ratio deco

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Permalink Reply by Marc Blackwood on January 14, 2009 at 11:03am

#1 To my understanding, the schedule isn't affected by altitude. The theory being that the in-water-decompression is done in such a way that the fast tissues contain such a small level of inert gas tension that the increased gradient (as compared to sea-level) upon surfacing won't hurt you.

Same schedule, same SIT. But hopefully an authority can confirm.

#2 Not always, or not all of it. As I've learned it, bottom time and average depth starts when you pass your the MOD of your deepest deco gas. Thus for a single bottle dive, the depth averag and bottom time starts as you fall through 70 (and ends when you begin your ascent).

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Permalink Reply by Andrew Georgitsis on January 14, 2009 at 3:37pm

Harald

I would suggest taking the OnLine Classroom. The three chapters with voice overs will really help cement you questions and understanding. To answer your questions we do the decompression in the water so the altitude does not affect us when we exit the water and we depth average so decent is inconsequential.

Andrew

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Permalink Reply by Mark Chase on December 8, 2009 at 12:38pm

NOTE: I am not a UTD diver and I am not an instructor but I have dived ratio deco using a slightly modified version of AGs old GUE system for about three years in the 40-80m depth range

When diving a computer you have safety settings. When diving tables you have safety settings and when diving ratio deco you have safety settings.

Decent in run time? Yes = padding No = no padding

Average depth? Plan on max depth for padding. Plan on deep avg depth for a little padding. Plan on shallow avg depth for no padding


Ratio deco isnt a deco program. It has no fixed level of safety based on a theoretical deco base line. It does not represent Bhulman + or - anything. It is not a RGBM or VPM bubble model


On some dives like 40mins at 45m it’s very conservative and on other dives like 40mins at 65m it’s very aggressive.

You can’t just use ratio deco. You need to build up experience using it and comparing it to profiles you know work for you with your present decompression system. If you have no experience with deco prior to using RD you need to plan dives and compare them to computer generated tables to see if your being aggressive or conservative in relation to accepted norms of deco.


I run Bhulman 10/90 Gradient factor for trimix decompresion dives. I manualy calculate my ratio deco and compare notes with my GF deco computer to get a feel for RD as a back up to my computer. Its a great way to lern how it works on real dives. And it works well once you have a feel for it.

HTH

Mark

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