Multiple decompression dives/day- planning

[gitterdun]

Our "gang" also prefers to do one deco dive per day, but when the odd occasion arises, there is usually a 3 hour surface interval. It's usually the Jodrey, so the boat will take us to Alexandria Bay for lunch.

 

[RJP]

I'll do two "significant" deco dives a day, running V-Planner with +2 conservativism and 2hr+ SIT. Would follow that schedule or my computer, whichever kept me in the water longer.

In Truk I did 4-5 dives a day. Usually would do a long one first thing in AM, deco'ing on 60% with a few extra minutes, then a short shallow second AM dive w/o deco or 5-10min max on backgas. Then on afternoon wreck would do a deco dive on first dive with minimal deco on 60% padded. Second afternoon dive and/or night dive would be shallow, short, slow, and no-deco.

On deeper/longer deep dives (San Francisco, etc) I'd skip the second morning dive, and possibly the first afternoon dive too, or at minimum run no-deco on the afternoon.

 

[liuk3]

Yups. It was back in no more than 30 min/50% days and we were switching to BG once 50% petered out. I don't remember exact schedules anymore. Nowadays I value bull****ting on deck slightly more than extra time in water at 20 feet.

Thanks, Maciek. That's interesting. I was also told as a strategy the same thing about doubling the shallow stops. Probably is the most conservative strategy. I never found anyone who actually was willing to do this with me on a multiple technical dive day since nobody I knew was willing to spend so much extra time in the water. So, in the end, I used a different strategy. However, I got to figure though that doubling the shallow stops is probably the safest way to go until you better understand through experience how your body tolerates various decompression profiles.

 

[syntaxerrorsix]

5% conservatism on an EMC-20H is very agressive and adding 10 minutes of O2 is just a really good idea. Anything under 30% strikes me as pushing it unless you are adding some additonal safety.

We run the 20H at 10% with IANTD tables. ~30% conservatism closely matches the Nitek Duo at the S0 setting.

 

[Kevrumbo]

This is another issue as well which IMO/IME warrants the use of a computer: two or more deep deco dives per day over a week or more, especially on deep air -you will start to N2 load your slow tissues over the course of several days such that they will not clear or perhaps even accumulate unless you elect to take a day-off or two.

Even if you use a bottom timer & Ratio Deco exclusively, a Shearwater Petrel computer helps by keeping a continuous record of your tissues' loading/saturation/off-gassing/residual tensions and provides info data you might have to use to start padding your shallow O2 deco stop times after Day 4 or 5 of consecutive dive days (i.e. Petrel computer's real time GF adjustments & tissue loading graph features etc, and CNS Ox-tox tracking very important in this instance as well!) in order to keep slow tissue tensions reasonably below surfacing M-value levels on ascent. (Got a type I hit right arm in Bikini Atoll on Day 8 with successful IWR last month, which prompted the purchase of the Petrel on returning home).

Just a general Rule-of-Thumb recommendation for those Ratio Deco divers out there: doing these types of deco dives (should be no more than two deep deco dives a day with minimum SIT 3hrs between them) over several consecutive diving days --even if using Standard Gases for bottom mix-- by Day 4 start adding more O2:break intervals at 20'/6m with a very slow ascent (0.5 m/min or a foot per minute) to the surface, monitoring for signs & symptoms of slow tissue DCS ("niggles" to obvious acute joint & limb pain and have an IWR contingency profile ready in your Wetnotes, just in case).

Better yet, take a day off. . .