Current Research on Deep Stops for Recreational Divers?

[gcbryan]

I suspect that the entire concept of "no stop" diving will, in time go by the way. I'd predict that we will see a system for all dives of faster ascents from deep, a deep stop, slower ascents in the shallower range with required shallow stops.

Ah, I see. I agree with that. I think most experienced divers do that anyway whether it's the "minimum deco" concept of GUE or just spending time shallow after the deeper portion of a dive.

The idea of just going to the surface has always bothered me. Even though the "tables" say you can do it and get away with it most times is not a great concept in my mind.

I think NAUI is most of the way there already aren't they?

 

[GrandpaScuba]

Very interesting paper, it makes me think that we will revisit the whole ascent rate and stop thing several times. If I needed to guess: a variable rate ascent (fast deep and slow shallow, with no stops) will prove to be best, and we will wind up approximating that with something like 120 fpm to 90 FSW, 60 FSW to 30, and 30 FSW to the surface with a short stop at 90 getting slightly longer at 60, 30, and 15. Just an educated guess.

Interesting... In my NASDS class, back in 1980, I was taught an ascent rate of 60ft/min up to a depth of 30ft, then 30ft/min to the surface, with no mention of a safety stop. When I became an instructor, I was told to teach a straight 30ft/min with a 3min safety stop at 15ft. I would find it interesting if we went back, more or less, to what I was taught in 1980.

 

[gcbryan]

Interesting... In my NASDS class, back in 1980, I was taught an ascent rate of 60ft/min up to a depth of 30ft, then 30ft/min to the surface, with no mention of a safety stop. When I became an instructor, I was told to teach a straight 30ft/min with a 3min safety stop at 15ft. I would find it interesting if we went back, more or less, to what I was taught in 1980.

The difference being the stops in Thal's scenario so it really isn't a 60ft/min ascent to the surface. There are stops at 90 fsw, 60 fsw, 30 fsw, 15 fsw. If you put the stops in correctly you can make the ascent rate anything you want it to be.

 

[Thalassamania]

The difference being the stops in Thal's scenario so it really isn't a 60ft/min ascent to the surface. There are stops at 90 fsw, 60 fsw, 30 fsw, 15 fsw. If you put the stops in correctly you can make the ascent rate anything you want it to be.

That's really true, but it is hard to have a varialbe ascent rate, it seems easier to vary the stop times.

 

[Matt S.]

Somebody, go get some goats.... We're going to need a #@*!load of goats!

 

[gcbryan]

Somebody, go get some goats.... We're going to need a #@*!load of goats!

Baaaaaaah.....we are the goats.

 

[Funky556]

The difference being the stops in Thal's scenario so it really isn't a 60ft/min ascent to the surface. There are stops at 90 fsw, 60 fsw, 30 fsw, 15 fsw. If you put the stops in correctly you can make the ascent rate anything you want it to be.

According to the afore mentioned paper the rate of ascend does matter. It was shown that slow ascent rates say 10 or 15 fpm to a deep stop did little to off gasing. According to their data divers off gased substantially more nitrogen when ascent rates were faster to your deep stop. 33fpm being optimal, 60 fpm didn't yield a significant change. Also longer deep stops(over 2min) didn't yeild any more nitrogen off gasing then shorter deep stops(1-2min). During your ascent to your shallow deco stop more nitrogen was off gased by ascending at a slower rate and spending longer time at that deco stop. I don't know if you got a chance to read the paper yet but the ascent rate was very much a factor in the amount of off gasing that occurs. Don't quote me on the rates, I'm just going off of memory, but the general principle is that the rate of ascent matters. Hope that makes sense

 

[Thalassamania]

I think that what gcbryan was observing is that in the calculus of decompression you can often trade off stop time and ascent rate against each other if you make the depth slices thin enough. The slice can be rather wide when deep, but must be finer when shallow.

 

[Funky556]

Ohh... I see thanks

 

[gcbryan]

Hi Funky556, yeah, I was just pointing out that an ascent rate of 60 fpm is one thing if no stops are involved meaning if you are at 120 fsw then at that rate you will be on the surface in 2 minutes...right?

However, an ascent rate of 60 fpm from 120 fsw with a 1 minute stop at 90,60,30, and 15 fsw (just to use Thal's scenario) would be 2 minutes plus 1 minute at each stop (4 stops) for a total of 6 minutes to cover 120 feet (120/6=20) which would really in that scenario be an ascent rate of 20 fpm.

So describing only the ascent rate up to the first stop and between stops as being a 60 fpm ascent rate would be meaningless without also considering the stops.