How would you do this dive ...

[boomx5]

And if so, what recommendations do they make for modifying the deco schedule in favor of addressing what may be a more pressing problem?

... Bob (Grateful Diver)

We had a dive one time and everything went perfect until we got to our 20' stop and made the switch to O2. The vis in the cove that we started from dropped to about 1'-2' and we were getting the crap beat out of us from the surge. So after about 35 minutes in to a 45 minute deco we decided we'd had enough and decided to call the dive. That is how we handled one senario and everything worked out fine, but each situation is different.

 

[RTodd]

We had a dive one time and everything went perfect until we got to our 20' stop and made the switch to O2. The vis in the cove that we started from dropped to about 1'-2' and we were getting the crap beat out of us from the surge. So after about 35 minutes in to a 45 minute deco we decided we'd had enough and decided to call the dive. That is how we handled one senario and everything worked out fine, but each situation is different.

I use to be really agressive. Got to the 02 bottle with about 15 minutes needed and got about one breathe out of it (stuck gauge). Oh well, deco's over, slow ascent up. I even had Trout question the shortened nature of my deco once. Then I took a few minor Type I hits because one little other contributing factor put me over the top, such as heaving lifting right after the dive, etc. Now, I am much more of a weenie, but relatively comfortable knowing if you get the deeper stuff right you shouldn't get too hurt if you have to get out. But, there is no reason to get in a hurry if you don't need to do so.

 

[boomx5]

But, there is no reason to get in a hurry if you don't need to do so.

I agree. I'm usually the weenie who wants to spend more time shallow. I figure I'm here to dive and I have plenty of burntime left, so let's keep on diving...no need to get out. Unfortunately, the conditions warranted this approach so we made a gametime decision. If we knew it was going to get bad we would've called the dive before we got in and went and had lunch. Thankfully everything worked out.

 

[nadwidny]

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)

Looks like there is no "DIR" answer so I'll post here...

For a 200' dive I would use DPlan and I'm using a 20/95 GF these days. Bottom gas would be 18/45. I would use both 50 and 100% for deco.

I get:
200 for 25
120-90 for 1
80 for 2
70 & 60 for 2
50 for 3
40 for 4
30 for 6
20 for 18


I would start pauses at around 160. I would start 1 minute stops at 120. I would go with the 2 minute stop at 80 because I like to take a bit of time to make sure that everybody is on the same page. My 70 and 60 I would extend to 4 minutes each, taking a couple minutes from the 40 and 30. The 50 I would leave at 3. 40 for 2 and the 30 I would do for 4 on Backgas. The 20 I would do for 18 with 6 up after that but with the knowledge that I could shorten that to 12 and 6up if things go south. I probably wouldn't do a BG break at the 20' stop. I used to do 5 minutes at 70 and 60, taking from the 30 and 40 but I didn't like that so I shortened them up a bit.

That's what I would do, for now.

 

[rainman_02]

Extrapolating on my T1 RD knowledge. Please correct if wrong, provide pointers, suggestions, etc. Looking forward to T2 sometime next year or so.

5 minutes to surface
20 - 20 (10 on, 5 off, 5 on)
30 - 5 (back gas, 70' bottle clean up)
40 - 3
50 - 3
60 - 7
70 - 7 (after team switched to 70' bottle)
70 - 1 (back gas before/during switch)
80 - 2
90 - 2
100 - 2
110 - 1
120 - 1
130 - 1
140 - 1
150 - 1

200 - 25


Yee haw.

 

[MonkSeal]

Monkseal typically has great english but I agree its a bit confusing.

Thanks. However, I see that you figured out what I meant. To be 100% clear this would be schedule:

3 min descending
22-23 min @ 60 m
2 min ascending to 45 m
------------------------ I consider this 45 min BT @ 60 m
1 min @ 45 m
1 min @ 42 m
1 min @ 39 m
1 min @ 36 m
1 min @ 33 m
2 min @ 30 m
3 min @ 27 m
3 min @ 24 m
5 min @ 21 m (nitrox 50)
5 min @ 18 m
3 min @ 15 m
3 min @ 12 m
4 min @ 9 m (going to back gas)
20 min @ 6 m (O2 12/6 breaks)
2-3 min to surface
------------------------ Total RT some 84 min

 

[MXGratefulDiver]

Well, this has turned into an interesting discussion … and the responses so far are pretty compatible with the way I was taught.

