repetative dives

[lamont]

Thoughts?

He's talking about accelerated deco with O2 and GI3 is a freak when it comes to clearing free phase gas -- applicability to your average recreational diver will be a little bit questionable.

Personally, I'd rather follow the NDL tables, but do 1's from 50% of max depth on the first dive and add at least 2's from 30 feet on the second dive, and take at least an hour in between dives. And if I was doing 3 or more I'd probably get more conservative on the deco and/or shorten the dives. So rather than track residual nitrogen I'd prefer to treat the dive as having some mandatory deco. YMMV and this is off the beaten path.

Theoretically if you take GI3 absolutely literally you should be able to drop down to 100 fsw for 30 mins on 32%, do 1s from 50 fsw to the surface, and then drop back down and do it all over again, and i don't think you'll be able to do that without getting bent fairly good. The problem is that you're not diving in the problem domain which he is talking about which is technical diving with accellerated deco, and with deco times that are a much more sizable fraction of the total runtime.

 

[Charlie99]

Theoretically if you take GI3 absolutely literally you should be able to drop down to 100 fsw for 30 mins on 32%, do 1s from 50 fsw to the surface, and then drop back down and do it all over again, and i don't think you'll be able to do that without getting bent fairly good.

It's funny that you mention 100fsw for 30 minutes. George Irvine's response that Floater quoted was in response to an audience question about repetive 90-130' dives of 30-35 minutes with hour and a half SIs.

I was hoping you could walk us through an example of how you would do something that we commonly do here like a boat dive. For a dive on the Cypress Sea charter boat, we'll go on what they call an advanced trip. You do three dives in one day, maybe between 90 to 130ft on the bottom. It's not terribly deep but you're doing three dives. You bring one set of doubles and maybe one or two small stage tanks. You have maybe an hour and a half between dives. Could you go through how you would plan which gas to bring and how you'd decompress from 30 – 35 minute bottom times or maybe a little longer on the shallower dives?

.

http://www.baue.org/library/irvine_baue_talk.html#Repetitive_diving

Unfortunately, the answer was mostly about a series of 250' dives with mutiple deco gases.

 

[AaronR103]

He doesn't seem to grasp the concept of a NDL recreactional dive. Course, when you reach that level you probably don't even consider it a dive unless you're saturated.

A

 

[lamont]

i like GI3s approach to liposuction-by-decompression:

There are certain tissues that just aren't perfused, like fat. Fat just might have one capillary per cubic millimeter. Nothing. It's like trying to take a stick of butter and decompress it. It's not going to work. On the other hand you don't care if you damage it, you'd like it to get damaged and get rid of it.

 

[*Floater*]

Theoretically if you take GI3 absolutely literally you should be able to drop down to 100 fsw for 30 mins on 32%, do 1s from 50 fsw to the surface, and then drop back down and do it all over again, and i don't think you'll be able to do that without getting bent fairly good. The problem is that you're not diving in the problem domain which he is talking about which is technical diving with accellerated deco, and with deco times that are a much more sizable fraction of the total runtime.

I don't think GI3 would ever suggest a bounce from 50' and back - I just think that he thinks that he can clear nitrogen very efficiently in the compartments that matter with a slow, controlled ascent.

So assuming you follow the min deco rules, then would it work? My DIRF instructor thought so albeit I was asking with minimum of 15-20 minute SI's between the dives, and he suggested I start the 9/6/3m stops at 12m on the 3rd and 4th dives, plus stressed the need for depth discipline and no streneous activity between or after the dives. I never got try it out though.

 

[cornfed]

So assuming you follow the min deco rules, then would it work? My DIRF instructor thought so albeit I was asking with minimum of 15-20 minute SI's between the dives, and he suggested I start the 9/6/3m stops at 12m on the 3rd and 4th dives, plus stressed the need for depth discipline and no streneous activity between or after the dives. I never got try it out though.

Have you tried running this through some deco software? I ran some back to back 100' dives through v-planner it wasn't very happy.

 

[lamont]

I don't think GI3 would ever suggest a bounce from 50' and back - I just think that he thinks that he can clear nitrogen very efficiently in the compartments that matter with a slow, controlled ascent.

by "do it all over again" i meant two back-to-back 30 min / 100 ft dives, not just doing the deco twice...

 

[*Floater*]

Have you tried running this through some deco software? I ran some back to back 100' dives through v-planner it wasn't very happy.

Yes, v-planner isn't happy about this. And neither is any set of tables out there that I'm aware of, yet these types of dives seem consistent with the min deco rules that I was taught and that I've seen posted by other GUE trained divers and instructors.

 

[*Floater*]

by "do it all over again" i meant two back-to-back 30 min / 100 ft dives, not just doing the deco twice...

Sorry, I misread your post, though not the "do it all over again" part.

 

[cornfed]

Yes, v-planner isn't happy about this. And neither is any set of tables out there that I'm aware of, yet these types of dives seem consistent with the min deco rules that I was taught and that I've seen posted by other GUE trained divers and instructors.

The minimum deco rules aren't magic. I think it's a little silly to assume that following them is safe when you admit that that everything else you've looked at says this is a bad idea. Maybe I got screwed in my fundies class but we didn't learn anything about doing back to back dives with (essentially) no surface interval.

Why don't you post your question on Quest? That way you'll get the answer straight from the horse's mouth.