Doing 'Light Deco' as a recreational diver

[jeckyll]

On a recent trip to dive some wrecks off Nanaimo I found that some of the people on the dive had their computers show a deco obligation.

My buddy and I had planned our dive profiles rather carefully before the trip and we decided on 20 min at 100 for dive one, a 2 hour SI and 20 min at 80 for dive 2 (all on air). All with 'minimum deco' ascents (i.e. stops for 1 minute at 40 & 30 and 3 minutes each at 20 & 10). I like slowing my ascents anyways, I seem to feel better and these ascent profiles are fairly common for us. FWIW, my computer cleared after our first deep stop and my buddies computer actually had NDL left, but I set the conservatism on mine to closely resemble the RDP + 10 fsw for cold water

There were at least a few people who seemed to be strictly diving their computer and who had both longer bottom time on the first dive and were deeper than my buddy and I on dive 2. As an aside, there were only a couple of us with pony's and that didn't include the divers in question.

I'm curious how many people are comfortable 'riding their computer up', i.e. is this a fairly common practice?

Thanks

Bjorn

 

[mthirsc]

I believe this is very common-- when I dove in Chuuk, everyone was riding their computers. Like you, I prefer to plan light deco ahead of time (with redundant supply) and use my own profile. Total time often closely follows the computer but I include deeper stops in line with v-planner. My computer has always cleared first. I have also found that even on no-deco dives, deep "safety stops" leave me ending the dive with more energy.

I used to be comfortable riding the computer on NDL dives, but now that I have learned more about decompression-- by actually studying and doing some deco dives-- I am much more conservative on ALL dives while ascending. I make deliberate stops at 80%, 50% depth, etc. Also in Chuuk visiting the chamber for work, I found that almost everyone who gets bent is within the NDL's on their computer. I think the saying taht there is no such thing as a no deco dive is correct.

 

[Bill51]

I don’t plan on riding my computer up, but by the time I round up divers and possibly clear an anchor after being the first one down to check the anchor, I’ve done it maybe a dozen times in the past couple years. It doesn’t bother me as I do deep stops that usually clear the computer before I even get to the ceiling it’s called for, but I still do a full stop at whatever depth it called for along with my previous stops.

I’ve seen some computers that will show what I call a theoretical deco stop. In other words it shows the stop as if you could instantly go up to that depth, but with a normal slow accent they clear before you get there.

Let me add the disclaimer that I’d chew out any but my most advanced students that did the same thing. Do as I say, not as I do until you understand exactly why you’re doing it.

 

[onfloat]

What is "light deco?" Either it's deco or it's not.


If we were in another forum I would say they are all deco dives.

 

[jeckyll]

onfloat: I tried to make the question appeal to a wider audience.

But if you think in terms of the 'computer crowd' (stay with me) then you can have situations where the divers computers are just entering deco, or one divers computer is entering deco and the other not yet.

In other words, a small obligation which would clear on a 3 - 5 minute 'safety' stop, if not on a deeper stop.

There, my definition of 'light deco' for the purposes of this thread

Bjorn

 

[onfloat]

onfloat: I tried to make the question appeal to a wider audience.

That's what I figured.

But if you think in terms of the 'computer crowd' (stay with me) then you can have situations where the divers computers are just entering deco, or one divers computer is entering deco and the other not yet.

Did you just call me slow?

In other words, a small obligation which would clear on a 3 - 5 minute 'safety' stop, if not on a deeper stop.

There, my definition of 'light deco' for the purposes of this thread

Bjorn

Just stirring the pot.

 

[terrasmak]

I dont mind riding my computer up , but when i do i always do a long safety stop . Usually 10 minutes or more. You just have to be smart about it when you do stuff like that.

 

[Dive-aholic]

You mean people really plan dives???

For recreational dives, I either already know the NDL or use the plan function on my computer before splashing. Anything beyond a regular rec dive, I'll run tables even if it's for a "light" deco dive where I just want to get a general idea of what I'll be doing. For "heavy" deco, I'll cut tables, dive a computer, and follow the most conservative of the two.

 

[MikeFerrara]

Doing a staged decompression dive is really simple. You dive just like on any other dive and follow a prescribed schedule of stops on the way up. If you have a computer to figure out the requirements of the ascent for you, it really becomes something that absolutely any idiot can do.

Except...recreational diving is based on the premise that the surface is always immediately accessible. If you find yourself with no gas you share or fall to the old stand by the CESA or even a buoyant emergency ascent. The greater the distance between you and the surface and the greater the inert gas load the riskier those options become. That's why we refer to a decompression obligation as a virtual overhead.

Most of the time nothing goes wrong. Most of the time, the "absolutely any idiot" that I mentioned above can pull the whole thing off just fine. The question is, if something does go wrong, are you able to solve those problems underwater and still meet the requirements of the planned ascent? Do you have enough gas to get you and a budy through your decompression...ie, what if one of you suffers a total gas loss at the furthest point in the dive? How are you at following a decompression schedule without a mask or replacing a lost mask in rout without blowing your schedule? What if your computer fails?

What model is your computer running? What kind of tissue critical tensions will your computer let you surface with? My schedules are based on buhlman, usually using gradient factors of 30, 85 and sometimes 20, 70. that means that I'm surfacing at only between 70% and 80% of the leading compartment's 'M' value. What are you at...100% maybe? It should be fairly low risk (all else being equal) but I'd rather not do it. It's no secret that lots of computer riding recreational divers are probably hitting the surface with greater gas loads than lots of technical divers would surface with. What I'm getting at here is that while I might do a 200+ foot dive and end up with a couple of hours of decompression, lots of recreational divers are diving profiles that I wouldn't touch with a 10 ft pole.

I think that if you can't fit the dives you want to do within "recreational" depths and times, then it's probably time for some more training and maybe some new equipment before you get yourself in trouble. Take an entry level technical course like "Advanced Nirtrox" or something. Those courses are designed to prepare divers to plan and do dives with a "little bit" of decompression. The chambers at popular resort locations are busy enough. They won't miss you when you don't show.

 

[MikeFerrara]

On a recent trip to dive some wrecks off Nanaimo I found that some of the people on the dive had their computers show a deco obligation.

My buddy and I had planned our dive profiles rather carefully before the trip and we decided on 20 min at 100 for dive one, a 2 hour SI and 20 min at 80 for dive 2 (all on air). All with 'minimum deco' ascents (i.e. stops for 1 minute at 40 & 30 and 3 minutes each at 20 & 10). I like slowing my ascents anyways, I seem to feel better and these ascent profiles are fairly common for us. FWIW, my computer cleared after our first deep stop and my buddies computer actually had NDL left, but I set the conservatism on mine to closely resemble the RDP + 10 fsw for cold water

There were at least a few people who seemed to be strictly diving their computer and who had both longer bottom time on the first dive and were deeper than my buddy and I on dive 2. As an aside, there were only a couple of us with pony's and that didn't include the divers in question.

I'm curious how many people are comfortable 'riding their computer up', i.e. is this a fairly common practice?

Thanks

Bjorn

Lots of things are "common" but that doesn't make them smart. In fact, stupidity is pretty common.

A review of your OW text should bring back tidbits of wisdom like...to avoid decompression sickness, don't push the limits of your table or computer.

For best results, don't follow the idiots.