How would you do this dive ...

[MXGratefulDiver]

As most of you know, I've got some GUE training, but most of my tech training is NAUI. My current NAUI Tech instructor also has some GUE training, and appears to be teaching us in a manner that's pretty DIR compatible.

Anyway, I'm curious as to how "DIR" my tech instruction really is. So I'd like to posit a dive scenario and ask what the DIR take would be on gas selection and deco schedule.

I'm thinking of a "typical" Lake Washington dive profile that I've been doing lately ... max depth 200 ffw, planned bottom time 25 minutes.

I know what my answers would be ... so I'm not looking for instruction ... I'm just curious as to if there are any substantive differences in approach between what I learned and what y'all were taught. I do want to respect the purpose of the new forum, and not impose or encourage what might be non-DIR answers (which is why I never asked the question in the old forum). Therefore I won't attempt to tell you what I would do (based on my NAUI training) ... but I may ask why you would make the choices you would make.

FWIW - I do know that there's some variance in how ... even among GUE instructors ... deco planning has been taught. It would be interesting to see what that brings out among GUE divers from different eras and locations.

... Bob (Grateful Diver)

 

[JeffG]

I don't remember the exact times (They are in my wetnotes)

But I have done that dive in a couple of ways. I have used Ratio deco to come up with the deco schedule and have done the dive with a modified decoplanner schedule (I believe thats what program it was. Nadwidny would know. It was on his Palm Pilot) We compared RD to his plan. added some stops..got rid of some.

I am also a bit of a deco weenie. I usually add extra padding in the 20' stops because twice now I have taken type 1 hits in the elbows. (more than likely it was due to exertion, which I am addressing in another way, but thats another thread)

 

[nadwidny]

I don't remember the exact times (They are in my wetnotes)

But I have done that dive in a couple of ways. I have used Ratio deco to come up with the deco schedule and have done the dive with a modified decoplanner schedule (I believe thats what program it was. Nadwidny would know. It was on his Palm Pilot) We compared RD to his plan. added some stops..got rid of some.

I used the DPlan program. I don't remember the exact times but we probably ran it with a 20/95 GF then made adjustments from there WRT the deep stops, intermediate times and the 20' stop and final ascent phase. 18/45 bottom gas. 50% and 100% deco gasses. Run time is about 68 minutes.

Now then, in the spirit of this forum, what I do for deco is not the same as what I've seen GUE instructors do and teach lately but rather what I've learned from other DIR types over the years, so any answer I give is probably not the DIR answer as practiced these days. So I should let someone more current tell the official DIR answer.

 

[ScubaAndDreams]

I'd be interested in this answer as well. Very much for the same reasons as the OP.

 

[JeffG]

I'd be interested in this answer as well. Very much for the same reasons as the OP.

I don't know if there is a "Right" answer (given that most of Deco is kinda voodoo like anyways).

There are some constants...
Use deep stops
Use standard bottom and deco gases
Use backgas breaks

but the actual curve/time is almost a personal thing (based on how your body reacts, or what tool you use to generate the schedule.)

Like when you get to the edges of Ratio deco limits, RD might not be the tool of choice.

 

[MXGratefulDiver]

Now then, in the spirit of this forum, what I do for deco is not the same as what I've seen GUE instructors do and teach lately but rather what I've learned from other DIR types over the years, so any answer I give is probably not the DIR answer as practiced these days. So I should let someone more current tell the official DIR answer.

In which case, I wouldn't mind a PM (if you don't mind sending one) ... I'd like to make some comparisons.

FWIW - I've done this with a few DIR-trained divers locally, and have discovered there's some variance in terms of who taught them ... and when. For example, some "weight" the 70-foot to 30-foot stops, putting more time on the high and low ends, and removing minutes from the middle stops. Others distribute the time over those five stops equally. Likewise with how the deco minutes get distributed for the 20 and 10 foot stops. It's my understanding that different methods were taught in their respective GUE Tech 1 and Tech 2 classes, depending on the instructor and when the class was taught.

