Safety Stop question...

[Uncle Pug]

Originally posted by Hanz
But with the PADI system considering Im only at 60' and Im not even"required" to do a safety stop, Im up in one minute!

We practice minimum deco of 1 minute at 30',20',10' as a discipline... and while not necessary on a dive like you mentioned (we rarely if ever do a 60' for 20 minutes) it does provide a margin of safety and maybe more importantly, training in proper ascents to deco stops.

30 fpm ascent to stops except last stop to surface at 10 fpm

We stay at the stop for 40 seconds and take 20 seconds to move to the next stop... from the last stop to the surface we try to discipline ourselves to an extremely slow ascent and take a full minute to do so... this is not easy but with practice it can become second nature.... and unless you can do it on the weenie dives you will never be able to do it on the big dives.

Getting out of the water is not usually our goal anyway and certainly not after only 20 minutes of diving!

 

[chaney]

Jar Head as in OOH RAH JAR HEAD? Anyway I might be "old school" but safety stops were put there for a reason I thought. Maybe things are changing again?

 

[voidware]

If memory serves, from Haldane all the way up to today, studies have shown that linear decompression profiles have produced more bends and silent bubbles than equivalent (in the algorithm) discreet stops. I believe there was a big controversy over it in the early twentieth. Seems someone else researched at the same time as haldane--just haldane's tables were more successful. I don't remember where I saw this, and I don't have time to find it as I am leaving to get my DM tomorrow in the BVIs.

Personally, I dive like uncle Pug on my wreck dives: 1min at 30', 1min at 20', and then I hang around at 10-15' for a while (I'd rather be in the water than on the boat.

brandon

 

[Hooligan]

It's better safe than sorry, and who would be able to go 10 ft per min. that's insanely slow, try it at home, time yourself. Im sticking to the stops.

 

[Dr Deco]

Dear Readers:

I would seriously doubt that with any data one could currently acquire from the field, that you could demonstrate much difference in the dive outcome between slow ascents and safety stops. (that is, gas phase as measured with either the Doppler bubble detector or with % of DCS). While I have not performed studies such as these, when you look for small differences in outcome between dives that have a very small incidence of DCS, it is necessary to have a very large number of dives. I would need to see the data for me to be able to decide one method over another (with recreational dive schedules).

Even with the reduction of activities that provoke tissue bubble formation (musculoskeletal straining such as running, lifting, and climbing), the effect on dive outcome is not visible for the average diver. This is because the tables (or deco limits) are very conservative to start with. In the “ASK DR DECO” forum, I have recommend that divers attempt to minimize the heavy physical activity follow a dive. This is more to reduce the risk of DCS over a large number of dives rather that reducing it in a few dives by one diver.

It is only when the DCS incidence is rather high (at least a few percent) that you can see specific effects in a reasonable number of decompressions (50 to 100). The effects [on decompression outcome] of straining your muscles is measurably greater than whether you have gone at 30 ft/min or paused at 10 feet for 1 minute. Regrettably, we do not have a large amount of data on either topic. Exercise effects are noted in the work of Ferris and Engels (1943), Franklin Henry (1945) and me (Michael Powell in 1992). These affects far overshadow ascent rates. Those activities that are relatively amenable to decompression modeling are stressed. Off gassing and bubble growth rates are modelable; musculoskeletal stress is not.

That is the simple fact of it.

Mike Powell ( Dr Deco )
:doctor:

 

[Jeblis]

With so many unknown variables I think I'll dive conservatively.
No harm in floating around at 15ft. I usually hang out there longer than recommended anyway.

 

[Uncle Pug]

Originally posted by Hooligan
who would be able to go 10 ft per min. that's insanely slow, try it at home, time yourself. Im sticking to the stops.

Why, I can... can't you?
No??
Perhaps you shoud try it sometime...

 

[JamesK]

Originally posted by Hooligan
It's better safe than sorry, and who would be able to go 10 ft per min. that's insanely slow, try it at home, time yourself. Im sticking to the stops.

It ain't that hard. Even in the high flow of Devils Ear Cave, I am able to go 5ft per minute, which is what I do from 15ft to 5ft. Then i spend about 5 minutes at 5ft playing around before surfacing.

 

[Jarhead]

Originally posted by chaney
Jar Head as in OOH RAH JAR HEAD?

Yes, guilty as charged. Also as in Semper Fidelis.

Whay part of Northern Arkansas are you in? Two years ago, I visited Bella Vista (near Bentonville).

Jarhead

 

[scubagatorgal]

Being a spoiled Florida diver who rarely dives anywhere that the bottom cannot be viewed from 15 ft. I often spend a lot longer than 3 minutes "chillin" enjoying the view with my buddy if everybody isn't waiting on us (My daughter and I are always the ones that have the most air left out of most dive groups and so we always buddy up)

Another advantage for us (we mostly drift dive) is that the boat is meandering our way while we are stretching our dive. At 15 feet you are safely out of harms way and can survey the boat traffic carefully before surfacing.

Best scenarios for me are to spend as little time as possible bobbing like a cork on the surface. When I enter I want to descend immediately and when I ascend I want back in the boat asap. Like I said I am an admitted spoiled diver...