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GUE/UTD Deco tables
A friend of mine who just wrapped up a fundies class was talking about the 130/120 rule for diving. I do plan on taking the fundies class and I would like to also take the UTD Ratio deco class but until I do I would like to learn and understand how this works. We talked over what he learned but I'm still a little rusty on the info. I picked up a bottom timer and run straight at a set depth but I get a little confused on multi depth dives.
The rule of 120/130 is NOT coming out from their Deco table. Rather, it is just a quick rule of thumb based on information on NDL/MDL table, which mean you are still in a recreation dive and without deco obligation. It has nothing to do with ratio deco either. Be very careful about incomplete information.
You should take a look at the GUE recreation dive planner, which is a GUE version of 32% Nitrox MDL table. Then take a look at a air table, from PADI, you will see why rule of 120 for air and rule of 130 for 32%.
Thanks eelnoraa. I had a feeling I was not absorbing the info correctly. This is what happens when you get a few different people talking on a dive boat about what they learned a few weeks ago from different schools. Where would I find the "GUE recreation dive planner" short of the class? I don't see it on the GUE site for sale.
I have a physical print out of the table only, not in front of me tho. But on top of my head, GUE one seems more conservative than this. How about take a look at the PADI 32% table. I remember they are similar.
GUE uses MDL concept as opposite to PADI's NDL (3 min at 15ft safety stop). GUE does 1 min of deep stop at 1/2 of your max depth, then 10ft ascent per minutes. There are a bit more detail than this, which I am afraid I am not the right person tell you. I don't want to give your incorrect/incomplete information. I think you should take the class, understand the procedure before you use GUE's method to plan dive.
The GUE tables are based on a couple of assumptions -- One is that you WILL be diving 32% Nitrox, and the other is that you will do a "minimum deco" ascent, which involves a 30 fpm ascent to half maximal depth, and then a 30 second stop-30 second move process through the shallow part of the ascent. I do not know how much validation this table underwent before it was published, but it is not hugely different from other 32% tables.
I don't actually know what GUE is teaching for multi-level dives nowadays, with the advent of the Rec 1 class. I was taught to use a time-weighted average depth to compute MDLs. As far as I know, outside of the anecdotal use by a great many people who were trained to do this, there is no real validation of this approach. I use it, but I am acutely aware that I am a bit of a guinea pig. However, as Dr. Sawatzky observed in an article in Diver Magazine a number of years ago, the big reduction in DCS came with Haldane's original insights -- everything that's been done since is chipping at the edges of the remaining incidence of DCS. It may very well be that the reason our approach works is that we all work within such generous safety margins that many approaches WILL work, in the majority of cases.
Take the class, and ask questions.
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