Manual calculation for accelerated deco

[hanymamdouh]

Hi all tecies,

Regarding decompression; I want to understand how to calculate accelerated decompression. In other words; using Buhlmann's tables I can calculate decompression stops for a dive if back gas is air. In case of Nitrox; I simply use EAD with Buhlmann's tables to figure out deco stops. But in real world; we use rich mixes (EANx50 and higher) to accelerate decompression at shallower depths (12, 9, 6 meters). Simply I can use computer software like MultiDeco to calculate the profile, but I'm eager to know exactly how to calculate this acceleration by hand.

Thanks so much.

 

[JohnnyC]

You could learn a decompression-on-the-fly strategy like GUE's Ratio Deco. It's something you'd want to seek out training for, it's not complicated, but it does require some mental math and requires standard gases or the ratios break down.

The easier thing to do would be to buy accelerated deco tables like those sold here:
IANTD Open Circuit Flexible Dive Tables | Dive Gear Express®

I carry several of these exact backup tables in my wetnotes, both OC and CCR.

 

[hanymamdouh]

You could learn a decompression-on-the-fly strategy like GUE's Ratio Deco. It's something you'd want to seek out training for, it's not complicated, but it does require some mental math and requires standard gases or the ratios break down.

Thanks Johnny, I have Ratio Deco training documents. In fact I'm seeking to understand how it is really calculated, I mean the science behind it.

 

[northernone]

Thanks Johnny, I have Ratio Deco training documents. In fact I'm seeking to understand how it is really calculated, I mean the science behind it.

Sorry... Science behind it doesn't exist in a definitive documented way.

 

[rsingler]

Deco For Divers

 

[boulderjohn]

Sorry... Science behind it doesn't exist in a definitive documented way.

There is no science behind it.

As Jarrod Jablonski explained its origins to me when I was trying to come to an understanding of the difference between RD for GUE and UTD, RD was designed as a way to approximate what DecoPlanner would have come up with for that dive. If you plan dives with any software program and then plan some contingencies for those dives, it won't be long before you get the sense of a pattern. You can pretty much predict what the contingencies will be, within a certain range. So they made a mathematical process that creates an approximation of what DecoPlanner would give you for a certain range of depths using certain specific gases.

 

[hanymamdouh]

There is no science behind it.

I think you mean Ratio Deco. What I really mean is the science behind MultiDeco and such software. In other words, if I want to do all the calculations without any aid of computer software nor Ratio Deco method.

 

[lowviz]

Maybe start by reading this: https://publications.csiro.au/rpr/download?pid=csiro:EP105042&dsid=DS3

 

[JohnnyC]

You'd pretty much just have to sit down with Buhlmann's algorithm and plug in all the variables and do the math. Besides some mental exercise, I can't really see a point to it when there are a plethora of other tools available that have already been checked for errors, and don't rely on you doing complex mathematical calculations.

It's not like RD where you have a set of simple rules that will dictate a deco schedule. Personally, I plan it in MultiDeco, run a Shearwater and backup, and carry a set of tables in my wetnotes. If all that fails I can run a ratio deco schedule that will probably get me out of the water ok. That pretty much covers all the failures and variables I would expect to have to deal with. All of which are an order of magnitude easier than sitting on a boat and trying to long-hand math everything in the Buhlmann algorithm.

What's your reasoning for trying to do this? If it's just for mental exercise, drive on, if you actually want to use it as a planning tool, you're trying to build a space shuttle with play-doh and a hammer, and potentially introducing some potentially hazardous conditions to your diving. Meanwhile everyone else is already using a (or several) much safer, and much more reliable method(s) of calculating deco.

 

[hanymamdouh]

What's your reasoning for trying to do this?

It is only mental exercise. I'm an engineer, and I'm always eager to know the basics and theories, it gives me mental satisfaction. In real life; sure I use software like MultiDeco (which I'm planning to purchase as trial version only works up to 50% O2).