Deco with too less air, options from the book

[orange_diver]

From my memory of this discussion on another forum I believe Kevin was using air as bottom mix, and using EAN50 and O2 for deco ...

... Bob (Grateful Diver)

i should have been more clear, i meant air on BG. since the deep part of the dive was conducted on air there's a lot of nitrogen saturation and i think it would be prudent to use more of a gradient than just the oxygen window, which you would with straight up RD.

i didn't plug in O2 in vplanner, but i did plug in ean50 and the difference was extra 4 mins deco for air. As Bismark posted, it only gets worse with longer bottom times...KR has to start factoring in more time for decoing on these air BG dives.

hope that's more clear.

 

[Blackwood]

I hear you and that is what we did when we were there. 18/45 dives on those same wrecks, 50%, 100%...........no drama.............

However, that is not what he was talking about so just trying to keep apples and oranges in their respective crates.

Fair 'nuff. I tend to reply to posts on an ad hoc basis.

 

[Kevrumbo]

Apples and Oranges people . . .total deco time in RD is that number coming after the requisite deep stops protocol per the WKPP Deep Stop Table (a separate quantity which I don't lump all together with eanx50 and O2 time into a grand total deco time per se). And again, the profile shape of RD compared to deco software is much different qualitatively (although the latest version of V-planner has options for exploiting the O2 Window, air breaks, accelerated stops etc.)

Bismark, if you can arrange getting the Odyssey Liveaboard to blend Helium . . .I"ll gladly pitch in and join you (they're not interested in supporting trimix diving). Tech Asia is running a trip in 2010, but also will be staying at land-based Truk Lagoon Dive Center afterward, the only place in Chuuk --as of right now-- where helium is readily available to blend.

 

[Bismark]

Apples and Oranges people . . .total deco time in RD is that number coming after the requisite deep stops protocol per the WKPP Deep Stop Table (a separate quantity which I don't lump all together with eanx50 and O2 time into a grand total deco time per se). And again, the profile shape of RD compared to deco software is much different qualitatively (although the latest version of V-planner has options for exploiting the O2 Window, air breaks, accelerated stops etc.)

Bismark, if you can arrange getting the Odyssey Liveaboard to blend Helium . . .I"ll gladly pitch in and join you (they're not interested in supporting trimix diving). Tech Asia is running a trip in 2010, but also will be staying at land-based Truk Lagoon Dive Center afterward, the only place in Chuuk --as of right now-- where helium is readily available to blend.

Before we go back to Truk, we have another plan this summer. I spent a week with Juha M on a boat in the Red Sea last summer doing some mix and recreational diving. He told me about your first trip to Truk and I saw the photos. He said you had a great time. I am meeting him again this June again (with some other people) and we are doing some more diving on the same liveaboard in the Red Sea. 11 days of wrecks and lots of relatively inexpensive mix. I think we have a couple of spots left. June 12-24 I believe. We have the whole boat........with scooters.............Not all tech diving either, some super recreational opportunities on a boat that is absolutely perfect for diving from. Drop us a line if you are interested or contact him to find out how the last trip was.

Guy

 

[Kevrumbo]

Thanks for the gracious invite --but I might be going on a back-to-back Galapagos Liveaboard Trip, with a separate trip to Cocos Island a few days afterward, for the whole month of July into August this year.

Yes, it was Juha's fantastic photography, and most of all --as a safe & sane dive buddy-- which made that Odyssey Charter on 17 to 22 Dec '07 fun & memorable. We did mostly RD Minimum Deco Limit Rules on eanx30, except for the San Francisco Maru which we used deep air and a 1:1 Schedule (and Juha did a correlation check with Decoplanner beforehand); planned 20min BT at 54m, but actually executed a 25min BT at a shallower average of 48m (see Excel Gas Calculation Plan in attached file below). It was the week after this charter on the Odyssey that I did the experimentation with deep air and that table I posted --as solo diver-- on the Maru's Nippo, Nagano, Shotan, Unkai and Shinkoku wrecks using the Blue Lagoon Dive Shop Ops.

Honestly and after further consideration . . . I might have to factor in little more time at the eanx50 and O2 switches because of my history with DCS type I --for both deep air and trimix dives now.

 

[orange_diver]

Honestly and after further consideration . . . I [-]might[/-] have to factor in [-]little[/-] more time at the eanx50 and O2 switches because of my history with DCS type I --for both deep air and trimix dives now.

good conclusion man. makes this whole thread worth it. [-]edits[/-] mine.

 

[jtivat]

Honestly and after further consideration . . . I might have to factor in little more time at the eanx50 and O2 switches because of my history with DCS type I --for both deep air and trimix dives now.

Just because you had a hit does not make you any more prone to getting hit in the future. But having been hit I do dive more conservatively because I don't want to go through it again.

 

[Kevrumbo]

Perhaps . . .but after this last Truk Trip (01 thru 11 Jan '09), I noticed a few transient spasms/mild ache during deco, in my Left Shoulder --the original site of the type I bends hit three months ago. Definitely will concentrate on that last 6m/20' slowing ascent on all dives now, both technical & recreational. . .

 

[dumpsterDiver]

Just because you had a hit does not make you any more prone to getting hit in the future. But having been hit I do dive more conservatively because I don't want to go through it again.

Why would you assume that tissue that has been damaged by "bubbles" (or some other injury) might not retain some susceptibility to re-injury in the future?????

I know a guy who has been bent in the same elbow a number of times, always the same side.

 

[dumpsterDiver]

......

One should not attempt to learn decompression on the Internet ... regardless of method used. It's entirely too subjective and situational. Sure, you can learn the theory and history by reading a book ... or (if you trust the information) by what someone posts in a forum ... but all you're getting is the tools. It is the APPLICATION of those tools that matters. And in that respect, ALL decompression theories are more an art than a science ... and no matter which one you choose, what you're really doing is making a choice of which method you think is less likely to hurt you........

Misinformation CAN be dangerous ... and no matter HOW you attempt to explain RD on the Internet, the risk of misinformation is very high. That's why I think people shouldn't try learning it here. But that's also why I think it's important to correct someone who says something that you clearly know is mistaken or misleading ... because someone else reading the thread may decide to take it as factual. And that path leads to injury ...

... Bob (Grateful Diver)

I think I will stay with tables and a computer, but if RD is so damn simple that a diver can do it correctly (even when stressed out and task loaded), then why the heck shouldn't this seemingly simple mathematical algorithm be easily taught on the internet? Obviously implementation of decompression is somewhat risky, but is disseminating the basic technique dangerous? (I learned how to rig a stage bottle on the internet, that could be dangerous too, yes?)