Deco planning

[Diver0001]

<snip>

I sounds like RGBM says that if you're going be off gassing slower (without the deco gas) that you're better off getting rid of more while you're deeper.

Actually, of all the things Brian ever wrote about 99,5% of it was over my head but I do remember him writing about this.

He said this about it :

1) bubbles are harder to get rid off than dissolved gas
2) Haldane models make bubbles and then you have to wait around for them to go away. Inefficient.
3) RGBM uses deep stops to *avoid* bubble formation and therefore the inert gasses can be off gassed more efficiently.

(of course I'm saying it in a way that can be understood by someone without a phd in the things you need a PhD in to write the way he does)

As for the reasons why the length and depth of deep stops changes according to the deco gas involved. That's easy. That's just an oxygen-window story..... At least that would be my first impression given that I only understang 1/2 of 1% of evreything he writes

R..

 

[DepartureDiver]

1) bubbles are harder to get rid off than dissolved gas
2) Haldane models make bubbles and then you have to wait around for them to go away. Inefficient.
3) RGBM uses deep stops to *avoid* bubble formation and therefore the inert gasses can be off gassed more efficiently.

(of course I'm saying it in a way that can be understood by someone without a phd in the things you need a PhD in to write the way he does)

yes ... clean and simple

As for the reasons why the length and depth of deep stops changes according to the deco gas involved. That's easy. That's just an oxygen-window story..... At least that would be my first impression given that I only understang 1/2 of 1% of evreything he writes
R..

Actually, no it's not an oxygen window situation. This can be a hard concept to grasp because it is so different from the way people have been trained to think. Trying to keep it as simple as possible, the theory is that the body can handle some "excess bubbling" for a short time. The model thus allows the diver to get to a shallower depth and then finish the decompression knowing that the diver is going to be on O2 at the final stops. So the times are shorter at the deeper stops since the model knows that O2 will be used at 20'. In one sense, the model is working backwards from the shallow stops to the deeper stops (really it is working all of them at the same time). So when no O2 is being used, the model knows it and knows that the "excess bubbling" it previously allowed by way of shorter stops with the O2 can no longer be done. So the loss of O2 at 20' requires the stops at all the other deeper depths to be lengthened. This may sound wrong or even a little off, but that is what models like VPM do and the theory is actually sound.

 

[MikeFerrara]

Good explaination. I like that.

 

[MonkSeal]

Could you plan this as a multi level dive, putting in the depths and times required for deco on back gas into the software ??? The program would then give you a correct time for the 6m stop on O2???
Not very elegant I agree but it might be a workaround

I thought about that but unfortunately GAP Lite (that I use) doesn't allow that. Maybe it's a bug or some kind of limitation. If I enter:

42 m 15 min
18 m 1 min

I get message "On stop 5m, we have more than 10hrs of decompression".