Given that, I’ll go ahead and answer my own questions …

My gas choices would be 18/45 for back gas (double 119’s), EAN50 (AL40) and O2 (AL40).

My dive plan would be:

Leave 200 (25)
2 min to 140 (27)
1 min @ 130 (28)
1 min @ 120 (29)
1 min @ 110 (30)
2 min @ 100 (32)
2 min @ 90 (34)
2 min @ 80 (36)
4 min @ 70 (40)
4 min @ 60 (44)
4 min @ 50 (48)
4 min @ 40 (52)
6 min @ 30 (58)
17 min @ 20 (75)
5 min up (80)

I’d take back gas breaks for 2 minutes at the end of the 30-foot stop and @ 20 feet just prior to the ascent.

Contingencies …

If I had to cut the deco schedule, I’d shave one minute off of each stop between 70 and 30. If necessary, I’d shave up to an additional 5 minutes off my 20-foot stop (depending on how desperate I was to get out of the water). In this case, I’d definitely be breathing the rest of my bottle back on the boat.

Lost 50% bottle … so far we’ve always had a safety diver handy with a spare bottle, but if that were unavailable we’d do 1.5x stops sharing, 3 min on, 3 min off per stop.

Lost O2 bottle … 1.5x stop @ 20 sharing the available bottle … double the ascent time from 20 to the surface.

… Bob (Grateful Diver)

 

[MonkSeal]

... If I had to cut the deco schedule ...

Regading shaving I made same dive with following schedule (dry suit leek):

1 min @ 45 m
1 min @ 42 m
1 min @ 39 m
1 min @ 36 m
1 min @ 33 m
1 min @ 30 m
1 min @ 27 m
2 min @ 24 m
4 min @ 21 m (nitrox 50)
4 min @ 18 m
3 min @ 15 m
3 min @ 12 m
3 min @ 9 m (going to back gas)
18 min @ 6 m (O2 10/5 breaks)
2 min to surface
-------------------- Total RT 74 min

with no consequences but I prefer less agressive one.

 

[vbcoachchris]

Well, this has turned into an interesting discussion … and the responses so far are pretty compatible with the way I was taught.

Given that, I’ll go ahead and answer my own questions …

My gas choices would be 18/45 for back gas (double 119’s), EAN50 (AL40) and O2 (AL40).

My dive plan would be:

Leave 200 (25)
2 min to 140 (27)
1 min @ 130 (28)
1 min @ 120 (29)
1 min @ 110 (30)
2 min @ 100 (32)
2 min @ 90 (34)
2 min @ 80 (36)
4 min @ 70 (40)
4 min @ 60 (44)
4 min @ 50 (48)
4 min @ 40 (52)
6 min @ 30 (58)
17 min @ 20 (75)
5 min up (80)

I’d take back gas breaks for 2 minutes at the end of the 30-foot stop and @ 20 feet just prior to the ascent.

Contingencies …

If I had to cut the deco schedule, I’d shave one minute off of each stop between 70 and 30. If necessary, I’d shave up to an additional 5 minutes off my 20-foot stop (depending on how desperate I was to get out of the water). In this case, I’d definitely be breathing the rest of my bottle back on the boat.

Lost 50% bottle … so far we’ve always had a safety diver handy with a spare bottle, but if that were unavailable we’d do 1.5x stops sharing, 3 min on, 3 min off per stop.

Lost O2 bottle … 1.5x stop @ 20 sharing the available bottle … double the ascent time from 20 to the surface.

… Bob (Grateful Diver)

I like that schedule Bob, I might take a little longer clean up break at 30 and I might spend a little longer off O2 to give my body time to recover. More than 10-15 min straight on O2 an I feel congested. It usually takes about 5 minutes to clear up.

 

[MXGratefulDiver]

I like that schedule Bob,

Lordy, I sure hope so ...

I might take a little longer clean up break at 30 and I might spend a little longer off O2 to give my body time to recover. More than 10-15 min straight on O2 an I feel congested. It usually takes about 5 minutes to clear up.

Well, I'm always amenable to a few extra minutes in the water (as you well know).

For the rest of you ... I'm talking to my instructor here ...

... Bob (Grateful Diver)