replacing Safety Stops with Deep Stops demands debate in respect to optimising safety from the risk of DCS.

Deep Stops are not without consequence. They potentially resolve faster tissue bubble sustainment. However, they simultaneously provoke increased slower tissue saturation.

Within recreational no-stop limits it's convenient to assume that slower tissue saturation must remain an irrelevant consideration.

However, certain aggressive recreational diving habits can make slower tissue saturation a much more relevant concern. If those considerations are not understood or acted upon, then it can be argued that Deep Stops can present more risk than a direct ascent to a safety stop.

Personally, I'd like to see computer manufacturers put more emphasis into extending shallow safety stops, rather than the 'novelty' of Deep Stop options.

I can only think of one or two dive computers on the market that empower users to define or select more comprehensive, or extended, Safety Stops as an integral feature for safer no-deco dive management.

 

[Basking Ridge Diver]

Doing Deep Stops as an additional measure is one thing. However, replacing Safety Stops with Deep Stops demands debate in respect to optimising safety from the risk of DCS.

Since it is recreational diving - the "deep stop" and the "safety stop" are both optional. There is no penalty for skipping either of these and they independent of each other. However - as I dive deeper and longer on some dives - it only makes sense to me that I do a safety stop.

The question for me is this - on occasion my safety stop is literally a "hang" on the anchor line if I am carrying mussels or fish. The draw back is I can have a safety stop swing of about 8 feet - generally not much more than that. I can start at 20 feet and due to the slack in the anchor line I can go up or down by several feet and then I will readjust my safety stop depth.

So which is worse - having a safety stop swing of several feet or just going straight to the surface within the NDL?

 

[dmaziuk]

So which is worse - having a safety stop swing of several feet or just going straight to the surface within the NDL?

If the fastest half-time is 4 minutes, how much (de-)saturation would you consider significant? -- 1/4-time? 1/8 time would be one minute. If your swing lasts less than a minute, how much gas do you expect to bubble in and out during that time?

The computer is probably going to penalize you on the next dive for repeated ascent rate violations.

 

[DevonDiver]

If the fastest half-time is 4 minutes, how much (de-)saturation would you consider significant?

Are we only considering the most rudimentary Haldanian concepts of dissolved gas?

I'd be more inclined to consider the implications of a sustained period of rapid pressure variances on free phase gas. . .

The half-time of a compartment predicts diffusion of gas, it does not account for gas leaving solution nor the stimulation of bubble growth. i.e. Half-times tell you when your glass of coke goes flat... but doesnt tell you that your can of coke will foam out of the can once shaken. . .

 

[Basking Ridge Diver]

The computer is probably going to penalize you on the next dive for repeated ascent rate violations.

My Oceanic VEO 2.0 never penalized me - just bought a Perdix and do not remember seeing any violations mentioned...

What PDC do you own? I am assuming you are talking about your DC?

 

[Basking Ridge Diver]

I'd be more inclined to consider the implications of rapid, but minor, pressure variance on free phase gas. . .

Not sure I understand - you seem to be more concerned about rapid pressure variance - rather than rapid but minor pressure variance?
Thanks - so I am reading this as long as I am not going crazy on the anchor line - not such a big deal?

 

[DevonDiver]

I'm really not aware of how different models would attribute risk to such fluctuations.

A minor depth fluctuation in sgallow water can still cause a significant spike in the tissue tension gradient.

On a no-stop dive you'd hopefully be well insulated from exceeding an M-value. . . but the issue might be in simply approaching those tolerance limits multiple times in a short timescale.

There may also be issues like increased cavitation effect, enabling more bubble seeds into existence.

Applying mathematical parameters to this is well above my intellectual capacity... and defining a +/- risk versus the safety stop would definitely be an algorithm exercise.

I own a Shearwater... so I'd be looking at my GF99 info to see what exact effect was being modelled in real time... and if it caused me concern, I'd make a decision accordingly.

 

[DevonDiver]

My Oceanic VEO 2.0 never penalized me - just bought a Perdix and do not remember seeing any violations mentioned...

The Oceanic Pelagic Z+ is a Buhlmann ZHL-16 based model. Its bubble models... especially RGBM that are likely to 'penalize' for ascent rates. They predict/recognize issues attributing to bubble formation and persistence.

 

[dmaziuk]

My Oceanic VEO 2.0 never penalized me - just bought a Perdix and do not remember seeing any violations mentioned...

What PDC do you own? I am assuming you are talking about your DC?

Not really.

I do own a cressi leonardo whose ascent rate alarm is a bit twitchy. Ascent rate is supposed to be one of the things it tracks. Looking at the log after a dive, it has way too many warning marks, probably just from moving my arm. I'm yet to notice any penalty on subsequent dives, so if it does indeed track ascent rates, there must be a duration that makes it "significant enough". I haven't bounced on the anchor line like that myself so I've no idea if those bounces could be long enough for it to count.

 

[uncfnp]

Off topic. @Basking Ridge Diver I have done very few anchored dives. Why the extreme bounce?