Improving Ascent/ Safety Stop Practices

[lamont]

using v-planner i can't get a "deep stop" lower than 20 fsw based on any profile that is roughly recreational. i'm starting to come to the conclusion that recreational divers would be better off just slowing down when ascending to up to 30 fsw and then doing more time at an extended 10 fsw stop.

 

[Scuba_Steve]

I agree Lamont, which is why I said before, I don't like it when people up and stop at an arbitrary depth, call it a deep stop, and feel all warm and fuzzy because of it. Odds are pretty good they've added to their over-all N2 loading. I do it as you do on rec dives. No deep stop per-say, just a slowing down of the ascent after we get to a certain depth. (No calcs provide on purpose!)

Even when deco diving in the 120-140ft range, I don't get a stop until 40ft, and that's only when the Bottom time is pushing 30-40 minutes or so. Usually it's only a few at 30ft. The ascent speed takes care of what might be called the deep stop.

 

[grazie42]

Even when deco diving in the 120-140ft range, I don't get a stop until 40ft, and that's only when the Bottom time is pushing 30-40 minutes or so. Usually it's only a few at 30ft. The ascent speed takes care of what might be called the deep stop.

On 120-140ft dives with the kind of bt´s you´re talking about v-planner starts asking for decostops @ 60ft. Just a few minutes but still...The mix may be what makes the difference as its usually a low He content mix for me at those depths but still...

 

[RTodd]

using v-planner i can't get a "deep stop" lower than 20 fsw based on any profile that is roughly recreational. i'm starting to come to the conclusion that recreational divers would be better off just slowing down when ascending to up to 30 fsw and then doing more time at an extended 10 fsw stop.

That is because traditional buhlman doesn't quite work right in this regard. Of course, most of the bubble stuff is probably too conservatively long. I have never used v-planner. With decoplanner you can set a low Gradient Factor (20%) for the first stops and start to get a fairly good "deep stop" indicator if you really want the model to tell you.

 

[Uncle Pug]

this is not new, see UP's big tick discussion (twice as long above 2ATA than below 3ATA) for an example.

Correction:
I like to do the same amount of time above 2ATA as spent below 3ATA.

 

[Scuba_Steve]

On 120-140ft dives with the kind of bt´s you´re talking about v-planner starts asking for decostops @ 60ft. Just a few minutes but still...The mix may be what makes the difference as its usually a low He content mix for me at those depths but still...

You weren't using the same mix as I use.

I keep it vague occassionally, but yes, if we're using the full 140ft and the full time it gets closer to 60ft. The point here for this discussion really is.....

What are folks doing "stopping" at 50-60ft for a rec NDL dive if we're hardly doing it for these types of deco dives? It's just not warranted IMO.

 

[simbrooks]

Correction:
I like to do the same amount of time above 2ATA as spent below 3ATA.

Fairly close in intent if not actual correctness Twice the time in the shallows cant hurt though!

 

[Rick Inman]

Another minor input.... Most divers have been conditioned (read, brainwashed) to never leave the water with less than XXX PSI in their tanks, and start to quake and shake and point at their SPG even in 8' of water and 10' from shore. What's wrong with breathing down the gas to, say 100PSI, between 15' and 0' to get maximum time to off-gas? I'm not saying to plan ending at 100PSI in your dive plan, but just to spend the additional time shallow if you've got the gas to do it. If I had to guess, I say that if you were vacation diving, and just hanging out on the line at 10' at the end of your dive, and the DM saw you had 250PSI in your tank, he'd give you a big thumbs-up and chew you out on the boat.

 

[Uncle Pug]

I've never had that kind of problem on a charter boat Rick.

 

[Charlie99]

using v-planner i can't get a "deep stop" lower than 20 fsw based on any profile that is roughly recreational. i'm starting to come to the conclusion that recreational divers would be better off just slowing down when ascending to up to 30 fsw and then doing more time at an extended 10 fsw stop.

That is because traditional buhlman doesn't quite work right in this regard. Of course, most of the bubble stuff is probably too conservatively long. I have never used v-planner. With decoplanner you can set a low Gradient Factor (20%) for the first stops and start to get a fairly good "deep stop" indicator if you really want the model to tell you.

Ummmm. Reality is exactly opposite of what you said.

V-planner is a dual phase, aka "bubble" model. GUE's Decoplanner is classic Buhlman, aka "bend and mend", with the addition of the gradient factors as an attempt to get the same results as RGBM / VPM bubble models..