Deco On the Fly

[Mark Chase]

Originally Posted by Dave Williamson

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.

Thanks Dave it makes more sense now. When I studdied the profiles for the set gas list I kind of figured there must be some variables.

ATB

Mark Chase

[Mark Powell]

The article below gives a good overview of a simillar type of approach. It is using 'alternative' gasses.

http://thedecostop.com/forums/showthread.php?t=3198

[Mdemon]

I think it's safe to assume that the best mixes are the two used by DIR - I can't see why they wouldn't pick the best (clue's in the name maybe? ). What's the Tech2 mix BTW?

The trouble is, in plotting for multiple gases you'd end up needing something resembling a PADI wheel, and then the thought occurrs "why not get a computer to work it out?". Catch 22. I suppose that's why DOTF is for so few gases IMHO.


(Couldn't find my notes - I'll see what I can find online)

[Doug Parker]

I (sort of) understand DOTF with GUEs set gases but i'm wary of 100%. I'd rather use 80% personally. I've seen a couple of people cop it with 100% and the thought of it scares me. Even if you had proof to say otherwise, it would still be in the back of my mind, which adds to the stress factor and makes it worse.

[jptaylor9]

[Mark Chase]

Originally Posted by jptaylor9

What is the last stop depth that DOTF assumes, 3m?

For UK conditions, 6m last stop is often used. Deco'ing at 6m on oxygen (assuming your bouyancy skills are OK) can result in a very high CNS loading for a limited reduction in stop time over 80%.

For oxygen, CNS% per min. at 6m is 2.22 whereas at 3m it's only 0.56.

The CNS% per minute for 80% at 6m is also 0.56, i.e equivalent to 100% @ 3m.

(I'm sure this is a recurring argument on YD!)

JT

It is, but the main protagonists have spat their dummies out and run for the safety of the DIR forums so you wont get much argument from the rest of the tech boys and girls on the forum.

I used to use 50 and 100% but when I started pushing the depth and bottom time CNS became a major issue. I also found 100% a sod to fill and very restrictive if the deco section of the dive did not go according to plan. JJ and GI3 would probably argue that if conditions are that bad don’t dive but conditions are always that bad off of Dover. The currents are very strong and it’s a very very busy shipping area forcing shot line deco. With 12 divers on the shot getting to 6m for your deco stop is NOT guaranteed and doing hangs at 3m in a swell & 5 knot current is just impractical.

ATB

Mark Chase

[Paul Oliver]

Originally Posted by Mark Chase

It is, but the main protagonists have spat their dummies out and run for the safety of the DIR forums so you wont get much argument from the rest of the tech boys and girls on the forum.

I used to use 50 and 100% but when I started pushing the depth and bottom time CNS became a major issue. I also found 100% a sod to fill and very restrictive if the deco section of the dive did not go according to plan. JJ and GI3 would probably argue that if conditions are that bad don’t dive but conditions are always that bad off of Dover. The currents are very strong and it’s a very very busy shipping area forcing shot line deco. With 12 divers on the shot getting to 6m for your deco stop is NOT guaranteed and doing hangs at 3m in a swell & 5 knot current is just impractical.

ATB

Mark Chase

Which is my thought process as well (which is very, very scarry ). And (poor sentance construction, but WTF) why i favour 50% or 80% as my deco mix when i carry one,which is not that often.

[Paul Oliver]

On the Fly is ok but i look at it as more of a gimmick, if my puter fails i carry tables and a bottom timer so i can WORK it out releving stress. If its a deep 'un i'm on tables with options and my 'puter as back up.

As long as i have two methods i am happy, and failing that buddies puter or abort and hang as long as i can.

[Mark Chase]

Originally Posted by Paul Oliver

On the Fly is ok but i look at it as more of a gimmick, if my puter fails i carry tables and a bottom timer so i can WORK it out releving stress. If its a deep 'un i'm on tables with options and my 'puter as back up.

As long as I have two methods i am happy, and failing that buddies puter or abort and hang as long as i can.

Come on Paul, thats just not tekie enough. You have to make it more complicated than that

ATB

Mark Chase

[Paul Oliver]

Hi Mark

But you know from the colour of my drysuit i am just an embarrasment to all things techie

Anyway i look forward to seeing the YBOD in action, could be some winding up going on then