Deco On the Fly

[Mark Chase]

In light of the response by Rossh I was curious to know of the deco on the fly system has any depth variables or if it is just a fixed formula for all dives be they Nitrox, Trimix, 20m or 120m?

Having looked at the minimum M values for deep stops there seems to be a lot of credence to the 2atm first stop idea.

Do DOTF or other systems have fast 10-18m/ min ascent rates to the first stop depth and is there any one out there using this method (or something similar) that has experimented with it.

It would be interesting to here some more about it.

ATB

Mark Chase

[Davey Willo]

Originally Posted by Mark Chase

In light of the response by Rossh I was curious to know of the deco on the fly system has any depth variables or if it is just a fixed formula for all dives be they Nitrox, Trimix, 20m or 120m?

Having looked at the minimum M values for deep stops there seems to be a lot of credence to the 2atm first stop idea.

Do DOTF or other systems have fast 10-18m/ min ascent rates to the first stop depth and is there any one out there using this method (or something similar) that has experimented with it.

It would be interesting to here some more about it.

ATB

Mark Chase

Hi Mark

Yes Ratio Deco has variables based on gas mixes depths and times, all very much of a muchness really.

Tech 1 depths and gasses have one variable, in Tech 2 theres another.

Remember though, they only work with GUE standard mixes and dive profiles, by that I mean someone who may be diving a "best mix" for their depth followed by an 80/20 deco gas or whatever, they then should be aware that even if they are in full knowledge of all of the sums, they are working outside of recognised GUE tried and tested parameters and are probably going to end up in a world of pain.

As far as ascent rates are concerned its 10m a minute up to the first deep stop and then 3m a minute thereafter

HTH's mate

Dave.

[Doug Parker]

Could the theory behind DOTF with GUE set gases be adapted for 'alternative' gases.

Not looking for a row, but what other word can you use without upsetting somebody. If i'd used 'normal' instead of 'alternative', i'd still get it in the neck, just from a different group.


Damned if you do

[Davey Willo]

Alternative.... LOL.. Nice one Dougie, although some would say that we were the alternative ones...

I can't really answer your question I'm afraid mate as I don't know the answer to it, sorry

Dave

[Doug Parker]

I couldn't come up with another word for gases not used by GUE. I'll be happy to use 'alternative' so it doesn't turn into a ruck, i just couldn't think of a word to use instead.

[Mdemon]

IIRC, it's based on an observation of the deco figures that for one mix (I guess this is the standard Tech 1 mix) are easy to predict. I heard a similar technique from an old commercial diver a while back for any mix - I'll dig out my notes.

In theory, shouldn't you be able to work something out for all mixes? A ratio is a ratio...

[Doug Parker]

Originally Posted by Mdemon

In theory, shouldn't you be able to work something out for all mixes? A ratio is a ratio...

Exactly. I'm not clever enough to do that myself though. DOTF could be adapted for an 'alternative' (not right, but it'll do) set of gases.

[Mdemon]

Must be. They use two in DIR judging by the post above, so don't see why more isn't possible.

[Doug Parker]

Oxygen window is variable with depth, i assume.

Not that i know anything about it.

[Andrew H]

If you cut an awfull lot of tables for dives using the same gases on a given program, you should start to see enough trends to make some rules of thumb. You could then test the profiles given by your rule of thumb in your program and arrive at a sort of Deco by Thumb sort of arrangement. It might well be that the DIR standard gases give unusually tidy answer in this respect. Seem like a lot of effort to avoid using DIR gases though. That said the particular rules used by DIR are not exactly common knowldge yet. If you narrowed it down to a praticular depth range and dive lengths it shouldn't be too hard, but probably not agood idea unless you really know what you are doing.

Andrew