repetative dives

[lamont]

yup, that's what i was thinking of and imprecisely trying to say, only much clearer... thanks rtodd...

 

[TSandM]

RTodd, thanks for the beautiful explanation -- ties right in with some of the stuff I sorted out from reading Lippmann's new book. Sometimes this all DOES make sense.

 

[nereas]

Yeah, that's exactly what I'm thinking.

Doing 30 min dives to 100 fsw it seems like you're dominated in your approach to decompression by the dissolved gas phase. Doing them back-to-back, the slightly longer compartments (compared to your deco time and short surface interval) are going to be way oversaturated and you'll probably take a type 1 hit after the second dive.

Its seems like you're in two different regimes on the different kinds of dives, where in rec diving, each successive dive tends to be additive, while in tech diving you deco from the previous dive and basically reset and can do it again...

Doing anything underwater "back to back" is not recommended nor wise.

The issue is always, how long does the surface interval need to be?

And the surface interval will need to vary from at least 1 hour up to 6 hours, depending on the dive.

VPM deco software gives you output to determine your required surface interval in order to plan a safe repetitive deco dive. And that's what I use.

For NDL diving, I have gotten away from the notion that there really exists a "true" NDL dive. Maybe 30 ft is a true NDL dive. But for anyting deeper, I will normally stop at 1/2 of my MOD for 1 minute, then egress like a techdiver every 10 ft from there, for at least 1 min each.

I simply have stopped believing that NDL dives exist. And thus, the DCS risk for me goes to -0- after a proper, long egression.

Then, having egressed nice and slowly, the question then becomes, how long of a surface interval, again?