"Riding your Computer Up" vs. "Lite Deco"

[uncfnp]

I have a hard time believing that DSAT would be more conservative than VPM, or, particularly Cressi RGBM. There must be more to this story, his profile, computer settings, something. The Cressi RGBM is among the most conservative of the commercially available decompression algorithms. DSAT is 2nd to Cochran as the most liberal. There's more to every story....

Sorry. Unclear post. I spent most of the dives at 80 or so until I spotted a lobster. He spent his dives mostly 100 or so. It wasn't meant as a comparison of computers but of approaches to dives and profiles. His deco accidental and on a liberal computer. Mine planned and managed on conservative settings.

 

[lowviz]

...//... he swims over to the guide and shows him his computer. The guide signals deco and 15 minutes then tries to tell him what to do. Several times throughout that stop the diver in deco would show his computer to the guide and the guide would signal level and time. ...

Your point was obvious to me, two divers in the water for the same amount of time and doing the same thing. You and diver X.

I'm quite aware that you routinely plan extended yet "conservative ascent" dives. You are able to do this by the judicious use of deco using a very conservative algorithm. I also know you gas plan. I doubt diver X had a gas plan.

But there is one more piece to this that hasn't been discussed yet. Both you and I know our individual limits as to what we can get away with when approaching deco. We both found them the same way, past experiences both good and bad. Our limits differ. Years, ago I came up with a rather accurate guesstimate to mine. 222,222 divided by depth in feet and the result of that division again divided by depth in feet. If I exceed that number in minutes (at the depth in question) then it is time for concern. Depending on depth, a few minutes past that may still be OK, but I'm not fooling around anymore as things are getting serious. Lite deco, for me, is any bottomtime this side of that value. Lite deco slows down the ascent and adds stop time, not a bad thing at all.

Good hunting! Have fun, be safe.

 

[redacted]

I find it quite easy to just stay out of deco on recreational dives and carry those credits to the subsequent dives. Why is that so difficult for others?

 

[dumpsterDiver]

I saw a good (meaning bad) example of what I would not call lite deco today on a recreation drift dive. Four divers plus guide. All lobstering and 1 also carrying a speargun. Sporty seas so the captain asked us to dive as a group. First dive was deepish. About 110 max. I floated at about 80 till I spotted a bug but 2 others dove mostly at depth. They had to have bumped into NDL limits. I had total about 5 minutes deco on the Petrel set for max VPM and cleared on ascent. Cressi never in deco.

Second dive max 115 and again two divers stayed low. We lose one diver early on but the other continued with us. I had about 5 minutes into deco when I went up to hang around 30. Eric and the guide came up shortly after and we hit the safety stop. I now have just the 3 minute safety stop on my Cressi and the Petrel cleared. Finely the last diver joins us. Sure enough he swims over to the guide and shows him his computer. The guide signals deco and 15 minutes then tries to tell him what to do. Several times throughout that stop the diver in deco would show his computer to the guide and the guide would signal level and time.

Fortunately Eric and I had plenty of gas so we chose to stay with the diver and guide. It turned into a 22 minute safety stop. On the boat I found out the diver was diving Oceanic and I believe it was DSAT.

That diver is not how I would define lite deco.

So the capt. is cool with customers pulling 22 minute deco stops? Did the guy have any redundancy?

 

[uncfnp]

So the capt. is cool with customers pulling 22 minute deco stops? Did the guy have any redundancy?

Total run time was still only 55 minutes and while I spent 22 minutes floating the other diver's deco obligation was only 15 minutes of that time.

So I am not certain when the captain heard about it and the guy was lucky in that the guide that dive is both very experienced and very low key. I do know that they had quite a long conversation afterwards and that the diver is known to the boat. I got the impression that this was very unusual for him and may be because he was 1) distracted and 2) deeper then his usual.

And no. He had no redundancy or dive buddy. The first dive he actually got separated from the group and finished that dive solo.

 

[lowviz]

I find it quite easy to just stay out of deco on recreational dives and carry those credits to the subsequent dives. ...

Some of us believe that there is a better way to surface from a dive that pushes the NDL with an aggressive DC. The problem is, you need to use a very conservative DC and you need to do the required deco for the very same dive.

 

[redacted]

Some of us believe that there is a better way to surface from a dive that pushes the NDL with an aggressive DC. The problem is, you need to use a very conservative DC and you need to do the required deco for the very same dive.

I am not sure why you would think that doing deco on a conservative computer is better than diving within NDL limits on a liberal computer. But if the dive op requires no deco dives then that is not what you are doing. I have never ridden my liberal computer limits. Don't need to. Yet I have seen other diver on the same profile with a deco obligation on there conservative computer. And their subsequent dives also have the same result. Is it just that you are trying to make the best out of buying the wrong DC? Maybe you should try one of each on a couple dives.

 

[lowviz]

I am not sure why you would think that doing deco on a conservative computer is better than diving within NCL limits on a liberal computer. ...

The more conservative deco ascent gives more effective off-gassing than just a 3 minute mandatory stop for the exact same dive.

...//... Maybe you should try one of each on a couple dives.

I often do. Usually, it is a Cressi and a Petrel 2 set either very aggressive or very conservatively.

 

[redacted]

The more conservative deco ascent gives more effective off-gassing than just a 3 minute mandatory stop for the exact same dive.

I often do. Usually, it is a Cressi and a Petrel 2 set either very aggressive or very conservatively.

Is there a reason the liberal computer does not allow you to do that same ascent if you choose?

 

[uncfnp]

Is there a reason the liberal computer does not allow you to do that same ascent if you choose?

Awap. Let me try and explain it as I practice it. The conservative dive computer tells me, based on more then just bottom time, where that conservative line in the sand lands. Then I can make a judgement call based on many factors if I follow that conservative line and not cross it, or if I have a little leeway to cross the conservative NDL line but then use other factors as an added safety margin, such as ascent but also longer and now manditory safety/deco stops, longer SI, shorter second dive, etc.

Yes, I could modify my Petrel, even during a dive, to give me almost any dive I want but then that line in the sand is blurred. If I have one computer set conservative then I always know right where I stand in relationship to that line and can make more informed choices about the rest.

Remember, conservative computers are not just about shorter bottom times, in fact they may give longer dive times on that first dive, but rather are mutifactorial in calculating NDL's

This works for me. It may not work for you.