It would be useful to discuss this, as it left me with the impression that there isn't really one specific "DIR" answer, but rather a "DIR" way of deriving one.

... Bob (Grateful Diver)

 

[rjack321]

In which case, I wouldn't mind a PM (if you don't mind sending one) ... I'd like to make some comparisons.

FWIW - I've done this with a few DIR-trained divers locally, and have discovered there's some variance in terms of who taught them ... and when. For example, some "weight" the 70-foot to 30-foot stops, putting more time on the high and low ends, and removing minutes from the middle stops. Others distribute the time over those five stops equally. Likewise with how the deco minutes get distributed for the 20 and 10 foot stops. It's my understanding that different methods were taught in their respective GUE Tech 1 and Tech 2 classes, depending on the instructor and when the class was taught.

It would be useful to discuss this, as it left me with the impression that there isn't really one specific "DIR" answer, but rather a "DIR" way of deriving one.

... Bob (Grateful Diver)

There is no "one and only way" DIR way to derive a schedule. At least if there is we weren't taught one.

In my T1 class how we distributed 20 and 10ft stops (with one deco gas) was very discretionary. Based on water conditions and to some extent how much time you'd spent at 30ft (to avoid major time jumps).

Weighting the O2 window was taught once by GUE. Its still taught by AG but at least at the T1 level its no longer emphasized by GUE. Someone with a more recent class than mine can discuss.

How to manage a lost deco gas in T1 has 2 distinct approaches. Share the 50% or deco on backgas. Your 1st choice seems to depend on who taught you and when. But I think we all recognize that both options can work and the one you'd chose "depends".

Overall deco instruction seems to be one of those things which is not entirely standardized within "DIR" or even GUE. As much as the naysayers think we're just mindless drones it does come down to the actual instructor, the era, and probably the greatest variance is due to individual experiences building a repetoire of working profiles with tweaks.

For instance, on my profiles I add about 3-5 minutes at the shallow stops when I'm on 21/35. I just feel better. I don't seem to need any padding when 18/45 is used. Once I did a T1 dive then 2 more rec dives in 1 day. I won't be doing that again - definately felt like poo after dive #2. So I'll be giving myself a longer SI or alot of shallow time on 2 dive charters next time.

 

[MonkSeal]

I would rather do it on 15/55 if all BT is spent at max depth. If the average depth is shallower then 18/45 is ok. I do such dives with ratio deco, ratio 1:2, set point 66 m (roughly 220'), double 16 liter of backgas, AL80 (or 7 liter) of nitrox 50 and AL40 of O2. Half of deco time at nitrox 50, half at O2. Deep stops from 80% of ATA. Half of nitrox 50 time spent in 120'-80' range. Backgas break at 30'. Backgas breaks 12/6 on O2. Always checked with Decoplan and VPM.

 

[MXGratefulDiver]

Richard ... pretty much the type of info I'm looking for ... not procedure so much as thought process.

Monkseal ... what do you mean by this?

Half of nitrox 50 time spent in 120'-80' range.

It seems to suggest something I'm sure you didn't mean (EAN50 switch at 120). Everything else you posted is very compatible with what I was taught ...

... Bob (Grateful Diver)

 

[TSandM]

What we were taught when we did the deco stuff during Rec Triox (which I think is basically the deco stuff for T1) was to start with Decoplanner (he didn't discuss what gradient factor settings). Add the deep stops, pad the stops at gas switches (O2 window) and adjust the shallow stops for surface factors.

It looked so much like the exercises we did last weekend in the Ratio deco seminar that it left me wanting to run some profiles both ways and see just how different the answers would be.

I had read somewhere that GUE had switched from trying to make a sigmoid curve out of each segment to doing the stops as linear stops, but we were taught, as I said, to add to the gas switch stops.