Multiple decompression dives/day- planning

[StreetDoctor]

I'd like to hear everyones opinions on doing two or more decompression dives in a day and how you plan them. It's something I don't remember much about from my tech class and I'd like to hear everyones varying levels of conservatism for the repetitive dives, if you do them at all.

 

[jtivat]

I let V-Planner do the planning. Dives from up to 150' I do at least 2 hour SI and in the 150' to 200' 3 hours. For dives deeper than 200' I just do one dive a day.

 

[rjack321]

I generally feel like poo if I do 2 in a day.

That said, I have done them on occasion and and probably will continue to do so. But I haven't figured out the deco. I need more but how much more seems erratic. The longer the SI the better (seems obvious, although its also obvious you "deco in the water" and while I may come out feeling stellar I suspect I'm not as clean as I feel).

 

[PfcAJ]

If I do two (rare event), I use deco planner's "Next Dive" feature, and just input the interval. I really don't like doing more than one per day because of how sketchy it is.

In tech class, there was some number of hours where past that, you were considered clean, but I forget what it is.

 

[Mike Edmonston]

Two things that you can do to help with your planning are:

1: Reduce your nitrogen loading on the first dive. This can be done with different mixes / depth / or bottom time, or a combination of all 3.

2: Extend your surface interval between dives as much as possible.

Even the US NAVY doesn't "condone" more than one decompression dive per day, but some software can get you workable profiles. RGBM / VPM (BE) etc...

You have to calculate your risks and dive accordingly. Generally speaking, I don't "feel great" after a couple of deeper DECO dives in one day either. Everyone is different though. Good luck.

Cheers,

 

[Rainer]

Since moving to CA, most of my T1 days are two dives. Minimum 90 min surface interval, but then we apply standard RD to the second dive (no additional time). So far we've been fine doing this (feel just fine). Some of us have started bringing O2 for the second dive. I'm fine with or without it (though it came in handy this weekend when I lost access to my 50% bottle).

The reason you don't remember too much discussion about it in your class is that Bob tends to strongly prefer only doing one deep dive / day.

Personally, I cap my days at two T1 dives followed by one rec dive.

 

[liuk3]

If you're not sure, run it on Deco Planner.

 

[Blackwood]

Like Rainer, a one-a-day T1 dive is a personal rarity and generally has to do ocean rather than deco considerations.

90 minute SIT is a minimum (standard ratio deco methodology), but it usually works out to closer to 2 hours.


Anecdotal and possibly placebo, but I felt better than normal last Saturday (not that I generally feel poorly). However it's hard to attribute that to anything since 1) I used oxygen on top of the 50% and 2) we did additional in water deco to accommodate a team-mate's lost deco gas.

 

[DA Aquamaster]

I use DPlan and as noted above for DPlanner, just input the surface interval with at least a 90 minute surface interval. Longer is better, so starting early and getting the first dive done as early as possible helps.

Your body will tell you when you are not getting out clean enough. I used to do 2 deco dives per day for 2-3 days straight on a regular basis and would generally feel like I had the flu on Monday morning until I started slowing the ascent by adding a minute or two to the deeper stops and adding 5-10 minutes to the 20 and 10 ft stops.

Now, on the average N FL cave trip, the deco dives are not short deep dives as much as they are longer dives at moderate 70-110 ft, and in some cases 150 ft depths. Two deco dives per day is not uncommon and again I tend to pad the deco with a few more minutes at 20' and maybe 5 more minutes at 10' followed by a very slow ascent over 3-4 minutes from 10 ft to the surface. That generally keeps me feeling fine over the course of a week of diving.

Three dives per day is pushing it and I think statistically the odds of getting bent start to rise considerably on the third dive per day.

Hydration is also vital and the more I drink the better I tend to feel, so going heavy on the fluids starting the day before the diving starts is pretty much a given.

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The US Navy was never a fan of repetitive dives, especially repetitive deco dives and generally only does them if it is an operational neccesity. I know in the 1980's the calculated hit rate for repetitive square profile deco dives on US Navy tables was almost 4%, so a healthy use of fudge factors such as rounding to the next greater depth and time, as well as avoiding square profiles whenever possible, was the norm.

The tables and software available today along with accellerated deco make repetitive deco diving a much more realistic proposition.

 

[StreetDoctor]

If I do two (rare event), I use deco planner's "Next Dive" feature, and just input the interval. I really don't like doing more than one per day because of how sketchy it is.

In tech class, there was some number of hours where past that, you were considered clean, but I forget what it is.

I could be remembering incorrectly but I believe 3 hours was what we were told. Keep the replies coming, good stuff.