half stops

[Puffer Fish]

If one looks at getting gas out of your system, the ideal accent would be a sort of reverse exponential curve... going ever slower, the closer one gets to the surface.

Problem is, that is one difficult accent for humans to do. Just try doing a No-deco dive to 100 ft, then when you get to 50 ft, begin exponentially decreasing your rate of accent...pick some nice time, like 10 minutes to reach the surface and see if you can make a nice smooth curve out of it.

A nice one would be 20 seconds from 50 ft to 40 ft, 40 seconds from 40 to 30, 1.33 minute from 30 to 20 and 2.66 minutes from 20 to 10 and 6 minutes to the surface. Don't forget to start slower and speed up slowing continously. Not fun to do actually.

As that is not very practical, anything that slows ones accent rate would seem to be a reasonable idea.

 

[Tanked]

i agree with you that there is an inherent risk to diving. however just for the sake of discussion at what depth would you start doing half stops.

I do a half stop on any dive over 100 feet. Air permitting of course. Its a habit I got into from and old, and way more experienced, dive buddy. I figure it can't hurt.
Does anyone know of any cons to half stops?

 

[PfcAJ]

I always do them, no matter what (unless I'm doing a tech dive, things change. Thats for a different thread).

 

[palmm]

thanks for the posts. i guess it is more personal preference, and how deep you go. it definetly helps to slow your ascent tho.

 

[mikemill]

the ideal accent would be a sort of reverse exponential curve...

Aka a logarithmic curve....

 

[Steve50]

Does anyone know of any cons to half stops?

drysuit .... no pee valve .... gotta go

 

[Rick Murchison]

I found Pyle's 1996 paper compelling and started doing "half-stops" the dive after I read it.
It makes sense to me for any dive over 60' (18m) or so; if over about 100' I do two.
My personal procedure is to stop at half my depth for a minute, then at half that for a minute, etc., until I intercept either my deco schedule or safety stop.
So, for example, on a 120' recreational dive I'll stop at 60' for a minute, at 30' for a minute, and at 15' for three or more minutes, then take at least a full minute to go from 15' to the surface. If I have the gas and am not too cold and the boat's not in a big bad hurry to leave I may spend thirty or forty minutes at 15' watching the plankton show.
Whether this provides any substantive benefit over the 30fpm all the way to "three to five minutes at 10'-20'" followed by 30fpm to the surface I can't prove... and I can't prove that my "feeling better" isn't psychosomatic. But I do feel better, and so I'll stick with it
Rick

 

[AndyNZ]

Might it be because ... like most of their curriculum ... it's geared toward the relatively unskilled diver who's either new or dives very occasionally and struggles with the finer aspects of buoyancy control?

I agree, Bob. A "safety stop" is a confused beast, my personal belief is that the purpose of the stop is to pause and get your buoyancy under control for the remaining ascent - as much as it is to limit any DCS issues.

Does anyone know of any cons to half stops?

Yes, you are still ongassing. From a deco perspective, if you put in deep stops they are primarily reducing risk of a fast tissue bend (spine etc), but your slow tissues (fats etc) are still absorbing inert gas. You need to worry about that in the shallower portion of the dive.

If you are doing deep stops on a non-deco dive, that "worrying about" might be as simple as just having a nice, slow and controlled ascent. Though personally I prefer to include shallow stops as well as deeper ones.

 

[svs]

I do a half stop on any dive over 100 feet. Air permitting of course. Its a habit I got into from and old, and way more experienced, dive buddy. I figure it can't hurt.
Does anyone know of any cons to half stops?

To add 1 min or 2 to 3 min safety stop at 15ft may provide more benefit then 1min at 50 or 60ft

 

[fdog]

To add 1 min or 2 to 3 min safety stop at 15ft may provide more benefit then 1min at 50 or 60ft

Oddly, if I was ascending from a 100' dive, I would much rather do a minute at 50', than add a minute to a 15' safety stop.

A Type-2 (fast tissue) bends hit is a nasty thing.


All the best, James